Techno-Economic Assessment of Biogas to Liquid Fuel Conversion via Fischer-Tropsch Synthesis: A Case Study of Biogas Generated from Municipal Sewage

Abstract

This research looks at how biogas (a renewable energy resource) can be harnessed using municipal sewage waste, and the potential of biogas use for generating liquid fuels (diesel and petrol) using Fischer Tropsch synthesis. The research also looks at the economic implications of carrying out the venture, and also determines the viability and feasibility of developing such an initiative in Zimbabwe. The production of biofuel from biogas via Fischer Tropsch synthesis was successfully simulated using the Aspen Plus simulation software which enabled a techno-economic assessment to be conducted based on these results. The minimum retail price of Fischer Tropsch diesel and petrol fuel was determined to be slightly under $1.10/litre for both fuels, with an annual total plant production capacity of 200 million litres per year. The plant was designed to produce around 270 000 L of petrol fuel per day that can be refined and further upgraded to premium quality grade petrol for export. The plant was also designed to produce nearly 320 000 L of diesel fuel per day for direct use as liquid transportation fuel. The total biogas input requirement for the plant is 700 tonnes/hour of biogas (2000 m3/hour) [1m3 = 0.353 tonnes]. The total sulphur production is 30 tonnes per day, and the total carbon dioxide extracted and captured is 1500 tonnes per day. The total plant cost was estimated at $200 million USD. The financial analysis for the plant operations shows positive financial performance with a nearly 20% return on investment. A payback period of 5 years is projected.