How can this energy be collected and transfered into a useable form of energy? First, the trash can be burned or incinerated to produce heat that is then used to produce steam and finally electricity. Or the trash can be gasified to produce syngas that can be burned to produce energy. Or how about just let natural decomposition of the trash take its course in landfills to produce landfill gas. Landfill gas consists of methane and CO2, the two main gasses that make up biogas from anaerobic digestion of cow manure. Of course there are efficiency losses in all of these processes, but why not use this energy, as it is just sitting there in the landfills waiting to be used.
Sunday, April 10, 2011
Shifting from cow manure to garbage
Throughout my blog I have focused on anaerobic digestion of cow manure. While this has been proven to be a valuable source of energy not everyone or every city is near a large population of cattle. Take for instance here is Colorado, northeast Colorado has a large population of dairy farms and cattle feedlots, however, Denver and the other front range cities are farther away. What do these large cities have instead of cows and there energy rich manure....TRASH. According to the EPA, the average person produces 4.4 pounds of trash per day. Multiply this by the population of Denver and the surrounding area of 2.5 million people and that totals 11 million pounds of trash per day. The average energy content of wood/paper is typically 5-7,000 BTU/lb, while plastics typically have an energy content of 15-20,000 BTU/lb. Using this data we are able to assume an average energy content of garbage as 10,000 BTU/lb. Multiply this by the 11 million pounds of trash produced in the Denver area to get 110 billion BTU's of energy. That is enough energy to power almost 360,000 homes that use on average 300,000 BTU/day.
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This sounds fantastic! And I hope we're able to do more of this. But why aren't we? Is it because the infrastructure is expensive? The technology isn't efficient enough? Are there unfortunate byproducts? I think we still need more information on the technologies you advocate for so we know how to judge our policy choices.
ReplyDeleteI feel that the reason we have not turned to these different technologies to produce energy is because the ones we have are so much easier and reliable. Drilling for oil and gas and mining for coal has been practiced for decades now here in the US. One interesting aspect of landfill gas is that "wells" have to be drilled into the layers of garbage that are producing the biogas to collect it. Maybe this can be a transition technology that will help the US develop more alternative energy sources.
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