Biochar as a tool to reduce the agricultural greenhouse-gas burden-knowns, unknowns, and future research needs

Authors: KAMMANN, CLAUDIA - Hochschule Geisenheim University; IPPOLITO, JAMES - Colorado State University; HAGEMANN, NIKOLAS - University Of Tubingen; BORCHARD, NILS - Center For International Forestry Research; CAYUELA, MARIALUZ - Centro De Edafologia Y Biologia Aplicada Del Segura (CEBAS); ESTAVILLO, JOSE - University Of Basque Country; FUERTES-MENDIZABAL, TERESA - University Of Basque Country; JEFFERY, SIMON - Harper Adams University College; KERN, JUERGEN - Potsdam Institute; Novak, Jeffrey; RASSE, DANIEL - Norwegian Institute Of Bioeconomy Research(NIBIO); SAARNIO, SANNA - University Of Eastern Finland; SCHMIDT, HANS-PETER - Ithaka Institute For Carbon Strategies; Spokas, Kurt; WRAGE-MONNIG, NICOLE - University Of Rostock

Submitted to: Journal of Environmental Engineering and Landscape Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/11/2017
Publication Date: 6/16/2017
Citation: Kammann, C., Ippolito, J., Hagemann, N., Borchard, N., Cayuela, M., Estavillo, J., Fuertes-Mendizabal, T., Jeffery, S., Kern, J., Novak, J.M., Rasse, D., Saarnio, S., Schmidt, H., Spokas, K.A., Wrage-Monnig, N. 2017. Biochar as a tool to reduce the agricultural greenhouse-gas burden-knowns, unknowns, and future research needs. Journal of Environmental Engineering and Landscape Management. 25(02):114-139.

Interpretive Summary: After a decade of intense biochar research, it has become clear that biochar as a soil amendment can reduce greenhouse gas (GHG) emissions such as nitrous oxide (N2O) and methane (CH4) emissions. However, great uncertainty still exists with respect to biochar use and its GHG reducing effect as associated with different biochars, soil types/conditions, and in animal production. This is due to the lack of understanding of mechanisms for how biochar influences soil conditions like pH, nitrogen (N) availability to soil microbial communities, influence on microbial denitrifier gene expression, or by N capture in biochar particles. It is likely that these mechanisms work in concert under field conditions. Other potential biochar characteristics that can influence CH4 emission reductions are the stimulation of soil methanotrophic bacterial communities as well as the electron shuttling and redox activity of biochars in ruminant guts. Biochar use in animal production offers a potential route to reduce GHG emissions, but research on it is lacking. Additionally, biochars use in composting as a method to reduce GHG production is understudied. We conclude that the use of biochar in agriculture systems provides a unique opportunity to reduce N2O and CO2 emissions, yet future research is required to maximize its benefits under different conditions.

Technical Abstract: Agriculture and land use change has significantly increased atmospheric emissions of greenhouse gasses (GHG) such as nitrous oxide (N2O) and methane (CH4). Since human nutritional and bioenergy needs continue to increase, at a shrinking global land area for production, novel land management strategies are required that reduce the GHG footprint per unit of yield. Here we review the potential of biochar to reduce N2O and CH4 emissions from agricultural practices including potential mechanisms behind observed effects. Furthermore, we investigate alternative uses of biochar in agricultural land management that may significantly reduce the GHG-emissions-per-unit-of-product footprint, such as (i) pyrolysis of manures as hygienic alternative to direct soil application, (ii) using biochar as fertilizer carrier matrix for underfoot fertilization, biochar use (iii) as composting additive or (iv) as feed additive in animal husbandry or for manure treatment. We conclude that the largest future research needs lay in conducting lifecycle GHG assessments when using biochar as an on-farm management tool for nutrient-rich biomass waste streams.