For comparison, the key performance parameters of TIM and RCG cropping systems are presented in Table 7. TIM was a climate-smart cropping system when compared to RCG during the three-year period since GWPtotal for TIM was about 50% of that for RCG. The main reason for that was that RCG was an annual source of CO2 (positive NEE) during the first year (2009) whereas TIM was already a sink.
In both cropping systems, common agricultural practices were applied which contributed to the annual NEE during the establishment year. RCG was sown late in the season and the RCG growth during the first season was not only slow but smaller when compared with later years. TIM system was established using barley as a cover crop, in this case barley, which was growing strongly during the first season, thus contributing to the CO2 uptake. Therefore, if only years 2010 and 2011 were considered, GWPtotal of the cropping systems would be similar. A higher N fertilizer rate was used on TIM cropping system than on RCG. In spite of that, the emission factor (%) was lower and N use efficiency (NUE) was higher with the TIM system. TIM thus efficiently used the applied N. In addition, the three-year averaged N2O emission was slightly lower on TIM than on RCG. Due to the high yields of TIM, the net CO2-eq balance was high when compared to RCG.
Additionally, both cropping systems showed higher CH4 uptake than other perennial grasslands in Finland.
In spite of the benefits of TIM discussed above, the LCA showed that the bioenergy production based on biogas from RCG biomass would be climate-smart option when compared with TIM biomass if the spring harvest method on RCG was applied. Because more grassland area of RCG is needed to produce the same MWh of energy than that of TIM, the CO2 uptake on RCG is higher and controls the overall gas balance. However, it is unclear what is the real CH4 production potential of the spring harvested RCG.
Coal is a dominant fossil fuel in energy production. Here, the energy production based on TIM and RCG biomasses was climate-smart when compared with coal.
When compared with coal, 70 to 80% of the emissions were avoided with the use of these biomasses. Therefore, perennial biomasses still give a possibility to reduce greenhouse emissions from energy production.
139 Table 7 Key performance variables determined for mixture of timothy and meadow fescue (TIM) and reed canary grass (RCG) cropping systems. Data are three-year averages with the exception of data marked with * which are mean values of two years.
Variable TIM RCG Unit
NEE -10000 -5300 kg CO2 ha-1
CH4 -1.4 -1.4 kg CH4 ha-1
N2O 6.0 6.7 kg N2O ha-1
GWPtotal -8600 -3500 kg CO2-eq ha-1
EF 4.0 6.2 %
NUE 80 63 kg DW per kg N
BALANCE 10 000 4000 kg CO2-eq ha-1
LCA, biogas 92 65* kg CO2-eq per MWh of energy
NEE = net ecosystem CO2 exchange, CH4 = methane, N2O = nitrous oxide, GWPtotal = overall GHG balance, BALANCE = net CO2-eq balance, EF = N2O emission factor, NUE = nitrogen use efficiency, LCA = life cycle assessment.
138
ha-1. Because of the diurnal variation in N2O exchange, measurements carried out only during daytime, can overestimate or underestimate daily average fluxes. Here the emissions were overestimated during post-application period and underestimated period of high night-time fluxes and in overall the annual emission could have been underestimated by 0.15 kg N2O ha-1. In total, the annual N2O emissions from RCG in 2011 could increase by 22%, i.e. from 3.0 to 3.6 kg N2O ha-1 yr-1.
6.4 SUMMARY OF THE ATMOSPHERIC IMPACT OF CULTIVATION AND BIOENERGY PRODUCTION
For comparison, the key performance parameters of TIM and RCG cropping systems are presented in Table 7. TIM was a climate-smart cropping system when compared to RCG during the three-year period since GWPtotal for TIM was about 50% of that for RCG. The main reason for that was that RCG was an annual source of CO2 (positive NEE) during the first year (2009) whereas TIM was already a sink.
In both cropping systems, common agricultural practices were applied which contributed to the annual NEE during the establishment year. RCG was sown late in the season and the RCG growth during the first season was not only slow but smaller when compared with later years. TIM system was established using barley as a cover crop, in this case barley, which was growing strongly during the first season, thus contributing to the CO2 uptake. Therefore, if only years 2010 and 2011 were considered, GWPtotal of the cropping systems would be similar. A higher N fertilizer rate was used on TIM cropping system than on RCG. In spite of that, the emission factor (%) was lower and N use efficiency (NUE) was higher with the TIM system. TIM thus efficiently used the applied N. In addition, the three-year averaged N2O emission was slightly lower on TIM than on RCG. Due to the high yields of TIM, the net CO2-eq balance was high when compared to RCG.
Additionally, both cropping systems showed higher CH4 uptake than other perennial grasslands in Finland.
In spite of the benefits of TIM discussed above, the LCA showed that the bioenergy production based on biogas from RCG biomass would be climate-smart option when compared with TIM biomass if the spring harvest method on RCG was applied. Because more grassland area of RCG is needed to produce the same MWh of energy than that of TIM, the CO2 uptake on RCG is higher and controls the overall gas balance. However, it is unclear what is the real CH4 production potential of the spring harvested RCG.
Coal is a dominant fossil fuel in energy production. Here, the energy production based on TIM and RCG biomasses was climate-smart when compared with coal.
When compared with coal, 70 to 80% of the emissions were avoided with the use of these biomasses. Therefore, perennial biomasses still give a possibility to reduce greenhouse emissions from energy production.
139 Table 7 Key performance variables determined for mixture of timothy and meadow fescue (TIM) and reed canary grass (RCG) cropping systems. Data are three-year averages with the exception of data marked with * which are mean values of two years.
Variable TIM RCG Unit
NEE -10000 -5300 kg CO2 ha-1
CH4 -1.4 -1.4 kg CH4 ha-1
N2O 6.0 6.7 kg N2O ha-1
GWPtotal -8600 -3500 kg CO2-eq ha-1
EF 4.0 6.2 %
NUE 80 63 kg DW per kg N
BALANCE 10 000 4000 kg CO2-eq ha-1
LCA, biogas 92 65* kg CO2-eq per MWh of energy
NEE = net ecosystem CO2 exchange, CH4 = methane, N2O = nitrous oxide, GWPtotal = overall GHG balance, BALANCE = net CO2-eq balance, EF = N2O emission factor, NUE = nitrogen use efficiency, LCA = life cycle assessment.
140
7 CONCLUSIONS
In this study, the timothy and meadow fescue mixture (TIM) and reed canary grass (RCG) were cultivated on a mineral soil under boreal climate from 2009 to 2011.
Fresh biomass from TIM cropping system was harvested once in 2009 and twice in 2010 and 2011. RCG was cultivated for biomass combustion and therefore, delayed spring harvest method was used. The main conclusions based on the three-year studies of the TIM and RCG cropping systems and literature data on annual and perennial cropping systems in northern Europe are as follows:
Radiation, temperature and plants controlled net exchange of CO2.
Climatic factors during the growing season had minor impact on the CH4 and N2O fluxes. However, the winter period contributed significantly to the annual N2O emissions.
Fertilizer N use efficiency of TIM was higher than that of RCG.
To increase the accuracy of estimations of annual N2O balance of agricultural soils, continuous measurements of N2O exchange are recommended due to the episodic and erratic nature of N2O emissions and to catch the diurnal patterns in the N2O exchange.
GHG emissions of the management have considerable role on the overall atmospheric of the biomass production. Here, these emissions were three times higher for TIM than for RCG.
Cultivation of the TIM system was more climate-smart than the RCG system in a three-year period but the climatic effect would be more similar if full rotation period of RCG is considered.
Energy based on RCG biomass was a climate-smart choice than that on TIM biomass.
Atmospheric impact of energy based on RCG biomass cultivated on mineral soil was not dependent on the climatic conditions like on organic soil.
Compared to the traditional energy source such as coal, the energy production from perennial biomass (TIM, RCG) was more climate-smart.
141
REFERENCES
Alm J, Talanov A, Saarnio S, Silvola J, Ikkonen E, Aaltonen H, Nykänen H &
Martikainen PJ (1997) Reconstruction of the carbon balance for microsites in a boreal oligotrophic pine fen, Finland. Oecologia, 110, 423-431.
Arny AC, Hansen MC, Hodgson RE & Nesom GH (1929) Reed canary grass.
Bulletin 252, pp. 19, Minnesota Agricultural Experiment Station.
Baldocchi D (2003) Assessing the eddy covariance technique for evaluating carbon dioxide exchange rates of ecosystems: past, present and future. Global Change Biology, 9, 479-492.
Beauchemin KA, Janzen HH, Little SM, McAllister TA & McGinn SM (2010) Life cycle assessment of greenhouse gas emissions from beef production in western Canada: A case study. Agricultural Systems, 103, 371-379.
Bernes G, Hetta M & Martinsson K (2008) Effects of harvest date of timothy (Phleum pratense) on its nutritive value, and on the voluntary silage intake and liveweight gain of lambs. Grass and Forage Science, 63, 212-220.
Bouwman AF, Boumans LJM & Batjes NH (2002) Emissions of N2O and NO from fertilized fields: Summary of available measurement data. Global Biogeochemical Cycles, 16, 1058.
Bruckner T, Bashmakov IA, Mulugetta Y et al. (2014) Energy Systems. In: Climate Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (eds Edenhofer O, Pichs-Madruga R, Sokona Y et al.), pp. 511-597. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
Burvall J (1997) Influence of harvest time and soil type on fuel quality in reed canary grass (Phalaris arundinacea L). Biomass & Bioenergy, 12, 149-154.
Caffrey KR & Veal MW (2013) Conducting an Agricultural Life Cycle Assessment:
Challenges and Perspectives. Scientific World Journal, 472431.
Casler M & Kallenbach R (2007) Cool-season grasses for humid areas. In: Forages, Volume 2: The Science of Grassland Agriculture (eds Barnes RF, Nelson CJ, Moore KJ & Collins M), pp. 211-220. Blackwell Publishing, USA.
Cherubini F & Strømman AH (2011) Life cycle assessment of bioenergy systems:
State of the art and future challenges. Bioresource technology, 102, 437-451.
Ciais P, Sabine C, Bala G et al. (2013) Carbon and Other Biogeochemical Cycles. In:
Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel of Climate Change (eds Stocker TF, Qin D, Plattner GK et al.), pp. 465-570. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
Collins M, Knutti R, Arblaster J et al. (2013) Long-term Climate Change: Projections, Commitments and Irreversibility. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I on the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (eds Stocker TF, Qin DM, Plattner
140
7 CONCLUSIONS
In this study, the timothy and meadow fescue mixture (TIM) and reed canary grass (RCG) were cultivated on a mineral soil under boreal climate from 2009 to 2011.
Fresh biomass from TIM cropping system was harvested once in 2009 and twice in 2010 and 2011. RCG was cultivated for biomass combustion and therefore, delayed spring harvest method was used. The main conclusions based on the three-year studies of the TIM and RCG cropping systems and literature data on annual and perennial cropping systems in northern Europe are as follows:
Radiation, temperature and plants controlled net exchange of CO2.
Climatic factors during the growing season had minor impact on the CH4 and N2O fluxes. However, the winter period contributed significantly to the annual N2O emissions.
Fertilizer N use efficiency of TIM was higher than that of RCG.
To increase the accuracy of estimations of annual N2O balance of agricultural soils, continuous measurements of N2O exchange are recommended due to the episodic and erratic nature of N2O emissions and to catch the diurnal patterns in the N2O exchange.
GHG emissions of the management have considerable role on the overall atmospheric of the biomass production. Here, these emissions were three times higher for TIM than for RCG.
Cultivation of the TIM system was more climate-smart than the RCG system in a three-year period but the climatic effect would be more similar if full rotation period of RCG is considered.
Energy based on RCG biomass was a climate-smart choice than that on TIM biomass.
Atmospheric impact of energy based on RCG biomass cultivated on mineral soil was not dependent on the climatic conditions like on organic soil.
Compared to the traditional energy source such as coal, the energy production from perennial biomass (TIM, RCG) was more climate-smart.
141
REFERENCES
Alm J, Talanov A, Saarnio S, Silvola J, Ikkonen E, Aaltonen H, Nykänen H &
Martikainen PJ (1997) Reconstruction of the carbon balance for microsites in a boreal oligotrophic pine fen, Finland. Oecologia, 110, 423-431.
Arny AC, Hansen MC, Hodgson RE & Nesom GH (1929) Reed canary grass.
Bulletin 252, pp. 19, Minnesota Agricultural Experiment Station.
Baldocchi D (2003) Assessing the eddy covariance technique for evaluating carbon dioxide exchange rates of ecosystems: past, present and future. Global Change Biology, 9, 479-492.
Beauchemin KA, Janzen HH, Little SM, McAllister TA & McGinn SM (2010) Life cycle assessment of greenhouse gas emissions from beef production in western Canada: A case study. Agricultural Systems, 103, 371-379.
Bernes G, Hetta M & Martinsson K (2008) Effects of harvest date of timothy (Phleum pratense) on its nutritive value, and on the voluntary silage intake and liveweight gain of lambs. Grass and Forage Science, 63, 212-220.
Bouwman AF, Boumans LJM & Batjes NH (2002) Emissions of N2O and NO from fertilized fields: Summary of available measurement data. Global Biogeochemical Cycles, 16, 1058.
Bruckner T, Bashmakov IA, Mulugetta Y et al. (2014) Energy Systems. In: Climate Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (eds Edenhofer O, Pichs-Madruga R, Sokona Y et al.), pp. 511-597. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
Burvall J (1997) Influence of harvest time and soil type on fuel quality in reed canary grass (Phalaris arundinacea L). Biomass & Bioenergy, 12, 149-154.
Caffrey KR & Veal MW (2013) Conducting an Agricultural Life Cycle Assessment:
Challenges and Perspectives. Scientific World Journal, 472431.
Casler M & Kallenbach R (2007) Cool-season grasses for humid areas. In: Forages, Volume 2: The Science of Grassland Agriculture (eds Barnes RF, Nelson CJ, Moore KJ & Collins M), pp. 211-220. Blackwell Publishing, USA.
Cherubini F & Strømman AH (2011) Life cycle assessment of bioenergy systems:
State of the art and future challenges. Bioresource technology, 102, 437-451.
Ciais P, Sabine C, Bala G et al. (2013) Carbon and Other Biogeochemical Cycles. In:
Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel of Climate Change (eds Stocker TF, Qin D, Plattner GK et al.), pp. 465-570. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
Collins M, Knutti R, Arblaster J et al. (2013) Long-term Climate Change: Projections, Commitments and Irreversibility. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I on the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (eds Stocker TF, Qin DM, Plattner
142
GK et al.), pp. 1029-1136. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
Creutzig F, Ravindranath NH, Berndes G, Bolwig S, Bright R, Cherubini F, Chum H, Corbera E, Delucchi M, Faaij A, Fargione J, Haberl H, Heath G, Lucon O, Plevin R, Popp A, Robledo-Abad C, Rose S, Smith P, Stromman A, Suh S &
Masera O (2015) Bioenergy and climate change mitigation: an assessment.
Global Change Biology Bioenergy, 7, 916-944.
Crutzen PJ, Mosier AR, Smith KA & Winiwarter W (2008) N2O release from agro-biofuel production negates global warming reduction by replacing fossil fuels.
Atmospheric Chemistry and Physics, 8, 389-395.
Dias GM, Ayer NW, Kariyapperuma K, Thevathasan N, Gordon A, Sidders D &
Johannesson GH (2017) Life cycle assessment of thermal energy production from short-rotation willow biomass in Southern Ontario, Canada. Applied Energy, 204, 343-352.
Dohleman FG & Long SP (2009) More Productive Than Maize in the Midwest: How Does Miscanthus Do It? Plant Physiology, 150, 2104-2115.
Fjellheim S, Rognli OA, Fosnes K & Brochmann C (2006) Phylogeographical history of the widespread meadow fescue (Festuca pratensis Huds.) inferred from chloroplast DNA sequences. Journal of Biogeography, 33, 1470-1478.
Glover JD, Culman SW, DuPont ST, Broussard W, Young L, Mangan ME, Mai JG, Crews TE, DeHaan LR, Buckley DH, Ferris H, Turner RE, Reynolds HL &
Wyse DL (2010) Harvested perennial grasslands provide ecological benchmarks for agricultural sustainability. Agriculture Ecosystems &
Environment, 137, 3-12.
Gong J, Shurpali NJ, Kellomäki S, Wang K, Zhang C, Salam MMA & Martikainen PJ (2013) High sensitivity of peat moisture content to seasonal climate in a cutaway peatland cultivated with a perennial crop (Phalaris arundinaceae, L.):
A modeling study. Agricultural and Forest Meteorology, 180, 225-235.
Haas G, Wetterich F & Geier U (2000) Life Cycle Assessment Framework in Agriculture on the Farm Level. International Journal of Life Cycle Assessment, 5, 345-348.
Hakala K, Nikunen H, Sinkko T & Niemeläinen O (2012) Yields and greenhouse gas emissions of cultivation of red clover-grass leys as assessed by LCA when fertilised with organic or mineral fertilisers. Biomass & Bioenergy, 46, 111-124.
Hämet-Ahti L, Suominen J, Ulvinen T & Uotila P (1998) Retkeilykasvio (in finnish), pp.656. Luonnontieteellinen kasvimuseo, Kasvimuseo, Helsinki.
Hénault C, Grossel A, Mary B, Roussel M & Léonard J (2012) Nitrous Oxide Emission by Agricultural Soils: A Review of Spatial and Temporal Variability for Mitigation. Pedosphere, 22, 426-433.
IUSS Working Group WRB (2007) World Reference Base for Soil Resources 2006, first update 2007. World Soil Resources Reports No.103, pp. 128, FAO, Rome.
143 Järveoja J, Laht J, Maddison M, Soosaar K, Ostonen I & Mander Ü (2013) Mitigation of greenhouse gas emissions from an abandoned Baltic peat extraction area by growing reed canary grass: life-cycle assessment. Regional Environmental Change, 13, 781-795.
Kätterer T & Andrén O (1999) Growth dynamics of reed canarygrass (Phalaris arundinacea L.) and its allocation of biomass and nitrogen below ground in a field receiving daily irrigation and fertilisation. Nutrient Cycling in Agroecosystems, 54, 21-29.
Kirkinen J, Minkkinen K, Penttilä T, Kojola S, Sievänen R, Alm J, Saarnio S, Laine J
& Savolainen I (2007) Greenhouse impact due to different peat fuel utilisation chains in Finland — a life-cycle approach. Boreal Environment Research, 12, 211-223.
Klebesadel LJ & Dofing SM (1991) Reed canarygrass in Alaska: Influence of latitude-of-adaption on winter survival and forage productivity and observations on seed production. Bulletin 84, pp. 26, Agricultural and Forestry Experiment station, School of Agriculture and Land Resource Management.
Koponen HT, Flöjt L & Martikainen PJ (2004) Nitrous oxide emissions from agricultural soils at low temperatures: a laboratory microcosm study. Soil Biology & Biochemistry, 36, 757-766.
Lakaniemi A, Nevatalo LM, Kaksonen AH & Puhakka JA (2010) Mine wastewater treatment using Phalaris arundinacea plant material hydrolyzate as substrate for sulfate-reducing bioreactor. Bioresource technology, 101, 3931-3939.
Lehtomäki A, Paavola T, Luostarinen S & Rintala J (2007) Biokaasusta energiaa maatalouteen - Raaka-aineet, teknologiat ja lopputuotteet (in finnish).
Research reports in biological and environmental sciences 85, pp. 70, University of Jyväskylä.
Lehtomäki A, Viinikainen TA & Rintala JA (2008) Screening boreal energy crops and crop residues for methane biofuel production. Biomass and Bioenergy, 32, 541-550.
Lewandowski I, Scurlock J, Lindvall E & Christou M (2003) The development and current status of perennial rhizomatous grasses as energy crops in the US and Europe. Biomass & Bioenergy, 25, 335-361.
Lind SE, Shurpali NJ, Peltola O, Mammarella I, Hyvönen N, Maljanen M, Räty M, Virkajärvi P & Martikainen PJ (2016) Carbon dioxide exchange of a perennial bioenergy crop cultivation on a mineral soil. Biogeosciences, 13, 1255-1268.
Mäkinen T, Soimakallio S, Paappanen T, Pahkala K & Mikkola H (2006) Greenhouse gas balances and new business opportunities for biomass-based transportation fuels and agrobiomass in Finland (in finnish). Research Notes 2357, pp. 134, Technical Research center of Finland.
Maljanen M, Virkajärvi P, Hytönen J, Öquist M, Sparrman T & Martikainen PJ (2009) Nitrous oxide production in boreal soils with variable organic matter
142
GK et al.), pp. 1029-1136. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
Creutzig F, Ravindranath NH, Berndes G, Bolwig S, Bright R, Cherubini F, Chum H, Corbera E, Delucchi M, Faaij A, Fargione J, Haberl H, Heath G, Lucon O, Plevin R, Popp A, Robledo-Abad C, Rose S, Smith P, Stromman A, Suh S &
Creutzig F, Ravindranath NH, Berndes G, Bolwig S, Bright R, Cherubini F, Chum H, Corbera E, Delucchi M, Faaij A, Fargione J, Haberl H, Heath G, Lucon O, Plevin R, Popp A, Robledo-Abad C, Rose S, Smith P, Stromman A, Suh S &