Wastewater generated by carpet production could potentially be used to grow yet another crop for biofuel - algae.
Yes, algae. The stuff that clouds swimming pools, mucks up ponds and clings to boat sides and buoys. More than 2,000 gallons of oil can be made from one acre of algae. One acre of soybeans produces 48 gallons per year. Only 18 gallons can be made from one acre of corn annually.
Dirty water left over from carpet production is perfect for growing algae, said K.C. Das, director of the University of Georgia Biorefining and Carbon Cycling Program.
In Dalton, Ga., the "Carpet Capitol of the World," 85 percent of the wastewater flowing into Dalton Utilities comes from local carpet factories. In total, the utilities company treats and releases between 30 million and 40 million gallons of treated wastewater a day, said Senthil Chinnasamy, a postdoctoral research associate with the UGA College of Agricultural and Environmental Sciences.
Instead of applying this treated wastewater to designated areas, it could be used to cultivate algae in open ponds. With that amount of wastewater, a million gallons of biodiesel made from algae could be produced annually, enough to run the Dalton's entire fleet of government vehicles for a year.
Wastewater already contains nitrogen, phosphorus and other minerals, nutrients that would cost extra money to add. Algae can be grown in saltwater, too.
Right now, Chinnasamy and his lab assistants are growing it in large plastic tubes and oversized plastic bags. He's got samples of different algae in closed beakers in a growth chamber. Later this summer, they'll place promising species in plastic ponds to see how well they grow in uncontrolled environments.
The UGA researches are working to find cost-effective ways to harvest it and express oil from it. The oil can be turned into biodiesel, the protein added to livestock feed and the remaining carbohydrates into ethanol and methane production.
The U.S. Renewable Fuels Standard, signed into law in January, calls for the production of 36 billion gallons of biofuel annually by the year 2022. Currently, the country produces 8 billion gallons a year.
It would take 750 million acres of soybeans, or an area twice the size of Alaska, to produce 36 billion gallons of biofuel, Chinnasamy said. The same amount could be produced on 7 million acres of algae, or an area half the size of West Virginia.
In addition to its biofuel possibilities, algae can help reduce carbon dioxide in the atmosphere. It is considered carbon negative, meaning it uses more carbon than it produces. A kilogram, or 2.2 pounds, of algae pulls 1.8 kilograms, or 4 pounds, of carbon dioxide out of the air.
Despite its upsides, algae are difficult to produce. The ideal growing location, which is outside in ponds, is hard to regulate. It's hard to harvest, too, and must dry. It's now harvested mainly for its protein, which can bring manufacturers $6 an ounce.
One big downside now is that it costs about $5 to make a gallon of fuel from algae. Chinnasamy and Das hope their work will lower the cost to $1.50 a gallon, which would lower the cost of biodiesel and diesel blends and still give producers a profit.
Fuel made from algae could be available commercially in five years, Das said.