Sustainability 61: Biomass Gasifiers
If you are looking to design a sustainable facility in a rural agricultural, livestock or timber community, your project may benefit from a biomass gasifier.
A gasifier is simply any installation that converts carbon-containing materials — peat, coal, oil, animal waste, wood, plant waste, organic materials, etc. — into a mix of gases that can in turn be burned to release energy. A biomass gasifier is an installation that uses one or more particular types of biomass, such as silage, wood chips, charcoal or organic waste, as its input fuel.
Fairly large scale gasifiers were first developed as local utilities in the 1800s, long before the spread of natural gas lines and electrical power grids, to provide a locally distributed fuel gas to be used for lighting, heating and cooking. The gas transmitted throughout such historical ‘town gas’ distribution systems was most often coal gas, derived from the combustion of coal. Though the residential use of such town gas was effectively supplanted by cheaper natural gas and electricity throughout the early 20th Century, gasification has since been consistently used in the production of synthetic fuels and chemicals.
However, small-scale biomass gasifiers, in which the inputs may include organic, animal and human wastes, have been around for quite some time as well. European wood gas generators supplied motor vehicle fuel through the gasoline shortages of World War II. Gasifiers consuming rural biomass and waste have long served the fuel needs of small farming villages and communities throughout the Indian subcontinent.
A typical biomass gasifier begins with a supply of biomass, whether wood chips, sawdust, corncobs and stalks, cattle dung, or other similar organic waste. Fed into the gasification, or combustion, chamber by some form of metering or measuring auger or conveyor, the biomass fuel is burned, with the assistance of a combustion fan or other oxygen input. Flammable gases given off by that combustion can be burned in turn to heat the water of a boiler-driven heating system. Those flammable gases burn quite hotly and cleanly, generating both substantial efficiency and little waste.
Biomass gasifiers must, of course, be developed and designed to suit their particular locale and installation. What is the intended input fuel? By what combustion process, sequence, and batch sizing is the greatest energy efficiency achieved? What is the residual waste? Must it be further treated? And, if so, how? Once such particulars are answered, and a final biomass gasifier designed, it may offer substantial savings over other more conventional heating systems. In some parts of the country, manufacturers offer ready-made ‘pre-packaged’ biomass gasifiers.