Livestock manure availability and syngas production: A case of Sudan

Abstract

Sudan is facing an energy crisis caused by a large deficit in electric power supply and transportation fuels such as gasoline and diesel. Only about 32% of the population have access to electricity. Fuels subsidies have been removed causing a huge prices-hike. Therefore, Sudan is in urgent need to promote its abundant biomass resources to mitigate the energy crisis. In recent years, syngas from biomass gasification has emerged as a potential energy source for power generation and manufacturing synthetic gasoline and diesel via Fischer–Tropsch (FT) synthesis. The paper reports (1) the availability of Sudan’s livestock manure for syngas production and (2) the optimization of syngas production for the applications of power generation and FT synthesis. The study covers eight (8) livestock manure of Sudan origin, viz. Cattle Dairy, Cattle Non-Diary, Sheep, Goat, Broiler, Layer, Horse, and Camel. Sudan has a large livestock population but poor manure management. Despite poor management, the available manure (10%) amounts to 17 Mt/year with an energy value of 300 EJ/year (7.14 Mtoe/year). The process optimization is accomplished using the optimization section of the Model Analysis Tools of the Aspen Plus simulator. The cold gas efficiency and H2/CO≥2.0 molar ratio are taken as the optimization objective function and constraint, respectively. The operating conditions under which the objective function and the constraint are satisfied are steam to biomass ratio (0<SB<5), equivalent ratio (0≤ER<1.0), and gasification temperature (500 °C≤Tg≤ 1300 °C). The optimum set of operating conditions are ER = 0, SB = 0.46-1.0, Tg = 750 °C -1000 °C. The syngas quality of all livestock manure except Camel are: H2 mole fraction = 0.47-0.56, LHV = 10.0-15 MJ/kg, and H2/CO ≥ 2.0. The syngas produced amounts to 22.42 Mt/year with an energy value of 270 EJ/year (6.44 Mtoe/year). This energy could level the deficit in electric power and transportation fuel demands.