Waste into Fuel


In the final scene of the 1985 classic film Back to the Future, Doc Brown zooms down in the Delorean to take Marty off to the future, but first he rummages through the trash to find garbage to feed directly into the car for fuel. Well, 26 years later, we still haven’t caught up with that future, but scientists and entrepreneurs are working hard to find the right technology for converting trash into fuel on an economic scale.

The first-generation biofuels, such as ethanol, biodiesel, and vegetable oil, are here; but they have done little to relieve the oil-dependency in the world. Almost all of them are generated from fresh organic materials, such as corn, sugar cane, or grain. Developers of second-generation biofuels are working with non-food organic materials, specifically waste biomass—garbage, corn and wheat stalks, wood chips, nut shells, etc. They are determined to use waste, avoiding landfills and incinerators.

The second-generation biowaste to liquid technology consists primarily of two conversion processes: thermochemical and fermentation. The goal of both is 100% efficiency using all of the byproducts—ethanol, steam, water, solids. Several companies have advanced to commercial scale; two of those are InEnTec, which uses the thermal-chemical process; and Ineos Bio, which augments the thermochemical reaction with a fermentation process.

The InEnTec PEM (plasma-enhanced melter) process accommodates a variety of materials—medical, radioactive, industrial, and municipal wastes—that can be converted to fuel and chemicals that replace petrochemicals in such products as plastics and roofing tiles. A pregasifier converts ≈80% of the organic material to syngas; the remaining material is fed into the PEM chamber, where a plasma arc gasifies the remaining organic matter. All of the syngas is fed into a thermal residence chamber and heated to gasify any remaining organic material; it is then “cleaned and conditioned in a series of standard processes to prepare it for use in final products”.

The IneosBio process uses a patented strain of bacteria to ferment syngas into ethanol. The syngas is produced from predried organic material that has been fed into a gasification chamber. Heat from the hot gas is used to generate the electrical power that drives the entire process.

Throughout the world, researchers are developing efficient ways to transform waste to fuel. In 2010, British Airways contracted with the Solena Group to build a facility to convert waste to jet fuel; they hope to begin using this fuel in their aircraft by 2014. Canadian officials are exploring processes that use wood detritus caused by the pine bark beetle infestation to create biofuel.

Perhaps someday we will feed trash directly into our vehicles in lieu of pumping gas. The future will bring third- and fourth-generation fuels; but for now, successful processes are available to turn waste materials into efficient fuels and practical chemicals.

[Editor’s note: The Aston Martin driven by Prince William and Princess Catherine on April 29 is fueled by 100% bioethanol fuel distilled from surplus British wine. Read more!]