OVERALL, THE Boston mayoral candidates agree with the city’s goal to cut greenhouse gas emissions. Several have mentioned that they want to see improvement in Boston’s recycling rate, which, at 20 percent, is 10 percent lower than the national average. But to match recycling rates of 80 percent in San Francisco, 65 percent in Los Angeles, or 55.7 percent in Seattle (a city comparable to our own size), we need to go a lot further than the suggestion of John Connolly and Felix Arroyo to add more recycling bins on streets and in parks or Charlotte Golar Richie’s idea of recycling competitions.
San Francisco’s high rate of diversion of waste from landfills is partly because the city has been collecting organic waste at curbside along with regular recycling since 1996. Organic waste, which includes food scraps, yard clippings, pizza boxes, paper, and paperboard, comprises 56 percent of the waste stream nationally. Once buried in a landfill, it produces methane — a greenhouse gas that is 20 times more potent than carbon dioxide, even though it stays in the atmosphere a shorter time. Food waste in Boston comprises 20 to 25 percent of the current waste stream (not including paper and paperboard), so recycling it would put us in line with other leading cities.
Organic waste is recycled through industrial scale composting or anaerobic digestion, the latter of which is supported by all the candidates who answered environmental questions posed by the Globe. Anaerobic digestion captures reusable biogas by breaking down bacteria in an oxygen-free environment. The resulting product, which is 60 to 70 percent methane and 30 to 40 percent carbon dioxide plus trace elements, can be used for fuel in many types of applications. Manure from agricultural sources is often used in digester projects, and organic waste from households and commercial enterprises could meet more of our region’s power needs through diverted waste materials.