Power from pollutants

Energy: British company boasts of world-beating waste technology
MUCH of the interest in power generation is focused on the upheaval in the electricity industry. But away from this, a British company is claiming a world lead in converting waste into energy.

Waste Gas Technology, of Romsey, Hampshire, says its ThermoCrack process can provide the typical home with three to four months of power from a tonne of waste. Moreover, adds Kevin Whiting, the company's head of marketing, it offers "a practical, cost-efficient solution to many current disposal concerns, including sewage, tyres and municipal waste". This pressure is likely to increase because many landfill sites are already full and the introduction of the landfill tax could double costs.

ThermoCrack is an advanced, environmentally-friendly technology that uses high temperatures to make waste "crack" into smaller gas molecules and so produce high heating-value gas. It is the result of a research and development programme that WGT embarked upon when it was set up in 1992.

The privately owned company claims the process achieves more than twice the average energy output of conventional incineration: depending on the energy value of the waste material (plastic and rubber waste from tyres rate among the highest sources of energy) between 1,000 and 4,000 kilowatts of electricity per tonne of waste. In addition, it says the efficiency of the process sharply reduces the amount of carbon dioxide produced and so helps control the greenhouse effect, while the typical payback period is about four years, compared with up to 12 years for incineration.

This makes the company confident of winning strong industry interest. It expects to announce the first commercial application next month.

Among the markets being focused on initially are:

q Municipal waste, because the pressure on landfill is so acute that some counties have to ship waste elsewhere;

q Tyres, as they are barred from landfill sites because of health and safety risks;

q Waste from sewage, also excluded from landfill sites because it is biologically active.

The company says the technique also works well on wood, straw, animal waste, plastics and a range of organic materials.

In the process solid waste material is first pre-treated to remove waste that can be recycled, dried, and then granulated to increase the surface area. The resulting small particles are either stored or fed directly to the reactor. (Liquid organic wastes do not need to go through the preliminary stages.)

Just before the material is put into the reactor it is "washed" with an inert gas, for example, carbon dioxide, to remove trapped air.

The technology is notable for using high temperatures without oxygen, which maximises both clean gas production and the potential for subsequent low-cost conversion to direct heat or electrical power.

In addition, many other conversion systems are geared to producing liquid fuels, which are less environmentally friendly and, because they require further refinements, less economically viable.

Finally, WGT envisages that its plants would, at an ideal size of 60,000 tonnes a year capacity, be less visible than those of competitors. The absence of the sort of chimney required for an incinerator, for instance, minimises the impact on the landscape. "Small in size, it is acceptable as a neighbour in many edge-of-city or industrial locations," it says.