Researchers at UC Riverside have unveiled a new process that can convert sewer sludge, wood, agricultural waste, plain old trash or even plastics into diesel oil for $1.00 a gallon. Viresco Energy, will pay $15 million for a pilot plant to be built in the next two years.
The the hydro-gasification conversion process, originally developed to produce clean-burning gases from coal has been adapted to be used with wet wastes. Whereas traditional gasification uses oxygen, the new technique uses hydrogen and steam at nearly 1,500 degrees to break apart the feed stock into a gas made up of its molecular components.
After gasification, the resulting gas then go through a couple of other steps and It comes out as water, wax and diesel. There is little waste, up to 85 percent of the feed material becomes usable liquid fuel at the other end.
"The system requires no additional fuel or energy other than the chemical energy in the waste feed," said Colin Hackett, manager of the Alternative Fuels and Renewable Energy Program at UCR. "This process has enormous potential for energy conversion from any wet-waste that contains carbon."
The program is conducted by the Bourns College of Engineering - Center for Environmental Research and Technology (CE-CERT) at UC Riverside.
This schematic diagram shows the component processes used in the Waste to Energy concept developed by UCR’s CE-CERT. Waste materials are ground into small particles (less than 1 mm in diameter) and mixed with water to form a slurry, which is then pumped into a steam generator that heats the mixture to about 700 C and 30 atmospheres pressure.
The superheated steam and hot waste particles are then mixed with hydrogen gas inside a long tubular reactor, known as a hydro-gasifier. Inside the hydro-gasifier, the hydrogen reacts with any carbon present in the waste particles and forms methane gas. The methane gas and the superheated steam are then fed into a second stage reactor, known as a steam reformer. In this reactor, the steam reacts with the methane to form hydrogen, carbon monoxide and carbon dioxide gases. Approximately half the hydrogen produced in the steam reformer is recycled back into the first stage hydro-gasifier, making it self-sustaining.
The remaining synthesis gases (hydrogen, carbon monoxide and methane) can either be used in a CE-CERT-developed variable gaseous fueled engine to produce electricity and process-heat, or sent on to a liquid fuel synthesizer designed to produce sulfur-free synthetic diesel fuel and recycled clean water. Molten salt heat transfer loops take heat away from the hydro-gasifier and fuel synthesis reactors and transfer it to the water steam generator and steam reformer reactor to make the system almost thermally self-sufficient. Thus carbonaceous waste and water feeds can be converted into fuels, process-heat, and recovered water in what is expected to be a series of self-sustaining processes.
The fuel has all the energy content of regular diesel without the sulfur, oxides of nitrogen and other components that led California to declare diesel fumes a cancer-causing substance.
Although the production cost may be about $1 a gallon, retail would be higher - but still far cheaper than current prices.
The process will be developed by a small company, Viresco Energy, that will pay $15 million for a pilot plant to be built in the next two years. The pilot plant will be built at the CE-CERT campus on Columbia Avenue and should be able to convert 10 tons of waste per day into fuel. Construction is expected to be complete by mid-2008.
If the performance requirements are met, a full-scale, 400-ton-per-day facility would be built. A plant of that size could produce 16,000 gallons of diesel from biomass materials or 30,000 gallons a day from coal.
Viresco Energy is already talking with the city of Riverside about building a 400 ton-per-day plant near the city's sewage-treatment facility, where sewer sludge can be turned to fuel, said Jim Guthrie, president of Viresco.
Costly gasification has been the step in Gasification-Fischer Tropsch processes that keeps them from being adapted. This type of process is more energy efficient than the biorefineries that are being used, but the capital cost of the process has been so high that the resulting product, which can be either ethanol, biodiesel or chemical feedstock, has been too expensive. If this gasification process proves economical it could pave the way to less expensive biofuels.
CE-CERT scientists developing process to convert wet bio-waste into energy as alternative to land application, UC Riverside Newsroom, April 3, 2002
From sludge to cheap and clean diesel, sbsun.com, Sept. 15, 2006