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Biodiesel revolution
Sean Woods - Popular Mechanics
Posted Thu, 30 Aug 2007

Okay, let’s be clear on this: unless something pretty radical happens, we’ll be relying on fossil fuels for quite a while yet. Although the pursuit of environmentally friendly alternatives is yielding encouraging results, many of the technologies are too complex or too expensive to be commercially viable — at least until economies of scale kick in.

Against that, there are signs that companies and people all over the world — and here we’re talking about practical folk rather than tree-huggers and idle dreamers — are eager to explore the potential of wind, wave, solar, geothermal and other renewable sources of power. The motivation could be financial gain, independence from utilities or sheer bloody-mindedness, but it has to be said that doing something to preserve the environment — even if it’s unintentional — is extraordinarily satisfying.

Take former production engineer Paul Maher of Johannesburg. He’s brewing up biodiesel in his garage, using old cooking oil in a simple, proven process that’s well within the capabilities of the average DIY type (in other words, the typical PM reader). If you can conjure up a batch of home-brewed beer, says Maher, making your own biodiesel should be easy.

Aromatic exhaust fumes

You won’t find vendors at intersections choking on the fumes from Maher’s car, although you might catch the odd puzzled expression as they try to locate the source of that aromatic blend of fish and chips.

His car isn’t complaining, either. For starters, there’s been a noticeable reduction in engine noise since he started topping up with biodiesel. He also gets the impression that the car accelerates more smoothly.

Research has shown that biodiesel’s superior lubrication qualities can extend an engine’s life, with minimal effect on fuel consumption, power and torque. It also has formidable solvent properties, acting as a cleaning agent in the fuel system — the more you use it, the cleaner things get. In fact, Maher is so impressed with the stuff that he’s acquired a diesel generator to power his home.

Relatively uncomplicated process

Making biodiesel is a relatively uncomplicated process, largely because vegetable oils and fossil fuels are chemically very similar. The major difference: fossil fuels release carbon dioxide (CO2) that’s been collected and trapped undergound for millions of years, then burned all at once.

Biodiesel also releases CO2, but it’s derived from “fresh” organic material (you’ll remember from your junior school science lessons that plants love the stuff). So as your car’s exhaust pipe pumps CO2 back into the atmosphere, the next crop absorbs it, effectively creating a closed loop.

What you’re doing, in effect, is removing one alcohol (glycerine) from the molecular chain of the waste vegetable oil (WVO) and replacing it with another (methanol, also known as wood alcohol) using a reagent (potassium hydroxide, KOH). The process, called transesterification, isn’t as complex as it sounds.

Says Maher: “Although I hated chemistry at school, it was the technical side of the process that initially attracted me to biodiesel. But it was when I found out how little it would cost me to fill my tank that I became really interested.”

If costs are an issue, you could probably get away with a simple installation, but Maher warns that the process requires a degree of caution. “The most dangerous part of the transesterification process begins when you buy the highly inflammable methanol, and it continues to the point where the methoxide (methanol mixed with KOH) is completely introduced into the oil. This is where the majority of accidents happen.”

Instead, Maher opted for a safer route and built an Appleseed processor from plans he found on the Internet. Because it’s a closed system (that is, no air is present), combustion cannot take place. A pressure valve removes unwanted methanol fumes.

Locate a supplier

If you’d like to set up your own biodiesel plant, says Maher, your first move is to locate a reliable source of WVO — ideally a restaurant that changes its cooking oil regularly. But be warned: if too many (carcinogenic) free fatty acids are created by the frying process, it can turn your entire batch into soap.

Says Maher wryly: “This gives you a good idea of which restaurants to avoid if you want a fine dining experience. The oil I got from one place was almost like treacle!”

Your next job is to conduct a titration test to determine how much potassium hydroxide should be added to neutralise the free fatty acids in 1 litre of the WVO, over and above the base requirement of 7 g/litre if only fresh oil was used. The desired amount of KOH is then mixed into the methanol (about 20 per cent of the oil’s volume) to get methoxide.

Cautions Maher: “When handling potassium hydroxide, be sure to wear gloves, a respirator and protective glasses. It’s wicked stuff, and you don’t want to inhale any.” It’s also an exothermic process — so expect things to heat up a little.

Removing fish heads and chips

After filtering the WVO to remove debris (fish heads and chips come readily to mind), heat it up to between 55 degrees and 60 degrees (but no higher, as methanol boils at 65 degrees C). Add the methoxide, leave it to circulate for about one hour, then shut down the system and leave the brew to settle overnight. In the morning you’ll find a layer of glycerine on the bottom, with unwashed biodiesel floating on top.

All that’s required is to drain the glycerine off the bottom, wash the biodiesel gently a few times — using warm water — to remove the remaining soaps and excess methanol, and leave it to dry. When it’s a clear golden colour, it’s ready for your fuel tank.

All told, it takes Maher about three man-hours over a three-day period to produce 113 litres of biodiesel. He sources his old oil from two restaurants, visiting them every two to three weeks; each has about 100 litres to spare.

If you’d like to try it for yourself, Maher will sell you a basic kit for about R4000 or an intermediate kit at about R6000. His advanced kit, including electronics and digital controller, costs about R10 000 (excluding barrels and geyser, which can be sourced easily). Contact Paul Maher at paul@nanoelf.co.za or visit www.nanoelf.co.za.