Yesterday, 2nd Green Revolution visited the Denver Arapahoe Disposal Site, commonly referred to as DADS, a landfill serving the greater Denver area. Currently the largest landfill in the state of Colorado and consistently in the top five nationally, DADS handles approximately 12,000 tons of waste a day or 3.7 million tons annually. The site is owned by the city of Denver and operated by Waste Management (WM), the largest handler of waste in North America. Although not often considered an environmentally friendly company, Waste Management is also the largest recycling firm in North America. Throughout the tour, our guide (a site engineer at DADS), pointed out the various steps that WM has taken to reduce its impact on the surrounding environment. One of the major projects is the recent addition of a $4 million (US) waste-to-energy plant. Installed in July of last year, the plant burns methane – landfill gas – to generate electricity, which it sells to the local utility, Xcel Energy. According to their website:
“Waste Management operates the largest network of landfills in our industry, with nearly 300 sites managing the disposal of millions of tons of waste per year. This provides us with a vast supply of a natural, renewable energy source: landfill gas, or methane. This gas, which is created naturally through the decomposition of waste in landfills, is a readily available, renewable energy source that can be collected and used directly as medium Btu gas for industrial use or sold to gas-to-energy plants to fuel engine or turbine driven generators of electricity. Landfill gas has lived up to its promise of being a reliable and economical form of energy.”
Some opponents argue that landfill gas is not a renewable energy source. While this argument has merits, the fact is that methane, CH4, is nearly 20 times more effective at trapping heat in the atmosphere than carbon dioxide. The waste-to-energy plant at DADS currently produces 2.8 megawatts of electricity, enough energy to power up to 3,000 homes. In addition, the site was built with future expansion in mind. There is space for four more generators. Furthermore, the current 16 cylinder generators can easily be replaced with 20 cylinder ones when the landfill starts producing more gas. This expansion could allow the waste-to-energy plant to generate upwards of 10 megawatts, enough energy for more than 10,000 homes. From the initial $4 million investment, our guide said that WM “broke even”, meaning that for the 6 months the plant was operational last year, they saw a return on investment in line with other investment opportunities. If the methane had not been used to generate electricity, the gas would have been released into the atmosphere or flared (resulting in the less potent carbon dioxide), which is a waste of energy.
- Eric Wilson