Landfill Energy Facts
- Waste decomposes anaerobically (non-oxygen environment) and produces landfill gas, approximately 200,000 cubic feet per day from the City's two closed landfills.
- Landfill gas is 50% methane, 48% CO2, and 2% other trace gasses. It is very moist and there are six condensation traps built into the piping to remove the moisture.
- The gas is primarily burned in the engines. If there is any excess gas it is burned in the flare.
- The generators are V-8 engines with stainless steel parts to withstand the very corrosive landfill gas.
- Landfill gas must be filtered to remove impurities and water, then brought to the correct pressure and temperature for the generators
- Burning landfill gas in an engine or a flare is 99% effective in eliminating the pollution effects.
- The City saves about $20,000/yr because it no longer has to filter landfill gas from Phase II. The State required the filtering to avoid odor problems near residential areas.
- DTE Biomass owns and operates the landfill gas collection system and pays City $15,000/yr for landfill gas rights. DTE Biomass also gets federal tax credits for capturing a pollutant.
- The City of Ann Arbor owns the electric generation system and Michigan Cogeneration Systems operates it.
- Michigan Public Act 2 allows public utilities to pay extra for energy from waste. Detroit Edison agreed to pay 5.75 cents/kWh for the Ann Arbor landfill electricity.
- Total landfill gas collected from Sep 1996 through Dec 2005 = 1.64 billion cubic feet. This is equivalent to removing 623,800 tons of CO2 from our atmosphere.
- Total electricity generated from Apr 1998 through Dec 2005 = 43,600 MWh, which were sold to Detroit Edison for $2.5 million. By displacing electricity that Detroit Edison would have generated primarily by burning coal this saves another 39,300 tons of CO2.
- Inside the stairwell of the City's Material Recovery Facility (MRF) is a mural of the landfill gas-to-energy system and the Waste Watcher characters illustrated by David Zinn. Read about it in this Refuse Into Power Brochure
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Recent landfill generation information and data below.
1930s: Landfill started as gravel pit.
1959-1984: Phase I was under City operation.
1984-1992: Phase II — "modern" landfill — was in operation.
1994: Landfill gas project planning began
1996: Landfill Gas Collection System constructed by DTE Biomass Energy:
- 38 wells in Phase I, surface collection system built into cap on Phase II
- Cost = approx. $1,000,000
- Over 2 miles of piping was buried in landfill to transport gas to blower/flare station.
Sep 1996: Landfill gas flare lit
1997: Landfill Gas-to-Energy Mural completed at the Materials Recovery Facility (MRF), illustrations by David Zinn.
Oct 1997: Electric generation system construction begins by Michigan CoGeneration Systems. Total cost was about $1.2 million.
Apr 1998: Landfill Gas used to power two 800 kW generators which produce enough electricity for 1,000 households.
(Currently only a single turbine generator is utilized at the landfill)
Electricity Production from Landfill Gas (per year) From 1998 to 2006 the landfill gas facility produced an average of between 5,000 to 6,000 MWh of electricity annually. This number is expected to decline as gas in the landfill is depleted. Each year these levels equate to the annual electricity use of 300 to 600 homes. The chart below shows annual electricity production (MWh) from 1998 to 2012.