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Future fuel: City mulls fueling buses, garbage trucks with landfill gas

Gas from Fargo's landfill is already used to generate power and heat, but there's enough left to fuel the city's buses and garbage trucks as well. By removing moisture and impurities, the landfill gas can be converted to natural gas suitable for ...

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Heavy equipment with spiked steel wheels compact garbage as it is hauled in to the Fargo landfill where methane gas is eventually captured. Dave Wallis / The Forum
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Gas from Fargo’s landfill is already used to generate power and heat, but there’s enough left to fuel the city’s buses and garbage trucks as well. By removing moisture and impurities, the landfill gas can be converted to natural gas suitable for use in specially equipped vehicles. That’s a good thing because fuel is one of the highest costs of operation for city vehicles. City buses, garbage trucks and police cruisers use an estimated 1,118 gallons a day or 407,900 gallons a year. City staff is mulling converting part of the fleet to natural gas, especially residential garbage trucks, which get terrible mileage due to stop-and-go driving.   How much gas is in there? Total emissions is estimated at: 1,300 standard cubic feet per minute. The city uses or sells: 900 scfm. Untapped gas: 400 scfm. How much?: Since the 1,300 scfm is an estimate, the city would likely invest in equipment to treat 100 scfm to start with. That can be converted to enough natural gas to replace 500 gallons of gasoline or 440 gallons of diesel a day. HOW MUCH fuel does the city fleet use daily? 48 buses use 673 gallons 24 garbage trucks use 247.1 gallons 43 police cruisers use 197.4 gallons TOTAL: 1,118 gallons   How much does clean fuel cost? All-in option   $6.3 million to refine landfill gas, build new fueling stations and retrofit garages $120,000 a year to operate  25 years to reach break-even point from savings Phased-in option $1.3 million to refine landfill gas for generator to start with. Fueling stations and other equipment may follow $40,000 a year to operate  1 year to break even Landfill gas is going to the generator now but it’s not refined enough and leaves a residue that requires annual cleanup. Refined gas will eliminate this cost. What’s next? City staff plan to go with the phased-in option and will issue a zero-interest bond to raise funds. The City Commission still has to OK any spending. As other funds become available, possibly federal grants, investments in natural-gas vehicles would follow.

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Heavy equipment with spiked steel wheels compact garbage as it is hauled in to the Fargo landfill where methane gas is eventually captured. Dave Wallis / The Forum

Collector pipes capturing methane gas can be seen around the perimeter of the Fargo landfill. FROM GARBAGE TO FUEL As garbage decomposes, it releases methane, CO2, water vapor and other gases that make it stink. Gas extraction wells tap into gas deep inside a garbage mound and pipe it away. Before it can be used, the gas is refined so it’s mostly methane, the combustible component of natural gas. Some CO2 and other gases are captured in filters and discarded. Compressors squeeze the refined gas into a smaller volume to make refueling faster. Besides saving money, natural gas burns cleaner than diesel or gasoline, which means less greenhouse gas and pollutants. But there’s the added cost of natural-gas vehicles, new fueling stations and garage modifications so leaked gas doesn’t cause a fire. Also, landfill-gas emissions may vary day to day, so purchased natural gas will be needed as backup.   SOURCES: Terry Ludlum, Fargo solid waste director; City OF Fargo; EPA

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