Ref. Ares(2022)3718318 - 17/05/2022
Ref. Ares(2022)4148847 - 03/06/2022
WWF
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world. Operating in over 100 countries with support from nearly six million
members, WWF works to halt damage to the planet’s natural environment and build
a future in which humans live in harmony with nature. It aims to conserve global
biodiversity, ensure the sustainable use of renewable natural resources and
encourage reductions in pollution and waste.
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1973. Backed by volunteers and 220,000 donors, WWF France takes concrete action
to safeguard natural habitats and the species that live there, promote sustainable
lifestyles, inform decision-makers, help businesses to reduce their environmental
footprint and educate the young.
But if change is to receive widespread support, everyone’s views must be respected.
This is why WWF’s philosophy is based on dialogue as well as action.
To find out about our projects on the ground, visit: http://projets.wwf.fr
Together, we are the solution.
The document “
Agricultural anaerobic digestion: what are the conditions
With contributions from:
for the sector’s sustainability in France?” was produced through a
collaborative process conducted jointly by WWF France and GRDF.
We would like to thank everyone who has contributed, taken part or shown an
interest in this approach and agreed to share their experience throughout the process
presented in this document. The series of workshops organised with GRDF on the
conditions for sustainability in agricultural anaerobic digestion would not have been
possible without their practical and technical knowledge. We are particularly
grateful to the contributors who have proofread the document and cast a critical eye
over its contents.
Finally, we want to thank the teams at GRDF, WWF France’s partner, for their active
help in preparing this document.
Report author: Isabelle Marx (WWF France)
Report coordinators: Isabelle Marx (WWF France), William Nait Mazi (WWF
France)
Thanks to the WWF France teams for their contributions: Arnaud Gauffier, Marie
Kazeroni, Aurélie Pontal, Pascal Quéru.
Document published in March 2020.
© 1986 Panda Symbol WWF - World Wide Fund for Nature (formerly World Wildlife Fund)
® “WWF” & “living planet” are WWF Registered Trademarks
WWF France, 35-37 rue Baudin - 93310 Le Pré Saint-Gervais - France
CONTENTS
Editorial .......................................................................................................................................................................... 4
Summary ........................................................................................................................................................................ 6
Introduction ................................................................................................................................................................... 8
Agricultural anaerobic digestion, where the energy and agricultural transitions meet ......................................... 8
Opportunities for developing anaerobic digestion in France .................................................................................. 8
A participatory approach ............................................................................................................................................. 10
… To identify the priorities for the sector’s sustainability ..................................................................................... 10
… To share scientific knowledge and agricultural practices ................................................................................... 11
… To formulate recommendations on scaling up .................................................................................................... 11
Note for readers ........................................................................................................................................................ 11
Conditions for the sustainability of agricultural anaerobic digestion ......................................................................... 12
First condition: Encouraging the use of agroecological practices at farm level ..................................................... 12
Second condition: Integration into the context of the territory ............................................................................. 13
Third condition: Helping to solve global societal challenges ................................................................................. 14
Intermediate energy crops and digestate spreading: how do they respond to the sustainability conditions? ......... 16
Preface ....................................................................................................................................................................... 16
Intermediate energy crops ....................................................................................................................................... 16
Returning digestates to the soil............................................................................................................................... 24
In summary ............................................................................................................................................................... 31
Priorities and recommendations for scaling up agricultural anaerobic digestion .................................................... 32
The need for a shared, consistent frame of reference ............................................................................................ 32
A need to supplement and disseminate knowledge, working with key operators ................................................ 34
Strengthen key factors for success involving local governance ............................................................................. 36
Conclusion .................................................................................................................................................................... 38
References .................................................................................................................................................................... 39
Expert presentations ............................................................................................................................................... 39
Articles and publications ......................................................................................................................................... 40
Guides to best practice ............................................................................................................................................ 43
EDITORIAL
Developing renewable energy while contributing to sustainable
agricultural production systems – that’s the challenge of
anaerobic digestion. Currently the most mature source of
renewable gas, it seems to provide responses to many different
priorities since it emerged in France in the 1970s. Supported by
the potential of agricultural biomass (livestock effluent, crop
residues, etc.), it contributes to the development of the
bioeconomy, which is now seen as a solution for decarbonising
the economy and preserving biodiversity.
Like many solutions that aim to contribute to the ecological and
solidarity transition, agricultural anaerobic digestion relies on industrial infrastructure
that is faced with major issues of environmental and territorial integration.
Incorporating it into food production methods can affect how they work in a variety of
ways. Given the importance of the agroecological transition on which our resilience and
our future food security partly depends, anaerobic digestion has to be compatible with
the principles of agroecology. This is why WWF France, in partnership with GRDF,
decided to take a closer look at the conditions for the sector to contribute to sustainable
development and respond to major environmental, agronomic and energy challenges.
Future energy and agricultural scenarios that focus on containing global warming within
1.5°C rely on the large-scale use of agricultural biomass to expand anaerobic digestion.
This document aims to highlight the conditions in which anaerobic digestion can
provide leverage for the agroecological transition in our production systems. Though it
currently appears to promise better nitrogen management on farms and an opportunity
to limit climate change through carbon storage, the overall impact of the changes in
practice induced by agricultural anaerobic digestion is not known. This document
proposes to review the current state of scientific knowledge and identify areas where
more research is needed to provide the answers. Areas that require particular attention
include the effects on soil biodiversity and adaptation to different soil and climate
conditions, the source of France’s agricultural wealth.
Arising from a year’s collaborative work with various stakeholders from across the
industry, the sustainability framework presented here lays the foundations for a debate
about how biomass can be mobilised to develop sustainable anaerobic digestion.
It makes no claims to be exhaustive, but aims to help project coordinators, decision-
makers and local authorities by highlighting new research topics and identifying needs.
The ultimate goal is to promote the widespread adoption of practices that will make
anaerobic digestion a virtuous sector.
Véronique Andrieux, Chief Executive of WWF France
4
FOREWORD
In 2018 and 2019, WWF France and GRDF, as part of their partnership on the
sustainability of the agricultural anaerobic digestion sector in France, organised a
consultation of the sector's stakeholders. The aim of this process was to identify a
sustainability framework that could be used by the various stakeholders in the
agricultural and energy sectors. At the same time, this work was meant to determine
whether the sector was compatible with the agro-ecological transition.
In pratical terms, the work took the form of:
·
A preliminary study to understand the current challenges of agricultural
anaerobic digestion in France, through bibliographic research and individual
interviews ;
·
A series of workshops bringing together stakeholders in the sector (public
authorities, research institutes, representatives of the biogas sector,
representatives of the agricultural community, associations), with whom the
issues addressed were framed and prioritised for further work
o
The drafting of a report presenting
o
The sustainability framework resulting from this work
o
The consistency of certain practices (intermediate crops and
digestates spreading) with this framework on the basis of the state of
the art at the time of writing
o
Recommendations for the development of the sector to be compatible
with the agro-ecological transition.
The conclusions drawn from various research studies or discussions with
stakeholders in the sector are specific to the French agricultural and energy
context from an agricultural, energy and regulatory point of view. Our
results are therefore not exportable to other contexts.
While the methodology used in this work may be a source of inspiration for
countries wishing to undertake similar approaches, it must be based on
data from these countries and assessed in the light of the organisation of
the sector in these countries.
This document proposes, at the end of a joint process with GRDF, a common and shared
vision, with the actors who participated in our process, of the overall conditions in which
the methanisation sector can develop in a sustainable manner in France. The reader
should also take into account the following areas of attention:
·
The work carried out is intended to provide guidelines and recommendations
at the national level. It does not take into account the territorial specificities of
the French agricultural and energy landscapes; the work carried out in 2018
and 2019 is now being pursued within the framework of coalitions of
stakeholders at the territorial level;
·
The work carried out focuses on the agricultural angle of methanisation,
targeting its environmental issues first and foremost, although social and
economic issues have been integrated into the reflection; no discrimination of
the size of projects has been taken into account in the analysis;
·
The work carried out on the accounting of practices focuses primarily on the
issues prioritised by the stakeholders, linked to the return of digestate to the
soil and intermediate crops for energy purposes, without looking in depth at
the mobilisation of dedicated crops or the problems identified with the mixing
of inputs (with slurry, manure, green waste, etc.).
5
SUMMARY
In its vision for a future world with greater respect for the environment, France is now
betting on the bioeconomy. As well as reducing its dependence on fossil fuel
resources, the sustainable use of biomass presents an opportunity for the country to
achieve the climate goals adopted at COP21.
Recent uses of biomass resources include agricultural anaerobic digestion, which has
developed strongly due to its potential as a means of decarbonising the energy sector.
As with any solution that can contribute to the ecological and solidarity transition,
special attention must be paid to the conditions for its sustainable development.
Specifically, because of its integration into agricultural production systems, the sector's
compatibility with the agroecological transition is an essential condition for this
sustainability.
Arising from a year's collaborative work with various stakeholders in the industry,
this
publication proposes a definition of sustainability in agricultural anaerobic
digestion that is intended to serve as a basis for consideration of how to manage
agricultural anaerobic digestion projects and, at a more macroscopic level, for the
development of public policy. The definition encompasses three conditions:
·
The implementation of agroecological practices at the level of both
individual parcels and whole farms: production systems that incorporate
agricultural anaerobic digestion must be tailored to an area’s specific soil and
climate conditions. They must preserve natural resources (soil, water, air and
biodiversity), as well as ensuring fair additional revenue for the farmer;
·
Territorial integration of projects: with their eminently local character,
involving multiple stakeholders and priorities, anaerobic digestion projects
need to consider local provision of biomass and competition between different
uses, local governance, societal ownership and the creation of shared local
value;
·
The scalability required to address global societal challenges,
helping to achieve national targets in terms of greenhouse gas emission
reductions and the resilience of agricultural systems.
The series of workshops organised by WWF France and GRDF in 2019 sought to identify
the degree to which two issues identified as priorities by the sector from an agricultural
viewpoint - namely the
management of intermediate energy crops and the
return of digestates to the soil - are compatible with this sustainability framework.
Knowledge and mastery of these practices, which represent a shift away from current
production methods, is still partial. However, national and local research projects as
well as field experience have provided insights into their benefits for the agricultural
system and identified the conditions under which they can be optimised from an
environmental viewpoint.
Both these practices can thus align with certain
principles of the agroecological transition.
These practices are still recent, and a need for more detailed analysis has been identified,
particularly with regard to their impact on biodiversity and their adaptation to each
area’s specific soil and climate conditions.
Continued research and
experimentation are thus essential to clarify and develop scientific knowledge and
practices suited to local contexts. The sector will then be able to draw on a
common
operational framework that promotes compliance with the sustainability
conditions. To support the implementation of such a framework,
agricultural and
energy policies must be aligned with each other.
Achieving the deployment goals underlined by the prospective scenarios for 2030 and
2050 will require stakeholders'
skills to be developed. By strengthening professional
development and the spread of existing knowledge, the sector will be able to ensure
6
greater integration of its sustainability issues and best practices at national, regional and
local levels.
Territorial integration of projects is also identified as a key to the success of these
projects. By involving all the direct and indirect stakeholders, anaerobic digestion helps
to strengthen links within local areas, recover waste locally, create local jobs that cannot
be offshored and create economic value that stays in the area.
This publication aims to initiate the development of a common core of knowledge within
the sector, building on existing tools and based on a shared vision of the conditions for
sustainability in the development of agricultural anaerobic digestion and its associated
practices.
7
INTRODUCTION
Agricultural anaerobic digestion, where the energy and
agricultural transitions meet
To ensure the long-term viability of our societies, preserving the climate and biodiversity
are crucial challenges across the globe. The Intergovernmental Panel on Climate Change
(IPCC) regularly sounds the alarm about the speed with which climate change is
occurring and the inevitable consequences. The Intergovernmental Science-Policy
Platform on Biodiversity and Ecosystem Services1 (IPBES) published a report in 20192
that underlined the urgent need for action to address accelerated biodiversity erosion.
How can we respond to these challenges? One of the primary levers is for various sectors
of activity to transition towards a more sustainable model. France has responded to the
international effort by setting a number of targets. The 8 November 2019 Energy and
Climate Act3 enshrines carbon neutrality and the urgency of environmental and climate
action in law. Forthcoming international gatherings in 2020, such as the UN
Biodiversity Conference (COP15) in October, are key opportunities to strengthen the
commitment of countries and the business world to addressing these issues.
The pressure on resources, ecosystems and the climate from power generation and
agriculture make these two sectors priorities for the transition4. From an agricultural
perspective, several potential future scenarios for agriculture and food production have
been developed5, revealing possible pathways towards more sustainable food and
agriculture models in France. One lever for this transformation is agroecology, which
aims to enable farms to combine economic and environmental performance with social
benefits. This avenue is now essential for a sector facing significant challenges – food
security and sovereignty, impact on the environment and human health, contribution
and adaptation to climate change, fair pay for farmers, attractiveness of farming etc.
From an energy perspective, though energy savings and efficiency remain the priorities
of the energy transition, developing sources of renewable energy is equally essential.
Anaerobic digestion is one of these sources, and its key feature is its integration into
agricultural production systems through the materials it digests and then returns to the
soil.
Opportunities for developing anaerobic digestion in
France
Anaerobic digestion is not a new process in France. However, its development was eased
by the National Renewable Energy Action Plan (
Plan national d’action en faveur des
énergies renouvelables) in 2010. This was followed in 2013 by the Energy, Anaerobic
Digestion and Nitrogen Autonomy plan (
Plan Energie Méthanisation Autonomie Azote,
EMAA), which aims to increase France’s nitrogen autonomy and resolve problems such
as green algae in Brittany.
1 Millennium Ecosystem Assessment (2005). The benefits (tangible or intangible) people obtain from ecosystems
2 IPBES (2019). Global Assessment Report on Biodiversity and Ecosystem Services
3 French law no. 2019-1147 of 8 November 2019 on energy and climate
4 Department of the Commissioner-General for Sustainable Development (
Commissariat Général au
Développement Durable) Datalab Climate (2019): energy use is the primary source of GHG emissions in France
(70.3%), followed by agriculture (16.7%)
5 Afterres 2050–Solagro (2016), ADEME’s Energy and Climate Scenario for Agriculture (
Scénario Energie-
Climate pour l’agriculture) (2018) and the French Agriculture and Food Ministry’s application of the national low-
carbon strategy to the agricultural sector
8
The 2015 Energy Transition for Green Growth Act (
Loi de Transition Energétique pour
la Croissance Verte) set a 10% target for renewable gas from all sources as a proportion
of gas consumption in 2030. This target was renewed in the 2019 Energy and Climate
Act (
Loi Energie Climat). Forward-looking work has sought to determine the potential
for renewable gas production by 2030 and 2050 and its technical feasibility. Depending
on the breakdown of biomass consumption by different sectors of the bioeconomy, this
potential could – under certain conditions – cover 100%6 of final gas demand by 2050,
with one third coming from anaerobic digestion. The hypotheses underlying these
scenarios are a determining factor in the sustainability of the anaerobic digestion sector,
which requires plentiful supplies of agricultural biomass. The widespread adoption of
intermediate energy crops, the use of agricultural residues and waste or the gradual
replacement of chemical fertilisers with digestates could all have a transformative effect
on current agricultural systems.
In practice, the country had nearly 700 anaerobic digestion units in 2018, with 442 of
them using agricultural resources7. Applications to build new projects are rising fast8.
This growing number of installations in operation or in construction is enabled by a
framework of financial support based on renewable energy generation. The model of
anaerobic digestion with biogas injection into the gas grid9 is gradually taking its place
alongside the historic model of anaerobic digestion with co-generation integrated into
livestock systems. It is currently the model showing the strongest growth in terms of
installed power, making significant use of intermediate energy crops. The initial goal of
reusing agricultural waste and co-products has thus been supplemented, or even
replaced, by the goal of generating energy10. This shift, together with high production
costs and competitiveness constraints, could overshadow the agronomic benefits
associated with introducing anaerobic digestion into agricultural systems. Regulatory
changes such as France’s Multi-Annual Energy Plan (
Programmation Pluriannuelle de
l’Energie or PPE) suggest that there will be less support for the sector and economic
conditions will become more difficult. These signs are likely to call the sector’s
compatibility with the agroecological transition into question by limiting its
development to the most profitable projects.
As with any solution that can contribute to the ecological and solidarity transition,
special attention must be paid to the conditions for agricultural anaerobic digestion to
be developed sustainably. The sector’s development must contribute effectively to the
transition towards a model of agroecological production that is economically viable in
the long term while improving environmental performance. This has been the ambition
of the partnership between WWF France and GRDF. They formed a working group
involving a variety of stakeholders to propose an approach to defining sustainable terms
for the anaerobic digestion sector.
6 ADEME (2018). A 100% renewable gas mix in 2050?
7 SINOE (2018)
8 GRDF (2019). 759 projects were pending, representing reserved capacity of 16.1 TWh
9 This model is based on heavier use of both intermediate crops and dedicated energy crops
10 ADEME (2016).
Opinion on anaerobic digestion: “Due to better energy performance, ADEME recommends
injecting biomethane into the natural gas network when possible”
9
A PARTICIPATORY APPROACH
What conditions will enable anaerobic digestion to contribute to both the energy
transition and the agricultural transition? How can it generate renewable energy
while also increasing the autonomy of agricultural production systems and preserving
ecosystems?
To help answer these questions, WWF France and GRDF brought together research
institutes, farming and biomethane representatives, institutions and associations
working for the environment or active in the field of renewable energy. The contributors
worked together to consider:
- the conditions that will ensure agricultural anaerobic digestion is developed
sustainably;
- practices compatible with these conditions;
- and the resources and guidelines needed for these conditions and practices to be rolled
out and adopted widely.
This work took the form of a series of four workshops between December 2018 and
October 2019.
… To identify the priorities for the sector’s sustainability
Defining the sustainability of an activity involves examining its contribution to the three
priorities of sustainable development: maintaining a liveable environment, economic
and social development and fair social organisation. The working group considered all
three of these dimensions.
During the first workshop (view the summary here), the participants were asked to
identify environmental, economic or societal issues likely to challenge anaerobic
digestion’s compatibility with a sustainable agricultural model (see box):
Figure 1. Principal sustainability challenges of agricultural anaerobic digestion identified
during the first workshop
This work led to a shared vision of the conditions for the sector’s sustainability (see the
section “Conditions for the sustainability of agricultural anaerobic digestion”).
10
… To share scientific knowledge and agricultural
practices
Among the environmental issues raised, intermediate energy crops11 and returning
digestates to the soil12 emerged as having a major role in the sector’s sustainability. As
a result, the decision was taken to devote a workshop to each of these issues. The
workshops aimed to review scientific knowledge about the environmental impacts of
these practices and share field experience (
see the section “intermediate energy crops
and digestate recovery: how do they respond to the sustainability conditions?”).
Each workshop took place in three stages:
1. Presentations by scientific experts to share the results of research work and
consolidate a common framework of knowledge
2. Sharing feedback highlighting sustainable agricultural practices and the benefits
observed at the level of individual farms
3. Work session to identify remaining questions and prioritise the work needed to
answer them
… To formulate recommendations on scaling up
A fourth workshop examined the resources and roles that would be needed for the
sustainability conditions and sustainable agricultural practices shared throughout the
series of workshops to be propagated, adopted and implemented. It highlighted
recommendations to ensure a sustainable model of anaerobic digestion can be scaled
up successfully (
see the section “Priorities and recommendations for scaling up
anaerobic digestion”). Scaling up is taken to mean establishing the sector on a large
enough scale to meet the targets for its development and for renewable gas production
in France.
This publication summarises the most important lessons learned from this
participatory approach.
Note for readers
The developments presented in this document apply to
anaerobic digestion. As
defined by France’s Rural and Marine Fishing Code13, this refers to units processing
material sourced primarily from farms and majority-owned by farmers.
The analysis does not discriminate on the basis of project size or feedstock mixture, and
the document presents the subjects identified by the working group as the highest
priorities. Certain issues are not covered, such as the use of dedicated crops or problems
with particular feedstock mixtures.
This document does not constitute WWF France’s position on agricultural anaerobic
digestion. Based on a programme conducted jointly with GRDF, it presents the
conditions for the sector’s sustainability and recommendations on how they should be
communicated to the stakeholders concerned, as identified by the organisations that
contributed to the workshops.
11 Read the summary of the workshop on intermediate energy crops here
12 Read the summary of the workshop on digestates here
13 Articles L.311-1 and D.311-18
11
CONDITIONS FOR THE
SUSTAINABILITY OF AGRICULTURAL
ANAEROBIC DIGESTION
At the point where the energy and agricultural transitions meet, the development of
agricultural anaerobic digestion must contribute to resolving the interwoven
economic, environmental and social challenges of these two transitions. A year’s
collaborative work with various stakeholders in the industry has led to a proposed
definition of sustainability in agricultural anaerobic digestion. The
definition involves three conditions and takes an integrated approach at several
levels: the individual farm, the territory and the national or global scale.
First condition: Encouraging the use of agroecological
practices at farm level
Agroecology is an approach to designing production systems based on the functions
offered by ecosystems14. It seeks to amplify these functions while reducing pressures on
the environment and preserving natural resources. It involves a set of techniques that
help to
make the farm less dependent on external inputs (pesticides, fertilisers,
irrigation water etc.),
more economically sustainable and more
environmentally friendly. Care must therefore be taken to ensure that the
agricultural practices introduced by anaerobic digestion, including supplying digesters
with biomass and using digestates for agronomic purposes, contribute to both
environmental and economic performance.
In environmental terms, these practices must
help to maintain or improve:
-
The regulation of elements that are essential for plant growth or habitat
preservation: carbon (C), nitrogen (N) and phosphorus (P);
-
The biological activity of the soil, to guarantee its function and maintain its fertility;
-
The physical soil fertility (structure and porosity) essential for effective water
circulation, solid plant rooting and the maintenance of aerobic conditions15 in the
soil;
-
Chemical soil fertility, including the chemical properties of soil needed for plants
to grow;
-
Water, air and soil quality;
-
Biodiversity in the agricultural environment.
Adapting these practices to suit local soil and climate conditions and diversifying crop
rotations are key elements in ensuring farms’ autonomy and maximising these services.
In economic terms, integrating anaerobic digestion into production systems must
represent an
opportunity to increase the farm’s autonomy by reducing its
dependence on inputs and energy and its costs. As well as this cost reduction,
agricultural anaerobic digestion must provide a new source of revenue for the farmer,
who can use the renewable energy generated or sell it. The sector must take care that
this additional revenue both
improves the farmer’s quality of life and finances
the farm’s transition towards agroecology while also giving the farm a more
robust foundation for the long term.
14 The French Agriculture and Food Ministry’s website. Though no single definition currently predominates, the
field involves a set of principles guided by the alignment between agronomy and ecology.
15 Presence of oxygen
12
Second condition: Integration into the context of the
territory16
The dynamism of an anaerobic digestion project’s backers is a crucial element in its
integration into the surrounding territory, as they define the content of the project and
hold the capital.
But they are just one element. Agricultural anaerobic digestion projects
are eminently local, involving multiple stakeholders and priorities. Within its territory,
each project involves multiple dimensions – agriculture, waste management, the
circular economy and the energy transition.
Therefore each stage of the project, from the first steps to the full operation
of the anaerobic digestion unit, must involve all the stakeholders: local
authorities, farmers, agri-food companies, chambers of agriculture, technical experts,
investors, building contractors – and of course neighbouring residents and citizens. This
approach ensures that the project is adapted as closely as possible to local
environmental, social and economic characteristics, bringing all these stakeholders on
board by ensuring the resulting benefits are shared.
Agricultural anaerobic
digestion projects should help to create social bonds, solidarity between
territories (e.g. urban–rural)
, shared value and a circular economy.
More specifically, the sector must ensure that agricultural anaerobic digestion projects
contribute to
sustainable biomass management across the territory and follow
the hierarchy of uses
17, especially if the anaerobic digestion unit imports biomass from
outside the farm. By coordinating with all the stakeholders, it should be possible to
harmonise the different uses for biomass and ensure feedstocks are available for
anaerobic digestion without creating competition for biomass resources, which could
threaten food security18. Specifically, the use of dedicated crops, currently capped at 15%
of feedstock by weight19, must be kept as low as possible. Where agricultural anaerobic
digestion units are used for the treatment and recovery of organic waste from the
territory, and from the agri-food industry in particular, this value creation should not be
an obstacle to efforts to prevent the waste being produced in the first place.
Finally, anaerobic digestion must address the priority of reintegrating farms into their
surrounding territory. This includes helping to reduce the specialisation of agricultural
regions that have previously responded to the demands of globalisation and
competitiveness. On a larger scale, it means helping to improve the
resilience of
production methods against climate and economic risks.
This systemic vision should enable
the design of an agricultural anaerobic
digestion project to result in a positive overall environmental footprint for
the territory. This will depend on thinking collectively about feedstock transport, the
local use of digestates and biogas (as vehicle fuel, for example) and how to reconnect the
farm to its territory in terms of both its supply chain and the distribution of its products.
16 The notion of “territory” is applied broadly here, covering various geographical areas defined by different
political, economic, social and cultural realities. The territorial approach to anaerobic digestion will be addressed
by specific additional work.
17 MTES. French National Biomass Strategy (
Stratégie Nationale de Mobilisation de la Biomasse), p. 29
18 IDELE (2015). Survey on the benefits of using co-products in anaerobic digestion and competition with animal
feed concluded that farmers can use products destined for animal feed when faced with difficulty in obtaining co-
products. The farmers and livestock breeders surveyed also expressed anxiety about competition in the future,
given the rapid growth in other anaerobic digestion units and the potential for them to be managed by industrial
companies based on the German model, using dedicated bioenergy crops such as maize.
19 Decree no. 2016-929 of 7 July 2016 applying article L. 541-39 of the French Environment Code
13
Third condition: Helping to solve global societal
challenges
The world is facing ecological and social challenges on a scale that has never been seen
before – climate change, biodiversity loss, fossil resource depletion, food security.
The
solutions we choose to help us through the transition must demonstrate
that they can address these challenges and scale up sustainably.
The greenhouse gases emitted by agricultural anaerobic digestion throughout its life
cycle20 are thus a crucial factor in its sustainability. Anaerobic digestion must
significantly reduce greenhouse gas emissions compared to power from
fossil fuels and help reduce the emissions of the agricultural sector. Its
overall environmental performance must be better than the total of the practices it
replaces (organic waste incineration, direct manure and slurry spreading etc.). The
practices used to supply digestion units with biomass and spread digestates must limit
the farm’s greenhouse gas emissions.
Agriculture is recognised as having a vital role to play in fighting climate change –
including carbon storage in the soil – and preserving biodiversity. All the processes that
go hand-in-hand with the establishment of an anaerobic digestion unit on a farm or in
a territory must therefore
promote this carbon storage in agricultural soil and
maintain biodiversity in farm habitats.
20 From feedstock production to digestate spreading
14
Without claiming to be exhaustive, the three conditions for sustainability emerging from
the consultation process highlight the key priorities for the agricultural anaerobic
digestion sector. Addressed to all its stakeholders, they provide a
basis for a common
frame of reference to support the sector’s sustainable development as a
lever for the energy and agricultural transitions.
Figure: Conditions for the sustainability of agricultural anaerobic digestion
15
INTERMEDIATE ENERGY CROPS AND
DIGESTATE SPREADING: HOW DO
THEY RESPOND TO THE
SUSTAINABILITY CONDITIONS?
Preface
This part of the document aims to identify whether the practices of growing
intermediate energy crops and returning digestates to the soil meet the sustainability
conditions described above from an environmental viewpoint. These are the practices
identified as priorities by the participants of the workshops, but
they are not the only
agricultural issues in the sector. Specifically, the broader question of other sources
of feedstocks for anaerobic digesters – the types of resources used, including dedicated
crops21 and crop residues, mixture types etc. – is crucial. Given that a number of
deviations from best practice have been seen on the ground, this issue will have a
decisive impact on the sector's future. Further work will examine this point in greater
detail.
The following sections also mention the socio-economic issues. Although these are part
of the sustainability framework, they were not specifically examined in detail during the
series of workshops.
Intermediate energy crops
Intermediate crops: from agroecology to renewable gas production
Intermediate crops are crops sown between two main crops within a crop rotation. By
covering soil that would otherwise be bare, they provide a number of
agroecosystem
services during the intercrop period – improving soil structure, recycling mineral
21 In 2018, ADEME estimated that the area of crops grown specifically for anaerobic digestion in France was
14,850 hectares, 0.05% of all French agricultural land in use and 0.08% of arable land
16
elements, storing carbon in the from of organic matter in the soil, reducing erosion due
to water and/or wind, maintaining biodiversity and controlling weeds22.
The concept of intermediate crops is not new (1970s23).
Several terminologies now
coexist depending on the main purpose for which they are planted. Cover
crops have long been grown during the intercrop period, primarily to
protect the
environment. In response to the Nitrates Directive24, cover crops are a means of
limiting the leaching of agricultural nitrates into vulnerable areas. These are known as
nitrogen-fixing cover crops25. The 2010s saw the concept of
multi-service cover
crops emerging – crops that are not harvested and provide a number of ecosystem
services26. They are now
recognised as one of the levers of the agroecological
transition27.
Recently, intermediate crops have also been a crucial element of potential future
scenarios for the energy transition. Additionally, they have been used on the ground at
farms developing the use of anaerobic digestion. We describe these as
intermediate
energy crops. The goal is to produce three crops in two years – two food crops and one
intermediate crop as a feedstock for anaerobic digestion. In the ADEME study
A 100%
renewable gas mix in 2050, published in 2018, the potential renewable gas production
for injection into the grid identified as coming from intermediate crops represents 51
TWh GCV28, which accounts for almost
40% of the potential production of biogas
from anaerobic digestion by this date.
Figure 2. Terminology and purpose of crops planted during the intercrop period (Source: E
Justes, G Richard. Contexte, concepts et définition des cultures intermédiaires multi-services
(Context, concepts and definition of multi-service cover crops).
22 Eric Justes, Guy Richard.
Contexte, concepts et définition des cultures intermédiaires multi-services (Context,
concepts and definition of multi-service cover crops). Innovations Agronomiques, INRA, 2017, 62, pp.1-15. hal-
01770348 / Eric Justes, Nicolas Beaudoin, Patrick Bertuzzi, Raphaël Charles, Julie Constantin, et al. (2012).
Réduire les fuites de nitrate au moyen de cultures intermédiaires : conséquences sur les bilans d’eau et d’azote,
autres services écosystémiques (Reducing nitrate losses with intermediate crops – Consequences for water and
nitrogen levels and other ecosystem services), INRA / Julie Constantin, Nicolas Beaudoin, Nicolas Meyer,
Romain Crignon, Hélène Tribouillois, et al.
Concilier la réduction de la lixiviation nitrique, la restitution d’azote à
la culture suivante et la gestion de l’eau avec les cultures intermédiaires (Combining reductions in nitrate
leaching, supplies of nitrogen for the following crop and water management with intermediate crops). Innovations
Agronomiques, INRA, 2017, 62, pp.1-12. <hal- 01770351> / Burgundy Chamber of Agriculture, 2012.
Cultures
intermédiaires (Intermediate crops)
23 Eric Justes, Nicolas Beaudoin, Patrick Bertuzzi, Raphaël Charles, Julie Constantin, et al. (2012).
Réduire les
fuites de nitrate au moyen de cultures intermédiaires – Conséquences sur les bilans d’eau et d’azote, autres
services écosystémiques (Reducing nitrate losses with intermediate crops – Consequences for water and
nitrogen levels and other ecosystem services), INRA
24 1991 European directive aiming to protect water from pollution with agricultural nitrates
25 By using the available nitrogen for their growth, plants limit the spread of the nitrates that cause environmental
pollution
26 Eric Justes, Guy Richard (2017).
Contexte, concepts et définition des cultures intermédiaires multi-services (Context, concepts and definition of multi-service cover crops). Innovations Agronomiques, INRA, 2017, 62, pp.1-
15. hal-01770348
27 Agronomic innovation seminars (Carrefours de l'innovation agronomique): "Multi-service cover crops for high-
performance agroecological production", 4 October 2017
28 Gross Calorific Value
17
First condition: do intermediate energy crops help to establish
agroecological practices across the farm?
Intermediate energy crops are grown in order to
recover the economic and
energy value of the biomass produced. Unlike multi-service cover crops, they are
harvested from the parcel to be fed into an anaerobic digestion unit and produce
renewable energy in the form of biogas. Do intermediate crops still provide
agroecological services in this context?
Figure 3. Comparison between multi-service cover crops and intermediate energy crops (source: after INRAE
– J Constantin)
18
·
Ecosystem services are maintained or maximised, as long as crop
management is adapted to local soil and climate conditions
Current scientific knowledge based primarily on the work of INRAE29 and Arvalis30,
suggests that
the services provided by a harvested intermediate crop can be
maintained or even maximised, as they generally develop for longer than a multi-
service cover crop.
Limiting water and air pollution: the research suggests that the services
of nitrogen fixing and runoff limitation can be maintained, depending on the
chosen species and crop management plan. Intermediate energy crops can
help to limit water and air pollution due to nitrate leaching, which occurs when
the fertilisation of the previous crop was not adequately controlled. However,
these crops reduce drainage, especially since the amount of biomass produced
is high, and could lead to a slight increase in nitrous oxide (N2O) emissions.
Care must be taken to ensure that the quest to produce biomass does not lead
to inappropriate fertilisation of the intermediate energy crop, which would
enrich the environment with nitrogen and cancel out the nitrogen
management services provided by the intermediate crop31. Fertilisation
management using digestates produced by anaerobic digestion is
recommended.
Limiting soil erosion: covering the soil during the intercrop period (before
the intermediate energy crop is harvested) limits water and wind erosion. The
plants give the soil physical protection against the rain, the ground cover
obstructs water flow and the root system gives structure to the soil.
Maintaining soil fertility: According to tests carried out by the OPTICIVE
project, although the above-ground biomass is harvested as a feedstock for
anaerobic digestion, organic matter is returned to the soil by the stubble and
roots of the plants, together with the digestates (2 tonnes of dry matter (tDM)
per hectare for each fraction returned to the soil, compared with 6 tDM/ha
harvested). Spreading digestates reinforces this return of carbon to the soil.
The tests are still limited in terms of their representativeness of different
cropping systems, but the scientific literature agrees that intermediate energy
crops increase the provision of carbon (via the roots and non-harvested crop
residues) compared with leaving the soil bare between crops. Intermediate
energy crops can thus help to maintain stores of organic matter and minerals
in the soil, as long as digestates are returned to the parcel. Without the
digestates, there would be a net export of minerals (nitrogen, phosphorus etc.)
from the parcel via the biomass, requiring the shortfall to be made up with
fertiliser in some cases.
The biomass production and ecosystem services that
intermediate energy crops
can provide depend directly on the species, the variety, the crop
management plan and the territory's soil and climate conditions, as well as
on the digestates being returned to the soil. Several projects are currently seeking
to define the "best" crop management plans to maximise biomass production and
agroecological services.
The impacts of an intermediate energy crop must be
29 INRAE's work has so far focused on multi-service cover crops, and not specifically on intermediate energy
crops
30 The OPTICIVE project run by the GAO economic interest group (Arvalis, Terres Univia and Terres Inovia) with
Euralis, supported by ADEME
31 If fertilisation is not properly controlled, the nitrogen left unused by the intermediate energy crop could intensify
the problem of water contamination
19
evaluated across a whole rotation, and not just over the period of the
dedicated intermediate crop.
·
Economic opportunities, but variable yields must be anticipated
Introducing an intermediate crop into a production system has
several effects on the
economic balance of the farm.
Reduced operating costs and increased autonomy for the farm: by
recycling nitrogen and limiting annual weed growth through direct
competition, intermediate energy crops help to limit the use of synthetic
inputs (fertiliser, crop protection products) and improve the farmer's
autonomy, especially when digestates are returned to the soil as an organic
fertiliser.
Additional revenue for the farmer: farmers can sell the intermediate
energy crop to an external anaerobic digestion unit or use it as a feedstock for
their own digester. Selling the intermediate energy crop or the resulting
renewable energy provides an additional source of revenue. However, this
must be balanced against the costs associated with integrating an anaerobic
digestion unit to be sure whether the financial outcome is positive for the
farmer32.
Loss of main crop yield: a loss of yield due to sowing being delayed or a
lack of water availability in summer has been observed on some farms33. In the
current economic climate, the margins achieved by the sale or self-
consumption of the intermediate energy crops, together with cost savings, can
make up for the opportunity cost associated with the loss of production for the
farmer. However, the impact of the intermediate energy crops must be
controlled to avoid disrupting the main food crops and changing the land use,
which could lead to economic costs. More knowledge is needed about the
impact of intermediate energy crops on water availability for the following
crop in order to manage the intermediate energy crops as effectively as
possible. This need is all the more pronounced in the context of climate
change, which will intensify water resource pressures.
32 The PRODIGE study of the technical and economic performance of anaerobic digestion units in operation,
conducted by APCA and ADEME, was unable to reach a conclusion on the benefits of intermediate energy crops,
because not enough farms had developed them (sampling based on a model processing livestock manure,
mostly for cogeneration).
33 The OPTICIVE project run by the GAO economic interest group (Arvalis, Terres Univia and Terres Inovia) with
Euralis, supported by ADEME: this loss is due to a combination of factors (delayed sowing, changes to variety
earliness etc.), not just to the intermediate energy crop consuming a non-negligible proportion of the soil's useful
water reserves. The frequency of rain when winter intermediate energy crops are harvested often replenishes
these reserves for the following crop. / INRA, 2008. Collective scientific expertise (ESCo) on "Agriculture and
biodiversity" – chapter 3. Incorporating biodiversity targets into agricultural production systems
20
Potential fluctuations in intermediate energy crop yields to be
anticipated: while intermediate energy crops represent a way for farmers to
secure supplies for their anaerobic digestion units against variations in the
organic waste market, fluctuations in production yields need to be taken into
account. Climatic conditions, combined with the crop management plans
chosen, will have a direct effect on plant growth. This high level of variability
from one year to the next (between 1 and 10 tDM/ha, depending on the source
and the tests conducted) determines the activity's cost-effectiveness – the yield
must be high enough to justify the harvesting cost.
These variables must
be included in the business model and the anaerobic digestion
project's secure feedstock plan. There may be techniques that could limit
the level of variability, such as planting
mixtures of species, but this has yet
to be proven. Leaving each species to develop according to the climatic
conditions could stabilise overall yield from one year to the next.
Second sustainability condition: intermediate energy crops and their
integration into the territorial context
·
Helping to maintain a territory's agricultural identity
The aesthetic appearance of the landscape is one of the intangible services provided by
intermediate crops34. By covering the soil during periods when it is usually bare, and by
choosing species with rapid growth cycles that favour flowering, intermediate energy
crops can
help maintain the diversity of the agricultural landscape.
·
Strengthening links between agricultural operators
On the scale of a territory, farmers' production of intermediate energy crops, either for
self-consumption or for sale, helps to diversify their revenue while providing feedstocks
for anaerobic digestion units. Aside from this purely financial aspect, these exchanges
of biomass can
balance returns of organic matter to the soil across the
territory. In exchange for their intermediate energy crops, farmers can receive a
proportion of the digestate produced by the anaerobic digestion unit in line with their
needs for fertiliser and organic amendment. The logistics of these exchanges must be
considered when contracts are signed between agricultural operators to limit the overall
environmental impact.
·
Vigilance about how intercrop periods are managed and possible
competition in biomass use
Although intermediate energy crops can strengthen links between agricultural operators
within a territory, using their biomass for energy purposes must not compete with
existing uses of biomass, such as animal feed if the intercrop period was previously used
for producing catch crops. The effects of intermediate energy crops on the crops that
follow them, and the potential extension of the intercrop period to produce biomass,
may also compete with food production, and this should also be monitored (see below).
Third condition: do intermediate energy crops help to solve global societal
challenges?
·
Potential contribution to carbon storage in agricultural soil
34 Eric Justes, Guy Richard (2017).
Contexte, concepts et définition des cultures intermédiaires multi-services (Context, concepts and definition of multi-service cover crops). Innovations Agronomiques, INRA, 2017, 62, pp.1-
15. hal-01770348
21
As we have already seen, the stubble and roots of intermediate energy crops can return
organic matter to the soil, though the final amount of carbon stored may be less than
with a nitrogen-fixing cover crop35.
Carbon storage has not yet been measured in the field over a long enough period for
results to be observed, but it has been modelled mathematically with AMG36 using the
CHN-AMG tool (Arvalis). The study compared the evolution of organic carbon content
in the first 30 centimetres of the soil37 between an intermediate energy crop with oats,
an intermediate energy crop with digestate returned to the soil and a control. Different
controls and resulting models were used based on different tests conducted by Syprre,
an agricultural research project. These included a monoculture of grain maize with the
soil left bare between crops and a rotation of wheat, winter barley and maize. The model
showed an increase in soil organic carbon resulting from intermediate energy crops,
which was higher still when digestate was returned to the soil38. These observations need
to be replicated with other production models and extended to a variety of other
contexts.
The carbon storage potential of planting intermediate crops39 identified by the "4 per
1000" initiative40 could still be present with intermediate energy crops even if the
biomass is removed.
Incorporating intermediate energy crops into
agricultural production models could thus contribute to carbon storage in
agricultural soil, helping to offset greenhouse gas emissions and fight
climate change41.
·
Intermediate energy crops and biodiversity: an interaction
requiring further study
The impact of integrating intermediate energy crops on biodiversity, particularly in the
soil, remains little-studied, though initial research has been carried out. As part of the
Agrifaune programme set up by ONCFS42, FNC43, APCA44 and FNSEA45, the intercrop
technical group looked closely at the intercrop variables that could promote biodiversity.
The programme evaluated the criteria that determine how an intermediate crop can
balance agronomic and environmental priorities while benefiting wild animal life. This
work resulted in the labelling of species mixes that support these criteria. The right
choice of species for producing intermediate energy crops can thus balance these
priorities while encouraging local wildlife.
35 However, a situation consisting of an intermediate energy crop combined with digestate would need to be
compared with a situation with a nitrogen-fixing cover crop alone.
36 Clivot, Hugues, Jean-Christophe Mouny, Annie Duparque, Jean-Louis Dinh, Pascal Denoroy, Sabine Houot,
Françoise Vertès et al. 2019. "Modeling Soil Organic Carbon Evolution in Long-Term Arable Experiments with
AMG
Model".
Environmental
Modelling
&
Software
118
(August):
99-113.
https://doi.org/10.1016/j.envsoft.2019.04.004.
37 The data integrated into the model are territorial data from Béarn
38 The long-term carbon storage of these digestates (see below) requires further study, as current results are
based on modelling
39 The 4 per 1000 initiative has highlighted the fact that intercropping and intermediate crops can represent 35%
of the total carbon storage potential in this type of system
40 The international "4 per 1000" initiative was launched by France on 1 December 2015 at COP21. It involves
bringing voluntary public and private-sector stakeholders together under the Lima–Paris Action Agenda. The
initiative aims to show that agriculture, and especially agricultural soil, can play a vital role in ensuring food safety
and fighting climate change. It builds on concrete actions that can be put in place to encourage carbon storage
in the soil.
41 Life cycle analyses in progress at INRAE Transfert should reveal the carbon balance of this practice in
comparison with other potential emissions (including NH3 and N2O)
42 ONCFS: French National Hunting and Wildlife Agency
43 FNC: French National Hunting Federation
44 APCA: Permanent Assembly of Chambers of Agriculture
45 FNSEA: French National Federation of Farmers' Unions
22
·
Intermediate energy crops and food security: practices must be
monitored as they become more widespread
As we have already seen, planting intermediate energy crops can sometimes delay the
sowing of the following crop or affect water availability in summer46. This can influence
the yields of the following crops, and thus have a direct impact on the production of
human or animal food. For example, the results of the OPTICIVE project show a yield
loss of one tonne per hectare for a grain maize/intermediate energy crop system, due to
the two-week delay in sowing the next main crop. Current research to optimise crop
management plans should characterise this impact more generally and suggest
solutions to mitigate it. In a context where the use of biomass offers a solution for
decarbonising several activity sectors,
coordination with main crop production
must remain a focus for the roll-out of intermediate energy crops. Apart from the
additional research required, the current regulatory framework for defining
intermediate energy crops remains vague and needs clarification. Excluded from the
15% cap on dedicated crops as anaerobic digestion feedstocks, they may constitute a
large proportion of the supply, encroaching on the food use of agricultural land, which
must remain the highest priority.
46 The OPTICIVE project conducted with Euralis, the GAO economic interest group, Terres Univia, Arvalis and Terres Inovia
23
Returning digestates to the soil
One digestate, many digestates
Every tonne of waste fed into an anaerobic digestion unit produces an average of 930 kg
of digestates, which are usually considered a waste product47. Most of these digestates
are currently spread on agricultural land for their agronomic benefits.
Figure 4. What happens to digestates in France (source: after ATEE Club Biogaz, 2019)
The agronomic value of materials returned to the soil depends on three components –
their
fertilising value48 (presence of nitrogen, phosphorus, potassium and trace
elements essential for plant growth), their
soil-conditioning value49 (capacity to
maintain the organic matter in the soil, the stability of the soil structure and its pH) and
finally their
impact on the environment (greenhouse gas and other atmospheric
pollutant emissions)
and on health (biological, organic and chemical contaminants
and trace metals).
The characteristics of the digestate depend heavily on the
quality of the waste and
the feedstock used in the anaerobic digestion unit (origin and composition), together
with the
process conditions (temperature, time spent in the digester) and
any post-
processing (aerobic maturation, drying etc.). The
spreading process can influence
the digestate's effectiveness and efficiency in the field. Consequently, there is
not one
digestate, but many digestates.
47 Club Biogaz
48 The fertilising value of a product can be expressed by the nitrogen fertiliser replacement value (NFRV), which
measures short-term fertilising value as a function of apparent nitrogen recovery (ANR), the ratio of the nitrogen
found in the crop to the total nitrogen added.
49 The soil conditioning value can be expressed with an organic matter stability index
24
First sustainability condition: does returning digestates to the soil help to
establish agroecological practices across the farm?
·
Digestate, an effective substitute for mineral fertilisers
The anaerobic digestion process is conservative – all the fertilising elements (nitrogen,
phosphorus, potassium and trace elements) fed into the process are present in the
output, sometimes in a different form50. Separating the phases of the raw digestate
produces a liquid phase and a solid phase. The fertilising elements (N, P, K) and organic
carbon are divided unequally between these two phases. This unequal distribution and
the properties it provides mean
the liquid phase is comparable to an organic
fertiliser with a high fertilising value, and the solid phase is comparable to
an organic soil conditioner51. Scientific research confirms the fertilising value of digestates52. They can
replace
mineral fertilisers. In particular, nitrogen that has been mineralised by the anaerobic
digestion process can be taken up more directly by plants, though it is also more easily
leached in water or volatilised in the air than a non-digested input53. Feedback from
farmers shows that the replacement is gradual, and many have used mineral fertiliser to
boost the intermediate energy crop initially before being able to rely directly on the
digestate.
·
Management practices necessary to protect the environment
As with the management of livestock waste (slurry, manure) and mineral fertilisers,
nitrogen losses can occur via several mechanisms during the digestate
storage, post-processing and spreading phases.
Figure 5. Impact of digestate post-processing strategies on gaseous emissions across
the sector (after Girault et al. 2017)
50 For example, the breakdown of nitrogenous materials in the absence of oxygen results in the formation of a
nitrogenous compost in reduced form, ammonia
51 A number of tests identified in the summary published by GERES in 2018 have shown that the nitrogen
fertilising behaviour of raw digestate is comparable with that of pig or poultry slurry, with an average effectiveness
(expressed as an NFRV) of 40 to 60% for cereals. Meanwhile, the organic matter stability index has been
measured for various digestates produced from different feedstocks with different degrees of post-processing.
This processing affects the stabilisation of the organic matter in the digestate.
52 Sources: INRAE, MéthaLae (Solagro), GERES literature review conducted in 2018
53 GERES, 2018.
Valorisation agricole des digestats : quels impacts sur les cultures, le sol et l’environnement ? (Agricultural use of digestates: what are the impacts on crops, soil and the environment?)
25
They depend directly on several known factors: digestate quality (concentration of
ammonium nitrogen N-NH4, dry matter percentage, pH), storage conditions and the
technical, soil and climate conditions of the spreading process. During spreading, a
number of conditions favour nitrogen losses: low soil porosity/roughness, warm
temperatures (spreading in late summer) and dry, windy conditions54. The variability of
the digestate makes it essential to know its composition in order to adjust spreading
practices and limit losses.
Volatilisation releases a gas into the atmosphere, ammonia (NH3), which
affects the
quality of the air (ammonia is a precursor of fine particles),
water and soil (acidification after resettling)
and contributes to climate change (transformation
into nitrous oxide N2O after resettling).
Best practice for limiting or eliminating the risk of ammonia volatilisation
is well-known:
·
Airtight covers on digestate storage areas reduce nitrogen losses by
90% compared with a situation with no covers, for digestates produced from
slurry for example55.
·
Using
the right spreading equipment and spreading at the right time are essential. Both must be adapted to the nature of the soil (bearing capacity,
pH, presence of stones), the crop type and the climatic conditions56. They must
also help the digestates to be incorporated into the soil quickly, because half to
90% of total nitrogen losses occur within six to eight hours after spreading57.
Using drag hose booms or incorporators reduces volatilisation but requires
high-quality phase separation58.
Like any fertiliser, applying digestate
may cause water pollution through excess
nitrates and phosphates if too much is applied or if spreading takes place at an
unsuitable time. The digestate quantity must be adjusted to the needs of the plants to
limit this pollution, taking into account their mineral nitrogen absorption period and
the remaining mineral nitrogen already available, as with any fertiliser. Precision
agriculture, which a number of farmers operating anaerobic digesters now seem to rely
on, can help with this.
Other losses may be caused by microbial reactions in the soil once the digestates have
been spread or injected, leading to emissions of
nitrous oxide N2O59. These emissions
are influenced by soil pH, temperature and humidity and by the nitrogen content of the
digestate. It is not currently possible to generalise from the conclusions of tests on
digestates.
Losses of methane (CH4) can also occur during the anaerobic digestion process and
during digestate storage before spreading.
·
Effects on the soil that require further study
The soil conditioning value of digestates has so far been studied less than their fertilising
value. The organic matter content of soil influences its physical, chemical and biological
properties and thus its fertility. This means that maintaining soil organic matter content
and producing humus, its stable fraction, are a priority in all types of agriculture. As the
54 Sources: GERES (2018), Grégory Vrignaud (2019), INRAE (Sabine Houot, Romain Girault – 2019)
55 Source: IRSTEA, 2019
56 The weather conditions that limit losses are cloudy, cool weather with no wind or rain in the 24 hours after
spreading. The soil should not be saturated with water and spreading should take place at the end of the day
when temperatures are lower, as close as possible to the period when crops absorb mineral nitrogen.
57 Sources: Arvalis, 2019 (EVAPRO test 2016) – GERES (2018)
58 MéthaLAE programme, Solagro, 2019
59 N2O has a global warming potential 265 times higher than CO2.
26
anaerobic digestion process breaks down some of the labile fractions of organic matter,
the digestates returned to the soil are richer in stable carbon, which breaks down more
slowly60. With anaerobic digestion, part of the dynamics of organic matter breakdown
no longer takes place in the soil. The impact of this transfer, particularly on the potential
redistribution of microbial populations in the soil, needs to be studied. By breaking
down labile organic matter, micro-organisms are responsible for forming aggregates
that create soil stability.
INRAE has begun looking at the issue and should undertake work in the short term on
the impact of returning digestates to the soil on the soil's biological quality, including
microbial activity. The environmental research laboratory working on Organic Waste
Products (SOERE PRO)61 is also conducting long-term field tests that include issues
relating to digestates.
·
Digestate sanitary safety: biomass inputs must be qualified
The
sanitary quality of digestates can also affect
water and soil quality.
Contaminants, whether biological (bacteria and other pathogens), organic or chemical,
pesticides and trace metals and minerals may all be present in the feedstock. Input and
output materials may be hygienised62, a step that can reduce the risk of these
contaminants being present in digestates.
Some bacteria may be eliminated by the process temperature, with the level of reduction
varying (Orzi et al. 2015, Solagro), but some are resistant (
Clostridium perfringens63),
even after hygienisation. The persistence of trace metals in the soil (copper, zinc,
chrome, nickel etc.) depends directly on their concentration in the digestate, but also on
the form of the digestate (liquid, solid, dried or composted). Work is in progress on what
happens to pesticides and pharmaceutical products64.
The literature review conducted by AILE (the French association of local energy
initiatives) and AAMF (the French association of farmers operating anaerobic digesters)
shows that the overall sanitary quality of digestates is better compared to raw effluents,
and highlights the parameters that can reduce pollution risks. As the presence of these
contaminants depends directly on their presence in the materials processed by the
digester, the risks of environmental contamination can be limited by at least the
following:
-
A good knowledge of the nature and source of the waste and effluents digested,
-
Combined with good management practice at the anaerobic digestion site
(including site organisation and layout, transport disinfection),
-
And good spreading practice.
These three phases must be given special attention to reduce the presence
of contaminants at source.
60 GERES (2018). Anaerobic digestion mainly breaks down hemicellulose-type compounds and volatile fatty
acids. More complex compounds such as lignins and complex fats are not broken down by the micro-organisms
in the digester. The output material is thus more stable.
61 https://www6.inrae.fr/valor-pro/SOERE-PRO-Presentation-de-l-observatoire
62 Hygienisation is essential for all category 2 and 3 animal by-products – see regulation EC 1774/2002, replaced
by regulation EC 1069/2009.
63 GERES, 2018.
Valorisation agricole des digestats : quels impacts sur les cultures, le sol et l’environnement ? (Agricultural use of digestates: what are the impacts on crops, soil and the environment?)
64 The DIGESTATE programme64, recently completed, sought to develop an environmental assessment of
organic waste processing (composting, anaerobic digestion) and agricultural recycling. It studied what happens
to various substances in digestates, including pharmaceutical products, but the conclusions are not yet available.
This initial work will be supplemented by research in progress at INRAE.
27
·
Savings achieved by replacing mineral fertilisers
By replacing mineral fertilisers, digestates can reduce the associated costs. The multi-
partner MéthaLAE programme coordinated by Solagro, which surveyed 46 farms over
three years before and after the introduction of anaerobic digestion, highlighted an
average reduction in synthetic fertiliser purchases of 20% at over half the
farms. The farmers questioned during the series of workshops presented similar or
even better results.
Introducing good practice to avoid nitrate losses may require the farmer to invest in
equipment (drag hose, disc or shoe for meadows, tine cultivator behind the tank before
maize etc.). For projects involving a whole territory, these costs can be shared between
the farmers, perhaps through agricultural equipment cooperatives, limiting the need for
individual investment.
These savings should thus be seen in the context of additional costs for the farmer,
relating particularly to working time, equipment and practices to be introduced
alongside anaerobic digestion.
Second sustainability condition: returning digestates to the soil and
integration into the territorial context
As well as being used directly by their producer, digestates can contribute to the
development of a circular economy across a territory. Produced through the processing
of one farmer's waste, they can be recycled agriculturally by others, as long as
traceability, safety and agronomic benefit criteria are met. Like existing exchanges of
straw and manure, recorded in exchange receipts issued by the producer and the
receiving farmer, they can contribute to recycling and complete biogeochemical cycles.
28
By making farms less dependent on external inputs, digestates help
increase their
resilience and maintain agricultural activity within territories.
Finally, from a social viewpoint, managing livestock waste with anaerobic digestion can
help
improve the acceptability of farming, which is sometimes viewed with
suspicion. When the anaerobic digestion process is well controlled (time, temperature
etc.), the volatile compounds in livestock waste responsible for unpleasant smells are
broken down. Although feedback from farmers during the workshops clearly supported
this view, little work has been done on the potential reduction of odour molecules65.
Depending on the author, the odour disappears within 30 hours of the digestate being
applied, compared with 60 hours without anaerobic digestion. These results vary
depending on the nature of the materials processed and the digestate fraction observed.
Third sustainability condition: does returning digestates to the soil help to
solve global societal challenges?
·
Controlling GHG emissions
Digestate management can be a source of greenhouse gas emissions (nitrous oxide and
methane), and work is in progress to quantify this precisely. So far there is little data on
the subject. According to Holly et al. (2017)66, the main greenhouse gas emissions occur
when digestate is stored (CH4) and after spreading (N2O). The performance of the
anaerobic digestion unit and the post-processing applied may increase or reduce these
emissions67. But by comparing different stages in the management (storage and
spreading) of non-digested raw materials and digestates, the authors showed that the
balance of greenhouse gas emissions is lower for digestates than for raw materials. In
reality, as these results do not include the avoided emissions associated with synthetic
mineral fertiliser production68, the actual result is even more positive.
·
A theoretically favourable impact on carbon storage in agricultural
soil according to modelling
Few studies have examined the soil conditioning value of digestates and the potential
for carbon storage in the soil following repeated digestate applications. Most of these
were carried out on the basis of computer models and simulations (AMG).
65 GERES, 2018. Valorisation agricole des digestats : quels impacts sur les cultures, le sol et l’environnement ? (Agricultural
use of digestates: what are the impacts on crops, soil and the environment?)
66 M A Holly et al. (2017).
Agriculture, Ecosystems and Environment
67 GERES, 2018. Valorisation agricole des digestats : quels impacts sur les cultures, le sol et l’environnement ? (Agricultural
use of digestates: what are the impacts on crops, soil and the environment?)
68 According to Solagro (2014), producing 1 kg of ammonium nitrogen consumes 1 kg of natural gas and releases
3 kg of carbon dioxide
29
Field trials carried out over 25 years in Germany on how digestates from manure/slurry
evolve after spreading show that, in the long term, the soil stores
a quantity of carbon
equivalent to that resulting from spreading the same manure/slurry directly6970. The
nitrogen enrichment caused by returning digestates to the soil, but also by planting
intermediate crops, would enable primary biomass production to be increased as a
whole while enriching the soil with organic carbon through the roots.
·
Impact on biodiversity requiring further study
The impact of digestates on biodiversity, and soil biodiversity in particular, has not so
far been covered by many studies. There are a few references in Germany, but they
concentrate on earthworm populations, which are not necessarily representative of
agricultural soil. However, work in progress in France, conducted through MétaMétha
trials at INRAE Nouzilly, has already shown that although a degree of mortality in anecic
earthworms was seen after spreading, this only represented a few percent of the total
worm population and the population grew in the medium term due to rapid resilience
and additions of organic matter.
69 Wentzel S, Schmidt R, Piepho HP, Semmler-Busch U, Joergensen RG, 2015.
Response of soil fertility indices
to long-term application of biogas and raw slurry under organic farming. Applied Soil Ecology 96,99–107
70 Thomsen IK, Olesen JE, Møller HB, Sørensen P, Christensen BT (2013).
Carbon dynamics and retention in
soil after anaerobic digestion of dairy cattle feed and faeces, Soil Biol. Biochem., 58, 82-87
30
In summary
·
Current scientific knowledge highlights the benefits to the agrosystem
of intermediate energy crops and returning digestates to the soil.
-
Though the crop is removed from the parcel, the ecosystem services provided
by an intermediate energy crop can be maintained or even maximised by
biomass production that is often higher than with a “conventional”
intermediate crop such as a nitrogen-fixing cover crop (reducing the risk of
nitrate pollution, limiting erosion and maintaining soil fertility);
-
The fertilising value of digestates is confirmed: they can replace mineral
fertilisers;
-
According to existing modelling, returning digestates and intermediate energy
crop residues to the soil are two practices that can maintain or encourage
carbon storage in the soil.
·
These benefits can only be observed under specific technical
conditions, which may alter current agricultural practices.
-
There are operational practices (including equipment choice and spreading
period in particular) that can limit the environmental impact of digestates
(volatilisation and nitrogen leaching) and optimise their agronomic value.
Depending on their form and any treatment they may have undergone, dosing
the digestates as accurately as possible to meet the plants’ needs limits the
transfer risk, as long as specific management practices are followed (limiting
ammonia volatilisation and loss of fertilising capacity through the use of
appropriate equipment);
-
Cropping systems that incorporate intermediate energy crops must be
reviewed in their entirety to avoid disrupting food production, improve their
resilience and their ecosystem functions (e.g. by extending the rotation,
improving soil structure etc.) and provide a source of biomass with high
methanogenic potential for digesters;
-
These new practices must be suited to the local soil and climate conditions.
·
Additional research and experimentation work is either already in
progress or required to guarantee that these practices are fully
compatible with the agroecological transition:
-
To deepen knowledge about certain environmental impacts and identify the
sustainable practices associated with them (e.g. the impact of intermediate
energy crops and digestates on biological activity in soil);
-
To adapt practices to the soil and climate conditions of each territory: choosing
intermediate energy crop seeds, rotation time and digestate spreading
conditions to limit nitrogen volatilisation, for example;
-
To assess the environmental benefits in terms of carbon footprint offered by
anaerobic digestion compared with other forms of gas production;
·
The implementation of these practices still depends on how their
application is encouraged, supported and controlled. Non-virtuous
anaerobic digestion units or sites have been identified in some territories under the
current context of support. Without adequate monitoring or supervision, certain
practices can be implemented despite being agronomically incoherent or ill-judged
from a food security standpoint. In these situations, anaerobic digestion supports
an agricultural model that makes no contribution at all to the agroecological
transition.
31
PRIORITIES AND RECOMMENDATIONS
FOR SCALING UP AGRICULTURAL
ANAEROBIC DIGESTION
How can we ensure these sustainability conditions are enforced on a large scale? The
series of workshops highlighted priorities for scaling up anaerobic digestion and led
to the collective formulation of recommendations to support its development
sustainably.
The need for a shared, consistent frame of reference
Agricultural anaerobic digestion is covered by French and European regulations in fields
such as renewable energy, agriculture and waste management.
By confirming a minimum target of 10% for renewable gas as a proportion of gas
consumption by 2030, the French Energy and Climate Act of 8 November 2019 supports
the development of renewable gas production sectors, including anaerobic digestion.
The challenge is to ensure that this encouragement from the energy side, notably
economic, also benefits the transition towards agroecological practices. Any weakening
in public financial support mechanisms could threaten the economic balance of
anaerobic digestion units and stimulate practices that undermine the sector’s
environmental sustainability.
To guarantee that agricultural anaerobic digestion can be scaled up sustainably,
sector-
specific policies and regulations (energy, agriculture, waste management)
must be consistent with each other. This requires an analysis of their
mutual and interrelated effects on all the environmental, social and
economic dimensions.
32
To make it easier to achieve this consistency,
a common vision of the sustainability
conditions for the sector must be shared with all its stakeholders. It would
clearly be useful to have a common frame of reference incorporating the criteria and the
expected levels of performance, for the practices themselves but also for territorial
integration and methods of consultation. This type of framework could ultimately lead
to shared reference systems for project evaluation or even labelling.
There are several voluntary initiatives that could provide a helpful basis:
-
The Méthascope, a tool for helping to evaluate anaerobic digestion projects
developed by France Nature Environnement with support from ADEME and
GRDF. This consists of a booklet and a multi-criteria evaluation grid, and helps
territories to take hold of the issues involved in anaerobic digestion.
-
The Qualimétha® label: Developed in 2019 by Club Biogaz with support from
ADEME and GRDF, this label covers companies that design and build anaerobic
digestion units. Consisting of 84 evaluation criteria, it aims to guarantee the quality
of an installation by capitalising on good design and construction practice. Starting
from 1 January 2021, this label should be required for projects to be eligible for
ADEME grants and meet the selection criteria for calls for proposals issued by
regional authorities.
-
The “Unis pour innover et progresser” (united for innovation and
progress) charter71 : : This charter, developed by the French association of
farmers operating anaerobic digesters (AAMF), aims to help farmers to fully grasp
the regulatory framework. It is a common system of requirements applying to all
the association’s members, helping farmers and providing the basis for audits. Its
consists of eight main commitments that are assessed using an evaluation grid
divided into ten chapters that cover the different stages of the anaerobic digestion
process. The charter aims for regulatory compliance as a minimum, and goes
further in certain areas such as digestate management. AAMF has set up a network
of contacts to help its members implement the charter and prepare for their audits.
The charter will evolve to certify the professionalism and continuous improvement
of the member sites, quickly outpacing the regulations.
-
The Énergie Partagée charter: In April 2017, Énergie Partagée published a
charter72, working with SOLAGRO, SERGIES, ERCISOL, ELISE, CIVAM 44 and
farmers, to promote anaerobic digestion projects compatible with the energy
transition and the agricultural transition. It applies to units already in operation
and consists of governance, agricultural, environmental and energy criteria.
Compliance with the charter is a condition for Énergie Partagée’s “Projet Citoyen”
labelling and enables access to the participatory funding set up by Énergie
Partagée.
33
Recommendation 1: Strengthen a common framework that promotes
compliance with the sustainability conditions73
·
Develop a shared culture within the energy, agriculture and waste sectors at
national and regional level
·
Evaluate the combined impacts of energy, agriculture and waste policies at all
levels (national, regional and local) and ensure they are consistent with the
shared objectives
·
Promote clarity about the roles of different stakeholders at national and
territorial level
·
Establish and share a common national reference system (charter, quality label
etc.) defining sustainable practices for all the conditions set out above,
adapting the criteria and requirements to the specific characteristics of
different territories
·
Clarify the definition of intermediate energy crops from a regulatory viewpoint
so that the development of the practice does not undermine higher priority
uses of agricultural land or its resilience
·
Put incentives in place (financial or not) to promote virtuous practices with a
local economic impact. Tools such as payments for environmental services
could be explored
·
Intensify feedback about the sustainability criteria of existing installations
A need to supplement and disseminate knowledge,
working with key operators
In recent years, stakeholders in the sector have developed their knowledge about the
environmental and economic impacts of integrating anaerobic digestion units into
agricultural systems. Though
further research and trials are still needed,
spreading and capitalising on existing knowledge now appears to be an
essential first step. Information is still very scattered, “siloed”, sometimes accessible
only to a limited or very local circle of players.
The current state of scientific knowledge and practice shows that intermediate energy
crops and returning digestates to the soil, when managed properly, align with
agroecological principles and can act as a driver for the agroecological transition. This
involves a
change of practice for farmers (crop rotation, harvesting, processing)
and
the development of new skills, entrepreneurial as well as agricultural.
To guarantee its sustainability, the sector must therefore
ensure that farmers take
ownership of these new techniques, acquire these skills and put them into
practice so that the expected environmental and economic benefits are
delivered. The farming profession is significantly affected by anaerobic
digestion, and it is important that the direction taken should be
agroecological rather than productivist74. The spread and adoption of knowledge
and sustainable practices at local level will enable projects to be created in accordance
with the conditions for the sector’s sustainability.
73 In line with the work planned in the broader context of the 2018–2020 Bioeconomy Strategy for France action
plan (Theme 4, Action 1)
74 CEREQ (2016).
Transition écologique et énergétique – la filière méthanisation (Ecological and energy
transition – the anaerobic digestion sector)
34
Chambers of agriculture can play a central role in this upskilling process,
because they have close relationships with the developers of agricultural anaerobic
digestion projects, and providing information and awareness is one of their functions.
Today all the chambers of agriculture are supporting the emergence of anaerobic
digestion projects. However, the level of support provided when projects are being
prepared can vary from one area to another.
Recommendation 2: Continue research and trials
·
Continue to develop scientific knowledge about the agronomic and
environmental effects of agricultural anaerobic digestion, the funding needed
for applied research being released
·
Intensify feedback (recommendation 1) and field trials to identify practices
appropriate to local contexts
Recommendation 3: Support the professional development of the sector
·
Promote the InfoMétha.org platform to capitalise on knowledge and practices
and encourage their development and spread. The site operates collectively
and evolves over time, collecting together the available knowledge about
anaerobic digestion and its effects
·
Identify stakeholders/channels able to distribute this knowledge and ensure it
is adopted at national, regional and more local level (ADEME, APCA and
chambers of agriculture, CTBM, INRAE etc.)
·
Circulate the sustainability conditions to all project stakeholders and promote
a framework for their adoption, perhaps involving a training programme75
·
Strengthen mechanisms for support, skills transfer and professional
development with the help of existing key territorial players (decentralised
services, chambers of agriculture, AAMF, GIEE etc.) and develop the resources
needed on the ground and for applied research
75 Stéphane Michun’s analysis in a Céreq Etudes publication (2016) on agricultural anaerobic digestion identifies
the need to launch training programmes to moderate the wide diversity of today’s training.
35
Strengthen key factors for success involving local
governance
Agricultural anaerobic digestion projects are means of creating synergies and a circular
economy approach between stakeholders within a territory. In response to the recurring
problems of social acceptability76, the most suitable level for the necessary public
dialogue and communication is the local territory into which the project must integrate.
Uniting all project’s stakeholders and creating forums for dialogue are
essential to guarantee its territorial coherence. Experience has shown that
cooperation between the territory’s stakeholders around the project should be
encouraged. There are many possibilities here: sharing engineering, biomass/waste
flows or financial resources. A factor making it easier to put these cooperative
arrangements in place is the shared motivation of these players to take advantage of the
territorial benefits provided by biogas: preserving agricultural activity, the transition
towards agroecology, local low-carbon energy production, a local waste processing
solution, the development of jobs that cannot be offshored.
This requires local governance to be put in place, which cannot be achieved without the
participation of local citizens and people living next to anaerobic digestion
units.
Territories are already getting organised, on smaller or larger scales (see the local
examples below). At a regional level, the GERES association is pursuing a number of
regional structural and leadership initiatives, especially in the south of France. In
Nouvelle-Aquitaine, the regional government has adopted the “100% renewable gas by
2050” scenario for application within the region. The Grand-Est region has established
a charter for the development of anaerobic digestion in the territory. It is based on four
themes: territorial approach; agriculture and environment; competitiveness and
innovation; and training. In Hauts-de-France, the CORBI collective (regional
biomethane injection steering committee) has been involved in structuring the sector
since 2014. CORBI has created the Métha’Morphose brand to underscore its initiatives,
and the Méthania development programme to support companies throughout the value
chain across the territory.
76 CEREQ (2016).
Transition écologique et énergétique – la méthanisation agricole (Ecological and energy
transition – agricultural anaerobic digestion)
36
Recommendation 4: Promote the integration of anaerobic digestion
projects within each territory
·
Create spaces for exchange between multiple stakeholders to share experience
and spread good practice, both locally and nationally
·
Create local forums for dialogue and consultation that include citizens, with
the aim of making it easier for anaerobic digestion projects to integrate into
their territories and the existing systems (district waste management plans,
regional development, sustainability and equality plans and territorial climate,
air and energy plans), taking inspiration from the experience of territories
where this type of action is already in progress
·
Give greater visibility to the tools available to local authorities that wish to
develop anaerobic digestion (including those listed by CERDD, CNFPT and
Énergie Partagée)
·
Encourage farmers and their advisers to have the courage to truly integrate
their anaerobic digestion project into their territory, using the tools available
to local authorities and citizen funding
37
CONCLUSION
This publication sets out a vision of the conditions for the sustainability of agricultural
anaerobic digestion. The sector can develop sustainably by
respecting the principles
of agroecology in the renewal of production systems,
establishing territorial
roots and demonstrating its ability to scale up sustainably to provide a solution that
can
address global societal challenges.
Helping to
improve the management and recycling of organic matter by
relocating flows, anaerobic digestion provides
renewable energy and contributes to
the energy transition in territories. Looking more specifically at two priorities identified
as major for the sector –
developing intermediate energy crops to supply
digesters and returning digestates to the soil – we have reviewed the existing
knowledge and the questions that remain to be answered. As long as good management
practices are adopted, intermediate energy crops and digestates are compatible with
several of the conditions set out. Anaerobic digestion and the agroecological transition
seem to be compatible, depending on the production system in question. But although
the agronomic, environmental, economic and social opportunities generated are very
real, more research is needed to examine the remaining questions and ensure that all
the conditions are fulfilled.
Safeguards must be put in place against practices that undermine the sustainability of
anaerobic digestion. Examples of such practices have been reported by the national and
local press and observed at grassroots level by stakeholders involved in this consultation
process. In the quest for profitability, anaerobic digestion must not lose sight of the need
for agriculture to produce food and the issue of agrosystem resilience.
A balance must
be struck between agricultural and energy interests, with conditions favourable
to maintaining this balance. At the same time, a shared vision of sustainability in
agricultural anaerobic digestion must provide the basis for capitalising on and spreading
existing knowledge, developing skills in the sector and thinking about the territory as a
whole. The sector’s development must also be integrated into more global thinking
about uses of biomass for all the relevant fields of activity.
The approach used in this process aims to initiate the establishment of a common
sustainability framework within the sector, based on a shared vision of the conditions
for sustainability in the development of agricultural anaerobic digestion and its
associated practices. The goal is to give the sector’s development an agroecological
direction. Further development work could be done to list the
principles of
successful territorial governance from an operational viewpoint on one hand, and
to specify the
conditions for
sustainable feedstocks for digesters from a more
systemic viewpoint on the other.
38
REFERENCES
Expert presentations
Workshop 1: definition of the issues
(1)
Solagro – Presentation of the ADEME study “A 100% renewable gas mix in
2050?”
(2)
INRAE Transfert – Evaluation of the environmental impacts of the
biomethane sector
(3)
INRAE Toulouse – The ecological services provided by intermediate crops
(4)
Arvalis – Intermediate energy crops: presentation of the results of the
OPTICIVE project
(5)
Agryfil’s Energie – Operational experience
Workshop 2: Returning digestates to the soil: what are the environmental
issues and best practices?
(1)
APCA – Good practice for digestate spreading: obstacles and levers
(2)
AAMF – The agronomic benefits of using liquid digestates properly: the
experience of GATINAIS BIOGAZ
(3)
ACE – Choosing spreading systems and equipment to limit volatilisation
(4)
IRSTEA – The impact of management practices before digestates are
returned to the soil
(5)
Arvalis – Fertilising and soil conditioning value of digestates
(6)
INRAE – Fertilising and soil conditioning value of digestates based on their
origin, issues relating to soil biology
(7)
AILE – Sanitary issues in agricultural anaerobic digestion
(8)
ATEE Club Biogaz – Regulatory framework for digestates: end of waste
status
Workshop 3: Intermediate energy crops: what are the sustainability issues
and best practices?
(1)
WWF – Proposed framework for interpreting the sustainability issues of an
intermediate energy crop
(2)
INRA UMR AGIR Toulouse – Intermediate energy crops, ecosystem
services and potential for introduction into rotations
(3)
ARVALIS – The OPTICIVE project’s response to the sustainability issues of
intermediate energy crops, other research perspectives
(4)
AAMF – Feedback on the integration of intermediate energy crops into
agricultural systems
39
(5)
SOLAGRO – Intermediate energy crops in the METHALAE study: how can
anaerobic digestion be a driver of agroecology?
(6)
SOLAGRO – Hypotheses on intermediate energy crops in the study “A 100%
renewable gas mix in 2050”
Workshop 4: Scaling up: what are the issues?
(1)
WWF France – Feedback on lessons learned from previous workshops
(2)
IDDRI – Evolution of agricultural and energy policy: considerations for the
sector’s development
(3)
Club Biogaz – Additional framework for anaerobic digestion activities and
presentation of the Qualimétha label
(4)
AAMF – Presentation of the AAMF Charter
(5)
ACE Méthanisation – Tiper Méthanisation, a territorial project with
multiple stakeholders: lessons and perspectives
Articles and publications
ADEME, 2016.
Fiche technique Méthanisation
ADEME, 2011.
Qualité agronomique et sanitaire des digestats.
ADEME, 2013.
Etude au champ des potentiels agronomiques, méthanogènes et
environnementaux des cultures intermédiaires à vocation énergétique – Projet
Expécive 2012
ADEME, 2015.
Etat des connaissances des impacts sur la qualité de l’air et des
émissions de gaz à effet de serre des installations de valorisation ou de production de
méthane
ADEME, 2015.
ExpéCIVE 2013-2014 – Etude au champ des potentiels agronomiques,
méthanogènes et environnementaux de cultures intermédiaires à vocation énergétique
ADEME, 2015.
ExpéCIVE 2013-2014 : Etude au champ des potentiels agronomiques,
méthanogènes et environnementaux de cultures intermédiaires à vocation
énergétique.
ADEME, 2015.
Introduire des cultures intermédiaires pour protéger le milieu et mieux
valoriser l’azote
ADEME, 2016. Avis de l’ADEME sur la méthanisation
ADEME, 2018.
Agricultures et énergies renouvelables : contribution et opportunités
pour les exploitations agricoles
ADEME, 2018.
Un mix de gaz 100% renouvelable en 2050 ?
ARVALIS, 2015.
Cultures à vocation énergétique : un itinéraire technique spécifique. Les innovations – Perspectives agricoles – N°421
Arvalis, 2016.
Pérenniser la filière avec les cultures intermédiaires. Les innovations –
Perspectives agricoles – N°430
40
Askri Amira, 2015. Valorisation des digestats de méthanisation agriculture : effets sur
les cycles biogéochimiques du carbone et de l’azote (thesis supervised by Sabine Houot
and Patricia Laville)
Blanco-Canqui H. et al. 2015.
Cover Crops and Ecosystem Services: Insights from
Studies in Temperate Soils
Bodilis A.-M., Trochard R., Lechat G., Airiaud A., Lambert L., Hruschka S. (2015):
“
Impact de l’introduction d’unités de méthanisation à la ferme sur le bilan humique des
sols. Analyse sur 10 exploitations agricoles de la région Pays de la Loire”, Fourrages,
223, 233-239.
Burmeister, J., R. Walter and M. Fritz (2014): Fertilisation à base de digestats – Effets
sur la faune du sol. Extract from: Biogas Forum Bayern N° I - 27/2015
CEREQ, 2016.
Transition écologique et énergétique - La filière méthanisation
Chambre d’agriculture Bourgogne, 2012.
Cultures intermédiaires
Chambres d’agriculture Pays de la Loire, Projet Vadimethan, 2016.
Digestat : optimiser
son usage dans les exploitations.
Constantin, J., Le Bas, C., Justes, E., 2015.
Large-scale assessment of optimal
emergence and destruction dates for cover crops to reduce nitrate leaching in
temperate conditions using the STICS soil – crop model. Eur. J. Agron. 69, 75–87.
https://doi.org/10.1016/j.eja.2015.06.002
Constantin, J., Mary, Bruno, Mary, B, Laurent, F., Aubrion, G., Fontaine, A., Kerveillant,
P., Beaudoin, N., 2010.
Effects of catch crops, no till and reduced nitrogen fertilization
on nitrogen leaching and balance in three long-term experiments. Agriculture,
Ecosystems and Environment. https://doi.org/10.1016/j.agee.2009.10.005
GERES, 2018.
Valorisation agricole des digestats : quels impacts sur les cultures, le sol
et l’environnement ? Literature review
IDELE, 2015.
Les coproduits en méthanisation : quel intérêt et quelle compétition avec
l’alimentation animale ?
INRA, 2012.
Réduire les fuites de nitrate au moyen de cultures intermédiaires –
Conséquences sur les bilans d’eau et d’azote, autres services écosystémiques
J. E. and G. Richard, 2017.
Contexte, Concepts et Définition des cultures intermédiaires
multi-services
Julie Constantin, Nicolas Beaudoin, Nicolas Meyer, Romain Crignon, Hélène
Tribouillois, et al.
Concilier la réduction de la lixiviation nitrique, la restitution d’azote
à la culture suivante et la gestion de l’eau avec les cultures intermédiaires. Innovations
Agronomiques, INRA, 2017, 62, pp.1-12. <hal-01770351>
Justes, E., Beaudoin, N., Bertuzzi, P., Charles, R., Constantin, J., Dürr, C., Hermon, C.,
Joannon, A., Le Bas, C., Mary, B., Mignolet, C., Montfort, F., Ruiz, L., Sarthou, J.-P.,
Souchère, V., Tournebize, J., 2012
. Réduire les fuites de nitrate au moyen de cultures
intermédiaires - Conséquences sur les bilans d’eau et d’azote, autres services
écosystémiques.
Justes, E., Mary, B., Nicolardot, B., 2009.
Quantifying and modelling C and N
mineralization kinetics of catch crop residues in soil: parameterization of the residue
41
decomposition module of STICS model for mature and non mature residues. Plant Soil
325, 171–185. https://doi.org/10.1007/s11104-009-9966-4
K. Thomsen Ingrid et al. 2013.
Carbon dynamics and retention in soil after anaerobic
digestion of dairy cattle feed and faeces
Meyer, N., Bergez, J., Constantin, J., Belleville, P., Justes, E., 2020.
Cover crops reduce
drainage but not always soil water content due to interactions between rainfall
distribution
and
management.
Agric.
Water
Manag.
231,
105998.
https://doi.org/10.1016/j.agwat.2019.105998
Meyer, N., Bergez, J.-E., Constantin, J., Justes, E., 2019.
Cover crops reduce water
drainage in temperate climates. A meta-analysis. Agron. Sustain. Dev.
https://doi.org/10.1007/s13593-018-0546-y
Möller K.
2015. Effects of anaerobic digestion on soil carbon and nitrogen turnover, N
emissions, and soil biological activity. A review
MTES, 2018.
Conclusions du groupe de travail « méthanisation »
Pellerin, S., Bamière, L., Launay, C., Martin, R., Schiavo, M., Angers, D., Augusto, L.,
Balesdent, J., Basile-Doelsch, I., Bellassen, V., Cardinael, R., Cécillon, L., Ceschia, E.,
Chenu, C., Constantin, J., Darroussin, J., Delacote, P., Delame, N., Gastal, F., Gilbert,
D., Graux, A.-I., Guenet, B., Houot, S., Klumpp, K., Letort, E., Litrico, I., Martin, M.,
Menasseri, S., Mézière, D., Morvan, T., Mosnier, C., Roger-Estrade, J., Saint-André, L.,
Sierra, J., Thérond, O., Viaud, V., Grateau, R., Le Perchec, S., Savini, I., Réchauchère,
O., 2019
. Stocker du carbone dans les sols français : quel potentiel au regard de
l’objectif 4 pour 1000 et à quel cout ?
Poeplau, C., Don, A., 2015.
Carbon sequestration in agricultural soils via cultivation of
cover crops – A meta-analysis. Agric. Ecosyst. Environ. 200, 33–41.
https://doi.org/10.1016/j.agee.2014.10.024
Pourcher Anne-Marie, Druihle Céline.
Impact de la digestion anaréobie sur les
bactéries indicatrices de traitement et les micro-organismes pathogènes zoonotiques.
Presentation to SPACE, September 2016
Programme Agrifaune (OFB, FNC, APCA, FNSEA).
La gestion de l’interculture :
comment concilier agronomie environnement et faune sauvage
SER, 2019.
Panorama du gaz renouvelable en 2018
Shahzad K. et al. 2018
. Biogaz production from intercropping (Syn-Energy)
Solagro, 2016.
Résultats et enseignements des travaux meés dans le cadre des
programmes DIVA et CIBIOM – Lancement du programme HYCABIOME
Solagro, 2018.
MéthaLAE : comment la méthanisation peut être un levier pour
l’agroécologie
Sylvie Recous, Fabien Ferchaud, Sabine Houot.
La valorisation énergétique des
biomasses peut-elle changer l’équilibre des cycles biogéochimiques dans les sols
cultivés ?. Innovations Agronomiques, INRA, 2016, 54, pp.41-58. hal-01543465
Szerencsits M. et al.
Biogaz from Cover Crops and Field Residues: Effects on Soil,
Water, Climate and Ecological Footprint
42
Tonitto, C., David, M.B., Drinkwater, L.E., 2006.
Replacing bare fallows with cover
crops in fertilizer-intensive cropping systems: A meta-analysis of crop yield and N
dynamics.
Agric.
Ecosyst.
Environ.
112,
58–72.
https://doi.org/10.1016/j.agee.2005.07.003
TRAME, 2013. La méthanisation agricole : de l’énergie et des idées !
Tribouillois, H., 2014.
Caractérisation fonctionnelle d’espèces utilisées en cultures
intermédiaires et analyse de leurs performances en mélanges bi-spécifiques pour
produire des services écosystémiques de gestion de l’azote. Université de Toulouse -
INP Toulouse.
Tribouillois, H., Constantin, J., Justes, E., 2018
. Cover crops mitigate direct greenhouse
gases balance but reduce drainage under climate change scenarios in temperate
climate with dry summers. Glob. Chang. Biol. https://doi.org/10.1111/gcb.14091
Guides to best practice
ADEME, 2019.
Réaliser une unité de méthanisation à la ferme (Setting up an anaerobic
digestion unit on the farm). – Read it here
ATEE Club Biogaz, 2011.
Guide de bonnes pratiques pour les projets de méthanisation
(Guide to best practice for anaerobic digestion projects) –
Read it here
IFIP, Brittany Chamber of Agriculture, IDELE, TRAME, 2017. Gestion et traitement des
digestats issus de méthanisation (Management and processing of anaerobic digestates)
– 11 “process” sheets produced during the Casdar METERRI project (no. 5344) –
Read
it here
INERIS, 2018.
Vers une méthanisation propre, sûre et durable – Recueil de bonnes
pratiques en méthanisation agricole (Towards clean, safe, sustainable anaerobic
digestion – Collection of best practices for agricultural anaerobic digestion). – Read it
here
43
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