Jason Palmer, BBC News 5 Oct 09;
A system that generates energy from rubbish is being sent by defence firm Qinetiq to the US army.
The PyTEC system heats mixed waste, releasing a gas that can be burned to produce five times more energy than is required to drive the system.
Qinetiq say that the system, already in use on British navy ship HMS Ocean, has been "containerised" for US army use.
The approach could see use in urban areas, reducing municipal waste volume by 95% while producing energy.
The process hinges on pyrolysis, in which waste subjected to high temperatures releases combustible gases.
In essence it is the same process that happens above a match; heating of the wood releases gases that burn in the presence of oxygen, producing the visible flame.
In pyrolysis, the heating occurs in the absence of oxygen, and the released gases are gathered and stored for later use.
This is in contrast to simple incineration or gasification - another energy-from-waste approach that heats particular kinds of waste in the presence of oxygen to create combustible gases.
Typically, such systems require that the waste be of a singular type, and diced up before entering the gasification chamber.
Waste not
In the PyTEC system, a large screw-shaped column takes in up to 100kg per hour of untreated mixed waste - including glass and tin, particularly troublesome waste sources for thermal waste approaches.
The waste is heated, releasing gases that are removed and used to power a steam turbine.
What exits the system is a glassy substance just 5% the volume of the waste that entered, along with 400kW of power.
A similar system was installed on the UK navy ship HMS Ocean late last year.
"We've taken the plant that we developed for HMS Ocean and containerised it for the US army as a means to make it more mobile, more easily deployable and reducing their fossil fuel requirements," said Pat McGlead, waste management business development manager for Qinetiq.
The systems will be deployed to one of 55 "forward operating bases" in Iraq and Afghanistan - temporary outposts of 600 front-line soldiers that, until now, had no formal arrangements for waste disposal.
"That means they're going to have to have trucks on the roads (to carry the waste), and that means people are going to be exposed to land mines and so on - and it increases the use of fossil fuels," Mr McGlead told BBC News.
"By providing them with a self-contained waste management capability, we're reducing their logistical footprint, reducing the number of body bags, and reducing their fossil fuel usage."
In addition, the size and complexity reduction of the system for US army use means the approach could see application outside the military.
"We're finding more and more people in the commercial sector want to take ownership of their waste, and they want to reduce their carbon footprint, so they see energy from waste as a good way to go," Mr McGlead said.
"There are people that are interested in it for blocks of flats - it has a number of different applications."
