Edmonton is Canada's chief oil city as well as the capital of Alberta, the province that hosts the bulk of the country's tar sands. Given the expense of converting this mix of dirt and heavy oils to more usable petroleum products, the province is not keen on alternative fuels. Nevertheless, in 2012 Edmonton will host a chemical plant owned by Enerkem that will turn garbage into 36 million liters of ethanol and methanol per year.

"Waste as a feedstock [for biofuels] has a number of advantages," says Enerkem's co-founder and chief technology officer Esteban Chornet, a former engineer at the U.S. National Renewable Energy Laboratory. "It is logistically available and it is low in value, if not negative in value."

Turning garbage into fuel is potentially an answer to two pressing problems—diminishing the world's dependence on fossil fuels and an alternative to burying trash in landfills. In fact, the 468 million metric tons of trash produced in North America each year could provide 47 billion liters of ethanol—or roughly the same amount as produced from corn, which presently supplies 10 percent of U.S. gasoline demand.

Enerkem takes the "fluff" of municipal solid waste—the plastics, textiles and wood that isn't recycled or the leftovers of agriculture or forestry—gasifies it and, using catalysts and water, transforms the gas via multiple chemical steps into ethanol or other products. Other companies, such as Wheelabrator, simply fortify the gas and burn it directly to produce electricity—although that can result in the emissions of toxic chemicals, such as dioxins—or employ additional complex chemical steps. For example, Range Fuels in Georgia similarly attempted to gasify waste from the pulp and paper industry and transform it into ethanol directly but foundered in perfecting its catalysts. "Nature has not given us that selectivity to shift syngas to ethanol," notes chemical engineer Chornet, who started Enerkem in 2000 to make fuel from forestry residues, inspired by his father on Spain's island of Majorca, who made electricity by burning wood waste from his sawmill in the 1930s.

Similarly, BlueFire Ethanol turns waste into ethanol by using sulfuric acid to release the cellulose in the trash and then adds enzymes and microbes to ferment it into fuel. Coskata, Inc., has had a large demonstration plant that uses microbes to turn gasified waste into ethanol since 2009, and argues that it should remain the "major renewable liquid fuel" due to the ease with which biomass (or waste) can be transformed into it—although subsidies are required to develop the technology. "It's a pittance being spent on reducing our dependence on oil than putting our boys in harm's way overseas," says Coskata's Wesley Bolsen, chief marketing officer and vice president for government affairs.

Compared with making ethanol from crops, the environmental benefits of making it from waste are clear: It diminishes the demand for landfills and cuts greenhouse gas emissions. And trash-based biofuels need not compete on cost with fuels, as long as they offer a lower cost than their other competitor—landfills. That's why Waste Management, Inc., has invested in a slew of such waste-to-energy companies, including Enerkem. Ethanol-maker—and oil refiner—Valero Energy Corp. has also invested in Enerkem. Companies such as Ineos Bio are turning trash into other chemicals such as plastics. "Essentially, we intersect [with the waste] before it goes to the landfill, where it would just contribute to the methane gas already coming from there," says Ineos business manager, Dan Cummings.

In the end, making a fuel from garbage remains a promising opportunity—as long as the waste is already divvied up into its own component parts, as is happening in Edmonton and at the Three Rivers landfill near Pontotoc, Miss. In 2013 Enerkem plans to open a plant there, too, with the help of $130 million in taxpayer funds from the U.S. Department of Agriculture and Department of Energy. The plant will turn 300 metric tons of raw fluff per day into 36 million liters of ethanol per year. "The business of ethanol is a very substantial market opportunity," Chornet says. "You can place it in refineries throughout North America. You can substitute it for corn ethanol if produced at a lower cost."

7 Comments

1. 1. Ragtrade 12:43 PM 8/10/11

   The Oil giants won't like that and will lobby as hard as they can to protect what they see as their territory. I think the waste to ethanol companies will find a lot of resistance one way or another. Look what happened with Corn to ethanol. It was only when the oil companies figured out that they could sell oil as fertiliser to the corn farmers that the oil companies removed the pressure.

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2. 2. chubbee 06:29 AM 8/11/11

   Whatever happened to thermal depolymerization?

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3. 3. rmflowe 09:29 AM 8/12/11

   Having read the print version "The False Promise of Bio-fuels" in the August SA issue, and this online-only article about extracting energy from waste, I wish SA had included this more hopeful aspect in their print article. This would have provided a more balanced treatment of the challenge to develop diversified, renewable energy to a wider audience. Instead it seems SA emphasized the technical and economic challenges of up-scaling non-food-based bio fuel production, and questioned the wisdom of public investment in these technologies.
   As one would expect from SA, a close reading of their print article provides an objective discussion of the relevant facts. But the title grabs attention, and biases the cursory reader to conclude that federal investments in developing bio-fuel technologies represent yet another wasteful federal boondoggle. In the current political environment, where every nickle of federal investment will be scrutinized, SA's apparent skepticism regarding the potential payoff of bio-fuels paints a target on such investments.
   I believe an equally valid case can be made that the modest amount of federal investment in solving the scale-up challenges is well worth the potential economic, political, and environmental benefits of developing non-food-based bio-fuels.
   But that more comprehensive cost-versus-benefit aspect did not emerge in the SA print issue. Instead, the article focused on the cost of bio-fuels relative to gasoline, which (due to the distortions in the energy market) make bio-fuels--or any renewable energy source--appear economically non-viable. This narrow and simplistic perspective leads to the conclusion that any benefit from bio fuel investment is far off and highly speculative, and the money invested thus far has been wasted. I can hear the budget cutters sharpening their knives already!
   This pessimistic view is contradicted, as the online article points out, by the fact that businesses are profitably mining our landfills for energy, addressing multiple energy/environmental problems at once, and illuminating the potential of the "green economy". These examples provide evidence that although the challenges are large, and haven't been solved yet, progress is being made, economic viability is not out of reach, and there is cause for patient optimism and sustained support.

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4. 4. coqui 11:36 PM 8/12/11

   It is very interesting how when talking about this very tantalizing subject of turning any garbage into energy, we see even in a scientific magazine like this proof of serious misconceptions regarding the most basic knowledge of the process of combustion. I refer to the line in this article where the concern about the production of dioxins is given when talking of the burning of a gas product from a previous process. It is the first process of "gasification" or whatever acronym you want to give to the basic process of combustion that these dioxins form due to the variety of molecules available for its formation. The combustion of a gas (that was produced in a "controlled manner") is fairly clean by comparison but it is too little too late. This is because by then, a fair amount of dioxins were formed in the previous process due to the sheer volume of raw materials used (and needed) to make my "clean energy process" rentable to the extent that allows me to pay for the loan needed to buy all the equipment and sophisticated technology.

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5. 5. eco-steve 10:07 AM 8/15/11

   The simple answer to trash disposal is to pyrolyse it, then transform the char into fuel using the Fischer-Tropsch method used by the germans during WW2 to convert coal into fuel. see www.eprida.com technical pages.
   This is basically copying how nature transforms plankton into oil. No fermentation or bio-catalysers are necessary, and the method is fast.

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6. 6. NotSoScientific 12:05 PM 8/24/11

   I get the very basic premise of these concepts. But for those of us who aren't chemistry/biology buffs - what are the benefits and drawbacks of these methods you're discussing? What is the true cost of these methods, when all subsidies are removed? And what can everyday citizens do to help make cleaner energy a reality (keep in mind I'm Canadian).

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7. 7. sibosf in reply to chubbee 12:27 PM 9/18/11

   Yes, what about catalytic cracking of cellulose? I had heard that although dynamic catalytic cracking requires a great deal of heat energy. The payback is that the cracked product itself (a form of liquid hydrocarbon) could be used to supply the energy needed to crack the incoming cellulose entering the "cat-cracker" (reactor). Simply put some of the biomass fed to the reactor (a percentage) is consumed in the polymeric cracking process. The remainder becomes a hydrocarbon product not all that different from crude oil! Wouldn't it have been a good idea to include this knowledge too in the SA article, "The False Promise of Biofuels"? Or, is the jury not "IN" on the catalytic cracking of biomass process? Anyone care to take a stab at this?

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