Straight Talk on Biodiesel, Veggie Oil

William Kemp is the author of Biodiesel Basics and Beyond, a how-to on making fuel from all manner of oil-producing plants. While he is an advocate of the technology, he offers a sobering assessment of its limitations in his answers here:

Mechanically, what is the difference between grease cars and biodiesel cars?
What it boils down to is biodiesel can be used with the existing fuel infrastructure of any diesel vehicle, while straight vegetable oil can’t be combusted in a modern diesel engine without modifications. Also, in grease cars you need a system to preheat the oil and filter it before the fuel can be combusted.

And what about the costs?
Straight vegetable oil has the advantage in that the cost and complexity of the fuel drops dramatically, compared to biodiesel. If you look at the costs of making biodiesel, 70 percent of the cost of the fuel is the feedstock — that’s the canola, soy or peanuts that are used to eventually produce the fuel. The rest of the cost is processing that feedstock. You don’t have those costs with straight-oil fuel, although capital costs must be amortized.

Which is easier to use?
Biodiesel. You still need some petrodiesel or biodiesel fuel to run a vegetable oil car. The car has to start on diesel and it has to be shut down on diesel. So owning a vegetable oil car becomes more of a tinker’s game.

Once the oil is hot, what’s the difference between the two fuels?
Once the temperature of the vegetable oil gets to 176 degrees, viscosity of the oil comes down to the level of diesel fuel and it becomes much like straight diesel fuel.

Will vegetable oil cars ever be a mainstream mode of transportation?
In a word, no. I think using virgin vegetable oil or waste vegetable oil is always going to be a fringe sector of the transportation industry. Automakers will never get behind it.

Which is better for the environment?
With biodiesel you have the farming and harvesting for the feedstock that’s eventually processed to make the biodiesel. That has to be taken into consideration in the overall formula for the carbon released when you burn it. Then there’s also the toxicity of the chemicals used to make biodiesel — those can endanger the environment. The beauty of using waste oil is it’s something that’s already been used and you’re giving it a second life, providing low carbon and air pollution emissions.

Do you support one fuel over another?
I’m not a big advocate of using food crops for fuel. Even if we exploited all the biofuel potential in North America it would be no better than enforcing higher fuel efficiency standards for all vehicles. And does anyone really need a 300 horsepower car to get to work? Energy efficiency first, energy generation second; that is the sustainable path.

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