Assessing the Potential of Rice Husk Briquette as a Sustainable Energy Solution and Climate Change Mitigation Strategy in Kaduna State, Nigeria

Abstract

Overreliance on solid fuels, especially fuelwood and charcoal has contributed enormously to Nigeria's growing rate of deforestation. As part of efforts to curb deforestation, and climate change and have a sustainable cooking energy solution, this study developed briquettes from rice husk using three binders. Before the production, a survey was conducted across 400 households in Kaduna State, Northwestern Nigeria, following a multi-stage sampling approach to comprehend the energy use pattern. To assess the energy potential of rice husk and how it would be a good substitute for fuelwood and charcoal, it was characterized alongside the wood species used as energy sources in the study area. The briquettes were produced in a low-pressure (4.5 MPa) hydraulic piston press utilizing two novel biomass binders (locust bean pulp and sweet potato peel) compared to cassava starch as control. The experiment was designed using Box Behnken Design (BBD) in Design Expert 13, and Response Surface Methodology (RSM) was employed to optimize the process variables and quality metrics. The thermal properties of the briquettes were also assessed using the standard water boiling test (WBT), and a cradle-to-gate life cycle assessment (LCA) was employed to determine the environmental impacts of the briquettes against charcoal. In conducting the LCA, the background data related to energy consumption and material utilization were obtained from the EcoInvent version 3.9.1 database, and other secondary data were sourced from the literature. The LCA model was executed in OpenLCA software (version 2.0) using the environmental footprint (EF) impact assessment method based on a functional unit of 1 MJ of energy. The findings from the household energy use characteristics depict charcoal as the most used cooking energy in the study area, this was followed by fuelwood and Liquified Petroleum Gas (LPG). The energy options were mainly influenced by cost, accessibility, and availability. Furthermore, the results from the multivariate probit regression analysis indicated that the choice of cooking energy is significantly influenced by household factors such as household size, household income, occupation of household head, marital status, age, and education level. The results of wood characterization show that Anogeissus leiocarpus (African birch), Khaya senegalensis (African mahogany), Parkia biglobosa (African locust bean), and Eucalyptus cam. (Red gum), are the most energy-efficient wood species. The findings from the assessment of the quality metrics of the developed briquettes show that the briquettes have compressed density between 0.495 g/cm3 and 0.691 g/cm3, relaxed density between 0.196 g/cm3 and 0.306 g/cm3, impact resistance between 12.5% and 100%, and compressive strength between 20 kN/m2 and 410 kN/m2. The optimum process metrics predicted by the model are a 15% binder ratio, 1 mm particle size rice husk, 0.5 min dwell time, and cassava starch binder, while the optimum quality metrics are 0.71 g/cm3 compressed density, 0.30 g/cm3 relaxed density, 84.8% impact resistance, and a transformed compressive strength of 0.032 kN/m2. The comparative environmental life cycle analysis results show that charcoal production and use have a higher environmental impact than briquette. In this vein, a climate change and land use impact of 0.021 kg CO2 eq and 0.028 kg CO2 eq; and 0.02681 Pt and 6.26585 Pt were obtained for briquette and charcoal, respectively. This implies a potential climate change and land use environmental burden mitigation of 0.01 kg CO2 eq (33.3%) and 6.23904 Pt (99.6%), respectively. Thus, the findings affirm that rice husk briquettes with optimal quality for domestic use can be sustainably produced under low pressure, offering a viable solution for energy sustainability and environmental conservation.