考研阅读精选：山珍海味
The fat of the landGreen-minded motorists are making car fuel at home, from used cooking oil
Dec 3rd 2011 | from the print edition
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DIESEL engines are famously unfussy about what they burn in theircylinders. Indeed, Rudolf Diesel’s original design ran on powdered coal.But even he might have been taken aback by the recipe concocted byPeter Ferlow. Mr Ferlow, who lives in a suburb of Vancouver, BritishColumbia, is one of the leaders of a growing band of enthusiasts whobrew their own car fuel. His diesel engine runs on oil collected fromthe kitchen of a local pub.
The recipe starts by filteringthe breadcrumbs out with a mesh screen. After that you warm the oil upand add sodium hydroxide and methanol. The sodium hydroxide (known as“lye”, in the trade) breaks the oil molecules into fatty acids andglycerol. The methanol reacts with the fatty acids to form esters. Drainaway the glycerol. Wash the remainder with water to remove impuritiesand surplus lye. Drain that water. Then aerate what is left with anaquarium bubbler to drive off the last traces of moisture. The result is175 litres of finest home-brewed biodiesel—enough to drive Mr Ferlow’spickup truck for 1,200km (750 miles). And the cost, he reckons, is amere C$45 (about $44, south of the border) plus two hours of his labour.The oil itself is free. Restaurants are glad to give it away, to avoidthe cost of disposal.
That may change. According to MilesPhillips, the head of the Cowichan Energy Alternatives Society, based inDuncan, British Columbia, local demand for veggie-oil fuel is alreadyoutstripping supply. Moreover, biodiesel made from restaurant oil can besold for a tidy profit. On the other side of North America, theBaltimore Biodiesel Co-op, in Maryland, says green-minded drivers areprepared to pay a premium of about 30% over the cost of petroleum-baseddiesel to fill their cars with biodiesel. The co-operative reports thatits sales are up by 20% this year. Eventually, presumably, restaurantowners will want a slice of the action, too. At the moment, though, theyseem glad to collaborate for nothing. The co-op can rely on anindustrial producer—a so-called “grease puller”—driving a lorry aroundthe area’s restaurants to collect its raw material free. And it plans,starting next year, to buy biodiesel from home producers as well.
Some of these producers rely, like Mr Ferlow, on Heath Robinsonlash-ups of their own devising to make their motoring equivalent ofhooch. Others use off-the-shelf reactors. Oilybits, a British company,will, for £395 ($620), sell you a device that produces batches of 120litres of biodiesel—and the firm’s owner, Adrian Henson, is modestenough to admit that many other firms do likewise. The process is notparticularly hazardous. Biodiesel esters are not so volatile that theyform an explosive vapour (which is why they can be used only in dieselengines, not petrol ones), and though the methanol and sodium hydroxideneed careful handling (they are unpleasant by themselves, and trulynoxious if allowed to react together), so far the health-and-safetyauthorities in countries where home-brewed biodiesel is taking off havenot stepped in to interfere. Even the taxman generally turns a blindeye. In Britain, which once tried to fine people for failing to pay dutyon home-brewed fuel, the tax-free manufacture of up to 2,500 litres ayear is now permitted.
Brewing up nicely
If theauthorities did ban home esterification, though, enthusiasts who wishedto declare independence from the oil companies could go down anotherroute. The advantage of esters is that they substitute directly forpetroleum-based diesel fuel. But, with a bit of modification, manydiesel engines will run on unesterified vegetable oil, too.
The main reason raw vegetable oils do not normally work in dieselengines is that they are more viscous than standard diesel oil, and thusclog the engine’s fuel-delivery system. Heat them, and that problemgoes away—at least in older engines (modern, “common-rail” motors, withhigh-tech fuel-injection systems, are less forgiving).
Acommon way of converting a vehicle to run on unprocessed vegetable oilis therefore to fit it with two fuel tanks. A small one filled withpetroleum-based diesel keeps the engine running until the car’s radiatorhas heated up. At that point water is diverted from the radiator intopipes that run through a larger tank filled with vegetable oil. Oncethis is nicely warm and runny, the driver flicks a switch and the enginestarts burning the vegetable oil.
Last year John Shepley, amember of the Baltimore co-operative, converted his 12-year-oldsports-utility vehicle to work this way. That cost him about $1,500. Butprices are falling as such conversions become more popular. An Oilybitsconversion kit costs about $315.
To Greece on grease
Once the conversion is made, the world is your oyster. In August 2008,for example, eight teams set out on a car rally from London. Theirintention was to drive across Europe fuelled only by oil scavenged fromrestaurants. All made it to Athens, the destination, without buyingfuel.
Even now, three years later, getting waste oil free isstill easy, according to Andy Pag, the rally’s organiser. He has drivenmore than 30,000km on vegetable oil, in countries as far afield asMauritania, without once paying for the stuff. There are wrinkles, ofcourse. In place of the screen used by Mr Ferlow, Mr Pag carries acentrifuge (solar powered, naturally) around with him. Before fillingup, he puts the oil he has scrounged through this. Food particles andwater are spun off as a creamy gunk that he removes with a rag. It takeshim about half an hour to purify a tank’s worth of fuel in this way.The chief difficulty, he claims, is keeping his clothes clean.
That, though, is a small price to pay for the warm, virtuous glow whichcomes from converting waste into motive power. It is cheap,environmentally friendly and, according to Mr Ferlow, even the exhaustgases smell sweeter.
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