Comparing first- and second-generation bioethanol by-products from sugarcane: Impact on soil carbon and nitrogen dynamics

• Published in: Geoderma Vol. 384; no. C; p. 114818
• Main Authors: Bera, T., Inglett, K.S., Inglett, P.W., Vardanyan, L., Wilkie, A.C., O'Connor, G.A., Reddy, K.R.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.02.2021; Elsevier
• Subjects: Bagasse; Biofuel; Fermentation by-product; Nitrogen mineralization; Priming; Fermentation by-product; Nitrogen mineralization; Priming; Biofuel; Bagasse
• ISSN: 0016-7061; 1872-6259
• DOI: 10.1016/j.geoderma.2020.114818

•Quality of bioethanol by-products impacts soil C and N dynamics.•1st generation by-products increased native soil C loss and N immobilization.•2nd generation by-product protected native soil C and increased N mineralization.•Bioethanol by-products temporarily decreased turnover time of soil microbial biomass. The first- and second-generation bioethanol by-products (bagasse and fermentation by-product, respectively) have different biochemical characteristics relating to carbon (C) and nitrogen (N) due to their production processes. To examine the impacts of fermentation by-product and bagasse on soil C and N dynamics, a 120 day laboratory incubation experiment was conducted by applying these amendments in soil at an equal carbon application rate (2.2 g C kg−1 soil). There was a significant increase in overall cumulative CO2-C production from amended soil compared to the control soil, though the loss was greatest in bagasse amended soil. However, δ13C-CO2 measurements suggested that fermentation by-product addition suppressed native soil C mineralization and prompted strong negative C priming (−57%). In contrast, bagasse amendment maintained similar native soil C mineralization to control soil. Decreased microbial biomass turnover time appears to be the major driving force for increased CO2-C production and soil C loss following bioethanol by-product amendments. Increased mineral N production indicated net N mineralization after fermentation by-product addition, while addition of bagasse resulted in lower N availability and N immobilization. Overall, results suggested that fermentation by-product application is advantageous in maintaining native soil C stock and N mineralization compared to bagasse. Thus, in a sustainable second-generation bioethanol production system, bagasse may be used for second-generation bioethanol production and the cogenerated by-product could be used as an amendment to improve soil C stock and N availability.