Effects of using walnut and woodchips as fuel on the performance of the modular biomass downdraft gasifier

This thesis is the evaluation of the performance of a small scale, downdraft gasifier internal combustion engine with nameplate power rating of 25 kW made by All Power Labs utilizing two different biomass feedstock. Varying compositions of agricultural wastes such as wood chips and walnut shells as means of biofuel affect the efficiency and overall performance of the gasification processes and engine combustion. The operational parameters such as the temperature of the gasification bed, electrical output, feedstock consumption, specific gasification rate and emissions were analyzed to observe the characteristics of the gasification system using different biomass fuel. The overall efficiency was then determined to provide a benchmark on the system's performance. The specific type of wood chips that were used have Tanoak woodchip quality similar to the one's used for children's playground. The experiments indicated that this downdraft gasifier engine operated at higher bed temperatures and higher specific gasification rate when using woodchips at various electric loads. However, the electric gasification system indicated a higher overall efficiency when using walnut shells, which range from 13% to 17% compared to 9% to 11% when using Tanoak quality woodchips. In addition, the experiments established the optimum air-to-fuel ratio (lambda) set points for both biofuels through evaluating the emissions.