Technoeconomic Analysis of a Small-Scale Downdraft Gasification-Based Cogeneration Power Plant Using Green Wastes

Abstract

In this work, the technoeconomic assessment of a small-scale gasification-based cogeneration plant (25–50 kWe) fed with green wastes (fallen leaves, spent coffee grounds, and paperboard) is presented. The cogeneration power plant is modeled using Thermoflex software under thermochemical equilibrium and steady-state assumptions. Subsequently, the performance of the cogeneration plant is numerically analyzed as a function of the feedstock moisture content (6–30%), air–waste equivalence ratio (0.20–0.55), and the system load (6.25–25 kWe). The results show that the best energy performance of the cogeneration plant is achieved with a feedstock moisture of 6.05%, an equivalence ratio of 0.358, and a load of 25 kWe. At this best performance mode, the electric generation and cogeneration efficiencies are 19.33% and 49.71%, respectively, with a specific biomass consumption of 1.19 kg/kWh. Two scenarios are established for the economic assessment. The baseline scenario considers a 25-kWe cogeneration plant, while, in the second one, the generation capacity of the system was assumed to be doubled (50 kWe). The financial results show that the power generation has an energy levelized cost of 11.7 ¢$/kWh and 8.4 ¢$/kWh for 25 kWe and 50 kWe, respectively. Nevertheless, none of the proposed scenarios were found to be economically feasible based on the negative net present value obtained. Therefore, further energy laws and regulations are required seeking to support the small-scale auto-generation units based on biomass gasification.