Five Los Angeles-area sanitation districts have signed on with Atlanta-based EnerTech Environmental, a developer of renewable energy technologies, to convert their biosolids into a renewable fuel, called E-Fuel.
Scheduled to open in mid-2008, the nation's first commercial “sludge-to-fuel” facility is expected to convert 675 wet tons per day of sludge into about 145 tons per day of E-fuel, which will be sold to a local cement kiln as a coal alternative.
Until the development of the patented “Slurry-Carb” process, wastewater treatment plants have disposed of their primary byproduct—biosolids—by selling it as fertilizer, shipping it to landfills, or incinerating it onsite to power their pumps and boilers. The latter option has become less popular in light of tougher air restrictions and other sludge-to-fuel technologies, such as thermal drying, that often consume more energy than the resulting product generates.
Using heat and pressure, the SlurryCarb process chemically carbonizes the organic matter in the biosolids and ruptures the cell walls, releasing bound water. The resulting slurry is dewatered to 50% total solids using centrifugation rather than evaporation; it then dries using about two-thirds less energy than conventional drying methods. The energy savings result in about one-third reduction in overall cost when compared to traditional biosolids drying methods. The final product, E-Fuel, can be sold as a renewable fuel with approximately 7000 BTU per pound.
The SlurryCarb facility will be located next to the wastewater treatment plant in Rialto, reducing hauling costs of the biosolids as well as fossil-fuel emissions. None of the public works entities involved—Rialto, San Bernardino, Riverside, Orange County Sanitation District, and Los Angeles County Sanitation District—contributed to funding the new facility, which is owned and operated by EnerTech. The $78 million project is financed through private equity funds.
While the new option won't necessarily save the agencies any money—in some cases, sending biosolids to the SlurryCarb facility will cost more than traditional disposal alternatives—it's environmentally friendly.
“Why spend more money on biosolids removal when you can spend less?” says Layne Baroldi, legal affairs liaison with the Orange County Sanitation District. “Because it's the right thing to do.” The county estimates that the SlurryCarb method will cost $72 per ton compared to the $50 per ton it's been spending to send biosolids to a landfill in Arizona.
But continuing to ship biosolids out of state is not environmentally beneficial. California is very sensitive to environmental issues, especially the reduction of fossil fuels. By allowing this facility—and possibly more in the future—to be built, the state will reduce fossil-fuel emissions from trucks. In addition, using a renewable fuel keeps power plants from using precious non-renewable fuel.
Rialto may even make money in the deal. EnerTech has helped pay to close the landfill on which the SlurryCarb facility will sit; the landfill was due to close anyway, so Rialto got off easy by not having to pay the whole price. Plus, Rialto will charge $0.50 per wet ton to agencies that bring their biosolids to the facility.
For a demonstration of the SlurryCarb process, visit: www.enertech.com/technology/slurrycarb.html