Dear EarthTalk: I understand that you can run a diesel car on used cooking oil. Why would I want to do that and how would I convert such a vehicle to do so?
—Benjamin Crouch, Boston, MA
The use of vegetable oil for diesel fuel has grown in popularity in recent years, thanks to both high fuel prices and ecological concerns. Analysts estimate that some 5,000 North Americans have converted their diesel cars or trucks to run on vegetable oil in the last few years alone. Those who do so usually make a deal with a local eatery willing to hand over its used cooking oil at the close of the business day.
The idea isn’t new. The first diesel engines built in the 1890s were created to run on peanut oil to be used in developing countries where oil reserves didn’t exist. And many of the older diesel cars and trucks still on the road today can use straight vegetable oil, especially in warmer climates where it won’t congeal as easily as in the cold. Many modern diesel engines, though, leave the factory requiring true diesel fuel to run well, as straight vegetable oil can muck up intricately engineered fuel pumps and injectors.
But drivers willing to spend between $400 and $1,000 on a conversion kit from one of two leading vendors, Missouri-based Golden Fuel Systems and Massachusetts-based Greasecar Vegetable Fuel Systems, can make the switch. And fryer-friendly restaurants are just about the only economical fuel source right now. Buying cooking oils at the supermarket would be costly, and consumers shouldn’t expect to find filling stations pumping vegetable oil anytime soon.
The benefits of a conversion are more than economic. Vegetable oil is a renewable resource derived from plants, which by nature absorb carbon dioxide (CO2) during photosynthesis. Vegetable oil is thus "carbon neutral"—burning it merely releases stored CO2 back into the atmosphere and therefore contributes no new greenhouse gases to the environment. By contrast, burning gasoline in a traditional engine releases CO2 that had been stored underground in oil, and thus contributes to global warming. Vegetable oil also burns cleaner than regular diesel, spewing no sulfur and much less particulate and carbon monoxide.
The conversion kits are only for diesel vehicles, as gasoline engines do not tolerate vegetable oil as a fuel. Since a conversion entails replacing and moving hoses and leads, as well as adding a separate fuel tank for the vegetable oil, it is best handled by a trained mechanic. Drivers should know that a converted vehicle does need a small amount of regular diesel fuel to get started, because at normal or cold temperatures vegetable oil is too thick to properly ignite. But the vehicle can switch over to vegetable oil once it is warmed up and the heat inside the engine loosens its thickness so it can run through efficiently.
Another way to use vegetable oil in a diesel engine is to blend it with regular diesel fuel. This blend has become known as biodiesel, and works fine in regular diesel engines with no conversion required. Biodiesel vendors have set up pumping stations across North America, although they tend to be few and far between. Canadians can locate biodiesel stations at the website of the Canadian Renewable Fuels Association; Americans can consult the website of the National Biodiesel Board.
Dear EarthTalk: Is it true that some commercial fishing nets are 40 miles long? I heard a TV commentator accuse fishing fleets of "strip-mining the oceans." If their nets are really that large, it certainly sounds like that’s what is happening!
—B. Johnson, Port Chester, NY
Considered the most destructive fishing technology ever devised, commercial "drift netting" involves vertically suspending near-transparent nylon nets in ocean waters with floats attached to the top and weights fixed to the bottom. Some are known to be as much as 50 miles wide, with a vertical height of about 50 feet deep. Once set, the nets are allowed to drift with the wind and currents (hence the term "drift net") and to snag just about everything in their paths. Drift netting is considered to be the most efficient way to catch large amounts of the ocean’s biggest fish, including tuna, swordfish, marlin and salmon.
The problem with these gigantic nets is that they don’t discriminate between fish that can be sold for dinner tables and so-called "by-catch"—marine life not intended for food but which get hauled up anyway and then subsequently discarded dead back into the ocean. Drift netting is responsible not only for killing fish that will never be sold commercially, but also for the unnecessary death of hundreds of thousands of dolphins, seals, whales and sea turtles every year, despite international agreements outlawing the practice.
Driftnets also sometimes break loose, sailing through the oceans unattended, "ghost fishing" until they sink to the bottom under the weight of their victims or wash up onshore where they snag seabirds, seals and other unsuspecting wildlife.
First developed by Japan in the 1970s, drift netting quickly caught on elsewhere and within just a decade scientists began to notice that the practice was taking a severe toll on marine biodiversity. Various experiments were conducted that bore out these concerns. A 1989 test using driftnets to catch tuna, for example, killed an average of four and a half marine mammals in every "set"—one whale or dolphin for every 10 tuna caught. Meanwhile, analysts observed a Japanese boat kill 59 dolphins and small whales in just 30 sets—a rate of almost two per set. With commercial fishing fleets legally deploying some 30,000 miles of driftnets around the world daily during the 1980s, the toll on marine life was no doubt staggering.
The first major effort to stop drift netting was the Wellington Convention, which was signed in New Zealand in 1989 and put into place a driftnet ban in the South Pacific. Four years later, the United Nations called for an international moratorium on the practice. Meanwhile, in 1992 Russia, Japan and the United States created the Convention for the Conservation of Anadromous Stocks in the North Pacific, banning all driftnets more than 1 1/2 miles in length ("anadromous" refers to fish like salmon that live in salt water but spawn in fresh water). South Korea signed on but China did not, though it agreed to let the U.S. Coast Guard help police its fleet. In 2002, the European Union banned drift netting by its member countries.
According to Earthtrust, a U.S. nonprofit committed to ending drift netting, despite such commitments commercial fishing fleets around the world still deploy tens of thousands of miles of driftnets on a daily basis. While efforts to stop the practice have no doubt had some effect, drift netting remains one of the biggest drivers of over-fishing today. As long as demand for tuna, salmon and other big fish continues, drift netting—illegal or otherwis
e—is likely to continue to wreak havoc on the world’s marine ecosystems.
CONTACT: Earthtrust’s DriftNetwork