he saves 30,000 a year on a piece of equipment that cost 1 million + a federal grant that is not spelled out. That means it only takes 25 years for the investment to pay off.
You are assuming that what was true almost 20 years ago is true today.
Ron Koetsier, who has 1,200 dairy cows on 160 acres near Visalia in Tulare County, invested about $1 million to get a digester built in 1985.
Technology has improved since 1985 and costs have come down.
http://sfgate.com/cgi-bin/article.cgi?f=/c/a/2004/05/14/BAGJG6LG3R15.DTL
The Straus Farms' covered-lagoon methane generator, powered by methane billowing off a covered pool of decomposing bovine waste, is expected to save the operation between $5,000 and $6,000 per month in energy costs. With those savings, Straus estimates he will pay back his capital investment in two to three years.