I am writing to you today because recently The Sun has published letters urging Governor O'Malley to veto the bill approved by the Maryland General Assembly according Tier 1 status to waste-to-energy (WTE) facilities. The Earth Engineering Center of Columbia University (www.eecny.org) has been engaged for several years in the study of various means of dealing with the ever increasing tonnage of municipal solid wastes (MSW). Also, every two years we conduct a national survey of MSW generation and disposition in the U.S. This survey is published in BioCycle journal and its results are used by EPA in estimating the greenhouse gas impacts of waste management in the U.S.

The Columbia/BioCycle 2010 national survey showed that Maryland is one of the top five states approaching sustainable waste management, precisely because it combines recycling and composting with energy recovery from post-recycling wastes. Even so, the state still landfills about 3.5 million tons of municipal solid wastes (50 percent of the total MSW generated), most of it out of state. If, somehow, this amount were to be combusted for electricity generation, it would reduce coal imports to Maryland by 1 million tons.

Therefore, encouraging the building of new WTE facilities in the state is a win-win situation, both economically and environmentally since one ton of MSW combusted rather than deposited in landfills reduces greenhouse emissions by as much as one ton of carbon dioxide.

It is surprising that well-meaning environmentalists continue to oppose WTE, thereby effectively perpetuating transport of millions of tons of MSW to other states where they result in transforming green fields to landfills. Instead of concentrating on ways to increase recycling and composting, they oppose the only alternative to landfills for post-recycling wastes: WTE. Yet the state at the very top of the "ladder for sustainable waste management" in the U.S. is Connecticut where 26 percent of the MSW are recycled or composted, 62 percent are combusted with energy recovery, and only 12 percent are buried in landfills. In contrast, San Francisco does an excellent job in recycling and composting but, in the absence of WTE, it deposits in landfills about 500,000 tons per year, or about 0.67 tons per capita, versus only 0.12 tons per capita in Connecticut.

By now, international experience and science have shown clearly that controlled combustion of MSW in waste-to-energy plants is environmentally much superior to using landfills. Twenty years ago, not enough was known about the emissions of incinerators; the same was true in earlier years for other high temperature processes, such as steel and copper smelting furnaces. However, in the early 1990s, EPA promulgated its MACT (Maximum Achievable Control Technology) regulations. As a result, the existing waste-to-energy facilities are one of the cleanest sources of energy, much cleaner than the coal-fired power plants that provide 50 percent of U.S. electricity.

Of course there are also people who, despite all the evidence to the contrary, are convinced members of the Flat Earth Society. Hopefully, Governor O'Malley will not reverse the wise decision of the state legislature.

Nickolas J. Themelis, New York

The writer is director of the Earth Engineering Center at Columbia University.