The world's largest biogas plant will co-digest manure with other 
feedstocks in 11- 1 million gallon tanks. The effluent will be 
applied as an inorganic fertilizer. The biogas will then be 
scrubbed for BTU value and pumped into the natural gas pipeline. 
"Sustainable" natural gas is  taking off!

http://www.siouxcityjournal.com/articles/2006/08/04/news_business/local/8e5ea70199ca80fb862571c0000d92d6.txt

James Gabriel Duncan

BioEnergy and Sustainable Technology Society
http://grove.ufl.edu/~bests/