Ashes to housesOne of coal's big messes is transformed into building blocks
Mary and Kee Augustine, Navajo elders, live in this home, which was built in 2005. For 35 years before that, their “home” was a 1960s cinderblock box. Its foundation was crumbling, it lacked insulation, and had bad heating and a leaky roof. This new home is comfortable, cool in the summer and warm in the winter, and it was designed with Navajo tradition in mind. It was made possible by a partnership between the Arizona State University Stardust Center for Affordable Homes and the Family and the Navajo Housing Authority. It was also made possible by flyash – the nasty gray soot that’s left over after burning coal.
Each year, along with all the pollution they put into the air, coal-fired power plants in the U.S. collectively regurgitate some 129 million tons of solid waste, about half of which is flyash. Both the sheer magnitude of the waste and its composition – it can contain high levels of various toxins, including selenium, arsenic, mercury and lead – make it a challenge to deal with. While power plants near surface coal mines can just dump the stuff back into the mine, other plants have a tougher time figuring out what to do with all of the junk. And a push by activists for stricter federal regulations could make things even more difficult, even for those who dump into the mines.
In Page, Ariz., however, the Navajo Nation’s housing authority has taken a novel approach to utilizing the stuff. In 2005, it opened the Navajo FlexCrete plant just a stone’s throw from the gigantic Navajo Generating Station. There, the company uses flyash from the power plant to create building blocks for homes.
The main structure of the Augustines’ Nageezi home is made of FlexCrete blocks. They look, at first glance, like conventional concrete cinderblocks, but they’re not. They are solid and much lighter than concrete and, because they are aerated, provide their own insulation. The blocks are between 60 to 70 percent flyash; the rest is a combination of nylon and conventional cement.
Using flyash in place of cement isn’t unusual; in fact, people have done it since Roman times. Today, some 15 million tons of flyash go into concrete products each year, with that much again recycled for other uses such as road base. But the Navajo FlexCrete plant uses more flyash in its product than many other companies, giving the power plant one more place – aside from a landfill -- to put its ash. According to Paul Ostapuk, an environmental engineer for the Navajo Generating Station, that helps the plant recycle 80 to 90 percent of its flyash (currently, only a small portion goes to FlexCrete, with the rest shipped to cement companies around the region). The average U.S. coal-burning plant only recycles about 40 percent of its ash. And, since manufacturing one ton of Portland cement kicks nearly one ton of greenhouse gases into the atmosphere, using flyash in place of cement helps air quality.
That’s not to say that the enviros are all holding hands and singing “Kumbaya” over all ash recycling. “Not all ash reuses are created equal,” says Lisa Evans, an attorney for Earthjustice who is an outspoken proponent of stronger regulations for disposal of coal combustion wastes. Sometimes, the stuff is used as road base, or even spread on icy roads for safety, which risks introducing particulates and potential toxins into the environment. Meanwhile, some flyash has been found to be mildly radioactive – depending on the source of the coal – which concerns Evans. But generally, she supports projects like FlexCrete, as long as tests show that the ash is not radioactive.
Jim Shirley, Navajo FlexCrete’s plant manager, says toxins are not a problem with his product. His company uses only the “cleanest” portion of ash, and it’s all tested by Arizona State University for contaminants before it’s used.
The plant produces some 2,000 pallets of bricks each year, which have been used in houses from Phoenix and Flagstaff, Ariz., to Durango, Colo., to Santa Fe and Nageezi, N.M. Shirley says the company is hoping to soon establish distributors in Phoenix, Telluride, Colo., and possibly in Utah.
Daniel Glenn, Stardust’s design director, hopes to expand his organization’s use of FlexCrete because he considers it a local, green material that fits Stardust’s criteria for building affordable homes. He also likes it because of it has a high insulation value, and discourages both termites and fire. In addition to the Nageezi home, Stardust has designed and built a home with FlexCrete in Guadalupe, Ariz., one of the poorest non-reservation areas in the country, and is hoping to use the blocks for a 200-home project on the Salt River Pima Reservation in Arizona. Meanwhile, Glenn and his colleagues are working with the Navajo Housing Authority to create a prototype of a FlexCrete home that can be mass-produced on the reservation.
“We need to find ways to build with local materials,” says Glenn. “We can’t rely on importing materials from other regions.” With Western power plants pumping out some 17 million tons of solid coal waste each year, ash is one regional material that’s not in danger of running out.