Methane gas emissions at landfills are used to run reciprocating engines 24/7 to generate electricity.  Waste Management  has 141 such landfill gas projects, nine of which are in Michigan.  One of its largest will be at Pine Tree Acres Landing in Macomb County where methane gas emissions are sufficient to generate 22 MW of electricity.  "Trash has become a fuel source,"  said Tom Horton, Vice President of Public Affairs, Waste Management.   DTE Biomass Energy operates twenty five landfill gas projects around the country, with two in Michigan including the new 3.2 MW project in St. Clair County.  Lansing-based Granger III and Associates LLC has seven landfill gas generating projects in Michigan, with a number of others out-of-state.  EPA counts more than 550 landfill gas projects across the country.