GM bets on new ethanol fuel from waste

Gerry Malloy

SPECIAL TO THE STAR

There are plenty of opposing opinions when it comes to what fuel or power source should replace gasoline. But few alternatives, if any, are as controversial as E85 ethanol (85 per cent ethanol and 15 per cent gasoline).

Its proponents say producing and using ethanol means reduced emissions of greenhouse gases (primarily carbon dioxide), as well as carbon monoxide and other toxic compounds. Also, it can be produced locally and it offsets the use of gasoline, which is a particularly big motivator in the oil-importing U.S.

Its opponents say that one or both of its CO2 and energy balances are negative (meaning it generates more CO2 and uses more energy than it saves), and using it in commercial quantities would upset the food supply and raise food prices.

In addition, because its energy content is lower than that of gasoline, fuel consumption goes up, which means shorter driving range and more frequent fill-ups. Unless E85 is substantially cheaper than gasoline – which is unlikely without subsidies – it will cost people more to use.

The problem in trying to understand what is valid about either argument is that you can find credible studies to support whatever position you choose.

But almost all have one thing in common: They are based on the production of ethanol from grain feedstocks, particularly corn, which is the predominant method for making ethanol in North America.

If ethanol were produced from sugar cane, as it is in Brazil, or from cellulosic plant matter such as straw, switchgrass or wood wastes, the equation would change. And if that process resulted in a fuel substantially cheaper than gasoline, most of the claimed drawbacks to ethanol use would disappear.

That is why General Motors' announcement at the Detroit auto show that it is endorsing and investing in a cellulosic-ethanol producer called Coskata is so promising. It could tilt the playing field inarguably in favour of ethanol.

Coskata claims to have developed a commercially feasible process for producing ethanol not from agricultural food products but from such sources as municipal solid waste (trash), agricultural and forest residuals, and other carbon-containing compounds.

The technology is said to convert materials that have frequently reached the end of their useful life cycle into renewable energy, in a process that is energy-positive.

The production process involves three steps:

Step 1 is the gasification of the raw material using existing technologies.

Step 2, which is key to the whole process, involves the use of "bugs" — what Coskata calls "proprietary micro-organisms." Those patented bio-organisms convert the resulting gas mixture into ethanol by consuming the carbon monoxide and hydrogen in the gas stream.

In Step 3, after the gas has been converted to liquid, the resulting ethanol is recovered from the solution using "pervaporation technology."

The Coskata process eliminates the need for costly enzymatic pre-treatments used in other cellulosic processes, and the bio-fermentation takes place at low pressures and temperatures, further reducing costs.

It's said to have the potential to yield more than 400 litres of ethanol per tonne of dry input material, reducing both operating and capital costs. The combined separation and recovery processes promise to reduce the required energy by as much as half.

Ethanol produced this way is forecast to cost less than 25 cents per litre in commercial quantities – more than competitive with gasoline, even considering its lower energy content.

A pilot plant is scheduled to begin production later this year. If it proves as successful as its backers, including GM, predict, chances are good that we will be pumping E85 into our tanks within a few years, saving money and helping the environment as we do so.

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