OPTIMISATION OF FRENCH ENERGY COVER CROP PRODUCTION IN DOUBLE CROPPING SYSTEMS FOR ON-FARM BIOGAS USE

Abstract

Double cropping systems including energy catch crop represent an innovative way to achieve the ambitious targets of the French energy transition strategy mainly for on-farm biogas use. The purpose of OPTICIVE program was to improve crop rotation management of these innovative cropping systems for food/feed and non-food use. Different parameters were assessed for farmers decision making: target yield and production costs. Both innovative cropping systems and analytic experiment were carried out to assess technical, economic and environmental parameters. From 6 to 8 tDM/ha and 125 €/tDM of complete production cost, energy catch crop production in double cropping system seem to be a good adaptation strategy for French farmers but has to be improved to decrease the high yield variability.

Full text

OPTIMISATION OF FRENCH ENERGY COVER CROP PRODUCTION IN DOUBLE CROPPING SYSTEMS
FOR ON-FARM BIOGAS USE
S. Marsac1, C. Quod1, V. Leveau1, M. Heredia1, N. Delaye2, F. Labalette2, V. Lecomte3, M. Bazet 4; EA. Sanner1
1GIE GAO (member ARVALIS - Institut du végétal): Station Inter-Instituts, 6 ch de la côté vieille; 31450 Baziège;
s.marsac@arvalis.fr
2GIE GAO (member Terres Univia): 11 rue de Monceau CS 60003- 75 378 PARIS 08 – France; n.delaye@terresunivia.fr
3GIE GAO (member Terres Inovia): Station Inter-Instituts, 6 ch de la côté vieille; 31450 Baziège; v.lecomte@terresinovia.fr
4Euralis; Avenue Gaston Phoebus 64231 Lescar marie.bazet@euralis.com
ABSTRACT: Double cropping systems including energy catch crop represent an innovative way to achieve the
ambitious targets of the French energy transition strategy mainly for on-farm biogas use. The purpose of OPTICIVE
program was to improve crop rotation management of these innovative cropping systems for food/feed and non-food
use. Different parameters were assessed for farmers decision making: target yield and production costs. Both innovative
cropping systems and analytic experiment were carried out to assess technical, economic and environmental
parameters. From 6 to 8 tDM/ha and 125 €/tDM of complete production cost, energy catch crop production in double
cropping system seem to be a good adaptation strategy for French farmers but has to be improved to decrease the high
yield variability.
Keywords: energy crops, biogas, economics, environment, assessment, double cropping system.
1 INTRODUCTION
Energy catch crops harvested in double cropping
systems are widely showcased in French energy transition
plans and bioeconomy strategies to avoid uses
competition. On-farm anaerobic digestion is focused on
for France.
Objectives of biogaz production included in EMAA
program (2013) are set on 1000 on-farm biogas plants until
2020 while 400 were running at the end of 2018. Cover
crops (intermediate crops or catch crops) are considered as
an important issue for digester feedstock and agroecology
(ADEME, 2009, 2012 ; Bardinal 2014). The aim is to
combine ecosystem functions i.e. nitrogen catch crop,
prevention from erosion, carbon or nitrogen stock (Justes,
2012 ; Berti, 2015 ; Martin, 2014 ; Goff, 2010) - with
economic and environmental ones : farmers income,
resilience, GHG emissions savings and renewable energy
production (Graß 2013 ; Marsac 2014 ; Szerencsits, 2014).
Biomass amount assessment reaches 20 MtDM from
these energy cover crops for a french scenario (ADEME et
al., 2018) and represents about 50 TWh HCV. In this
scheme cover crops are grown into a large panel of
cropping systems and harvested only over 4 tDM/ha of
biomass yield.
Many researches were only carried on cover crop
management (ExpeCIVE – Psilor, 2013 ; CIBIOM ––
Marsac, 2015) but not on the whole crop rotation : 3 crops
over 2 years (Marsac 2015, Szerencsits, 2014). The overall
impact of each crop on the previous or the following one
was not assessed.
Benefits from these double cropping systems were
shown during these programs. High yield variability was
noticed with needs in i) reducing production costs; ii)
optimisation of crop management – soil tillage between
crops and over the crop sequence, choice of the cover crop
species, optimisation of growing cycle; iii) assessing risk
factors : soil, water balance…
GIE GAO (Association between ARVALIS – Institut
du vegetal, Terres Univia and Terres Inovia (Cf. [4[)
worked on the optimisation of the crop management of
double cropping systems for both food/feed and biomass
production during OPTICIVE program. The aim of this
project was to build management rules on the whole crop
sequence and to carry out a technical, economic and
environmental assessement at the biogas plant level.
This paper focuses on experiment methodologies and
technical results to build crop management
recommendations. Methodologies and first extrapolation
of the results are detailed before technical, economic and
environmental assessment.
2 BUILDING RECOMMENDATIONS
2.1 Materiel and methods
Double cropping systems are concerned by annual and
multi-year time scale. We carried on two types of
experiments (Table I) in order to optimise crop
management of the whole crop chain over 2 years:
• Analytic trials which aimed to work on specific
technics as the species, sowing an harvesting
date, fertilization. Some of these trials allowed
us to measure the impact on cropping chain.
• Cropping system experiments to study the
impact of these changes on the whole cropping
system, and especially on the previous or the
following crop into the chain. The experiments
were built in French program Syppre® with
different R&D companies: ARVALIS – Institut
du végétal, Terres Inovia, ITB. These
experimental platforms (5 in France) were built
to test new cropping systems increasing
profitability and sustanability. New cropping
systems are compared to a reference,
representative of their area. These systems were
built in co-construction approach with farmers,
researchers, advisors and economic companies
to reach these objectives and to take into account
a specific environmental issue for the area.
We worked on two different sites in Southwestern
France for OPTICIVE program. Models could help us to
extrapolate first results with 2 different pedoclimatic
conditions with restricting factors or good conditions:
27th European Biomass Conference and Exhibition, 27-30 May 2019, Lisbon, Portugal
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Table I: Experiment design during OPTICIVE program
Characteristics
Lauragais (31)
Sendets/
Burros (64)
Castétis/
Larreule (64)
Lay Lamidou (64)
Uzan (64)
Soil
Chalky clay
Deep organic loamy
clay
Deep / medium loam
Gravelly loam
Surface Loamy sandy
clay
Useful water
reserve (mm)
110-120 (Syppre)
150/175
120-140
/100-120
150
Rainfall (mm)
Average(18
ans)
688
1144
1144
1144
1144
2016
591
1149
1149
1149
1149
2017
647
998
998
998
998
2018
946
1202
1202
1202
1202
Experimented
factors
2016
Species Screening
(Winter cover crop)
Sowing date
Species Screening
(Winter/Summer
cover crop)
Species Screening
(Winter cover crop)
Fertilization (Winter
cover crop hiver)
Energy cover crop
impact on following
corn silage
Species Screening
(Winter cover crop)
Sowing date
Species Screening
(Summer cover crop)
2017
Species Screening
(Winter cover crop)
Soil tillage and impact
on the following crop:
sorghum
Species Screening
(Winter/Summer
cover crop)
Fertilization (Winter
cover crop)
BMP depending on
harvest date (Winter
cover crop)
Species Screening
(Winter/Summer
cover crop)
Fertilization
2018
Species Screening
(Winter cover crop)
Soil tillage and impact
on the following crop:
sorghum
Species Screening
(Winter/Summer
cover crop)
Species Screening
(Winter cover crop)
27th European Biomass Conference and Exhibition, 27-30 May 2019, Lisbon, Portugal
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• Vieillevigne (31) in a chalky clay soil and rainfed
conditions (around 650 mm per year). The reference
cropping system was based on hard wheat and
sunflower. The main environmental issue was to
decrease erosion risks and to improve soil fertility.
A new crop rotation on 8 years was built, including
an energy cover crop. Low tillage is deployed.
• Sendets (64) in deep and organic loamy clay soil
with regular and important rainfall (1100 mm per
year). The objective was to change corn mono
cropping systems (reference system) to decrease
biotic risks and take into account European rules.
New cropping systems are concerned with 2 or 3
years crop rotation, the use of cover crops and
energy intermediate crops.
2.2 Results
2.2.1 Energy intermediate crop species
Winter energy cover crops were sowed from October
1st to November 3rd and harvested at the end of April in
Lauragais area or beginning of May in Béarn area. All the
experiments on the species were fertilised from 40 to 80
kgN/ha depending on the sites.
We noticed a very high yield variability from 2
tDM/ha to 16 tDM/ha with significant differences between
years in the statistical review (Figure 1). Oat is the best
specie for the 3 years program in cropping system
experiments. We could not observed significant
differences between species just for one year analysis. But
differences were noticed between varieties on oat and rye.
This screening would have to be improved for stronger
observations on froze risks and early growth.
Cereals were studied associated to leguminous species
because of the issue in terms of nitrogen self-supply at
farm level. These trials especially worked on Castetis site
(64) confirmed this interesting way for 20 to 40% of
leguminous species. Total biomass yield of the association
decreased while increasing this part of legume crops.
For summer intermediate crops, sunflower, corn, sorghum
and other species were tested. The same variability was
noticed between years. Summer cover crops were sowed
in late June or beginning of July only in Béarn area. We
could not include 2016 results on an experiment site
dealing with potential yield because of a storm at the
beginning of September. For the other years, we could not
find significant differences between species but corn with
its high genetic availability seem to decrease risks. In a
specific experiment (2017) to study species and
fertilisation, we measured yields from 7.4 tDM/ha to 12.5
tDM/ha All the experiments carried on fertilisation
confirmed the positive impact of this fertilisation with low
inputs: from 40 to 80 kgN/ha (60 kg N/ha for Figure 2).
Nitrogen always increased yields (Figure 2, Figure 3), both
for cereal grasses and associations. Digestate valorisation
is a good option for these energy intermediate crops. But
farmers have to follow good practices to decrease
ammonia volatilisation. For our experiment on summer
cover crops, digestate could not be incorporated into the
soil, we decided to spread on the soil just before a rain. In
this case it has been well used. Figure 2 for crops fertilised
and sowed in late July with direct drilling.
Figure 1: Biomass yield of various winter energy
intermediate crops from 2016 to 2018 during OPTICIVE
program
2.2.2 Fertilisation
All the experiments carried on fertilisation confirmed
the positive impact of this fertilisation with low inputs :
from 40 to 80 kgN/ha (60 kg N/ha for Figure 2). Nitrogen
always increased yields (Figure 2, Figure 3), both for
cereal grasses and associations. Digestate valorisation is a
good option for these energy intermediate crops. But
farmers have to follow good practices to decrease
ammonia volatilisation. For our experiment on summer
cover crops, digestate could not be incorporated into the
soil, we decided to spread on the soil just before a rain. In
this case it has been well used.
Figure 2: Summer intermediate energy crop production
and impact of fertilisation during OPTICIVE project 2017,
Larreule (64)
0
2
4
6
8
10
12
14
16
18
Oat Triticale Rye Barley
tDM/ha
Biomass yield from various energy winter cover crop
2016-2018
2016 2017 2018
0%
5%
10%
15%
20%
25%
30%
35%
0
2
4
6
8
10
12
14
Corn (average)
Sorghum
Sunflower
Corn (average)
Sorghum
Sunflower
Corn (average)
Sorghum
Sunflower
Mineral
fertilisation
(60 kg N/ha)
No
fertilisation
Digestate
fertilisation
( 60 kg
N/ha)
%DM
tDM/ha
Biomass yield (tDM/ha) DM (%)
27th European Biomass Conference and Exhibition, 27-30 May 2019, Lisbon, Portugal
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Figure 3: Biomass yield of various energy intermediate
crops for different fertilisation strategies
Figure 4: Comparison of soil nitrogen content from bare
soil to energy winter intermediate crops during OPTICIVE
program on Vieillevigne experiment (31)
2.2.3 Sowing and harvest date
For summer intermediate crops, various programs
have demonstrated the need in sowing early after the
harvest of the previous crop, in late June or beginning of
July. This date is confirmed by models and farmers
practices. But winter energy catch crop would have to be
sowed earlier than conventional cereals to improve
biomass yield early during the spring and decrease
competition with sowing date of the following crop. In this
case, energy cover crop fronts froze and disease risks. Our
experiment confirmed the need in early sowing for these
cropping systems. End of September to 1st October is the
best option in Southwestern France. This date has to be
earlier in Northern conditions.
Concerning harvest date for winter catch crop,
beginning of flowering is the best option for biomass
production, low impact on the following crop and
regrowth risk to prevent from glyphosate use. For summer
catch crop, it is interesting to harvest late in order to
increase dry matter content. But depending on the species
and lodging risks, harvesting at the end of September is the
best option, especially at heading for biomass sorghum.
2.2.4 Intermediate energy crops and carbon content into
the soil
One main issue for these cropping systems concerns
trends of organic carbon into the soil harvesting cover
crops. We measured aboveground biomass and roots mass
in various trials. For these long cover crops, stubble
represented around 2 tDM/ha for a cutting height of 15 cm
in our case. Root mass represented 2 tDM/ha into the first
30 cm of soil.
These parameters have been used to implement AMG
model (Andriulo, 1999, Clivot, 2019) in order to simulate
trends of organic carbon’s stock.
Two digestates from biogas plants mobilising mainly
energy cover crops were analysed. Their composition
(Table II) confirmed previous references (Vadimethan,
ADEME)
Table II: Digestate composition analysed for OPTICIVE
simulations
Digestat
1
Digestat
2
pH
7.7
9.8
DM
(% Fresh
matter)
5.38
5.71
Organic
content
(% FM)
3.7
4.3
Organic
Carbon
(g/kg FM)
18.5
21.5
Total N
(g/kg MB)
4.2
5.4
P2O5
(g/kg MB)
1.6
3.1
K2O
(g/kg MB)
4.5
2
Soluble
(% VC dry)
80.22
45.89
Hemicellulose
(% VC dry)
9.74
17.53
Cellulose
(% VC dry)
2.25
20.63
Lignine
(% VC dry)
7.79
15.95
Cmin3 day
(% Corg)
7.92
5.31
ISMO
(% MO)
71.4
62.3
0,0
5,0
10,0
15,0
20,0
25,0
30,0
35,0
0
1
2
3
4
5
6
7
8
9
% DM
tDM/ha
Biomass yield of winter energy intermediate crops -
2016
Biomass yield no fertilised
Biomass yield fertilised
Dry matter content
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Soil nitrogen content for energy intermediate crops
compared to bare soil
Winter beginning Harvest 2017 Harvest 2018
27th European Biomass Conference and Exhibition, 27-30 May 2019, Lisbon, Portugal
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Figure 5: Evolution of soil organic carbon content
simulated from AMG V2 during OPTICIVE end Solebiom
programsw
For the whole situations estimated, energy catch crops
confirmed their role in carbon storage, depending on their
frequency in cropping chain. The example in (Figure 5) ,
for Béarn situation on deep organic loamy clay soils
demonstrated this evolution especially in the first 40 years
after shift in cropping systems.
2.2.5 Impact and management of the following crop
Soil water content was measured at the energy cover
crop harvest (0-30 cm, 30-60 cm, 60-90 cm) and compared
to bare soil in Syppre® experiments and analytic trials.
Soil characterisation, as resistivity and soil density of these
experiment platforms were valorised.
For summer energy cover crops in Béarn soil water
reserve finished empty.
Results were the same for winter energy cover crop
without significant difference between species. These
results confirmed high water consumption for this
development phase.
Growing risks got higher with such soil water content
for the following crop. Water balances were realised on the
whole crop chain using our measures to correct initial
statement. In France, May is one of the rainiest months.
Soil water reserve was filled in during our experiments in
the first weeks of the growing phase of summer feed/food
crops. Their yield would not be affected by water
consumption of the previous energy intermediate crop.
Despite this result, corn yield (grain) decreased by 0.9
t/ha in Syppre® experiment for the year project :
Corn yield for monocropping reference (inc.
Mulching): 12.8 t/ha ;
Corn yield for Innovative crop rotation corn – winter
energy intermediate crop : 11.9 t/ha ;
winter energy intermediate crop: 6.1 tMS/ha
Later sowing date (10 to 15 days) for corn in new crop
rotation could explain this yield. An earlier variety was
employed to adapt to these conditions. Corn was harvested
with higher dry matter content, decreasing drying costs.
Earlier genotypes are highly expected for all crops
included in these crop rotations. It is an important issue for
farmers and the whole cropping sector.
Earliest varieties have to be employed for energy cover
crops, especially for summer intermediate crops.
2.2.6 Results extrapolation
We wanted to extrapolate firsts results from our two
contrasted pedoclimatic conditions. Models can be used
but they have to be set with numerous physiologic and
agronomic parameters. Some of the measures carried on
OPTICIVE experiments allowed us to work on a part of
these parameters: nitrogen and water uptake… A model
comparison during RMT ERYTAGE network was used to
choose one between STICS® (Brisson et al., 1998),
PERSYST® (Guichard, Bockstaller et al., 2010) and CHN
(Soenen et al., 2018). A frequency analysis is allowed by
CHN, an ARVALIS model, working with a low number of
parameters. Nitrogen, Water and carbon flows are
estimated between plant, soil and atmosphere.
Conventional crops or mandatory catch crops are included
in CHN, but not for long cycle ones as our energy cover
crop. We tried to use soft wheat parameters to value
biomass yield of our winter cover crops for an immature
phase and corn parameters for summer catch crop as
sorghum.
We compared measured yields to the estimated ones
(Figure 6) with the soft wheat parameters. This correlation
is appropriated especially for biomass yield of oat as
energy winter intermediate crop. Other parameters as
nitrogen or soil water content have to be improved. We
were confronted to various uncertainties for field
parameters in analytic experiments but Syppre® ones were
quite good. A better characterisation of these fields would
improve our results.
Figure 6: Biomass yield comparison for energy winter
cover crops studied in OPTICIVE program with CHN
simulations (soft wheat parameters)
This correlation for summer catch crop was not so
good. Others parameters and uncertainties on water
availability or plant density and space between rows could
explain these results.
For winter catch crop we tried to use soft wheat
parameters of CHN to value biomass yield in 6 French
regions just for one type of soil and meteorological data
per region (Table III). This work was carried on the last 15
years, to include variability. Cover crops were fertilized
with 80 kg N/ha.
85
90
95
100
105
110
115
120
125
130
135
020 40 60 80 100
Stock ok organic carbon on first
30 cm (T/ha)
Years
TEMOIN T1
TEMOIN T1 - CIVE
TEMOIN T1 + Digestat
0
2
4
6
8
10
12
14
-1 4 9 14
Estimated yield from CHN (tDM/ha)
Measured Yied (tDM/ha)
Biomass yield comparison from trials and model 2016-
2018
Corn monocropping
Corn + energy cover crop
Corn + energy cover crop + digestate
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Table III: Characteristics of soil and climatic conditions
used for winter energy cover crops simulation with CHN
model in OPTICIVE framework
Biomass yield simulated with CHN is the aboveground
biomass. This yield reaches 8 tDM/ha in different regions
(Table IV) for the median simulation. Including stubble,
the harvestable biomass could reach 6 to 7 tDM/ha.
Variability between years stayed high.
Table IV: Simulation of biomass yield of winter cover
crops harvested for energy in different pedoclimatic
conditions with CHN model (soft wheat parameters)
Area
Sowing date
Harvest date
Median
Biomass
yields
simulated
(tDMS/ha)
Midi-
Pyrénées
01-oct
01-mai
8.7
Poitou-
Charente
15-sept
01-mai
7.8
Bretagne
15-sept
01-mai
7.8
Centre
15-sept
01-mai
7.3
Béarn
01-oct
01-mai
9.3
Champagne-
Ardenne
15-sept
01-mai
5.6
2.2.7 Biomethane potential (BMP)
An analysis design was discussed and adapted with
stakeholders. BMP was analysed for 3 cover crops on 3
different harvest dates (March 15th; April 1st; April 20th).
BMP was significantly different decreasing along growing
period. Regarding the trend for total biomass production,
biomass yield was the main factor for total biogas
production.
Other species were analysed and compared to previous
results. No significant difference was observed for our 24
samples (Table V) of different species and way of storage.
Table V: BMP of different energy intermediate crops
measured in OPTICIVE and CIBIOM programs
Species
BMP (LCH4/kgVC)
Corn
261.9
millet
251.2
Sorghum
244.89
Sorghum
264.4
Sorghum
290.54
Oat vetch
243.4
Cereal + leg
284.93
Cereal + leg
287.16
Cereal + leg
295.88
Oat
273.44
Oat
280.72
Oat
301.49
Oat
321.8
Wheat
334.18
Oilrape
265.10
Oilrape
287.19
Barley
277.05
Barley
289.84
Barley
303.9
Rye
318.8
triticale
248.3
triticale
277.58
triticale
328.8
3 TECHNICAL, ECONOMIC, ENVIRONMENTAL
ASSESSMENT
3.1 Matherial and methods
Cropping chain can be changed by the introduction of
intermediate crops, but also crop management.
Farmers are confronted with many questions on labour
time, energy efficiency, competitiveness of their
production and profitability of the whole system.
We built different cropping (Table VI) systems
including crop management from our experiments in order
to make this overall assessment.
From the field level to plant delivering before storage
we used Systerre ® for this assessment. Systerre ® is a tool
created by ARVALIS and now shared with different
technical institutes. Technical, environmental and
economic indicators for field crops are calculated from a
large data base including machinery or pesticides and
fertilisers references. This tool and methodologies were
described last 2015 (Marsac, 2015).
Users can analyse these performance indicators
without any aggregation: production cost, energy balance,
GHG emissions, labour time, nutrient balance, fuel
consumption…). Net margin of the whole crop chain can
be calculated: sales revenue deducted from inputs (seeds,
Area
Soil description
Wheather
station
Champagne-
Ardenne
Deep loamy clay .
Septsangres
Bretagne
Surface and
hydromorphic loam
Ploërmel
Poitou-
Charente
Deep chalky clay
Saintes
Midi-
Pyrénées
Medium chalky clay
En Crambade
South
Aquitaine
Deep organic loamy
clay .
Pau-Uzein
Centre
Deep Loamy clay and
hard
Chateaudun
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fertilisers, pesticides), mechanisation, manpower, land and
other expenses as social fees, taxes…
Calculation of production costs is dependant to
expenses distribution especially fixed expenses :
• complete cost includes all the costs
• total cost excludes annual fixed costs which
could be affected to food/feed crops like
nowadays or distributed along the 3 crops over 2
years. This distribution could be equal for each
crop or affected to sale revenue or energy
potential.
First option was applied in OPTICIVE. Losts due to
energy intermediate crop on the following one (2.2.5) are
included in these costs. Digestate spreading cost was
included, but no price of digestate (raw material) was
affected. The impact of digestate price has been estimated.
Biogas turnover or energy intermediate crop price has
to be included in net margin calculation. To take into
account all the issues of this developing sector, we
organised a workshop for a co-construction strategy of the
biogas hypotheses at the whole on-farm biogas plant level.
Farmers, advisors, gas conveyors, institutions participated
to the workshop. Five case studies were built from
feedbacks of the farmers with 2 plants injecting in gas grid
(70 to 135 Nm3.h-1 ) and 3 combined heat and power
generation (80 à 300 kWe) (Table VIII). Other
stakeholders had improved economic hypotheses in
complement to Methasim ®. This tool for economic
assessment of biogas plants use DIGES model to assess
GHG emissions and savings.
3.2 Results
3.2.1 Production cost
Complete production cost reached 95 to 125€/tDM.
Annual fixed expenses represented from 30 to 50 €/tDM
for total production cost of 70 to 90 €/tDM (Table VII).
Summer energy intermediate crops seemed to be more
expensive due to seeds, especially for many hybrids
varieties for corn, sorghum and sunflower.
The impact of digestate value could reach 34 to 68 €/ha
according to mineral value: half of current value or similar
price as mineral fertilisers.
These costs ranged from 20 à 50 €/MWh. Added to
biogas plant costs including investment (amortisation, loan
interest) and functionning costs (manpower, energy
consumption, maintenance) we could calculate total
energy cost. For a biogas plant with 135 Nm3CH4.h-1
flow, this cost reached 118 €/MWh (Figure 7) without any
subsidy for the investment with a variation from 90 à 140
€/MWh for a complete production cost of the ressource.
This cost was equivalent to current energy purchase price.
Energy cost is a bit higher for the other biogas plant
with lower flow. For CHP biogas plants, energy cost is
higher than energy purchase price apart from plants using
biowaste with treatment fees (CHP3).
Table VI: reference cropping systems and double
cropping systems with management shifts assessed in
OPTICIVE program
Area
Crop
rotation
Référence
Shift in tillage
Béarn
Soft
wheat –
Winter
Energy
cover
crop
(ECC)-
Corn
Corn
monocroppin
g
Corn : Strip-
till
Soft
wheat –
Summer
ECC-
Corn
Winter
ECC -
corn- -
Winter
ECC-
Soja
Winter
ECC -
Corn
Barley,
Summer
ECC –
Soft
wheat
Barley,
Soybean
produced as
intermediate
food crop –
Soft Wheat
Corn and
soybean : Strip
Till
Lauragai
s
Barley-
Winter
ECC-
Sorghum
Hard wheat -
sunflower
None
Hard
wheat-
Winter
ECC-
Sunflowe
r
Direct drilling
for Soft wheat
+ 1 weedkiller
1 herbicide
supplémentair
e
Sunflower:
Strip Till
27th European Biomass Conference and Exhibition, 27-30 May 2019, Lisbon, Portugal
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Table VII: Complete production costs and cost not
including annual fixed expenses for different energy
intermediate crops in areas worked during OPTICIVE
program
Costs were calculated for optimum digestion and
valorisation yield but technologies and scale up are used to
decrease yield so as for CHP engines or gas purification.
The whole heat produced was valorised in our cases for
CHP.
Figure 7: Total energy cost for biogas plants studied for
OPTICIVE program, with a feedstock of oat as energy
intermediate crop (7.5 tDM/ha) in Béarn area
Table VIII: Biogas plant characteristics built during co-
construction workshops for overall assessment during
OPTICIVE program
Maximum purchase price for energy cover crop was
calculated in a second time with the same process
hypotheses. Biogas plant costs, including a rate of return
of investment of 8%, not including energy cover crop
supply, are substracted to total energy sale.
This maximum price for our substrate ranged from 120
to 160 €/tDM according to biomethane flow for grid
injection plants. For CHP3 which valorises biowaste
generating fees, this price reached 140 €/tDM. The other
CHP cases were not able to purphase such feedstocks.
3.2.2 Biomass price and profitability yield
Profitability yield had been calculated (Figure 8).
Depending on a biomass purchase price, this yield allowed
the total expenses compensation.
Six tons (dry matter) per hectare were necessary for a
biomass price of 125 €/tDM (27 €/t fresh) to balance the
complete expenses. In the case where fixed expenses were
not included, this yield was 2 tDM/ha lower. For lower
purchase price, profitability yields got higher : 17 €/t – 80
€/tDM.
0
50
100
150
200
250
CHP
1
CHP
2
Gas
grid
1
Gas
grid
2
CHP
3
€/MWh
Total energy cost from biogas plants –Energy
Cover crop : Oat 7.5 tMS/ha SW France
Biomass costs not inc. Fixed expenses
Biomass complete costs
Biogas plant costs
Energy price
Area
Crop
chain
Species
Yield
(t
DM/h
a)
Complete
Production
Cost
(€/tDM)
Production
cost
without
fixes
expenses
(€/tDM)
Béarn
Winter
energy
cover
crop
(ECC) -
Corn
Oat
6
139
87
7.5
112
69
9
93
58
Oat-
Vetch
5
156
93
7
112
66
8.5
92
55
Lauragais
Hard
wheat –
winter
ECC -
Sunflow
er
Oat
5
160
105
6.5
123
80
7.5
107
70
Oat-
Vetch
5
150
94
6
125
78
7
107
67
Béarn
Soft
wheat –
winter
ECC -
Corn
Sorghum
6
144
94
9
96
63
12
72
47
Bioga
s plant
Gas
grid 1
Gas
grid 2
CHP1
CHP2
CHP3
Energ
y
cover
crop
(t)
8 000
16 000
2 300
4 500
5 500
Manur
e (t)
4 000
4 000
2 000
2 000
11 000
Biowa
ste (t)
1 833
FlowC
H4
(Nm3.
h-1)
69.8
134.9
Power
(kWe)
284
564
81
151
295
OPEX
(not
includ
ing
digest
ate
spread
ing
and
bioma
ss
cost)
(k€)
291
406
58
86
151
CAPE
X (k€)
(sourc
e
GrDF,
€.kWe
-1)
2 700
9 507
4 400
7 801
900
11 111
1 359
9 000
2 419
8 200
27th European Biomass Conference and Exhibition, 27-30 May 2019, Lisbon, Portugal
47

Figure 8: Profitability yield calculated during OPTICIVE
program for 2 production cost hypotheses
3.2.3 Cropping chain profitability
We could calculate farming profitability for two
options :
• A farmer selling its energy cover crops to a
biogas plant;
• A farmer who has invested in a biogas plant and
self supply a part from the feedstock.
In the first case, for a farm oriented in corn
monocropping systems, inputs and mechanisation cost
increased over a two year analysis : seeds, digestate
spreading, drilling, harvest). But the earlier variety
employed for corn to compensate a later sowing date
allowed drying economies for corn. Including energy catch
crop sale for 6 tDM/ha and 125 €/tDM, net margin is
improved about 93 €/ha.
For the same previous hypotheses of biogas plants and
process yield, excluding subsidies for investment, energy
cover crop valorisation to its complete production cost did
not improved this margin for 6 tDM/ha yield (Table IX).
Intermediate crop productiveness is a central issue.
Increasing yield to 7.5 tDM/ha in Béarn as obtained in our
experiments could improve net margin by 56 €/ha.
Table IX: Net margin comparison between a reference
cropping system and a whole farming system based on
energy catch crop use in on-farm biogas plant which inject
into gas grid (135 Nm3CH4.h-1), Hypotheses from
Opticive program
Cropping
system
Corn
monocropping
référence
Corn – Energy cover crop
€/ha
6 tMS/ha
7.5 tMS/ha
Net margin
263
159
319
3.2.4 Further issues
Many other sustainability issues were assessed in our
innovative cropping systems. Production of 3 crops over 2
years needs to reduce time between 2 crops. Low tillage
management could decrease this time and mainly labour
time at field level.
GHG emissions could be equal to the reference
system, decreased or increased regarding superficy. But
towards energy production these emissions are decreased
on confirmed firt assessments (Marsac, 2015).
Anaerobic digestion could decrease emissions with
fossil energy substitutions but global balance depends on
transportation distance for the harvested biomass.
4 LIMITATION AND PERSPECTIVES
Hypotheses of the overall assessment were the main
source of uncertainties. These limits were due to two
different parameters.
The first one concerns the project length and the
analysis of the impact of the shifts in cropping systems. A
three year program allowed us to study 3 crop chains. But
observations have to be kept up into Syprre® experiments
to assess a long term impact on weeds, disease, yields. The
overall analysis at field level is highly dependent on these
hypotheses. Potential inputs economies, variability
analysis will have to be included. .
The multicriteria analysis at farm level took into
account economic parameters from biogas plants. No
biogas plant developer wanted to give us these parameters.
We assessed them from different sources (gas conveyors,
available tools but not specialised for gas grid
valorisation). These hypotheses would have to be
improved from feedbacks of real cases. A survey on
different biogas plants based on a large feedstock of
intermediate energy crops would be interesting.
Production costs of the energy provided are too
important nowadays and demonstrate a need in financial
support for on-farm biogas plants. With around 120
€.MWh-1, these costs are higher than the objectives
included in multi-year French energy program (PPE - 67
€/MWh to 2023 ; Jan. 2019). Costs and variability have to
be decreased in double cropping systems. Bioeconomy
development is based on different issues as cost decreasing
and profitability distribution between stakeholders. Cost
decreasing ways were identified in recent work ordered by
the whole stakeholders (ENEA, 2019). All production
steps are concerned, from substrate, digestion process, to
biogas valorisation.
From these issues, first farmers or advisors feebacks
have demonstrated need for further works :
Proceed in regional experiments to build regional
recommendations and take into account local crop
rotations, pedoclimatic constraints;
• Bring together experiments and build a national
network on this topic to improve exchanges
between farmers and advisors.
• Widely communicate these first results and
recommendations to decrease risks for farmers.
Farmers have to anticipate shifts in cropping
systems and to improve their assessment of their
profitability.
Other assessment will be done more specifically on
remuneration factors of positive externalities (carbon
storage, pesticides decreasing…).
Partner oriented research with all stakeholders is an
important challenge for such development lines on circular
economy and farming systems improvement.
5 ACKNOWLEDGEMENTS
This work was supported by French National Agency
for Energy end Environment (ADEME) and was carried
out in collaboration with EURALIS, farming cooperative.
0,0
2,0
4,0
6,0
8,0
10,0
12,0
010 20 30 40 50
Profitability yield (tDM
/ha)
Energy catch crop purchase price (€/t)
Oat profitability yield
COMPLETE Excl. Annual fixed costs
27th European Biomass Conference and Exhibition, 27-30 May 2019, Lisbon, Portugal
48

ARVALIS – Institut du vegetal is a French technical
institute (non for profit) in charge of applied research on
cereals, potatoes, flax, tobacco and forage crops. Terres
Inovia is another technical Institute for oil, protein crops
and industrial hemp sector. Terres Univia is the
interbranch organisation for oilseed and protein crops
sectors.
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