Building on Britain's MSW to energy process
As the number of landfills continues to dwindle, Green Power Technologies Inc. believes North America could learn a lesson from the British, who widely use organic portions of municipal solid waste in biomass energy processes. And with a few changes to that system, North America could reduce landfilling and harmful emissions, while creating significant revenue for municipalities, according to the company.
The company essentially reversed the common British process. In Britain, the material goes through an autoclave first, where injection of high pressure and high temperature steam sterilizes it and also shrinks its volume by about 60 percent, according to Steve Gilchrist, vice president of Green Power Technologies. Next, the plastics, metals and glass are separated from the organics. That separation is made more difficult, though, by the fact that the autoclave deforms plastics, trapping some organic materials within them. “The end result is they don’t do a very good job so they end up scrapping or landfilling anything that can’t be separated perfectly,” Gilchrist said.
Green Power Technologies’ design separates the organics from the waste first. “What’s left are almost exclusively the organic fractions,” Gilchrist explained. With the reversed process, only the organic portions enter the autoclave, yielding a homogenous-looking, pulpy mass—not unlike shredded wood—that can then be baled, pelletized or briquetted for use in power plants, cement plants, cellulosic ethanol processes, or fertilizer. “You’re not creating additional unnecessary handling of the plastics,” Gilchrist said. The tweaked system also increases the amount of organics in each processed batch. “It’s just a far more streamlined process.”
The lack of space for landfills in Britain, along with incentives for diversion of organic waste, has driven the push for waste-to-energy processes there, Gilchrist said. “We see this as a way to leapfrog over their generation one approach to municipal solid waste-to-biomass and do something a lot more efficiently at a lower cost.”
In addition, municipalities can earn revenue by selling the resulting biomass product, instead of paying for the waste to be landfilled, according to Gilchrist. Tipping fees are already astronomical in some areas and will only go up as the number of landfills decreases. “The benefits of this are only going to increase as landfills keep closing.”
Gilchrist will discuss the process further during the panel Energy Production Opportunities for Communities from MSW and Wastewater Streams at Biomass Power & Thermal’s International Biomass Conference & Expo May 2-5 in St. Louis. For more information or to register, click here.
Gilchrist will be joined by Valentino Tiangco of the Sacramento Municipal Utility District, Andre Levchenko of Setaram Inc. and Caixia Chen with the East China University of Science and Technology.