Investigation of the environmental impacts of bioethanol production: a case for ethanol from sugarcane in KwaZulu-Natal, South Africa

Abstract

At the current global population growth rate, the world is experiencing an unprecedented demand for natural and processed resources such as energy resources. Bioethanol being a comparatively sustainable source of energy has gained global traction as one of the suitable replacements for fossil fuels. However, the production of bioethanol has contributed to several environmental issues globally. This study was done based on specific objectives which include the evaluation of the environmental impacts in clearing natural vegetation for the purpose of sugarcane agriculture in uMlalazi, KwaZulu Natal (KZN), to evaluate how three different scenarios of sugarcane agricultural practices contribute to the emission of GHG and to identify GHG emission hot spots, to assess the environmental impact of sugarcane production for bioethanol on water catchments of uMlalazi in KZN, South Africa, and to analyse the wastes, waste management issues, gaseous emissions and their impacts from case studied sugar and bioethanol plants in KZN, South Africa. These objectives were motivated by the need to assess the environmental impacts of bioethanol production across its value chain in the KwaZulu Natal province of South Africa. Environmental impacts of bioethanol production through the analysis of waste generation in relation to potential environmental issues in some significant stages of the production value chain of bioethanol was the focus of this project. Various methods and models were incorporated in this study. GIS models helped with the analysis of the impact of land use changes versus sugarcane farms size changes over time. The Cool Farm Tool was used to analyse the amounts of greenhouse gasses emitted throughout sugarcane farming activities while identifying emission hotspots. Both GIS models and Water Quality Index (WQI) modelling techniques were used in analysing the quality of the water within the catchment areas under study. Secondary data on individual water quality parameters were sourced from the Department of Water Affairs (DWA). The DWAF (1996) guidelines for aquatic ecosystem standards were compared with the measured water quality. Finally, document analysis that followed observations and informal interviews were employed to analyse the waste generated from a case studied sugar mill and a bioethanol plant. The impact of such waste was analysed following the collection of primary and secondary data. It was noted in this study that although the overall sugarcane farm size in uMlalazi has reduced since 1985, the conserved ecosystems are seen to have increased in sizes between 1985 and 2020. Findings from the CFT model, present emission hot spots which include fertilizer production, fertilizer use in the soil, residue management, and diesel use in the various farm machinery. While single case studied emerging sugarcane farms from KwaDukuza (KDZ), Richards Bay (RB), Pietermaritzburg (PMB), and Port Shepstone (PS) all emit an average of about 550 000 kg CO2eq per farm, per farming cycle, their counterpart commercial sugarcane farms in the same regions emitted 1295970, 210310 and 10024970 kg CO2eq from KDZ, RB and PMB, respectively. Water pollution was confirmed in parts of the catchments. The results show very poor to poor water quality. For the 2014 scenario, 20% of the catchment contains water unsuitable for aquatic ecosystems, 33% is very poor and 47% shows poor to good water quality. While the 2018 scenario shows 15%, 10% and 75% for unsuitable, very poor and poor to good water qualities respectively. The sugar mill presented an average effluent production from 2010 to 2019 amounted to 310061.2 tons, 67318.79 tons filter cake, 37302.83 tons molasses, and 306349.2 tons bagasse. With no reference to the waste management strategy and effluent treatment employed at this mill, its high COD levels of 13023 mg/L, will negatively impact nearby aquatic ecosystems. On the other side, the bioethanol mill was also seen to generate waste in which the management strategies could not be accounted for during this study. In conclusion, the value chain of bioethanol therefore presents several environmental issues of concern that range from land use change impacts to both air and water pollution. Sugarcane agricultural practices have contributed to both air and water pollution likewise the sugar and bioethanol milling processes. It is therefore recommended that waste minimization and mitigation strategies be put in place in these sectors.