Great article from Dave Roberts in Grist about biodigestion and biomass energy in Austria.  He always gets to the heart of the matter at energy conferences he attends for the magazine.  This is how the process described in the article works.

One part manure to 30 parts wood chips, straw, or other waste cellulose, that is the carbon.  At that nitrogen/carbon ratio, biogas is produced.

The manure would combine with carbon in the environment if it were allowed to run off or put directly on fields, producing methane (biogas) that is released into the atmosphere.  By trapping and burning the gas in this energy system that methane emission is halted.  Thus offsetting 20 times the CO2 that is released by burning the gas.

Combustion of wood chips just releases CO2, no offset occurs.  It's not carbon neutral just because it's from biomass, this is a myth.

If only 5% of the combustion energy  used came from biogas it would offset all the rest of the CO2 produced from combustion energy.  

This is why I keep harping on the plan to backup renewable (solar, wind, water, plugin hybrids)  power systems with natural gas/biogas, with 5% biogas (from the waste stream) in the mixture.

The stuff left over after the biodiogestion in organic fertilizer/soil ammendment.  By replacing ammonia fertilizer it prevents the release of nitrous oxide (296x the GHG effect of cO2) and the use of natural gas to make the ammonia fertiltzer.

The GHG effect prevented is equal to 2/3 of the CO2 uptake of the crop fertilized.  

Farms scattered all over the US are using biodigestion, it has around an 8 to 10 year payback at current electric rates, with the biogas turned into kwh sold onto the grid with ICE generation.

Solid oxide fuel cell/turbine generation reduces the payback by tripling the efficiency.  likewise economy of scalwe by combining manure from 10 to 100 farms instead of manure and biomass from only one farm.  

Furthermore, if government subsidized this to the tune of 5 to 10 cents per kwh, it could revive the small farm economy.  Through the energy sold and subsidized and chemical fertilizer costs defrayed.

We the people would get clean renewable backup for a renewable/conservation energy revolution and a huge reduction in GHG.  

This process could offset all the CO2 produced by a renewable/conservation energy economy, relying mainly on wind, solar, water, plugin hybrids, renewable electric mass transportation, ground source heat pump heating/cooling, and natural gas as the ultimate emergency backup fossil fuel component.

And of course all this would fight inflation with lower energy costs and it would revive the economy with a manufacturing stimulus, powered by increased productivity and efficiency.  With oil and coal and nuclear eventually phased out over 20 years or so.