Feature

The hidden danger in home biodiesel production

Dr Garth Cambray

Scientists follow basic safety guidelines in regulated laboratories but as a growing number of hobbyists utilise chemicals for anything from thinning paint to home alternative energy fuel production, accidents can happen if the science behind chemicals is poorly understood. 

Many home producers of biodiesel are unaware of the dangers of their hobby. Methanol, an extremely valuable reagent in the production of many useful products and in processes such as biodiesel production, can also be  dangerous in the wrong hands.  This article shows why and how to mimimise some of the risks associated with working with this chemical. In a related article read about the chemistry behind methanol synthesis.

In the production of biodiesel there are two types of producers - large professional companies with carefully designed plants, and small hobby producers with home made apparatus. Both use similar recipes involving the reaction of methanol with vegetable oil and or animal fat to produce biodiesel. Methanol is a highly toxic alcohol, and, on a hobby scale many producers inadvertently expose themselves to methanol through inhaling small quantities of fumes, and occasional skin splashes. It is very important to understand that methanol vapour is very easily absorbed by the lungs - in addition to that, methanol condenses on the eyes and skin, leading to absorption this way. Protection from these fumes is hence very very important

To understand how methanol damages the body, it is important to understand the basics of alcohol metabolism in humans. Alcohols are simple chemicals consisting of a chain of carbon atoms with hydrogens around them and one or more sets of a hydrogen and an oxygen attached to one or more of the carbons. Once alcohol enters the blood stream from the gastro intestinal tract it passes through the liver. The dominant alcohol in alcoholic beverages is ethanol, an alcohol with two carbons and one oxygen bonded to a hydrogen - the liver detects the presence of ethanol easily and begins producing the enzyme alcohol dehydrogenase which converts ethanol to acetaldehyde. A second enzyme, acetaldehyde dehydrogenase, converts the acetaldehyde to acetic acid (vinegar). From this point the alcohol has been rendered relatively non-toxic and many metabolic pathways can continue the process of converting it into either energy or a storage molecule like fat.

As we have mentioned already, ethanol as an alcohol contains two carbon molecules in its backbone. Methanol contains one. The exact same enzymes which break down ethanol are able to break down methanol. However, the products of this process are far more toxic than with ethanol and the actual poisonous effects of methanol are from its metabolic breakdown products. Hence, methanol is first broken down to formaldehyde (highly toxic) and then to formic acid (highly toxic). Unlike the ethanol process, each metabolic step in this process is highly toxic and damages the liver.

The enzymes responsible for alcohol degradation have a higher affinity for ethanol than methanol - hence the rate of formation of toxic methanol metabolites can be reduced by co-administration of ethanol. This is a confirmed medical procedure in cases of methanol poisoning. Other chemicals such as Fomepizole have similar effects.

Hence if low concentrations of methanol enter the body, it is healthiest for the body if they are not in fact metabolized at all, but if they instead leave the body via the breath, sweat and urine. Hence a low background level of ethanol in the blood will help to stop the body metabolizing methanol and force the methanol to leave the body by other routes. In short however, it is just best not to have any methanol enter the body.

If methanol does enter the blood stream it causes liver damage, swelling of the retina of they eye (which can cause blindness), brain damage and a host of other highly unpleasant symptoms.

In biodiesel making catalysts such as potassium or sodium hydroxide are dissolved in methanol to form methoxides. Alternatively commercially produced methylates are added. Either way, these compounds are even more toxic than methanol and cause instant and painless nerve death upon exposure to the chemicals. Hence skin splashes will cause patches of skin with no feeling.

It is also very important to understand that methanol is a highly flammable substance. Methanol burns explosively, and a rule of thumb is if you can smell methanol in the air, there is a good chance that somewhere in the room enough methanol is present to cause an explosion. The flame can find methanol even better than your nose can.

To avoid these problems, it is advisable that anybody who comes into contact with methanol wear goggles (so that whiffs of methanol vapour will condense on the goggles not the eyes), gloves, a lab coat (cotton preferably as this will not burn as easily if there is an explosion), a gas mark which is rated to remove methanol vapour - note that normal activated carbon masks for removing organic solvents are not effective at removing methanol, and that a special methanol removal cartridge is required. All reactors should be rigged to vent methanol fumes into a place where they will not cause an explosion, or be inhaled by people. The biodiesel production area should have an open flow of air to ensure that the atmosphere in the room does not slowly accumulate methanol. If an extractor fan is used, it must be a spark free extractor fan.

In this way, the average biodiesel maker will live to see the effects of the global warming their fuel helps to reduce.

For anybody working in the laboratory, it is advisable to know what to do in the case of poisoning. The Merck Manual for Mobile Devices (also available in print form) is the best known global reference dealing with how different chemicals cause toxicity, and what to do about exposure to these toxins. Currently sold at a cost of US$49.99 for a years subscription, including bi-monthly updates, this reference is in some ways as important to a scientific organization as its computer anti-virus software - you never know what virus your computer will catch, and you never know what toxin you will accidentally poison yourself with, so in both cases, having access to a global network of experts who deal with these problems offers you and your colleagues a safer existence. 

More information:

  For more information visit http://www.unboundmedicine.com/merckmanual 

Related articles:

 The science behind methanol synthesis

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