Tue | Mar 28, 2023

Grow your own gas

Published:Saturday | March 6, 2010 | 12:00 AM

Mario James, Gleaner Writer

Dear Mario:

Is it possible to really make your own fuel? With rising energy costs, and idle lands, could individuals really do this?

Pocketbooks everywhere are feeling every bit of the near $450 a gallon for Petrojam's premium 90 gasohol. Six years ago, $1,000 filled your average 45-litre tank. The other day I saw an old picture of a Petcom station price board trumpeting premium at $17.70 a litre. I felt really, really old.

With the advent of ethanol-blended gasolene, the State hopes to save money, kick-start a new industry and usher in an age of independence from foreign oil. All well and good. With our consumption trends, and a lack of creativity from the benchwarmers in Parliament, it wouldn't be a stretch of the imagination to see the newly introduced cess on gas increased by 100 per cent.

What if, though, you could grow your own ethanol? Wouldn't it be great to don a pair of water boots, grab some seed and, with a little elbow grease, grow some corn and just convert the vegetable to fuel-grade alcohol. People in the US South have been 'stilling' for years!


It is possible - though not as easy as making grits. Quite a few obstacles have to be overcome. Here are the most important in no relevant order:

1) Most 'stills' that can be built in your backyard to produce a fuel that, while flammable, has too much water in it to be of much use in a modern engine.

2) Pure alcohol is a highly oxygenated fuel. Denatured alcohol has an octane rating greater than 110. But the extra oxygen it carries will upset how the fuel-to-air mix is metered and burnt in modern fuel-injected engines and, long term, alcohol might destroy your carburettor, depending on its metal make-up.

3) One acre of corn can yield 180 gallons of ethanol. While growing corn ain't rocket science, it can be backbreaking work for one person to farm one acre. Alcohol also has about 33 per cent less energy than gasolene, so in a car that is not built to take advantage of alcohol's superior octane, a tank of gas won't last as long in the car as good ol' dino oil.

4) Alcohol has a great affinity for water. More bad news for parts commingling with it.

5) For every acre of land devoted to corn or sugar cane produced for fuel harvesting, one less acre exists to provide food.


However, there is hope. Enzymes that convert waste biomass (plant material, like sawdust and dead leaves) into alcohol have now been developed. Lignin, the protein that gives wood its firmness, is attacked by these new enzymes and cellulose is released, which can be converted to glucose - which is the sugar fermented to produce ethanol. Old paper products such as newsprint are almost pure cellulose - with a corresponding high yield in ethanol. If providing enzymes for your home spirits proves too expensive, acid can break down the paper into something that can be fermented. Green plant material also yields more available cellulose, which means more yum-yum juice per tonne. The sky's the limit!

The real drawback to home-brewed gas is the difficulty in drying the alcohol (contrary to popular belief, even the famed JB Overproof will not run an automotive engine efficiently). Alcohol concentration is measured on a proof scale - a scale which dates back to the days of pirates.

Alcohol has a great affinity for water, and when produced industrially (in rum making, for example) it becomes diluted. The standard was set way back when by measuring the concentration that would ignite gunpowder - real pirate stuff here. Rum containing roughly 50 per cent concentration would achieve a positive result, and was designated '100' proof. Anything above is overproof; below, underproof. JB, I am reliably informed is, greater than 120 proof, or 60 per cent alcohol. And my sources say that such a liquid is not something that will power your vehicle!

Making alcohol at home

To make alcohol at home, a mix must first be produced. Cellulose-based feedstock usage will be the focus of this article as it is readily available cheaply (how much newspaper do you have at home?) Celluclast, an enzyme used in the baking industry, can be utilised in conjunction with cellobiase to degrade cellulose and release glucose that packaged yeast can then ferment. Feedstock should be shredded as fine as possible and free of debris and foreign matter.

After shredding, the material is put in a container and mixed with just enough water to make a thick, soup-like mass. The pH of the mix at this stage must be monitored and, if needs be, adjusted by adding an available acid or base until its pH is between 4.5 and 6.0. The amount of enzyme needed for the mix depends on the lignin content; newspaper has a very high cellulose content - little lignin - and so the enzyme needs for such a mix would be greater as it yields more fermentable sugars.

Ideal temperature for the enzyme reaction would be around 140 degrees Fahrenheit, and the mash would have to be held at this temperature for about 16 hours, after which the temperature would have to be reduced to 80 or so degrees and fermentation started by adding a commercial-grade yeast such as Fermipan. Prior to the introduction of yeast, the mix should be adjusted for proper pH as indicated by the yeast strain used.

Fermentation will begin with the addition of the yeast - mash temperature is to be maintained, however, at 75-85°F. Higher temperatures will make the yeast less productive in terms of alcohol production. Carbon dioxide will be given off - the mash will be seen to literally boil as it effervesces. Cooling the mix can be done with sealed bags of ice or, more efficiently, by a refrigerated cooling coil (more efficient, but adds to expense and adds to energy used in making the fuel).

It is important to note when cooling the mash with ice bags that the water not contaminate the mash - more distilling energy would be consumed as more water would need to be separated.

The actual time needed to ferment the mash would be about two days. Fermentation is complete when the bubbling stops and the yeast 'cake', which forms at the top, sinks to the bottom. At this stage, time is of the essence, as it is possible to go too far with the fermentation process and end up with vinegar. Once that reaction starts, the mash is lost. There is no cure. So as soon as the cake sinks, it is time to distill.

An alcohol 'still' is an apparatus designed to produce alcohol from a biomass 'soup' that has been fermented. Getting over 190 proof (which is the bare minimum to run an automotive engine) requires more than just distillation, as a 190 proof alcohol - water combination forms a homogenous mixture called an azeotrope, which is impossible to distil. Distillation takes advantage of the different boiling points of water and alcohol; water boils at 100°C, and ethanol starts to boil at 73°C. When a mixture of the two is heated, the alcohol becomes a vapour first, leaving the water behind. The vapour is then trapped and cooled down to a liquid. Multiple distillations are needed to drive off the water - which is time and energy consuming.

While adding complexity, a device called reflux column can be added to the still to improve the alcohol concentration. The vapours from the still pot are passed through a column filled with packing material - such as glass tubes as seen in the diagram - and as the vapours ascend they will condense on the packing material and fall - only to be revaporised by newly ascending gases.

As the gases move slowly up the reflux column, the gases become richer and richer in alcohol until at the top the gases are almost pure. At this stage, the fuel is good enough to run in an engine that is designed to run on pure alcohol - but if it is to be mixed with fuel, the distillate should be filtered through a salt, like rock salt, to remove a further percentage of the remaining water. Concentrations of 99 per cent are beyond the scope of this article.

Engine-wise, if your car is made after 1995, it is likely that the fuel fittings are up to the rigours of fuel-grade alcohol, and the car is fuel-injected. Forget about making carburettors work - jetting carbs to run on a fuel that is constantly changing its phase is problematic and usually leads to problems, plus the corrosive nature of alcohol can attack brass jets, and the rubber seals and other elastomers need to be replaced. However, the biggest obstacle to running pure ethanol in a modern automobile not designed to do so is the vehicle's computer.

Ethanol brings extra oxygen into the combustion chamber - a condition the computer will read as rich (having excess oxygen). It will try to compensate by leaning out the mixture (withdrawing fuel) but finds that it can't, and an engine check light will glow on the dash. Your engine will run rough and can be hurt in such a case.

If you have an aftermarket, programmable computer, or your stock computer can be modified (unlikely), you are ahead of the game. However, for someone who is going about this to save money, they might find the $2,000-$3,000 price tag a mite hard to swallow. And for this to work, a computer is a must-have.

The Brazilians make a government-subsidised kit for their cars called the FlexTek - which is basically a piggyback computer that is able to change the injection timings but this writer has not been able to ascertain how well it works or how expensive it is.

The above is rather simplified, but it does contain the essential steps to brewing your own fuel. People have done it abroad, with varying results. For some, it is all about beating the man, and some just like the independence it offers. Some claim if the cost of their labour and initial investment is not included - and the feedstock is free, fuel might work out to $20 a litre. This might not be so far-fetched. With the rising cost of fuels, though, more and more people worldwide are starting to do this. If you are technically capable, it might just make 'cents'!

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