WALTHAM, Mass.--In the quest for renewable sources of energy, the military is giving garbage a go.
The Edwards Air Force base in Southern California will test out a shipping container-sized trash-to-energy unit from IST Energy. The Air Force will be the first customer for IST Energy's Green Energy Machine (GEM), which is designed to convert waste into electricity and heat, according to the company.
Two years ago, IST Energy showed off the prototype of the GEM and earlier this month began showing the unit to potential customers. About 20 companies, which either have a sustainability initiative or pay a lot for waste disposal, have come to check out the unit here so far.
IST Energy is one of a number of companies seeking to draw usable energy from everyday garbage with a less damaging environmental impact than incinerators. The company projects a 5- to 10-year payback on the $1.1 million GEM, depending on its waste and energy costs.
Instead of burning waste, the GEM uses a gasifier, where dried and pelletized waste is heated to above 600 degrees Celsius in a vessel with limited oxygen. The heat causes the material to break down into what is called a synthetic gas, or syngas, made mostly of carbon monoxide, hydrogen, and methane in IST Energy's gasifier, explained Matt Young, the engineering group leader for waste-to-energy systems at IST Energy.
The syngas is the fuel for either a natural gas engine or boiler after some modifications. Or the gas can be mixed with diesel fuel to run a generator. Three tons of waste a day is enough to power a 100-kilowatt generator, but the net output is 72 kilowatts because of the power needed to operate the machine. Heat can be fed into a building's heating system as well.
The companies that have come to see the GEM are seeking to lower the amount of trash they need to remove and to generate energy on site, Young said. "It's really changing the way they look at waste. They see it as a resource rather than a burden," he said.
The military in particular is keen to reduce its waste and carry less diesel fuel in the field, which is a security liability. In 2008, the Army tested a portable waste-to-energy unit, called Tactical Garbage to Energy Refinery (TGER), in Iraq. The Army says it's still interested in the technology but the TGER has not yet been deployed elsewhere.
Edwards Air Force base will receive its GEM in April, where data will be collected for a report to the Department of Defense.
Gasification is a technology that's seeing a resurgence of interest from energy entrepreneurs in part because it produces a fuel--syngas--which can be used to make electricity or heat. Ze-Gen, for example, has built a larger waste-to-energy system designed to convert construction and demolition waste into electricity.
The GEM is optimized for certain types of waste, such as food waste and packaging, which an office building would typically generate. It is not designed to work with construction debris or biohazard waste.
Using an EPA model, IST Energy calculates that the greenhouse gas emissions are lower from the GEM than hauling garbage to a landfill. If a facility were to use three tons of trash in the GEM each day rather than sending it to the landfill, it would reduce its greenhouse gas emissions by 540 tons for that year, said Young.
In terms of other air pollutants, IST Energy expects to meet air quality standards for the diesel generators or natural gas engines that the syngas would be used in, he added.
The roots of the machine's development go back to the Department of Defense, which funded two projects that led to the creation of IST Energy. One was to improve on a mobile gasifier and the other was around creating pellets from a stream of waste. Over the past two years, IST Energy has worked on improving the reliability and efficiency of those components.
Inside the GEM is a whirl of machinery and ducts crawling in different directions. Apart from the gasifier and pelletizer, much of the equipment is off-the-shelf. For example, gases from the unit are "scrubbed" to remove particulate matter, and ferrous metals are removed with a magnetic belt. Ninety-five percent of waste put in is converted to energy, leaving an ash that's approved for landfills, Young said.
It's also heavily instrumented with sensors and an Internet connection so IST Energy and customers can monitor the output and spot maintenance issues.
A waste-to-energy system is not the first thing organizations will think of to showcase corporate sustainability efforts and lower their environmental footprint. But now waste is part of the distributed energy picture.