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GCB Bioenergy

Cover image for Vol. 9 Issue 1

Edited By: Steve Long

Impact Factor: 6.151

ISI Journal Citation Reports © Ranking: 2015: 1/83 (Agronomy); 9/88 (Energy & Fuels)

Online ISSN: 1757-1707

Associated Title(s): Global Change Biology

Impacts of Miscanthus Production on Soil Carbon

To determine if an energy source is economically and environmentally viable, it is important to determine where the crops might be grown, what levels of productivity can be achieved, and the net effect on Greenhouse Gas (GHG) emissions. One benefit of bioenergy is that carbon from CO2, the most abundant GHG, is not only taken up through photosynthesis, but can also be stored in the soil as soil organic carbon (SOC), thus reducing atmospheric C long-term. Mishra and coauthors modeled the potential yield and change in SOC stocks due to Miscanthus adoption, and identified cropland where Miscanthus growth could be sustained in the US. Biomass yield was predicted using temperature and rainfall data and growing season length. The predicted biomass productivity values were then validated with the observed yields of Miscanthus at seven sites in Illinois. Another model predicted SOC based on a fraction of the previously estimated biomass yield. Croplands that could sustain Miscanthus cultivation without supplemental irrigation were identified using GIS-based spatial analysis based on water demand and a minimum threshold for economically viable production rates. The productivity values for continental United States croplands ranged from 1 to 23 Mg ha-1 yr-1. Based on this yield and using Miscanthus as feedstock, meeting the targets of the US Energy Independence and Security Act of 2007 would require 19 million ha of cropland. This represents about 16% less than is currently dedicated to US corn-based ethanol production. Cultivating Miscanthus would result in a soil organic carbon (SOC) sequestration at the rate of 0.16–0.82 Mg C ha-1 yr-1 across the croplands. This increase is likely due to four Miscanthus growth and management practices factors that differ compared to traditional annual crops: 1) deep roots place biomass deeper in the soil 2) increased input of organic matter due to increased biomass carbon, and 3) the cessation of tillage and 4) reduced organic matter decomposition due to lack of nitrogen. The authors identified 81 million hectares of cropland that could sustain economically viable production of Miscanthus without supplemental irrigation and assuming an average production of 13 mg ha -1 yr -1. Of the 81 million hectares, supplemental irrigation of 67 million ha would enhance average yield while 14 million hectares would reach optimal yield without irrigation.

Mishra, U., Torn, M. S. and Fingerman, K. (2012), Miscanthus biomass productivity within US croplands and its potential impact on soil organic carbon. GCB Bioenergy. doi: 10.1111/j.1757-1707.2012.01201.x

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