This document evaluates the effects of different crop management practices on greenhouse gas emissions and energy balances of rye grown as an energy crop for electricity production in Spain. Six management practices were tested, combining two seeding doses (typical and low) with three fertilization doses (zero, low, and typical). Results showed lower fertilization improved emissions but reduced yields, potentially depleting soil nitrogen over time. Using low seeding doses also reduced yields without offsetting lower inputs. A nitrogen balance assessment found most practices led to annual soil nitrogen losses. Overall, the study aims to optimize rye management for electricity production while maintaining soil sustainability.

1. CAN CROP MANAGEMENT IMPROVE EMISSIONS SAVINGS?: PRELIMINARY RESULTS OF THE
OPTIMIZATION OF RYE (Secale cereale L.) AS ENERGY CROP FOR ELECTRICITY PRODUCTION IN SPAIN
Martín-Sastre C.1*, Maletta E.2, Ciria P2, Perez P.2, del Val A.2, Santos A. M.1,
González-Arechavala Y.1 and Carrasco J. E.2
1
Institute for Research in Technology (IIT) - ICAI School of Engineering - Comillas Pontifical University - E-28015, Madrid
(Spain). Phone: +34 91 542-2800, Fax: +34 91 542-3176
2
CEDER-CIEMAT. Energy Department. Biomass Unit. Autovía de Navarra A-15, salida 56.
42290 Lubia (Soria). Phone: +34 975281013
*Corresponding author: carlos.martin@iit.upcomillas.es
Several studies suggest that lignocellulosic energy crops for electricity production may have a better performance
compared to those crops for liquid biofuels production, when assessing GHG savings with respect to fossil
references. Winter cereal residues and some annual winter grasses, as dedicated energy crops, are currently being
grown in Spain and harvested as bales to be burned for electricity production in biomass power plants. Previous
studies of our group analyzed GHG emissions and energy balances of winter cereals for electricity production by
means of Life Cycle Assessment. We selected highly productive genotypes of three annual winter cereals (rye,
triticale and oat) and compared them with Spanish electricity produced using natural gas. This paper compares effects
of the use of different crop management practices for rye growing in the assessment of energy balances and GHG
emissions. We analyzed the effects of six different management practices consisting of two different sowing doses
(suboptimal and normal) combined with three top fertilization doses (zero, 30 and 80kgN ha-1). We made a
characterization analysis of biomasses to estimate the nitrogen uptake of the crops in order to compare it with the
nitrogen provided by the fertilizers. This comparison evaluates if lower fertilization doses are sustainable for the soil
nitrogen stocks. Our results suggest that there is trade-off between soil nitrogen and emission savings. The use of zero
or low top fertilization doses (30 kg N ha-1) improves GHG emissions and energy balances even with a yield
reduction. Nevertheless the use of these doses imply an annual lose in soil nitrogen stocks for the majority all of our
trials. Using suboptimal sowing doses resulted in yield decreases that did not compensate the lower input consumed.
Keywords: electricity, energy balance, energy crops, greenhouse gases (GHG), life cycle assessment (LCA),
sustainability criteria
1 INTRODUCTION nitrogen balance was made to assess the sustainability of
lower fertilizer doses for soil nitrogen stocks. To evaluate
The climate change problem coupled with declining the effects of management practices three plots were
oil and gas reserves has led to the development of energy established for each practice in the northern of Spain
sources to minimize greenhouse gas (GHG) emissions (Soria’s province). The parcels were grown by famers
and expand energy supplies from solar, wind, hydraulic, using traditional management practices for cereals in the
geothermal and bioenergy sources [1]. Solid and liquid zone, except for sowing and top fertilization doses as
biofuels guarantee the energy security and reduce GHG objectives of the assessment. Farmers prepared the land,
emisions when compared to fossil referecences in many pesticides and NPK fertilizers were applied, seeds were
studies [1–3] [4–6]. Several studies suggest that spread, top fertilization was made (in case it applies for
lignocellulosic energy crops for electricity production the trial) and crop was harvested through mowing,
may have a better performance compared to those crops swathing and baling. The system analyzed considers real
for liquid biofuels production, when assessing GHG data collection from farmers, transportation of square
savings with respect to fossil references [7,8]. bales and a real power biomass plant for electricity
Winter cereal residues and some annual winter production in northern Spain. The results were compared
grasses, as dedicated energy crops, are currently being to electricity production from the National natural gas.
grown in Spain and harvested as bales to be burned for
electricity production in biomass power plants [9].
Previous studies of our group analyzed GHG emissions 2 MATERIALS AND METHODS
and energy balances of winter cereals for electricity
production by means of Life Cycle Assessment [10]. We Life Cycle Assessment (LCA) is the environmental
selected highly productive genotypes of three annual tool we selected to determine the energetic and
winter cereals (rye, triticale and oat) and compared them environmental performance of rye to produce
with Spanish electricity produced using natural gas. lignocellulosic biomass for electricity generation.
In this article we compare the effects of the use of LCA is a systematic set of procedures for compiling
different crop management practices for rye, grown as and examining the inputs and outputs of materials and
dedicated energy crop for electricity production, in the energy and the associated environmental impacts directly
assessments of GHG emissions and energy balances by attributable to the functioning of a product or service
means of Life Cycle Assessment. For this purpose six system throughout its life cycle [11]. This environmental
crop management practices were considered. These assessment tool is regulated by ISO 14040 [11] and ISO
practices consists of combining the use of low (24 kg ha - 14044 [12] standards, and according to this, LCAs should
1
) and typical (120 kg ha-1) seed doses with zero top follow four steps: (1) goal and definition, (2) inventory
fertilizer dose (0 kg N ha-1), low fertilizer dose (30 kg N analysis, (3) impact assessment and (4) interpretation.
ha-1) and typical fertilizer dose (80 kg N ha-1). Also a Simapro 7.2 [13,14] software tool and Ecoinvent 2.2

2. [15,16] European database have been selected for the Table II: Biomass productivity
LCAs.
Also a rough nitrogen balance was made considering Seed
Top Trial productivity
nitrogen supply by fertilizers and measuring the amount Crop Fertilizer (odt ha-1)
Dose
of nitrogen contended in the crops as the nitrogen Management Dose
(kg ha-1) 1st 2nd 3rd
(kg N ha-1)
extracted.
Prior to the description of the LCAs conducted and TSD & ZTF 120 0 9.001 10.142 7.092
the nitrogen balance methodology, some methodological TSD & LTF 120 30 10.792 10.442 8.182
aspects regarding the experimental design and the TSD & TTF 120 80 13.200 11.815 10.548
biomass characterization and productivity are described LSD & ZTF 24 0 7.758 6.992 4.773
in the two following subsections.
LSD & LTF 24 30 7.860 6.447 4.403
2.1 Experimental design LSD & TTF 24 80 9.045 8.099 6.087
To assess the effects in energy and GHG balances of
crop management practices a plot of 8500 m2 was Average data about dry basis composition and net
established to grow rye. The management practices heating value of the managment practices trials are
consist on the application of two different sowing doses shown in Table III. The net heating value at constant
and three top fertilization doses resulting in six possible pressure has been calculated for humidity contents of 0%
combinations. For its possible combination three trials and 12%, as 12% is the average humidity of burned
were done dividing the 8500m2 of the parcel eighteen biomass in the biomass power plant selected for this
smaller plots. The Table I summarizes the characteristics research.
of the site selected for the study as well as the conditions
of the each crop management practice used. Table III: Aerial biomass characterization
Table I: Experimental design summary Crop C N NHVcp,0 NHVcp,12
1. Location Soria Management (%) (%) (MJ kg-1,db(1)) (MJ kg-1,wb(2))
41º 36’ 40.0” N TSD & ZTF 44.8 0.84 16.70 14.40
Coordinates
2º 28’ 55.6”W TSD & LTF 45.1 0.86 16.76 14.46
Altitude 1035 m TSD & TTF 45.4 0.87 16.90 14.58
2. Experimental period 2010-2011 LSD & ZTF 45.10 1.00 17.11 14.76
Continental LSD & LTF 45.40 1.03 17.17 14.81
3. Climate Mediterranean with cold LSD & TTF 45.7 1.04 17.31 14.94
winters
Average Temperature / rainfall 10.4ºC, 446.5 mm 3 RYE LCA METHODOLOGY
4. Soil type
Clay (%) / Sand (%) / Silt (%) 13.56 / 80.66 / 5.09 The following sub-sections describe the methodology
Texture Sandy loam
Organic matter (%) 1.07
follow to conducts the rye optimization life cycle
Nitrogen (%) 0.06 assessments.
5. Genotype
Specie (variety) Secale Cereale (Petkus) 3.1 Goal and Scope definition
6. Plots The aim of this study is to evaluate the energy
Quantity / type / size 18 / Strips / 0.04-0.05 ha balance and environmental impacts of six crop
7. Crop management practices management practices for growing rye in Spain for
electricity generation and compare them with electricity
Typical Seed Dose (TSD) 120 kg ha-1
generation from natural gas, as a reference for generation
Low Seed Dose (LSD) 24 kg ha-1 from non-renewable fossil sources.
Common Top Fertilization (TTF) 80 kg N ha-1
3.2 Functional unit
Low Top Fertilization (LTF) 30 kg N ha-1 The functional unit chosen is 1 TJ of electrical energy
Zero Top Fertilization (ZTF) 0 kg N ha-1 generated from rye biomass for the studied system and
from natural gas for the reference system. This amount of
electrical energy is a round number corresponding to 12
2.2 Biomass characterization and productivity
In order to assess the environmental and energetic hours of functioning of the 25Mw power plant selected
performance of rye biomass as solid fuel for electricity, for this study (see 3.3.2).
The electricity production per hectare of rye trial is
the productivity of crop management trials was measured
the product of the crop yield (see Table II) at 12 %
(see Table II).
humidity by the net calorific value at 12 % humidity (see
Table III) and by the efficiency of the biomass
conversion process into electricity (29.5 % for this case
study). According to this, between 17 ha and 51 ha are
needed to produce 1 TJ for the higher and the lower
yielding trials.
3.3 Systems description
The bioenergy systems analyzed includes three
subsystems: agricultural biomass production, electricity
generation and the transport of products and raw
materials.

3. 3.3.1 Agricultural system inputs consumed. This information is shown in Table IV
The agricultural system could be described by the for all the crop management trials made in Soria for the
crop schemes followed, the machinery used and the rye bioenergy cropping system.
Table IV: Agricultural system summary for the Soria trials.
Operation Tractor Implement Inputs
Operating
Weight Power Type Weight Fuel consumption
rate
(kg) (kWh) (kg) (h ha-1) (L ha-1)
Moldboard
Primary tillage 5470 103 1390 1 20
plow
Secondary tillage 5470 103 Cultivator 400 0.66 10
Base fertilization 3914 66 Spreader 110 0.20 4 NPK fertilizer 8-24-8 300 kg ha-1
Hybrid rye seeds (kg ha-1):
Sowing 5470 103 Seeder 830 0.60 8
TSD (24), LSD (120).
MCPA 0.332 kg ha-1, Dicamba
Herbicide Boom
3914 66 230 0.50 4 0.125 kg ha-1, 2 ,4-D 0.370 kg ha-1
treatment sprayer
Calcium ammonium nitrate 27% kg
Top fertilization 3914 66 Spreader 110 0.20 4
ha-1: TTF (300), LTF (100), ZTF (0)
Rolling 3914 66 Roller 1000 0.40 8
Mowing-Swathing 3914 66 Mower 150 0.70 8
Baling 3914 66 Baling packer 1700 0.40 4
Loading Bales 5470 103 Trailer 1870 0.40 4
3.3.2 Biomass power plant system 3.3.3 Transport system
All the data considered to model the biomass power The transport system is summarized in Table VII.
plant system are real data from a 25 MW biomass plant This table shows all modes of transport used and the
located in northern Spain. This plant consumes biomass distances between origin and destination points for every
at an average humidity of 12% and produces electricity transport in the LCAs carried out.
with a conversion efficiency of 29.5%. The plant The transportation means and distances for the
consumes natural gas for maintenance operations and transport of agricultural inputs until the regional
pre-heating and produces ashes and slag from biomass as storehouse are taken from the Ecoinvent database [17].
residues. The average consumption of natural gas and the The distance from the regional store house to plots was
productions of ashes and slag per kilogram of burned 10 km approximately. The transport of workers to the
biomass are shown in Table V. parcel has not been considered because of the highly
variability of transport distances depending on cases.
Table V: Biomass power plant consumptions and Biomass, ash and slag means of transport and
residues produced distances were provided by company in charge of the
biomass power plant.
Consumed or produced
Amount
substances Table VII: Transport system summary
Natural gas consumption 0.0342
(MJ Kg-1 Wet Biomass Burned) Material From To Distance Vehicle
Slag production Processing Lorry
82.47
(g Kg-1 Wet Biomass Burned) Seed Field
center
30 km
20-28t
Ashes production 8.25 Processing Regional Lorry
(g Kg-1 Wet Biomass Burned) center storehouse
100 km
20-28t
Regional Demonstration Lorry
The emissions of the plant into the air are submitted 10 km
storehouse parcel 16-32t
regularly to the local government. The emissions Fertilizers
Regional
accounted are only those which affect the global warming and Manufacturer 600 km Train
storehouse
potential (GWP). In the power plant studied these herbicides
emissions come from gas natural combustion (see Table Lorry
100 km
>16t
VI). Carbon dioxide emitted from biomass combustion Regional Demonstration Lorry
was not considered because it was previously fixed from 10 km
storehouse parcel 16-32t
the air by the crop. Demonstration Lorry
Biomass Biomass plant 60 km
parcel 16-32t
Table VI: Biomass power plant aerial emissions Ash and
Biomass plant Disposal 37 km
Lorry
slag 16-32t
Substance Origin Amount
(g Kg-1 Wet Biomass 3.3.4 Natural gas system
Burned) The natural gas system includes the gas field
Fossil carbon operations for extraction, the losses, the emissions and
Natural gas 1.94
dioxide the purification of the main exporter counties of natural
gas to Spain (Algeria 73 % and Norway 27 %). Also
includes the long distance and local transport of gas to

4. the power plant in Spain, considering the energy 3.4.4 Diesel consumption and combustion emissions of
consumption, loses and emissions for distribution. Finally agricultural machinery
the substances needed and the average efficiency of The diesel consumption of agricultural machinery is
Spanish natural gas power plants to produce electricity obtained from Table V. The inventories for the
are taken into account [18]. extraction, transport of petrol, the transformation into
diesel and its distribution are taken from Ecoinvent [25].
3.4 Life cycle inventory analysis The exhaust emissions of diesel in agricultural
The inventories used to consider natural gas machinery engines are also considered [26].
consumption [18] of the biomass power plant, transports
[19] of agricultural inputs, and biomass and power plant 3.4.5 Agricultural machinery manufacture
residues are taken from Ecoinvent. The inventories for agricultural machinery
The methods used for the inventory analysis of the manufacture are specific to the different types of
agricultural system mainly follow that proposed on Life machinery (tractors, harvesters, tillage implements or
cycle inventories of agricultural production systems [17]. general implements).
To consider N2O emissions we follow the formula The amount of machinery (AM) needed for a specific
proposed by de RSB GHG Calculation Methodology v process was calculated multiplying the weight (W) of the
2.0 [20]. This formula is basically based on the formula machinery by the operation time (OT) and dividing the
proposed in the Ecoinvent Agricultural Report [17], that result by the lifetime of the machinery (LT) [17]:
considers the new IPCC guidelines [21]. Also we
consider the nitrate emissions affecting to Global AM (kg FU-1) = W (kg) OT (h FU-1) LT-1(h);
Warning Potential as the RSB purposes [20], making and
estimation of them by means of nitrogen balance, the soil Where FU (See 3.2) is the functional unit of the LCA.
and crop characteristics and the rainfall of the zone. The life time of the machinery was provided by its
owners.
3.4.1 Fertilizers productions
The fertilizer inventories consider the different steps 3.4.6 Nitrous oxide emissions
of the production processes, such as the use of raw The calculation of the N2O emissions [20] is based
materials and semi-finished products, the energy used in on the formula in Nemecek et Kägi [17] and adopts the
the process, the transport of raw materials and new IPCC guidelines [21]:
intermediate products, and the relevant emissions [17].
The production of calcium ammonium nitrate starts N2O=
with the production of the ammonium nitrate by the 44/28∙(EF1∙(Ntot+Ncr)+EF4∙14/17∙NH3+EF5∙14/62∙NO3-)
neutralization of ammonia with nitric acid. The final
product is then obtained by adding dolomite or limestone With:
to the solution before drying and granulation [22]. N2O = emissions of N2O [kg N2O ha-1]
No inventories are given in Ecoivent for multinutrient EF1 = 0.01 (IPCC proposed factor [21])
fertilizers due to the amount different possible ways to Ntot = total nitrogen input [kg N ha-1]
mix nitrogen, phosphorous and potassium compounds to Ncr = nitrogen contained in the crop residues [kg N ha -1]
produce NPK fertilizers [22]. The modeling of NPK EF4 = 0.01 (IPCC proposed factor [21])
fertilizer inventories has been approximated by NH3 = losses of nitrogen in the form of ammonia [kg
combining inventories of single fertilizers according to NH3 ha-1]. Calculated as proposed in the RSB [20] and
multinutrient fertilizer specific contents of N, P 2O5 and Nemecek et Kägi [17] methodologies.
K2O, as well as the form of the nitrogen provided 14/17= conversion of kg NH3 in kg NH3-N
(ammonium, nitrate or urea) [22]. EF5 = 0.0075 (IPCC proposed factor [21])
NO3- = losses of nitrogen in the form of nitrate [kg NO3
3.4.2 Herbicides production ha-1]. They were estimated through the RSB formula [20]
The data related to emissions, energy and substance which considers nitrogen supply, the nitrogen uptake, the
consumption in the production of the herbicides sprayed soil and crop characteristics and the local rainfall.
is taken from Ecoinvent [23]. The quantities of active 14/62= conversion of kg NO3- in kg NO3-N.
matters considered are taken from the formulations of the
commercial fertilizers used. 3.4.7 Land use changes
Direct land used change does not take place because
3.4.3 Seed production the parcel selected was previously a winter cereal crop
Annual cereal seeds are produced in Spain under land. Indirect land use change is a complex process that is
similar conditions compared to the operations of fertilizer not fully understood by the scientific community and so
and management practices used for commercial grain or is not included in this study [1].
forage cultivation techniques. Rye is frequently produced
under irrigation in high quality soils under contract with 3.5 Life cycle impact assessment
real farmers, thus their normal operations and yield Life Cycle Impact Assessment (LCIA) is the phase in
production were assumed to be similar to that of the local an LCA where the inputs and outputs of elementary flows
common management practices cosidered in this study. that have been collected and reported in the inventory are
Then, a grain production yield of 5.5 odt ha-1 was translated into impact indicator results [27].
considered as harvest index of 35 % for Petkus variety as LCIA is composed of mandatory and optional steps.
a non hybrid rye genotype. Mandatory steps of classification and characterization
The energy consumption for cleaning, drying, seed have been carried out and optional steps normalization
dressing, and bag filling of the cereal seed in the and weighting have been avoided in order to make results
procesing plant has been estimated in 32.8 kWh t -1[24]. more comparable and to avoid introducing value choices.

5. In the classification steps elementary flows shall be 80 80 Kg N ha-1
Top Fertilization
assigned to those one or more impact categories to which 70
& 24 Kg ha-1
Seed Dose
they contribute. In the characterization steps each 80 Kg N ha-1
Top Fertilization
60 & 120 Kg ha-1
quantitative characterization factor shall be assigned to
GWP (Mg CO2 eq TJ electrcity-1)
Seed Dose
30 Kg N ha-1
all elementary flows of the inventory for the categories 50 Top Fertilization
& 24 Kg ha-1
that have been included in the classification [27]. 40
Seed Dose
30 Kg N ha-1
Top Fertilization
& 120 Kg ha-1
3.5.1 Environmental impact assessment method 30 Seed Dose
0 Kg N ha-1
We have selected the software tool Simapro 7.2 [13] 20
Top Fertilization
& 24 Kg ha-1
and the impact assessment method of the IPCC 2007 [28] Seed Dose
0 Kg N ha-1
10
to assess the 100 years time horizon Global Warming Top Fertilization
& 120 Kg ha-1
Seed Dose
Potential (GWP). 0
3000 5000 7000 9000 11000 13000 15000
Yield (kg d.m. ha-1)
3.5.2 Energy assessment method
In order to assess the energy consumed to generate Figure 1: Relationship between global warming potential
electricity from winter cereal biomass and from natural of rye biomass electricity and whole plant yield
gas, we have selected the software tool Simapro 7.2 [13]
and the Cumulative Energy Requirement Analysis The Figure 2 shows that the GWP savings with
(CERA) [29]. This method aims to investigate the energy respect to natural gas go from 50 % to 85%. We obtained
use throughout the life cycle of a good or service [29]. a very high amount of savings for the typical
The primary fossil energy (FOSE) has been obtained management practices of the site (blue circles), due to the
using this method. high yields of trials for this management. All the points in
red, corresponding to low sowing doses, have result in
worse balances when comparing them with their
4 RYE NITROGEN BALANCE METHODOLOGY equivalent management with conventional seed dose
(blue points).
A rough nitrogen balance was made. This estimation
considers nitrogen supplied in base and top fertilizations 90%
80 Kg N ha-1
Top Fertilization
as the entrance of the system and total nitrogen content of 85% & 24 Kg ha-1
Seed Dose
% GHG Savings (Natural Gas as reference)
rye aerial biomass trials as exit of the system. The total 80% 80 Kg N ha-1
Top Fertilization
amount of nitrogen extracted and exported by the crop 75%
& 120 Kg ha-1
Seed Dose
harvest is calculated by multiplying the yield of each trial 70%
30 Kg N ha-1
Top Fertilization
& 24 Kg ha-1
(see Table II) by its respective biomass nitrogen content 65% Seed Dose
30 Kg N ha-1
(see Table III). As roots remain into the soil we assumed 60%
Top Fertilization
& 120 Kg ha-1
that all nitrogen from roots return to the soil. Therefore Seed Dose
0 Kg N ha-1
55%
we did not take into account any proportion of root Top Fertilization
& 24 Kg ha-1
50%
nitrogen content as extracted nitrogen. Seed Dose
0 Kg N ha-1
45% Top Fertilization
& 120 Kg ha-1
40% Seed Dose
3000 5000 7000 9000 11000 13000 15000
5 RESULTS AND DISCUSSION Yield (kg d.m. ha-1)
In the following sub-sections the final results of rye Figure 2: Relationship between greenhouse gas
optimization assessments are presented for GWP, fossil emissions savings of rye biomass electricity compared to
energy consumption and balance of nitrogen. Besides we natural gas and whole plant yield.
present the contribution of the phases considered in the
life cycle assessment of the systems to GWP and fossil 5.2 Rye biomass electricity energy assessment
energy consumption of the typical management practices The Figure 3 shows that electrical energy obtained is
scenario. between two and five times the fossil energy invested.
The differences between results for different fertilization
5.1 Rye biomass electricity global warming potential doses are lower for the fossil energy consumption than
The Figure 1 shows that for all the rye managements for GWP, because N2O emissions are irrelevant for
there is an inverse relationship between yield obtained energy assessments. We have again worse results for
and the GWP emissions. The results are contended in the lower sowing doses (Red points) compared to typical
interval that goes from 20 to 75 Mg CO2 eq. TJe-1. This sowing doses (Blue points).
means that every trial produce less GWP than the
generation of electricity from gas natural in Spain, that is
about 145 Mg CO2 eq.TJe-1 [18].

6. 5.4 5.4
80 Kg N ha-1 80 Kg N ha-1
Top Fertilization
NITROGEN DEFICIT NITROGEN SURPLUS
Top Fertilization
4.9 & 24 Kg ha-1 4.9 & 24 Kg ha-1
Seed Dose Seed Dose
4.4 80 Kg N ha-1 4.4 80 Kg N ha-1
Top Fertilization Top Fertilization
& 120 Kg ha-1
Energy output per fossil energy inputs
Energy output per fossil energy inputs
& 120 Kg ha-1
3.9 Seed Dose 3.9
Seed Dose
(TJ electricty TJ fosil energy-1)
(TJ electricty TJ fosil energy-1)
30 Kg N ha-1 30 Kg N ha-1
3.4 Top Fertilization 3.4 Top Fertilization
& 24 Kg ha-1 & 24 Kg ha-1
Seed Dose Seed Dose
2.9 30 Kg N ha-1 2.9
30 Kg N ha-1
Top Fertilization Top Fertilization
2.4 & 120 Kg ha-1 2.4 & 120 Kg ha-1
Seed Dose Seed Dose
0 Kg N ha-1
1.9 1.9 0 Kg N ha-1
Top Fertilization
Top Fertilization
& 24 Kg ha-1
& 24 Kg ha-1
1.4 Seed Dose 1.4
Seed Dose
0 Kg N ha-1
Top Fertilization 0 Kg N ha-1
0.9 0.9 Top Fertilization
& 120 Kg ha-1
& 120 Kg ha-1
Seed Dose
0.4 Seed Dose
0.4
3000 5000 7000 9000 11000 13000 15000 -80 -60 -40 -20 0 20 40 60
Yield (kg d.m. ha-1) Nitrogen Balance (kg N ha-1 year-1)
Figure 3: Relationship between electrical energy output Figure 5: Relationship between electrical energy output
per fossil energy inputs of rye biomass and whole plant per fossil energy inputs of rye biomass and the annual
yield. nitrogen balance of the soil.
5.3 Rye biomass electricity nitrogen balance 5.4 Relative contributions of the phases considered in the
The Figure 4 shows that there is a trade-off between assessment
emission savings and soil nitrogen deficit. This trade-off
is clear for both low and typical sowing doses (24 and The Figure 6 shows that for the typical management
120 kg ha-1). For typical seed doses and zero top practices fertilizers and nitrous oxide emissions represent
fertilization there is an annual loss of 50 kg N in soil about 75 % of total GWP generated. However the
nitrogen stocks with 85 % of savings. However with biomass power plant represent only 1.7% of GWP
typical sowing and fertilization doses the nitrogen according to our modeling.
balance is neutral and the savings are lower, about 70 %.
Seed and Pesticides production &
GWP; 1,7% transport
90%
80 Kg N ha-1 GWP; 2,6%
NITROGEN DEFICIT NITROGEN SURPLUS Top Fertilization
85% & 24 Kg ha-1 GWP; 5,8% Fertilizers production & transport
Seed Dose
GWP; 11,6%
80 Kg N ha-1
% GHG Savings (Natural Gas as reference)
80%
Top Fertilization
& 120 Kg ha-1 Nitrous Oxide emissions
75% Seed Dose
30 Kg N ha-1
70% Top Fertilization
& 24 Kg ha-1 GWP; 46,5%
Seed Dose Field Works (Machinery amortization
65%
30 Kg N ha-1 and Diesel consumption & combustion
Top Fertilization emissions)
60% & 120 Kg ha-1
Seed Dose Biomass transport to power plant
GWP; 31,8%
55% 0 Kg N ha-1
Top Fertilization
& 24 Kg ha-1
50%
Seed Dose Biomass Power Plant (Residue disposal
0 Kg N ha-1 and Natural Gas consumptions &
45% Top Fertilization
& 120 Kg ha-1 combustion emissions in maintenances)
40% Seed Dose
-80 -60 -40 -20 0 20 40 60
Nitrogen Balance (kg N ha-1 year-1)
Figure 6: Relative contribution of phases to Global
Warning Potential (GWP) for the average of the three
Figure 4: Relationship between greenhouse gas trials with typical seed doses and top fertilization doses as
emissions savings of rye biomass electricity compared to crop management practices.
natural gas and the annual nitrogen balance.
The Figure 7 shows that for fossil energy
The Figure 5 shows the same previous trade-off consumption seed and pesticides as well as field works
between nitrogen deficit and fossil energy consumption, have double their importance with respect to GWP
although correlation appears to be less strong for this impacts. This happens because emissions do not affect to
case. We find more red points generating nitrogen surplus fossil energy consumption.
because the crop did not take all the available nitrogen
due to the small amount of plants per hectare. FOSE, 4.1% Seed and Pesticides production &
transport
FOSE, 3.9%
Fertilizers production & transport
FOSE, 13.5%
Field Works (Machinery amortization
and Diesel consumption)
FOSE, 25.9% FOSE, 52.6%
Biomass transport to power plant
Biomass Power Plant (Residue disposal
and Natural Gas consumptions in
maintenances)
Figure 7: Relative contribution of phases to Fossil
Energy consumption (FOSE) for the average of the three
trials with typical seed doses and top fertilization doses as
management practices.

7. 5 CONCLUSIONS cropping system in southern Europe. Biomass
Bioenergy 2007;31:543–55.
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