Environmental impact of second-generation biofuels production from agricultural residues in Cameroon: A life-cycle assessment study

Abstract

The world in general, and Cameroon in particular, are facing three major problems which are population increase, natural resource decrease and climate change. This work focuses on assessing the environmental impact of the production of second-generation liquid and gaseous biofuels by means of the life cycle assessment method, in order to contribute to sustainable development with emphasis on environmentally concerned decision-making and appropriate choice of technologies. The increasingly essential Life Cycle Assessment method is at the heart of this work. Avocado, cocoa and peanut residues have been converted on a laboratory scale to second generation gaseous biofuels (biogas) and liquid biofuels (ethanol). Biomethane yields are 177, 127 and 73 mL/g for avocado seed, cocoa pods and peanut shells respectively. When it comes to bioethanol, avocado seed, cocoa pods, and peanut shells produced yields of 178, 61 and 49 mL/kg biomass respectively. Based on the annual production of the three crops, 200,000 kg and 30,376,960 m3 of bioethanol and biomethane respectively can be produced at the national level of Cameroon. The SimaPro software version 9.1.1.1, the Ecoinvent database v.3.6 and the ReCiPe Midpoint impact method v.1.04 were used for the assessment. All categories of resulting environmental impacts are assessed and quantified. The categories with the most significant impacts are land use, global warming, Human non-carcinogenic toxicity, Terrestrial ecotoxicity, Fossil resource scarcity and water consumption observed in the agricultural phase. Global warming, Land use and Terrestrial ecotoxicity are the hot spots observed in the process of converting biomass into bioethanol and biomethane. The main sources of detected impacts are the processes of seed production, the use of electricity, distilled water and chemicals during the process of converting waste to biofuel on a laboratory scale. This laboratory-scale work will serve as a reference for decision-making of pilot plants and then large-scale production of liquid and gaseous biofuels with the objective of promoting the development of a sustainable biomass-energy industry based on avocado seeds, cocoa pods and peanut shells through identification of critical factors.