Several Michigan livestock farms have now installed anaerobic digesters that are being used to produce electricity and natural gas
from the manure generated by cows and pigs. The manure is collected and put into the digesters where it is heated and bacteria can consume it to produce methane. Some of the methane is burned locally to produce electricity that is then used on the farms with excess being fed back into the grid. The remaining methane is purified and fed back to natural gas pipelines for re-sale. The remaining solid bio-fiber is used as bedding for the cows with the liquid waste used as fertilizer on the fields.
Michigan State University is working with small- and medium-sized farms to implement these systems to reduce the amount of waste generated by the livestock and put it to use. The digester equipment is pricey, but the sale of excess electricity and gas helps offset some of the cost for farmers.
[Source: Detroit Free Press