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Purdue Makes Trash To Electricity Generator
musicon writes "A group of scientists at Purdue University 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. It could also have widespread civilian applications in the future. Researchers tested the first tactical biorefinery prototype in November and found that it produced approximately 90 percent more energy than it consumed."
Actually, they combine trash with ethanol to run a diesel engine ... The electricity produced is 90% higher than it would be with only ethanol. ... is what I understood :)
This is described as energy returned on energy invested, or EROEI, of 1.9, which is not all that great. Ethanol from corn has a value of about 1.25, and that number is from its proponents. Anything below 1.0 is a lose.
US oil production has a value of about 3. That number declines over time; it was as high as 100 in the early days of oil production. (Look up "Spindletop") Saudi oil production has a value of about 10. Wind energy has a value of around 5. Solar power values depend on how long the equipment lasts; energy breakeven on solar cells happens some time around 5 years.
Not on a large scale, I think. This is likely to be a very polluting energy source. Hence it being described as "tactical." Good for emergency use - or for a desperately poor village that doesn't have any electricity to meet basic needs. But not to power your Plasma TV or Playstation.
... and then they built the supercollider.
The local landfill where I live, the Johnston landfill, here in Rhode Island, operates a methane recovery plant. This methane gas then flow through eleven twelve-cylinder turbocharged engines, to power a bank of generators.
This produces 15.3 megawatts of power. 1.3 megawatts is used to power the plant and landfill site. The remaining 14 megawatts is sold back to the grid, and provides power for 21,000 homes.
It's not quite 1.21 gigawatts, but it's still pretty cool.
RTFA they say the generator has to run off diesel oil for several hours to power the bioreactor/reformer. Once the components have had time to break the waste material down into ethanol, methane, and propane that gets funneled back into the generator that the net result is 90% additional output. If it was to take 10 liters of diesel to start the process, after using those 10 liters, and also burning the resultant fuels from the bioreactor/reformer it would be approximatly equal in electric output to having only used a plain old generator with 19 liters of diesel. In addition it reduces the trash input to aproximatly 1/30th of the volume in ash. It is bascially a mobile trash incenerator/generator that can be jumped started with diesel. Electrical plants that burn trash to produce electricty has been around for a long time. This sounds only slightly more efficent/environmentally friendly in that they use a bioreactor to produce ethonal from the biowastes, and use gasification techniques on the other types of trash instead of just plain burning all the trash together with a steam generator.
No matter is 'converted' to energy, it is only a chemical process to rearrange the the energy in the chemical bonds of the existant trash into a more useful form of energy(ie. electricity). Same as burning coal or any other fuel, the energy is released in the form of heat to provide work.
Easy enough to do. What the article means is that for every joule the energy consumes it generates 1.9 joules. The joules it is consuming are not from the trash itself. It might be converting the trash at an efficiency of only 5% (making that number up, of course). It's just saying that it does, in fact, actually generate a net positive amount of energy while consuming the trash.
Somehow I suspect I haven't made this any clearer.
Consider the "Mr. Fusion" reference. We've created fusion generators that actually produce energy through fusion. However, so far, they've all produced less energy than it has actually required to run them, thus resulting in a net negative. All that 90% figure means is that this is a net positive.
Ben Hocking
Need a professional organizer?
Not all materials are metals which can be relatively inexpensively melted back down and used with no negative effects in the next recycled generation. Paper recycling, for example, might be a cure worse than the disease.
The harsh chemicals used to remove the many and varied dyes from paper to be recycled are pretty terrible to begin with (And unlike bleaching regular pulp, you don't know what's going to be there, so you can't reformulate all that well), then you end up throwing the recovered pulp right back into the pulper anyway, so while there are likely some gains in energy, it's not necessarily friendly to the environment. Making matters worse, recycled paper seems to have less strength than original pulp.
In the end, you're making more use of toxic chemicals for a product of lower quality. I'm sure there are other similar materials where the friendly concept meets unfriendly process control reality.
It's been a long time.
2 stroke engines are far more polluting than either 4 stroke gas or diesel engines. They must mix their oil with their fuel, creating an exhaust that cannot be cleaned up (well) with catalytic converters or urea injection. This is why they have been all but banned in advanced industrialized nations.
Did you RTFA? What leads you to believe that this will be a "very polluting energy source"?
From TFA:
"Much of the fuel the system combusts is carbon-neutral... Carbon-neutral fuels like ethanol do not cause an appreciable net increase in atmospheric levels of the greenhouse gas carbon dioxide. This is because the fuel releases carbon that has only recently been taken up by plants during photosynthesis, the process by which plants convert carbon dioxide to oxygen and sugars...
The machine produces a very small amount of its own waste, Warner said, mostly in the form of ash that the Environmental Protection Agency has designated as "benign," or non-hazardous. Any leftover materials from the bioreactor are put into the gasifier, which has to be emptied every two to three days.
"It's about enough to fill a regular sized trash bag, and it represents about a 30-to-1 volume reduction," Warner said."
So it burns clean AND it reduces the garbage that you put into it by a 30:1 ratio. Sounds pretty non-polluting to me. My only question is... why can't I have one of these things powering my house? I could dump my garbage into it every day and lower/eliminate my electric bill. Or maybe that's not practical. Maybe it requires an inordinately large amount of waste to run it. But still, they could build a bunch of these right next to a garbage dump and just start powering the city off of all our old garbage.
WATYF