Biodiesel: Gas from Grease

It can stir up more than fast-food cravings and grumbling stomachs—the smell of French fries just might inspire people to go green.

At least, that was the case for Brad Biddle, co-founder of a biodiesel think tank in Phoenix, Ariz.

Groups in Arizona and New Mexico are working to increase local biodiesel production and distribution.

When his buddy, Eric Johnson, drove his car up Biddle’s driveway, stinking up the air with homemade biodiesel fumes, Biddle was intrigued.

After finding out that making biodiesel only requires some household chemicals and a bucket of old grease, Biddle asked himself, “Why isn’t everyone doing this?”

Together they launched the Desert Biofuels Initiative—one of several Southwest organizations aimed at advancing the local production and use of biofuels.

They have focused on the waste vegetable oil market, working toward a day when “every drop of waste veggie oil is converted to biodiesel,” Biddle said.

“Homebrewers” like Johnson collect used oil from restaurants and turn it into fuel by performing a chemical process called transesterification. The process requires adding lye and methanol to the oil, which changes the oil’s chemical structure and allows it to power a conventional diesel engine.

Unused vegetable oil – also called straight vegetable oil – can be used as fuel, but requires the installation of an engine conversion kit.

Biodiesel can be made from nearly any animal fat or vegetable oil, but about 90 percent of the biodiesel used in America comes from domestically grown soybeans.

The U.S. produces about 3 billion gallons of waste vegetable oil every year, according to the U.S. Environmental Protection Agency (EPA). Converting every drop into biodiesel would meet about 5 percent of the U.S. diesel demand.

Figure 1. Percent change in pollutant emissions with biodiesel content as estimated from 2002 U.S. EPA study.
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Credit: Environmental Protection Agency

Emissions Reduction

When compared to burning petroleum diesel, pure biodiesel cuts greenhouse gas emissions by nearly 70 percent, said Michael Guymon, president of the Tucson-based Arizona Biodiesel Board.

“The main benefit of using biodiesel is environmental,” Guymon said.

Using a B20 blend—a mixture of 20 percent biodiesel and 80 percent petroleum diesel—cuts emissions by 20 percent, he added.

Greenhouse gases—such as carbon dioxide, methane, and nitrous oxide—contribute to global warming. But not all greenhouse gases are created equal. While carbon dioxide is the most commonly emitted greenhouse gas, nitrous oxide (NOx) is about 310 times more effective at trapping heat in the atmosphere, according to the EPA.

That fact has created some controversy about whether biodiesel may be more harmful for the environment than the petroleum diesel it is designed to replace. A 2002 study by the U.S. Energy Information Administration (EIA) found that nitrous oxide emissions increased by 2 percent when using B20, and nearly 10 percent when using B100, compared to petroleum diesel.

Figure 2. Comparison of Nitrogen Oxide (NOx) emissions for conventional diesel and B20.
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Credit: National Renewable Energy Laboratory

The National Renewable Energy Laboratory conducted a new study in 2006 that contradicted the EIA’s findings. After eight different diesel engines were tested, the results showed the smaller vehicles had no impact on B20 nitrous oxide emissions, while the impact of larger vehicles varied with engine design. Some larger engines caused a slight increase in nitrous oxide emissions, while others caused a slight decrease, compared to petroleum diesel.

Still, the debate continues. “The nitrous oxide issue has created almost a religious fervor in the biofuel community,” Biddle said.

A need remains for “extremely evidence-based academic analysis,” he said, adding that his group is looking to recruit a researcher and conduct its own study. “Our working theory is that [the nitrous oxide issue] is not a show stopper.”

Forget Food-based Feedstocks

And the show is moving toward non-food feedstocks. Biddle and Johnson’s Desert Biofuels Initiative is working to open a biofuel production facility in Phoenix, using algae as the source.

“Algae is probably the most exciting crop of them all,” said Paul Sment, co-founder of the Albuquerque Biodiesel Project in New Mexico.

By some estimates, algae can produce 10,000 gallons of oil per acre, and may become a steady source of oil within three years, Sment said. Other non-food sources also show promise, like Jatropha—a shrub that can grow on wasteland and reseed itself.

Sment, and his partner, are in discussion with University of New Mexico students who are working with farmers in Mexico to explore the possibility of growing Jatropha crops for biodiesel production.

“The only way this is going to work for the people of the world is our moving away from food crops as quickly as possible,” Sment said.

But “Until we can bring sustainably produced, specifically produced non-food oil crops into the picture, waste vegetable oil will have to be the choice,” he said.

Sment sees biodiesel as a “bridge” to more logical, but harder to attain fuel sources like hydrogen and electricity.

“I am convinced that the automobile as we know it is dead,” he said. “It is just not gone yet.”