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 P.2, Santos A. M.1, del Val M. A.2, Pérez P.2, González-Arechavala Y.1 , and Carrasco J. E.2

(1) Instituto de Investigación Tecnológica (IIT) - Escuela de Ingenieros de ICAI - Universidad Pontificia de Comillas Alberto Aguilera 23, 28015 Madrid (Spain) Phone: +34 915422800, Fax: +34 915423176 (2) Centro de Desarrollo de Energías Renovables-CIEMAT (CEDER-CIEMAT). Autovía de Navarra A15, S56 - 42290 Lubia, Soria (Spain), Phone:+34 975281013, Fax: +34 975281051

*Corresponding author: carlos.martin@iit.upcomillas.es

Acknowledgements: The authors wish to thank to Dr. Ruth Barro for her collaboration on biomass laboratory analysis. This work has been developed in the framework of the Spanish National and Strategic Project `On Cultivos’ co-funded by the Spanish Ministry of Economy and Competitiveness and the European Funds for Regional Development under the dossier PSE-120000-2009-15.

CONCLUSIONS 1. Biomass square bales from rye grown in semiarid regions in Spain may be used in power biomass plants for electricity production and become a real alternative for the replacement of

electricity from natural gas as non renewable fossil reference. 2. Typical rye top fertilization doses of about 80 kg N ha-1 (NAC 27 %) appear to be sustainable for soil nitrogen stocks and can achieve 70 % of GHG savings when comparing to electricity

from natural gas. 3. Although reduced and zero top fertilization doses (30 & 0 kg N ha-1) produce considerable deficit in soil nitrogen stocks, they can achieve greater GHG savings (75-85 %). Due to this fact,

if we want to obtain higher savings, we need to combine the use of reduced fertilization doses with some soil nitrogen improvement management practices as rotation with legumes, fallow management and no-tillage farming.

4. Other optimization in rye might be achieved through: a) using less emitting fertilizers (e.g. ammonia sulphate) instead of typical nitrogen products used for most farmers in our study region (like NAC 27% and UREA); and b) splitting nitrogen fertilizer in two application in order to increase nitrogen application use efficiency.

5. The use of lower sowing doses (24 kg ha-1) instead of typical sowing doses (120 kg ha-1) have produced worse results for both GWP and fossil energy consumption.

OBJECTIVE The aim of this study is to compare the effects caused by the use of different crop management practices for rye growing in the assessment of energy balances and GHG

emissions to produce electricity from biomass. 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). Three trials were established per management scenario of rye for electricity production and results were

compared to electricity from natural gas. Then a nitrogen balance was made to assess the sustainability of lower nitrogen top fertilization doses for soil nitrogen stocks.

RESULTS AND CONCLUSIONS

MATERIALS AND METHODS

Figure 1: Relationship between greenhouse gas emissions savings of rye biomass electricity compared to natural gas and whole plant yield.

Figure 2: Relationship between greenhouse gas emissions savings of rye biomass electricity compared to natural gas and the annual nitrogen balance.

Figure 4: Relationship between electrical energy output per fossil energy inputs of rye biomass and whole plant yield.

Figure 5: Relationship between electrical energy output per fossil energy inputs of rye biomass and the annual nitrogen balance of the soil.

Figure 3: Relative contribution of phases to Global Warning Potential (GWP) for

the average of the three trials with typical seed and top fertilization doses

as crop management practices. The total emissions of the scenario are 39.8 Mg

CO2 eq. per TJ of electrical energy.

Figure 6: Relative contribution of phases to Fossil Energy Consumption (FOSE) for

the average of the three trials with typical seed and top fertilization doses as crop

management practices. The total amount of fossil energy consumed in the scenario

is 0.265 TJ per TJ of electrical energy.

NITROGEN BALANCE RESULTS

TOTAL NITROGEN EXPORTED IN RYE AERIAL BIOMASS

TOTAL NITROGEN PROVIDED BY FERTILIZERS

Field works and raw materials consumed for rye trials (0.04-0.05 ha)

Rye aerial biomass productivity and characterization of trials established in the Spanish province of Soria

% N BIOMASS PRODUCTIVITY

BASE FERTILIZER

TOP FERTILIZER

Operation

Tractor Implement Inputs Weight Power Type Weight Operating

rate Fuel

consumption

(kg) (kWh) (kg) (h ha-1) (L ha-1) Primary tillage 5470 103 Moldboard

plow 1390 1 20

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

Sowing 5470 103 Seeder 830 0.60 8 Hybrid rye seeds (kg ha-1): Typical (120), Low (24).

Herbicide treatment 3914 66 Boom

sprayer 230 0.50 4 MCPA 0.332 kg ha-1

Dicamba 0.125 kg ha-1 2 ,4-D 0.370 kg ha-1

Top fertilization 3914 66 Spreader 110 0.20 4

Calcium ammonium nitrate 27% kg ha-1: Typical (300), Low (100), Zero (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

Crop Management Seed Dose

(kg ha-1)

Top Fertilizer Dose

(kg N ha-1)

Trial productivity (odt ha-1) C

(%) N

(%) NHVcp,0

(MJ kg-1,db) NHVcp,12

(MJ kg-1,wb) 1st 2nd 3rd Typical Sowing Dose

Zero Top Fertilization 120 0 9.001 10.142 7.092 44.8 0.84 16.70 14.40

Typical Sowing Dose Low Top Fertilization 120 30 10.792 10.442 8.182 45.1 0.86 16.76 14.46

Typical Sowing Dose Typical Top Fertilization 120 80 13.200 11.815 10.548 45.4 0.87 16.90 14.58

Low Sowing Dose Zero Top Fertilization 24 0 7.758 6.992 4.773 45.10 1.00 17.11 14.76

Low Sowing Dose Low Top Fertilization 24 30 7.860 6.447 4.403 45.40 1.03 17.17 14.81

Low Sowing Dose Typical Top Fertilization 24 80 9.045 8.099 6.087 45.7 1.04 17.31 14.94

LIFE CYCLE IMPACT & ENERGY ASSESSMENT

Global Warming Potential IPPC 2007 100 year

Fossil Energy Consumption Cumulative Energy Demand

FERTILIZERS TRANSPORT CONSUMP.

PESTICIDES TRANSPORT CONSUMP.

LIFE CYCLE INVENTORY ANALYSIS

SEED TRANSPORT CONSUMP.

FIELD WORKS

DIESEL EMISSIONS CONSUMP.

MACHINERY AMORTIZATION

N2O EMISSIONS (RSB METHODOLOGY) N (Fertilizers + Residues) NH3 NO3-

BIOMASS

TRANSPORT CONSUMPTION

BIOMASS POWER PLANT OPERATION

NATURAL GAS(MAINTENANCE)

EMISSIONS CONSUMP. ASH & SLAG

DISPOSAL

BIO ELECTRICITY

1 2

1

2

3

3

3