Superstructure Optimization for the Production of Fuels, Fertilizers and Power using Biomass Gasification

The production of renewable fuels and decreasing the dependency on fossil fuels is an integral component of sustainable development. As the production and utilization of petrochemicals represent an extremely important economic pillar of modern society, there exists an impetus to identify alternative routes of production in order to conserve finite resources. Furthermore, there is an additional necessity to utilize waste to produce value-added products in order to reduce greenhouse gas (GHG) emissions. Biomass, a CO2 neutral energy source, serves as a potential basis for the production of fuels, which would have otherwise been produced from natural gas. The gasification of biomass produces a hydrogen-rich syngas, which can be utilized in the petrochemical industry to produce ammonia and methanol or processed through the Fischer-Tropsch synthesis to produce liquid fuels. In this study, the utilization strategy of biomass gasification feedstock for the poly-generation of different products is environmentally and economically evaluated. The potential production volumes of fuels and green chemicals are increased by the addition of multiple biomass sources, and thereby gaining potential positive scale effects, and by the optimization of the gasification process, in terms of operating conditions and feed blending to yield high-quality syngas. This form a superstructure network of multiple biomass feedstocks (sources) and multiple potential applications (sinks) that can be optimized to yield the most economical and environmental-friendly production configuration. The base model developed is an oxygen-steam gasification process of different feedstocks available in the State of Qatar to generate H-2-rich syngas that is utilized in the production of value-added products: methanol, urea, power through integrated biomass gasification combined cycle (IBGCC) and Fischer-Trospch liquids (FTL). The results of the optimization problem demonstrated the domination of urea generation with an overall net cost objective function of $ 0.096 per kg of biomass input and an overall net emissions objective function of 0.83 kg of CO2-e emitted per kg of biomass input. The manure based biomass is more suitable than sludge and date pits in the resulting optimum blending option for this utilization technique.