In this article we will talk about biomass gasification which means the gasification of biomass as distinct from carbonaceous fuels. The idea of gasification has been practiced for a long time, and most notably on coal to produce town gas until the 1950s when oil and oil derived fuels became the more popular, and coal production reduced in most developed nations.

Only recently with the rising cost of fossil fuels has the idea of gasification come once more to the fore. Expect to hear much more about gasification over the next few years!

Gasification works best as an efficient means of converting low value-residual biomass (such as municipal solid waste) into higher value products including power, steam, hydrogen, and basic chemicals.

It is a process that produces mixtures of hydrogen and carbon monoxide (synthesis gas or syngas) from carbon-based feedstocks such as coal, petroleum, coke and heavy oils. Gasification can play a significant role in large scale biomass gasification plants delivering a sustainable energy economy and is therefore one of the most technically and economically convincing energy possibilities for a carbon neutral economy.

To give you an idea what gasification is let us start by considering first the small scale and a simple wood gasifier. In this example gasification works by way of a downdraft that sucks wood gas from the firebox in the top chamber down into a bottom chamber where superheated combustion occurs. In most cases this can be achieved without a fan, and the downdraft can be powered by the gasifier itself once the system is lit.

In principle gasification produces very efficient clean combustion especially at large scale biomass gasification plants where economy of scale helps reduce costs. In these plants, ensuring that the action of burning takes place at a high temperature and controlled oxygen levels by creates a gas known as "syngas" within the process. Syngas may be removed from the process and as we have already indicated used as a feedstock in the creation of other organic chemicals. If syngas is stored and burnt later it can be used very efficient to run power generation units in large scale biomass gasification plants.

Gasification can be used for fertilizer and chemical manufacture and in the quest for lower carbon emission technologies , it is forecast that production will grow dramatically particularly in China.

Gasification can be used at any level from the small scale on-farm utilizing farm waste as a feedstock to highly technological uses and at extreme heat seldom seen on earth outside volcanic eruptions, and lightning strikes but it is more complex to run at the small scale and works best in large scale biomass gasification plants.

One such example of large scale biomass gasification plants is gasification in the form of plasma arcs. The very high temperatures created in a plasma arc reduce matter to its basic elements, and they do this remarkably cleanly which avoids the production of the majority of the unwanted combustion products which bedevil so many other waste to energy technologies requiring huge cost to remove and imposing high parasitic loads on the plant itself.

Gasification of wood and wood-type residues and waste in large fixed bed or fluidized bed gasifiers with subsequent burning of the gas for heat production is also state of the art and destined to become commonplace in the quest to use renewable fuels to their fullest.

Wood gasifiers are nowadays employed ever more frequently, for example, in the Scandinavian countries where they are used almost entirely for heat generation and use local forest wood, replacing that nations previous large appetite for fossil based fuels (oil, gas and coal) to heat its population during the long cold winters.

The Scandinavians see gasification of their nation’s renewable forest asset as a major player in their progression toward ever diminishing fossil fuel dependency, and many of these will be large scale biomass gasification plants.