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On the job

Used cooking oil has its uses still

Marc Watson’s company turns used cooking oil into clean-burning biodiesel.STEVE HAINES FOR THE BOSTON GLOBE/Boston Globe

This winter, much of the oil used to cook fried clams and onion rings on Cape Cod may end up heating homes.

Cape Cod Biofuels refines waste vegetable oil into biodiesel, a fuel that can be used for heating and transportation. Biodiesel emits fewer harmful pollutants into the air, according to Marc Watson, one of the company founders.

Cape Cod Biofuels collects the waste oil from more than 600 restaurants across the Cape, South Shore, and Rhode Island and employs seven workers out of its plant in Sandwich. Watson jokes that it’s one of the dirtiest jobs on the Cape.

“Everything in the plant, including us, is covered in grease,” said Watson. “On most days I go home smelling like burned french fries.”


Is used restaurant oil becoming a commodity?

This oil used to be free. But now that there’s demand, we need to pay for it. The price varies from 40 to 50 cents to $1 a gallon. If it goes over $1.50 a gallon, it doesn’t work in our business model.

What types of oil can you use to create biodiesel?

Ninety percent of our biodiesel comes from waste vegetable oils.

How are you making your process more efficient?

Our newest addition, a centrifuge, will extract more oil from restaurant food waste. The centrifuge is a time machine and speeds everything up, so what used to take a day now takes 15 minutes.

What is the process of converting the oil?

Vegetable oil is more viscous than biodiesel, so it’s treated with other fuels and solvents to make it thinner. To create biodiesel, a chemical catalyst and an alcohol, such as methanol and lye, is added to the oil, which brings the consistency closer to that of petrodiesel. The oil is then refined, removing unwanted components.

What’s the future of the biodiesel industry?


The future of biodiesel has a lot of uncertainty. What we really need here in Massachusetts is more political support. New York has mandated all diesel has to have that 5 percent of biodiesel in it. Rhode Island is also five years ahead of us. At one point, Massachusetts mandated 2 percent, but that’s not on the table anymore. We need to catch up.

Is converting biofuel a DIY ­endeavor?

We did start by buying a kit online. We blew up some equipment.

But it’s not something I would recommend. It took us many years to figure out how to do it right, and the tricky part is that conversions need to be under the right temperature. There’s definitely a science to it.

Do you look covetously at your wife’s cooking oil remains?


Cindy Atoji Keene can be reached at cindy@cindyatoji.com.