By Allen Hershkowitz, Natural Resources Defense Council
Should municipal solid waste (MSW) be converted into energy? Is it a renewable fuel?
Renewable Portfolio Standards (RPS) require electric utilities to generate a certain percentage of electricity from renewable energy sources. Although there are no federal renewable energy standards, as of 2010 twenty-eight U.S states had adopted an RPS standard.
While there is near unanimity among environmentalists, policy makers, and industry officials that recycling should be given priority in how we manage our wastes, in numerous states with RPS standards municipal waste is in fact classified as a renewable fuel and strong lobbying efforts are underway working to expand the number of jurisdictions that classify municipal waste as a renewable fuel.
It would be a mistake to classify municipal solid waste as a renewable fuel without carefully examining the facts. Most of the materials found in MSW cannot be considered a renewable fuel.
Let’s start with a description of what we are dealing with.
Here is the characterization of municipal solid waste according to the EPA, for 2009, the last year for which data are available:
- Plastics: 12.3%
- Metals: 8.6%
- Glass: 4.8%
- Paper: 28.2%
- Food scraps: 14.1%
- Yard waste: 13.7%
- Wood: 6.5%
- Rubber, Textiles, Leather 8.3%
- Other: 3.5%
Each category of waste has its ecologically optimal disposal route, and both public policy and private investments should encourage the routing of materials found in the waste stream to their best use. How should each category of municipal waste be handled for best ecological result? For the reasons summarized below, most, about 75% – 80%, should be recycled.
Plastics (12.3% of MSW) are petroleum. Some are made from natural gas, and a small amount might be made from coal. Although plastics contain about 12,000 Btus/lbs, they are fossil fuels and cannot be classified as a renewable energy source. Petroleum based plastics should be recycled.
Metals (8.6% of MSW) are made from non-renewable ores and minerals. They cannot be classified as a renewable fuel. Nor are they well suited for combustion. Metals are low in Btus (300 Btus/lbs compared with 12,000 Btus/lbs for plastics) and should be recycled. It is as a secondary raw material at the manufacturing sector, not in a combustor, that metals provide the greatest energy benefit.
Glass (4.8% of MSW) is manufactured using non-renewable fossil fuels, and is made from a non-renewable, albeit currently plentiful raw material. Nor is glass ideally suited for energy recovery. It is not high in Btus, containing only 60 Btus/lbs. Glass should be recycled.