Land-Use Change to Bioenergy Production in Europe: Implications for the Greenhouse Gas Balance and Soil Carbon. Don, A., Osborne, B., Hastings, A., Skiba, U., Carter, M. S., Drewer, J., Flessa, H., Freibauer, A., Hyvönen, N., Jones, M. B., Lanigan, G. J., Mander, Ü., Monti, A., Djomo, S. N., Valentine, J., Walter, K., Zegada-Lizarazu, W., & Zenone, T. GCB Bioenergy, 4(4):372–391, July, 2012.
doi  abstract   bibtex   
Bioenergy from crops is expected to make a considerable contribution to climate change mitigation. However, bioenergy is not necessarily carbon neutral because emissions of CO2, N2O and CH4 during crop production may reduce or completely counterbalance CO2 savings of the substituted fossil fuels. These greenhouse gases (GHGs) need to be included into the carbon footprint calculation of different bioenergy crops under a range of soil conditions and management practices. This review compiles existing knowledge on agronomic and environmental constraints and GHG balances of the major European bioenergy crops, although it focuses on dedicated perennial crops such as Miscanthus and short rotation coppice species. Such second-generation crops account for only 3\,% of the current European bioenergy production, but field data suggest they emit 40\,% to $>$99\,% less N2O than conventional annual crops. This is a result of lower fertilizer requirements as well as a higher N-use efficiency, due to effective N-recycling. Perennial energy crops have the potential to sequester additional carbon in soil biomass if established on former cropland (0.44 Mg soil C ha-1 yr-1 for poplar and willow and 0.66 Mg soil C ha-1 yr-1 for Miscanthus). However, there was no positive or even negative effects on the C balance if energy crops are established on former grassland. Increased bioenergy production may also result in direct and indirect land-use changes with potential high C losses when native vegetation is converted to annual crops. Although dedicated perennial energy crops have a high potential to improve the GHG balance of bioenergy production, several agronomic and economic constraints still have to be overcome. [Excerpt: Conclusions and critical knowledge gaps] [::] For the most common conventional energy crops such as maize and oilseed rape, no data on the production area are available for most European countries. Thus, data to evaluate the GHG footprint of bioenergy production and land-use change or effects on food prices and food and animal feedstock import is lacking. Data identifying where and when conventional and dedicated energy crops are, or have been, established (including the former land-use of these production areas) are required. [::] Land-use change for bioenergy production should be restricted to land that is or has been cultivated. Any conversion of native vegetation or perennial grasslands would cause C losses from soils and biomass that compromises the CO2 savings of bioenergy. The GHG balance of bioenergy feedstock is dominated by the SOC balance if land-use change from ecosystems with high SOC stocks is involved, such as conversion from grasslands, forest or peatlands. Perennial energy crops provide the potential for C sequestration for a transitional period if they are established on former croplands. [::] There are no enough data to provide GHG balances for different energy crops. However, it is unequivocal that the majority of current annual energy crops have a low GHG efficiency. The CO2 savings due to bioenergy production are compromised by GHG emissions during feedstock production. These need to be reduced by crop type selection, yield improvement and crop management. Perennial energy crops provide a large abatement potential for N2O emissions due to low N fertilization demand and higher N-use efficiency and may provide additional CO2 savings from SOC sequestration. [::] More field studies are required to evaluate the impact of perennial energy crops on GHG fluxes in comparison to conventional annual energy crops. The uncertainty of LCAs for bioenergy use can be reduced with better estimates of the field GHG balance. Only through long-term studies can the effects of inter annual climate variability be assessed. [::] Biomass yield is the key factor underpinning GHG efficiency and the economic viability of energy crops. Future production of dedicated energy crops depends on the contribution of improvements in yield and productivity due to appropriate selection, breeding and management practices. Dedicated energy crops should be improved for growth on marginal land with low fertility soils that are either water logged or subjected to water deficits. In addition, the N fertilizer use efficiency drives the GHG balance of bioenergy feedstock, as a certain fraction of N fertilizer is lost as N2O. The challenge for agricultural research is to optimize energy crop yields under the combined constraints of restricted or no fertilizer use and sub optimal soil and water conditions. [::] Given the limited area that is available for bioenergy production, the contribution of energy crops to climate change mitigation is likely to remain small (below 10\,% of global energy supply in 2050) (WBGU, 2008) and can only contribute to a larger assemblage of mitigation measures. However, perennial bioenergy production provides an array of advantages that should be considered additional to the GHG mitigation effect: increased rural area employment and agricultural income diversification, enhanced biodiversity, improved landscaping, reduced nutrient losses to the ground water and adjacent water bodies. Thus, there are enough reasons to promote the wider use of dedicated energy crops.
@article{donLanduseChangeBioenergy2012,
  title = {Land-Use Change to Bioenergy Production in {{Europe}}: Implications for the Greenhouse Gas Balance and Soil Carbon},
  author = {Don, Axel and Osborne, Bruce and Hastings, Astley and Skiba, Ute and Carter, Mette S. and Drewer, Julia and Flessa, Heinz and Freibauer, Annette and Hyv{\"o}nen, Niina and Jones, Mike B. and Lanigan, Gary J. and Mander, {\"U}lo and Monti, Andrea and Djomo, Sylvestre N. and Valentine, John and Walter, Katja and {Zegada-Lizarazu}, Walter and Zenone, Terenzio},
  year = {2012},
  month = jul,
  volume = {4},
  pages = {372--391},
  issn = {1757-1693},
  doi = {10.1111/j.1757-1707.2011.01116.x},
  abstract = {Bioenergy from crops is expected to make a considerable contribution to climate change mitigation. However, bioenergy is not necessarily carbon neutral because emissions of CO2, N2O and CH4 during crop production may reduce or completely counterbalance CO2 savings of the substituted fossil fuels. These greenhouse gases (GHGs) need to be included into the carbon footprint calculation of different bioenergy crops under a range of soil conditions and management practices. This review compiles existing knowledge on agronomic and environmental constraints and GHG balances of the major European bioenergy crops, although it focuses on dedicated perennial crops such as Miscanthus and short rotation coppice species. Such second-generation crops account for only 3\,\% of the current European bioenergy production, but field data suggest they emit 40\,\% to {$>$}99\,\% less N2O than conventional annual crops. This is a result of lower fertilizer requirements as well as a higher N-use efficiency, due to effective N-recycling. Perennial energy crops have the potential to sequester additional carbon in soil biomass if established on former cropland (0.44 Mg soil C ha-1 yr-1 for poplar and willow and 0.66 Mg soil C ha-1 yr-1 for Miscanthus). However, there was no positive or even negative effects on the C balance if energy crops are established on former grassland. Increased bioenergy production may also result in direct and indirect land-use changes with potential high C losses when native vegetation is converted to annual crops. Although dedicated perennial energy crops have a high potential to improve the GHG balance of bioenergy production, several agronomic and economic constraints still have to be overcome.

[Excerpt: Conclusions and critical knowledge gaps]

[::] For the most common conventional energy crops such as maize and oilseed rape, no data on the production area are available for most European countries. Thus, data to evaluate the GHG footprint of bioenergy production and land-use change or effects on food prices and food and animal feedstock import is lacking. Data identifying where and when conventional and dedicated energy crops are, or have been, established (including the former land-use of these production areas) are required.

[::] Land-use change for bioenergy production should be restricted to land that is or has been cultivated. Any conversion of native vegetation or perennial grasslands would cause C losses from soils and biomass that compromises the CO2 savings of bioenergy. The GHG balance of bioenergy feedstock is dominated by the SOC balance if land-use change from ecosystems with high SOC stocks is involved, such as conversion from grasslands, forest or peatlands. Perennial energy crops provide the potential for C sequestration for a transitional period if they are established on former croplands.

[::] There are no enough data to provide GHG balances for different energy crops. However, it is unequivocal that the majority of current annual energy crops have a low GHG efficiency. The CO2 savings due to bioenergy production are compromised by GHG emissions during feedstock production. These need to be reduced by crop type selection, yield improvement and crop management. Perennial energy crops provide a large abatement potential for N2O emissions due to low N fertilization demand and higher N-use efficiency and may provide additional CO2 savings from SOC sequestration.

[::] More field studies are required to evaluate the impact of perennial energy crops on GHG fluxes in comparison to conventional annual energy crops. The uncertainty of LCAs for bioenergy use can be reduced with better estimates of the field GHG balance. Only through long-term studies can the effects of inter annual climate variability be assessed.

[::] Biomass yield is the key factor underpinning GHG efficiency and the economic viability of energy crops. Future production of dedicated energy crops depends on the contribution of improvements in yield and productivity due to appropriate selection, breeding and management practices. Dedicated energy crops should be improved for growth on marginal land with low fertility soils that are either water logged or subjected to water deficits. In addition, the N fertilizer use efficiency drives the GHG balance of bioenergy feedstock, as a certain fraction of N fertilizer is lost as N2O. The challenge for agricultural research is to optimize energy crop yields under the combined constraints of restricted or no fertilizer use and sub optimal soil and water conditions.

[::] Given the limited area that is available for bioenergy production, the contribution of energy crops to climate change mitigation is likely to remain small (below 10\,\% of global energy supply in 2050) (WBGU, 2008) and can only contribute to a larger assemblage of mitigation measures. However, perennial bioenergy production provides an array of advantages that should be considered additional to the GHG mitigation effect: increased rural area employment and agricultural income diversification, enhanced biodiversity, improved landscaping, reduced nutrient losses to the ground water and adjacent water bodies. Thus, there are enough reasons to promote the wider use of dedicated energy crops.},
  journal = {GCB Bioenergy},
  keywords = {*imported-from-citeulike-INRMM,~INRMM-MiD:c-13878876,~to-add-doi-URL,agricultural-resources,bioeconomy,bioenergy,biomass,europe,forest-resources,ghg,land-use,soil-carbon,soil-resources},
  lccn = {INRMM-MiD:c-13878876},
  number = {4}
}
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