U.S. Army is turning ‘green’

Purdue University News reported in February of last year that a group of scientists had created a portable refinery that can convert food, paper and plastic trash into electricity. The machine was originally designed for the U.S. military to allow soldiers in the field to convert waste into power. If successful it could be used in civilian applications in the future.

The biorefinery is able to process several kinds of waste at once, so you don’t have to go through the tedious job of separating everything first. Trash is converted into fuel via two parallel processes. The system then burns the different fuels in a diesel engine to power a generator. The machine's ability to burn multiple fuels at once, along with its mobility, make it unique.

It’s portability reduces the potential danger associated with transporting waste and fuel. Also, from a purely military standpoint, the elimination of garbage remnants protects the unit's security by destroying clues that such refuse could provide to enemies.

Testing of the device showed that it produces about 90% more energy than it consumes.

The complex processes involves separating organic food material from residual trash, such as paper, plastic, Styrofoam and cardboard. The food waste goes to a bioreactor where industrial yeast ferments it into ethanol, a "green" fuel. Residual materials go to a gasifier where they are heated under low-oxygen conditions and eventually become low-grade propane gas and methane. The gas and ethanol are then combusted in a modified diesel engine that powers a generator to produce electricity.

Possible civilian uses would be in disaster situations where emergency crews could use the machine to turn debris into electricity to aid in lighting, heating, and communications. An added benefit would be, in some small way, in aiding in the cleanup effort. Also, it could be used as supplemental energy for factories, restaurants, stores, etc.

After successful testing, the U.S. Army installed one of these units in Iraq, at a cost of about $1 million, including the cost of development. The unit weighs about 4 tons and powers a 60-kilowatt generator. A second unit is now under construction.

Photo credit: Purdue Agricultural Communication photo by Tom Campbell