The economics of waste-to-energy lie in calculations that are based on an EPA Waste Reduction Model. That takes into account all aspects of the change in a life-cycle evaluation and is universally accepted as the model for calculating greenhouse gas emissions. The model uses whole life calculations, which consider the cost of producing new products from virgin materials when it’s looking at recycling, and looks at avoided costs when talking about trash. Transportation costs, mining costs, and manufacturing costs, as well as materials costs, are included.

Negative numbers mean that more greenhouse gas emissions is avoided using a specific process than is created. Aluminum, for example, is environmentally very bad to create new, so shows enormous savings with recycling. Paper is also good, and glass is about even because of its weight and the difficulties associated with handling it.

Next to transportation and home heating, municipal solid waste is the largest contributor of greenhouse gases. More than half the nation’s municipal solid waste is sent to landfills. Landfills are essentially inefficient anaerobic digesters that allow methane to outgas, mostly due to organics decomposition. They need to be covered every day, but the covers are mostly for birds, rats, and odors, not gas containment. In fact, the cover needs to be permeable for gasses.

Since methane is 28 times worse than CO2 as a greenhouse gas, it has to be burned to turn it into CO2, but that gas capture and burning is only required when a cell is closed.

In Maine, Juniper Ridge (Casella’s landfill) captures the gas and flares it off, which just makes more CO2. Unfortunately, the plan for the now-closed Brunswick Landfill is also to capture and flare of the methane. Not great, but a lot better than just letting the methane escape into the air, and a much smaller landfill than Juniper Ridge.

Norridgewock (operated by Waste Management Systems) captures and burns the gas for Waste to Energy. 2,500 tons per day of trash goes into that landfill, and the outgassing generates 3.2 megawatts of power for the grid, but the big savings in is avoided alternative sources of the 3.2MW. Better than using fossil fuel natural gas, The captured methane is cleansed of silicates, then simply burned to run large diesel engines to turn turbines and generate electricity.

EcoMaine takes in about 500 tons per day, but generates 15-18 megawatts of power by using a much more efficient system of burning the trash directly and scrubbing the stacks of offending materials. Only water steam is allowed to escape after it passes through the turbines to make the electricity.

Members of the Brunswick Recycling and Sustainability Committee have done the calculations with the Waste Reduction Model. Overall, the charts demonstrate that waste-to-energy avoids about 3 metric tons of CO2 per ton of municipal solid waste that is collected. Much of that is because energy recovery displaces other electricity generating sources, and much is because we avoid putting the methane into the air when we either flare it off or burn the trash directly.

For Brunswick, the end result is a net reduction of about 2,800 metric tons of CO2 equivalent per year fewer emissions if we go to EcoMaine and their waste-to-energy plant for the trash now being landfilled by Casella.

The Recycle Bin is a weekly column on what to recycle, what not to recycle, and why, in Brunswick. The public is encouraged to submit questions by email to brunsrecycleinfo@gmail.com. Harry Hopcroft is a member of the Brunswick Recycling and Sustainability Committee.

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