One creature's waste is another's power.

This is more cost effective at bigger operations than small family farms. As it should also reduce the noxious odors, I would almost favor legislating this process for pig farms.

Cow power could generate electricity for millions:
"The journal paper, 'Cow Power: The Energy and Emissions Benefits of Converting Manure to Biogas', has implications for all countries with livestock as it is the first attempt to outline a procedure for quantifying the national amount of renewable energy that herds of cattle and other livestock can generate and the concomitant GHG emission reductions.

Livestock manure, left to decompose naturally, emits two particularly potent GHGs – nitrous oxide and methane. According to the Intergovernmental Panel on Climate Change, nitrous oxide warms the atmosphere 310 times more than carbon dioxide, methane does so 21 times more.

The journal paper creates two hypothetical scenarios and quantifies them to compare energy savings and GHG reducing benefits. The first is 'business as usual' with coal burnt for energy and with manure left to decompose naturally. The second is one wherein manure is anaerobically-digested to create biogas and then burnt to offset coal.

Through anaerobic digestion, similar to the process by which you create compost, manure can be turned into energy-rich biogas, which standard microturbines can use to produce electricity. The hundreds of millions of livestock inhabiting the US could produce approximately 100 billion kilowatt hours of electricity, enough to power millions of homes and offices.

And, as manure left to decompose naturally has a very damaging effect on the environment, this new waste management system has a net potential GHG emissions reduction of 99 million metric tonnes, wiping out approximately four per cent of the country's GHG emissions from electricity production.

The burning of biogas would lead to the emission of some CO2 but the output from biogas-burning plants would be less than that from, for example, coal."