Juan Gao, Key Laboratory of Soil and Pollution Remediation, Institute of Soil Science, Chinese Academy of Science, Nanjing, Jiangsu Province, China, Kurt D. Thelen, Michigan State University, East Lansing, MI and Xinmei Hao, College of Water Resources and Hydraulic Engineering, China Agricultural University, Beijing, China
Corn (Zea mays L.) and corn stover are currently considered the most abundant and readily accessible feedstock resources for renewable bioethanol. Whole-plant corn harvest could increase bioethanol yield compared to a conventional separated grain and stover harvest. However, there is limited research on the environmental effects of whole-plant harvest strategies, including non-renewable energy efficiency, greenhouse gas (GHG) emission intensity and soil organic carbon (SOC) changes. In this study, harvest methods together with bioprocessing steps were combined through life cycle analysis (LCA) models, and SOC changes of corn farming with different harvest methods were simulated by a Daycent ecosystem model. The LCA results showed that a whole-plant harvest strategy could increase energy efficiency 3.4 - 4.3 times and reduce GHG emissions by 38 ± 2 % relative to a traditional separated grain and stover harvest strategy. However, the analyses indicated whole-plant harvest could reduce SOC (66.9 ±22.9 gCO2,eq m-2) annually during 50-yr continuous corn farming at Branch, Ingham and Huron, and the conventional harvest system could sequestrate CO2 into SOC at Ingham, Huron and Menominee. The Daycent simulation also showed that a winter cover crop planted after immature cut whole-plant corn harvest could compensate for part of the SOC loss associated with a whole corn plant harvest.
