Techno-economic Assessment of Co-gasification of Rice Husk and Plastic Waste as an Off-grid Power Source for Small Scale Rice Milling - an Aspen Plus Model

Abstract

Inadequate access to electricity has necessitated other alternative energy sources in Nigeria. As a result, small modern rice milling uses mainly energy from diesel-fired generator, while traditional milling still uses energy from the combustion of wood. Consequently, the cost of diesel as fuel has contributed to the high operating cost of the rice mills. Moreover, these sources of energy contribute hugely to CO2 emission. Also, rice husk (RH) generated as waste from the mill is not utilized properly in the country, thereby adding to the environmental issue due to open burning disposal. In addition, a large amount of sachet water plastic waste (SWPW) is also generated in Nigeria. This research therefore presents co-gasification of RH and SWPW in the presence of CaO with integrated combined heat and power (CHP) generation for small scale rice mills in Nigeria using Aspen plus model. Optimum operating conditions in the gasification section were determined as inputs to the CHP section. At 800 °C gasification temperature with feed capacity of 30 kg SWPW/hr and 70 kg RH/hr, the system showed a CHP efficiency of 70%, which is sufficient for the rice mill energy requirement. The economic assessment of the system showed promising economic feasibility with a net present value (NPV) value of $1.47 million over 15 years. While the levelized cost of electricity (LCOE) value of $0.07-0.11/kWh indicates the cost attractiveness of the system as compared to other sources of energy in Nigeria. The system demonstrated an alternative cost and GHG emission savings source of energy. The project will promote the UN’s sustainable development goals of affordable and clean energy.