February 03, 2007
Purdue Portable Waste Biomass Energy Converter

A portable "tactical biorefinery" designed for big military units on the go converts waste matter into energy.

WEST LAFAYETTE, Ind. - A group of scientists have created a portable refinery that efficiently converts food, paper and plastic trash into electricity. The machine, designed for the U.S. military, would allow soldiers in the field to convert waste into power and could have widespread civilian applications in the future.

"This is a very promising technology," said Michael Ladisch, the professor of agricultural and biological engineering at Purdue University who leads the project. "In a very short time it should be ready for use in the military, and I think it could be used outside the military shortly thereafter."

The "tactical biorefinery" processes several kinds of waste at once, which it converts into fuel via two parallel processes. The system then burns the different fuels in a diesel engine to power a generator. Ladisch said the machine's ability to burn multiple fuels at once, along with its mobility, make it unique.

Roughly the size a small moving van, the biorefinery could alleviate the expense and potential danger associated with transporting waste and fuel. Also, by eliminating garbage remnants - known in the military as a unit's "signature" - it could protect the unit's security by destroying clues that such refuse could provide to enemies.

It has a favorable ratio of energy inputs to energy outputs. But that does not tell us what fraction of the energy in the waste material gets converted into electric energy.

Researchers tested the first tactical biorefinery prototype in November and found that it produced approximately 90 percent more energy than it consumed, said Jerry Warner, founder of Defense Life Sciences LLC, a private company working with Purdue researchers on the project. He said the results were better than expected.

The U.S. Army subsequently commissioned the biorefinery upon completion of a functional prototype, and the machine is being considered for future Army development.

It reduces waste volume by a ratio of 30 to 1. But the article provides no indication of production costs. It starts up running on diesel fuel until its processing apparatus starts producing burnable fuel. At that point the fuel it produces powers continued processing to make more fuel. But most of the fuel produced is usable for other purposes.

If the refinery can be made cheaply enough it could provide supplementary power for a number of uses.

The refinery also could provide supplementary power for factories, restaurants or stores, Ladisch said.

"At any place with a fair amount of food and scrap waste the biorefinery could help reduce electricity costs, and you might even be able to produce some surplus energy to put back on the electrical grid," he said.

Much of the fuel the system combusts is carbon-neutral, said Nathan Mosier, a Purdue professor of agricultural and biological engineering involved in the project.

So what would this unit cost to mass produce and operate? If the waste was free from trash collection then what would the cost be per kilowatt-hour? A much larger unit would probably have lower labor costs per kwh. Also, the portability could be sacrificed for lower operating costs.

Share |      Randall Parker, 2007 February 03 02:29 PM  Energy Biomass

DougDante said at February 3, 2007 7:47 PM:

Future pundit, please note that fuel and electricity are much more valuable on the front lines than at home. I think that Amory Lovins calculated the effective cost of a gallon of gasoline at something like $300 after 3 helicopter airlifts.


This makes a conversion process which would be five times too expensive as compared to commercial electricity in Witchetaw a very compelling alternative in rural Afghanistan, where electricity from shipped fuel is 20x as expensive.

DougDante said at February 3, 2007 7:49 PM:

Oops, meant Wichita.

Sione Vatu said at February 4, 2007 9:31 AM:

Amory Lovins also makes the point that enormous expenditures of energy and consumption of other resources would be saved were the military to stay at home in the US. He argues that approach would be economically far more efficient than invasions or even merely stationing troops in other people's countries. Given that military activities consume resources without producing anything, his coments are difficult to refute. The first President of the USA, George Washington argued from a similar position, although for different reasons.


TTT said at February 4, 2007 6:05 PM:

Isn't this what Doc Brown had in 'Back to the Future' to power his car, which was available to consumers in 2015?

David A. Young said at February 5, 2007 9:18 AM:

My apartment complex has a large, centralized trash compactor the residents bring their trash to. In such a situation, could one replace the compactor with one of these conversions units (in the future) to make the complex "energy independent?" Depending on how the actual economics of it worked out, I could see this being a big selling point . . . especially here in Florida, where it's not unusual to lose power for long periods of time during hurricane season.

John Leyzorek, consulting engr said at April 9, 2007 11:06 AM:

The conversion ratio is given curiously; I do not know if we are to assume that the ratio of energy in to energy out is 1 : 1.9.
If this is the case, as long as operating and maintenance costs are low, and equipment life long, almost any initial capital cost will eventually be repaid, with interest.

From the description, the process does not seem fundamentally different from wood gasifiers, which have proven their ability (and impracticality) to run otto-cycle engines since circa 1900. A diesel engine would have to burn a small amount of Diesel fuel for ignition, to run at all on gases produced from organic matter. An engine with spark ignition would not. Gases from destructive distillation of trash would be corrosive, and would require post-processing to be burned in an engine without adversely affecting its longevity.

Peter said at April 11, 2008 2:29 PM:

how much is this machine going for and is it just reserved for war time? I know people who needs this machine at peace time and can pay for it, they would also not like to leave their waste behind as it may poison thier enemies and friends.

J T said at July 16, 2008 3:05 PM:

Purdue University staff and students developed a biomass unit, in the 1970's, that replaced an existing residential septic tank. The family powered their home and cars with methane produced from this unit. Simple, cheap, effective, environmentally friendly. Corporate America must think there is no "profit" in this type of a home-based "free" energy system. What about the profit in manufacturing such home-based power sources? Somebody has to fabricate the biomass tank, pressurization hardware, and potential storage tanks for excess methane that could be sold to large users. The "Big 3" used to hide technology like this. It's about time we bring it out into the open.

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