Energy is expensive, whether it is from fossil fuels or other sources. As we become more aware of the depletion of fossil fuels, renewable energy is increasing in demand. One possible source of renewable energy is the energy produced from anaerobic digestion .
So where does the anaerobic digestion come in? Right after the barn gets cleaned the manure gets put in the digester where microbes break it down and excrete biogas which contains methane. The biogas is collected and used as fuel to power a large engine that runs a generator which creates electricity. This electricity can then be used to power the farm. If enough electricity is produced the farm can even sell it to the utility company, depending on the laws and regulations in their state.
If you’ve ever driven by a farm or field that just had manure spread on it you probably noticed an odor. The nice thing about manure that goes through anaerobic digestion is that the unpleasant odor is no longer there. This makes digesters even more desirable to farms in more densely populated areas. By reducing the smell of the manure, some farms are able to improve their relationships with neighboring land owners.
So we know how that you can generate electricity using an anaerobic digester but there must be some other things that they can produce.
The simplest most straightforward one is heat. The same gas that is collected and used to power generators can also be used to produce heat. Generators also produce lots of heat which can be collected as a byproduct of electricity production. The heat can be used for things as simple as heating buildings and hotwater to kiln drying lumber, pretty much anything you could do with normal heat.
One farmer in Indiana has found a really neat way of using the gas produced by his digester. Have you ever seen a car or truck that runs on compressed natural gas? Well this farmer has retrofitted a fleet of tractor trailer trucks to run on the gas produced by his digester. The biogas has to be purified a little further than it would to run a generator but it is well worth the effort for what he does with it. Dairy farmers get paid a price for every 100 pounds of milk they sell this price varies from region to region. The price in Indiana where there are lots of dairies is significantly lower than the price in another region lets say Florida where there are relatively few dairies.
So this enterprising farmer who also happens to have a lot of cows uses his trucks that are powered by biogas to haul all of his milk to Florida where he gets paid a much higher price for it than he would in Indiana. By using the biogas produced by his digesters he saves a lot of money that would otherwise be spent on diesel fuel, plus it's renewable. He estimates he will save 2 million gallons of diesel in 2013.
Well there you go farmers are using digesters for anything from heating their hot water to fueling their trucks, so next time you drive by a farm there is always a chance that the lights could be powered by poop.