Monday, June 11, 2007

Trash and Energy

Over the weekend I read an interesting article in the Economist on the merits of recycling municipal waste (MSW.) Normally "premium content", the article appears to be accessible through a sponsored link. It got me thinking about the future of trash, and its two main energy implications. The Economist provides some interesting statistics on the energy and greenhouse gas savings associated with recycling, but largely ignores the potential conversion of non-recyclable waste into energy streams, either electricity or fuels. Such efforts have gotten significant media attention recently, including a high-profile project of ConocoPhillips and Tyson Foods. Given the volume of waste generated globally, the energy benefits of getting smarter about its management are too big to ignore.

The Economist starts with the question of whether recycling is truly beneficial and quickly confirms this, based on an analysis of life-cycle studies. I was struck by the potential to improve recycling rates in the US, which they cite at about 30%, to levels comparable to Germany's more than 50%. The example of San Francisco, which apparently recycles 69% of its waste, shows what is possible, though it might be hard to achieve this nationally. Even at current rates, recycling apparently saves 49 million tons of CO2 emissions here, the equivalent of about 0.7% of our total emissions. Doubling that won't get us off the hook for reducing emissions from other sectors, but together with making better use of the energy content of the non-recyclable waste, it could prove to be one of the cheaper sources of emissions reductions.

The article gives some hints about how recycling rates could be increased, and better technology seems to be the key. Much of our current recycling effort depends on households and businesses separating recyclable material from other waste, and sorting it into categories of plastic, glass, metal, paper, etc. The "single-stream" recycling technology mentioned in the article eliminates the pre-sorting but still requires separation of recyclables from non-recyclables. That step might benefit from some financial incentives, such as crediting can and bottle deposits at the point of trash collection, rather than returning them to the point of purchase, generating additional fuel and handling savings in the process. Finally, it ought to be possible to increase the scale of the sorting equipment at trash facilities to eliminate entirely the need for pre-sorting into categories by waste producers. With the entire MSW stream separated into recyclables, energy feedstocks, and residual non-recyclables, only a small fraction would still need to be landfilled. The environmental advantages of that are obvious, but the energy benefits should be quite meaningful, as well.

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