Comparative life-cycle assessment of maize cobs, maize stover and wheat stalks for the production of electricity through gasification vs traditional coal power electricity in South Africa

Abstract

Currently, coal is the most widely used feedstock for electricity generation, including South Africa with a 77% dependence. However, coal-fired power stations also result in adverse environmental impacts, including air, water and soil pollution. The conversion of biomass, such as maize cobs and other agricultural residues, to electricity, could play a vital role in reducing the dependency on coal power in South Africa as well as reducing these environmental impacts. However, there are very few environmental impact studies in the country to address the production or preparation phase of energy feedstocks for electricity production. This study used life-cycle assessment (LCA) to evaluate the environmental burdens associated with the production of maize and wheat, and the extraction of residue (maize cobs, maize stover or wheat stalks) for producing electricity through gasification and compared these to coal-fired electricity production. The results showed that the main areas of concern for electricity production from biomass were from gasification and transport, contributing roughly 47% each to fossil fuel depletion, just over 46% each towards climate change, 44% and 40% towards particulate matter formation, and 32.8% and 33.2% towards land occupation, respectively. The impacts associated with wheat stalks and maize stover production were higher than those of the maize cobs system. Agricultural land occupation results for the production of 1 ​kg of maize cobs, maize stover and wheat straw were 4.83 ​× ​10 −7 , 4.76 ​× ​10 −7 and 2.38 ​× ​10 −6 ​m 2 , respectively, in one year, with similar trends for the other impact categories as well. The most significant impacts of using coal-fired methods of electricity generation were fossil fuel depletion, ozone depletion, natural land transformation, urban land occupation and climate change, with these burdens being over 90% higher than from the gasification of maize cobs. To improve the environmental performance of the biomass energy sector, improvements in agricultural practices should be implemented, including further research on fertilization, water use, agricultural practices, land transformation, biomass conversion technologies, and transportation. • Maize cobs, maize stover and wheat stalks gasified to produce electricity. • Life cycle assessment used to compare the environmental performance. • Major areas of concern were fossil fuel depletion and climate change. • Wheat stalk production has greater environmental impacts than maize stover and cobs. • The impacts related to coal power are over 90% higher than those of maize cobs.