Utilization of Biochar in Sugarcane and Sugar-Industry Management

Abstract

The sugarcane industry in many parts of the world produces food and energy (stationary and fuel). The industry is well positioned to offer greenhouse gas abatement and climate change mitigation. The thermal conversion, via a slow pyrolysis process, of cane residues such as green harvest trash and bagasse can produce thermal or electrical energy as well as biochar. Studies have shown that a commercial slow pyrolysis unit could generate over 1 MWhr of electricity from every two tonnes of trash (dry basis), with a biochar recover of between 31.3–33.6 %. Due to its highly stable nature, biochar has recently been suggested as a sequestration pathway to remove CO2 from the atmosphere. One tonne of bagasse derived biochar would sequester in the order of 2.3 tonnes of CO2 equivalents. In addition to C sequestration, biochar has other significant benefits (when used as a soil amendment) such as offering improved soil quality, higher CEC and nutrient availability, and improved soil physical characteristics. This work demonstrates that biochar application can reduce emissions of greenhouse gases from cane soils, such as nitrous oxide. Biochars derived from cane trash and bagasse were applied in incubation studies to soils from the Burdekin region in Australia. We found declines in emissions of the greenhouse gas nitrous oxide (N2O), from urea-fertilised soil when bagasse biochar was applied at a rate of 10 t/ha. The agronomic performance of biochar is being assessed in a 15 plot trial conducted on a sugar cane property in the Tweed Valley, NSW. Biochars (from non-sugarcane sources) were tested using relevant controls. Each plot consists of 3 rows of cane and was 30 m in length to enable commercial-scale harvesting. Although no significant effects in yield have been recorded this trial is expected to continue for several more seasons allowing additional data on yield effects to be evaluated. Our work has demonstrated that implementing slow pyrolysis and biochar utilisation in the sugarcane industry has potential to provide (1) renewable energy (2) income from waste (3) climate mitigation through stabilisation of carbon and (4) climate mitigation through reduced emission of N2O from soil. Further research is required to demonstrate agronomic benefits of sugarcane biochars and to develop an understanding of how they may address soil constraints in these systems.