Impact of bioenergy by-products on soil
Increased energy production from biomass could lead to higher levels of its by-products in soil. However, it is not yet clear how these by-products will affect microbial processes in soil, including the production of greenhouse gases. Particular attention therefore needs to be given to changes in the carbon balance of soil and changes in nitrous oxide (N2O) emissions from soil. The BESOS project was therefore established to investigate the impact of different by-products from bioenergy fuels on biogeochemical cycles. The initiative focused on residues from two forms of bioenergy: anaerobic digestion and pyrolysis. Anaerobic digestion breaks down organic material using microorganisms in the absence of oxygen and produces biogas and a solid by-product called digestate.Pyrolysis implies the thermal decomposition of biomass at high temperatures and generates bio-oil, a mixture of gas and a solid by-product named charcoal. Biochar is the name given to charcoal when it is added to soil. BESOS applied the material to 15 agricultural soils with different pHs and textures from different areas of Brazil, Spain and the United States. Researchers observed a consistent and significant decrease in N2O emissions following biochar application. The mineralisation of carbon and nitrogen in soil was studied both in the field and under laboratory conditions using nitrogen-15 and carbon-13 labelling isotopes. Scientists also measured levels of N2O. Results from these experiments were compared with the different properties of the bioenergy by-products. They showed that biochar helps in the last step in denitrification, whereby N2O is transformed to nitrogen gas. Biochar reduced N2O from soil on average by about 54 % Results from the BESOS project will provide a better understanding of the impacts of bioenergy by-products on carbon and nitrogen cycles. This may have a significant impact on life-cycle analysis calculations for different forms of bioenergy. In addition, the data can inform future policy decisions related to biochar as a soil additive and its effect on greenhouse gas emissions in agriculture.
Keywords
Bioenergy, bioenergy by-product, soil, biomass, renewable energy, microbial processes, greenhouse gases, carbon balance, nitrous oxide, bioenergy fuel, biogeochemical cycle, anaerobic digestion, pyrolysis, organic material, biochar
