Experimental Characterization of a Small-Scale Downdraft Gasifier for Biomass Waste

Abstract

Biomass is essentially organic garbage obtained from many sources of dead or live vegetation including yard waste. According to recent data, approximately sixty million bone dry tons of biomass are produced in California each year [1]. Of this, only five million tons are used for the generation of electricity. At a global scale, 8700 Tg of biomass (dry matter) were burned without energy recovery in 1991. This number has increased especially in developing countries with the main sources being the savannas, agricultural waste, tropical forests, and fuel wood. Inefficient burning of waste, through combustion in open-air or in open dumps are a significant source of pollutants leading to possible health effects. An alternative to open air combustion is gasification, which involves the conversion of biomass to generate synthesis gas (syngas) by adding heat and limited amounts of oxygen. Several gasifying agents can be utilized, but air is commonly used in small-scale gasifiers. The use of air causes a large molar fraction of nitrogen in the syngas composition. This papers shows the experimental results obtained with a commercially available small-scale downdraft gasifier. Woodchips obtained from a nearby landfill are used as input to the gasifier and temperatures, flow rates, and syngas composition are reported and analyzed.