Impact of Various Biochars on Greenhouse Gas Production Potentials

Authors: Spokas, Kurt; Reicosky, Donald

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/2009
Publication Date: 8/9/2009
Citation: Spokas, K.A., Reicosky, D.C. 2009. Impact of Various Biochars on Greenhouse Gas Production Potentials [abstract]. Meeting Abstract. On-line proceedings and recording of presentations. http://cees.colorado.edu/biochar_environment.html.

Interpretive Summary:

Technical Abstract: A potential abatement strategy to increasing atmospheric levels of carbon dioxide (CO2) is to sequester atmospheric CO2 into a more stable form through the use of pyrolysis. The biomass feed stock generates energy and a more stable carbon form (biochar) that then can be returned to the soil sequestering atmospheric carbon into a slower cycling pool. Research is needed on the soil and environmental system impacts of biochar amendments before initiating large scale applications. We evaluated the impacts of 14 different biochars from different processes and feed stock materials (corn stover, peanut hulls, wood chips, and turkey manure plus wood chips) as well as an activated coconut charcoal on net CO2, methane (CH4) and nitrous oxide (N2O) production potentials through a 100 day laboratory incubation with a Minnesota agricultural soil (Waukegan silt loam) at field moisture capacity. The addition of biochars (0.5 g biochar to 5 g soil) resulted in higher CO2 respiration activity for 10 out of 14 biochars tested that varied from 116 to 290%, as a function of the feedstock type and production differences. A mixture of pine biochar + compost resulted in a 1266% increase in CO2 respiration largely due to the added compost C. Three biochars (two corn stover and one pine wood chips) had no significant impact on soil CO2 respiration, while a turkey manure plus wood chips biochar resulted in a 26% decrease in CO2 respiration. Given that biochars are recalcitrant with a half-life on the order of hundreds to thousands of years, a majority of the increased CO2 production was assumed to originate from the soil organic pools, oils sorbed to the surface of the biochar or CO2 physically trapped in pores rather than from the biochar decomposition itself. The most consistent behavior was the reduction in net CH4 oxidation. Eleven of the biochars decreased CH4 oxidation activity at ambient levels (1.9 ppm CH4) and the remaining 3 had insignificant decreases. Six of the biohcars caused the soil to be a net producer of CH4 during the incubations. None of the biochars resulted in the enhancement of ambient CH4 oxidation activity. All biochar additions significantly suppressed CH4 oxidation rates (25 to 100% reduction). For N2O, only 2 biochars stimulated production of N2O compared to the control soil. The largest production of N2O resulted from the biochar+compost mixture (40200% increase), while the turkey manure plus wood chips biochar resulted in a 495% increase related to the nitrogen content. All other biochars decreased N2O production, ranging from 20-100%. The majority of the biochars tested resulted in higher CO2 production (which presumably translates to higher losses of C from the soil organic pools), reduced methane oxidation activity and reduced formation of N2O in laboratory incubations. The magnitude of these impacts is both dependent on feedstock types and process parameters (temperature, heating rate, pressure, moisture, and the vapor phase residence time) during the biochar production.