In fact, when Dr Rudolf Diesel first developed the "Diesel" engine in 1895, his intention was to run it on a variety of fuels, including vegetable oil. Since Rudolf Diesel's time, the Diesel engine has been modified to run on the cheapest fuel available - petroleum. After Diesel's death, the petroleum industry capitalised on the Diesel engine by labelling one of the by-products of the distillation process "diesel fuel". Thus, cheap, dirty "diesel fuel" became the fuel of the Diesel engine and vegetable oil was all but forgotten as a fuel source.

However, with the energy crisis of the 1970s researchers revisited Rudolf Diesel's original vision and came up with a simple process of turning vegetable oil into usable diesel fuel. The process that I am going to advance in this article was developed in the late 1970s and is called "trans-esterification" and involves "blending vegetable oil" with alcohol (ethanol or methanol); in the presence of a catalyst (sodium hydroxide or potassium hydroxide) and water. These four are an absolute must.

A vegetable oil molecule is made up of three esters attached to a molecule of glycerin and is also referred to as triglyceride. Tri refers to the three esters and glyceride refers to glycerin. About 20 percent of vegetable oil molecule is glycerin. Glycerin is also called glycerine, glycerol and glyceride. Glycerin makes vegetable oil thick and sticky. The esters are the basis of bio-diesel fuel and during the process of making bio-diesel; the esters in vegetable oil are separated from the glycerin.

In order to break triglycerides or vegetable oil, a catalyst is added in the vegetable oil. The catalyst will break the triglycerides and release the esters. Once the esters are free, they will combine with the alcohol. The catalyst will combine with glycerin, and will fall to the bottom of the bio-diesel reaction container or tank in the process producing alkyl esters and glycerin soap. The possible catalysts for the bio-diesel reaction are sodium hydroxide (NaOH) and potassium hydroxide (KOH). Sodium hydroxide, which is commonly referred to as lye or caustic soda, is the same chemical used to unclog kitchen or bathroom drains. Potassium hydroxide can be used instead, but large quantities are required. A word of caution: Before you rush out to start your own backyard brewer, these chemical ingredients are very reactive and present some very serious safety concerns.

The glycerin component is replaced with an alcohol; this makes the oil thinner and less viscous. Either ethanol or methanol alcohol can be used. Ethanol is an alcohol made from grains whilst methanol is made from coal, natural gas or wood.

My recommendation is methanol because it is less expensive and produces a more stable bio-diesel reaction. However, methanol is an aggressive alcohol which dissolves rubber, is fatal if swallowed, and, therefore, calls for a lot of care in handling. It is also extremely flammable, but unlike most flammable liquids, it does not have a visible flame when burning. Once it is mixed with lye, the resultant sodium methoxide will burn anything it comes in contact with. In addition, you will not realise that you are burning because it immediately kills all nerve endings. Furthermore, if you have used common lye to open clogged drains or make soa, you should know that lye is very dangerous to your skin and gets to be extremely hot when it comes in contact with water. Lye will also quickly corrode aluminium, tin pans, zinc coating and most paints, so you are advised to use only stainless steel or chemical grade polyethylene containers when handling these caustic chemicals.

Methyl esters refer to bio-diesel that is made from methanol and vegetable oil esters. Ethyl esters refer to bio-diesel that is made from ethanol and vegetable oil esters. Alkyl esters is a more general term which refers to any combination of alcohol and vegetable oils esters. Regardless of which alcohol or type of vegetable oil is used, the bio-diesel reaction always involves breaking each triglyceride molecule into three esters and one glycerin molecule. Each of the three esters attaches to some alcohol. From one triglyceride molecule we get three alkyl esters molecules.

The amounts of catalyst used in the bio-diesel reaction will depend to a large extent on the pH of the vegetable oil. Therefore, the success of the bio-diesel reaction will depend in large measure on your ability to measure the pH or the acidity of the vegetable oil. Real quick, the pH scale is numbered 0 through 14. Seven (7) is neutral or equal to pure water. Numbers below 7 on the pH scale show that a liquid is acidic. Numbers above 7 on the pH scale show that a liquid is basic. The lower the pH number, the stronger an acid the liquid is. The higher the pH number, the stronger a base the liquid is. The rule of thumb with pH is that opposites attract and react. For example, the bio-diesel reaction occurs between an acid and two bases. Vegetable oil is an acid (surprise!). Alcohol and the catalyst are both bases.

Used or waste vegetable oil is more acidic as a consequence of having been heated or fired. When vegetable oil is heated in the presence of hydrogen it becomes hydrogenated, resulting in free fatty acids. These fatty acids float amongst the triglycerides, "free" to attach themselves to anything basic. Now, free fatty acids increase rather than decrease the gelling temperature of vegetable oil. That is why hydrogenated vegetable oil is solid at room temperature. When making bio-diesel it is important to eliminate free fatty acids. To do this, more of the catalyst is used in the bio-diesel reaction. This process neutralises the free fatty acids. How much of the catalyst is used will depend on how acidic the oil is.

One of the greatest challenges to the widespread deployment and process of making bio-diesel is developing dedicated energy crops that are cost-effective, easy to sustain and can produce greater yields. Such energy crops that produce bio-fuels and hold particular promise for sustainable development and a sustainable environment are oil palm, coconut and jatropha. One acre of jatropha can yield between 600 and 1 000 gallons of bio-fuel per year, although at least two companies marketing the plant say they have varieties that yield much more. The oil palm plant produces more gallons of bio-diesel per acre than jatropha but requires fertile land, and uses valuable food-producing land.

The bio-fuel yield of various crops has been measured, and is usually given in barrels of oil per square mile per year. Maize is a common bio-fuel crop in the USA, but it yields less than 200 barrels (per square mile per year). Rice, for example, yields almost 1 000 barrels, however it is an essential worldwide food crop as are most of the other potential bio-fuel crops.

It is simply not viable to use good quality arable farmland for growing bio-fuels; bio-fuel crops need to be grown on marginal land if we are to benefit from them. This is where jatropha scores highly. Not only does it have a great yield of well over 2 000 barrels of oil per square mile per year, it also increases the fertility of the land on which it is grown so that it can potentially be used for food crops in subsequent years.

One concern though is that the production of crops for bio-diesel will always be limited by time and space. On that score I agree with Harare-based economist John Robertson when he said: "There should be total utilisation of the land to ensure the required feedstock supplies." (Zimbabwe Independent issue of Thursday, 29 November 29, 2007). I guess he was referring to the more than 25 220 000 hectares in Natural Regions IV and V which are practically lying fallow.

However, to say that the project will not take a lot of time and money to be fully operational is a clear demonstration of lack of substantive understanding of the ecology of jatropha, its context and its subtext. Jatropha is the crop of choice in Natural Regions IV and V. It can grow on dry wasteland. Jatropha can be harvested twice a year -- as quickly as 18 months after planting -- can thrive up to 50 years, does well in both good and poor soils and doesn't require heavy cultivation, fertilisation or irrigation. Clearly, not a lot of time and money.

I call upon developed nations to take a lead in financing renewable energy production and new generation technology advances for efficient energy consumption. My take on this is; the expense and financing needed to construct this network would clearly be enormous but less than the total spent on the current "War on Terror" in Iraq. It would require innovation and research funding at universities and industry throughout the whole world and would have the potential to employ tens of thousands of people.

Look at pond algae, for example. It may look like a bizarre source of bio-diesel, but most of the world's petroleum resources were formed from vast amounts of algae that were transformed by heat and pressure over millions of years. Today algae can be grown in ponds in just a few days and oil can be extracted from the harvested algae. Some experts predict that one acre of algae could yield an enormous amount of oil 3 654 gallons per year or more. That is awesome.

Researchers at the Massachusetts Institute of Technology and within private industry are experimenting with methods of growing high oil content algae. Incredibly the algae reduce carbon dioxide emissions by 40 percent and nitrous oxide emissions by 86 percent. Both oil and cellulose can be extracted from the algae, with the potential to produce 15 000 gallons per acre of both bio-diesel and ethanol.

Let me conclude by saying, bio-diesel is not a panacea for all our energy problems, but it can be part of the transition from our current near total dependency on fossil fuels to the use of a wide range of renewable energy resources. At the same time it would create jobs, assist farmers, reduce pollution and promote greater energy security.

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