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Making Gas From Trash

Even as the world scrounges for improved sources of energy and seeks to depend less on the desert oil barons, the US Army is investing in technology that converts garbage into fuel. The US Army has developed a mobile machine that consumes trash and converts it into diesel, mitigating the troublesome issues of both garbage disposal and fuel transportation in foreign, often hostile lands. 

Anytime the Army goes into a foreign country, it has to make sure its personnel and their vehicles are properly supplied. That means millions of gallons of gas have to be transported to support US forces, often in the middle of hostile territory. According to the US Government Accountability Office, the US Department of Defense supplied forces in Iraq and Afghanistan with an average of 68+ million gallons of fuel every month in 2008. That's a lot of fuel transport convoys – convoys that can get attacked.

Waste disposal is another issue in foreign lands; the military can generate quite a bit of trash. According to the Army, a 550 person unit can create about 2500 pounds (1130 kg) of garbage every day. Getting rid of that waste can be a problem because it's expensive to build incinerators that will only be used for a year or two, and burn pits produce smoke that can causes health problems.

The US Army has been solving both difficulties by taking its garbage and turning it into diesel fuel by means of a big machine that uses pressure and heat to break long chain polymers like plastics into short-chain petroleum hydrocarbons - trash to gas. The Tactical Garbage to Energy Refinery (TGER) is now on its second version - a huge garbage disposal on wheels. The updated TGER uses an auger to rotate refuse in a horizontal gasifier. Steam can be injected into the gasifier, increasing the percentage of useable gas generated.

The new and improved machine can produce 550 BTUs of gas, and 12 hours after starting it up, it can cook up enough diesel to power a 60 kW generator continually - as long as somebody keeps feeding the TGER its garbage diet.

The TGER is environmentally friendly to boot. "TGER reduces the volume of waste in 30 to one ratio. If you start off with 30 cubic yards of trash, you end up with one cubic yard of ash, and that ash has been tested by the Environmental Protection Agency. They call it a benign soil additive. You could actually throw it on your roses," said ECBC project director for TGER, Dr. James Valdes.

A desert tough, mobile power station that digests garbage could prove a much-needed form of energy generation if it got around, but the TGER garbage eater is not the only trash-to-energy truck on the block. Other methods of making the most of our refuse have been in place for years.

Burn It:
The idea of turning waste into energy is not new. The US-based company Covanta operates 44 power plants that each take local garbage and burn it in order to heat water that turns turbines that create power. Burning trash for power plants is a useful idea, as long as the plants employ air-pollution controls (which Covanta's plants do). The leftover ash is then transported to landfills at a fraction of the garbage's original weight.

Superheat It:
A process called pyrolysis has been around for decades. Pyrolysis involves breaking down organic matter by heating it to extremely high temperatures and is used in the chemical industry to produce charcoal or methanol from wood, or to make the PVC plastic used in water pipes, or syngas (synthesis gas) from biomass.

Depolymerize It (KDV):
The German company AlphaKat has developed what it calls the KDV (Katalytische Drucklose Verolung) process, a catalytic low pressure depolymerization of waste materials.

Metals and glass and sand are removed from trash, leaving only plastics and other carbon-based materials like food and paper, grass, tires and grease. This waste is dried and chopped up and mixed with used oil. A catalyst containing aluminum, sodium and silicon is then added, and the whole mess is dumped into a turbine that spins at 1500 rpm. Frictional heat alone raises the temperature to about 270 degrees Celsius. Inside that spinning turbine all the organic matter is broken down to a pure hydrocarbon diesel that is much like the stuff that gets drilled out of the ground - and at a much faster rate than oil is created naturally. Throw the stuff in the mixer, spin it, and in a few minutes you've got oil. Not only does this process turn garbage into fuel, but all the gasses and liquids are contained in the specially-designed turbine itself, protecting the outside world from possible pollution caused by the diesel production.

The question is, does KDV really work? Have they actually taken milk jugs, banana peels, and leftover burger bags and turned them into oil, or have they succeeded only in creating diesel from used cooking oil, which isn't half so big a deal? 

It appears the technology truly transforms garbage to energy. Alphakat has built at least seven KDV plants around the world; the first in Monterrey, Mexico in 2005. Canada feeds waste plastics into its KDV system, and plants in Spain, Bulgaria and the United States use KDV to generate diesel from household waste.

While windmills have popped up on the horizon from east to west, and people grieve over the high price of gasoline, the key to energy self sufficiency may not soley require sucking oil from the ground if we can put fuel into people's trucks by keeping it out of our landfills.
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