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New Life for Crematories' Waste Heat

The idea of capturing waste heat for other purposes is well known and very green, but what about when the waste heat is derived from burning the dead?
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Imagine a swimming pool heated by your dead grandmother. The town council in Redditch, England, recently approved a plan that will make this possible. Waste heat from a local crematory will heat water that will be piped to a nearby recreation center and used to heat the facility and its pool, saving about $23,000 a year in heating costs.

The idea has some asking if the process honors the dead or exploits them. "Some grieving families like the idea of their loved ones 'giving back something,'" John Troyer, deputy director of the Centre for Death and Society at the University of Bath, told the Guardian newspaper last month. "I see that becoming predominant, and this research as an opportunity to do something innovative and respectful to the funeral mourning process." Troyer, whose career has been spent looking the intersection of death and culture, is the lead author of a paper exploring crematoria heat capture.

"We are aware that it's controversial, but the people who oppose this don't understand exactly what we're doing," said Ceridwen John, the Redditch Borough Council's climate change manager. "People are dying anyway, and many choose to be cremated. Our options are to expel the waste heat into the atmosphere or to do something useful with it."

Redditch is acting in response to recent European Union legislation that requires crematories to reduce mercury emissions by 50 percent by 2013. Mercury is in dental amalgam fillings, which millions of people have. Upon cremation this mercury is volatilized and released into the atmosphere with the flue gas, where it can pollute lakes and accumulate in animals, like eagles and fish. Extracting the mercury requires cooling flue gas from 800 degrees Centigrade to 150 degrees; this waste heat is then pumped through a heat exchanger, a network of parallel pipes that allows two fluids, in this case flue gas and water, to transfer heat without contacting one another.

As flue gas cools, the water warms. Industrial facilities that generate a great deal of heat, like petrochemical plants or incinerators have long used heat exchangers to conserve energy, but the practice is just beginning to blossom in crematories.

"Recapturing energy is not rocket science, but you need to have a use for that energy," said Paul Rahill, the environmental and technical adviser for the Cremation Association of North America and president of the cremation division of Matthews International.

His team is working on several crematory heat recovery projects in Europe. In Stockholm, they will use the water heated by crematory waste heat to warm cemetery roads in winter, melting snow and saving salt. In summer, the hot water will be put through an absorption chiller, generating cold air for general air conditioning and the freezer rooms where bodies are kept before cremation. In the United States, the company is working on a way to transform crematory waste heat into electrical energy that can be put back on the grid, a technology they hope to have operable within the next few years.

But as of now, U.S. crematories don't utilize waste heat. For one, crematories in Europe are larger, performing on average about 1,100 cremations a year, verse 400 in the U.S., making energy recovery projects there more feasible. Amalgam fillings are also more popular in Europe, helping to inspire the mercury emissions laws that have promoted crematory heat recovery projects. (While the U.S. currently has no law restricting crematory mercury emissions, cremations are on the rise, making some health officials think we need one.)

But there is another reason; Europe is simply ahead of the U.S. on urban energy conservation.

"I don't think we have been good systematic thinkers," said Paul Mankiewicz, who directs The Gaia Institute, a New York City-based organization that aims to better integrate human communities and natural systems. "We have moved industry away from urban centers, which is problematic. If you don't connect the flow of waste materials to the flow of production, you're missing the boat."

In New York City's Bronx neighborhood, Gaia has generated a space for water capture storage in sidewalk tree planters by using glass bits recycled from the city's waste stream and processed at a nearby plant. Another project involves mixing shredded Styrofoam coated with organic pectin and a compost made from discarded pumpkins and Christmas trees to create "GaiaSoil," which weighs one-fourth as much as silica-rich regular soil, making it advantageous for green roofs.

Will crematory-heated pools ever become popular in the U.S.? Mankiewicz is matter of fact: "I am sure the idea of having a dead body so close to water would be a problem for some people," he said. "But if you breathe air, you're breathing air breathed by someone who is now dead."

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