Can castor bean,rubber and tea seeds solve Sri Lanka’s diesel deficit?

by Chandre Dharmawardana
chandre.dharma@yahoo.ca

According to the “Dilbert Principle“, we rarely recognise our own idiocies, yet we can clearly identify the idiocies of others. Everyone from the Aragalaya man to the “Aemathi Thumaa” has faulted others for the current crisis. And yet, although ordinary citizens can act to resolve the crisis, a culture of confrontation, nurtured by revolutionary ideologies, coupled with unrealistic demands for various “rights” or the resuscitation of ancient myths, has become second nature to Sri Lankans. The government has ground to a halt, and action via citizen groups is essential to deal with the crisis in food and fuel.

In my article in The Island commenting on Mr. Dhammika Perera’s plan to race forex (The Island 13-June-2022), I briefly stated that “Castor is a fast-growing ‘weed’ that is not attacked by pests or livestock. It can be grown among coconut trees or on infertile lands. Its seeds yield a clear oil, directly usable in most diesel engines”. I received many queries on how diesel fuel may be replaced by cheap local oils.

Diesel fuel and electricity are the main energy sources, more important than petrol, that drive the modern world. Wealthy countries produce diesel and maintain reserve stocks as a part of their national security. However, small countries are abjectly dependent on powerful countries that wage war for fossil fuels and control them.

Rudolf Diesel was a 19^th century scientist-inventor, influenced by Sadi Carnot’s work in France, that led to the second law of thermodynamics. Diesel was strongly social conscious and moved to help small entrepreneurs, trampled down by wealthy conglomerates who alone controlled the giant steam engines of industry, trains and ships of the late 19^th century. In 1892-1895 Diesel patented a compression-ignition engine that ran entirely on vegetable oil, ideally suited for small-farm applications using farm-produced oil. Dashing Diesel’s socialist objectives, his engine became a tool of the Western industrial and military enterprise. By the 1920s, the inexpensive distillate from petroleum crude became the main fuel for Diesel engines, replacing vegetable oil. It is this distillate that is today called “diesel fuel”.

Today, people express surprise that diesel engines may use vegetable oils, since modern engines have been adapted for the distillate from petroleum crude. We describe below how vegetable oils can be used to overcome the fuel crisis, with little or no modification of the engines.

Although coconut oil, peanut oil, etc., can be used, they are very expensive, compared to non-edible waste cooking oil, waste animal fats, castor oil, rubber or tea seed oil, or oils from Madhuka (Sinhalese mee thel) and Neem. Biodiesel is a chemically modified form of vegetable oil, compatible with diesel engines. Our interest is in directly using vegetable oils WITHOUT converting them to standard biodiesel by chemical processing. However, in the following we discus both bio-diesel and use of untransformed vegetable oils.

The 2020 world market prices of natural gas, gasoline, diesel and bio-diesel were US$ 2.18, 2.18, 2.4, and 3.33 per gallon respectively. The current prices change rapidly, but the international price of bio-diesel is irrelevant when the fuel is made locally, without forex. Untransformed vegetable oils, produced in the farm, is an unbeatable option when used for running farm machinery and generating electricity.

Lankan scientists and engineers have argued, even before independence, that unlike many countries, Sri Lanka has unique attributes to achieve self-sufficiency in food and energy, due to its rainfall, reservoirs and biodiversity. In the 1970s some of us had undertaken a study of what was then called “alternative technologies”, and the concepts evolved were presented in a BBC movie. That, too, was a time of food and forex shortages under the Sirimavo government. Today, Sri Lanka is in more dire straits. Hence a return to basic “alternative technologies” achievable within the naturally available resources of the country, is needed, irrespective of the availability of more loans and moans from the IMF.

Direct use of vegetable oils as diesel fuel.

Oil from castor seed (up to 3 tonnes/ha of which nearly 50% is oil) is a good fit to meet Sri Lanka’s urgent needs. It grows easily and rapidly on infertile soil, with few pests or enemies. Similarly, rubber seed (up to 2 tonnes/ha) and tea seed (3-4 tonnes/ha) are mostly left discarded. The main difficulty in using castor or other vegetable oils in modern diesel engine is their high viscosity. Castor oil is some 75 times more viscous than diesel fuel at 40⁰C. Tea-seed oil and rubber-seed oil are better, being only 9-12 times more viscous. We found in our experiments that castor oil, at suitably high temperatures, achieved a viscosity matching diesel.

However, the use of elevated temperatures (above the boiling point of water) raises serious safety and insurance issues, and the method is more suited for stationary diesel engines. Stationary engines can generate electricity and charge batteries that power electric cars and farm equipment. The viscosity of the oils from rubber and tea seed, depending on quality, may be lowered to the viscosity of diesel fuel at easily accessible temperatures. Thus, the hot coolant water (radiator fluid) of the diesel engine could be re-circulated to heat the rubber-seed oil for direct use in a diesel engine. However, more research is needed to implement the hot-fluid system for which only preliminary studies are available.

A simple approach for the direct use of vegetable oils in diesel engines is to dilute the vegetable oil with compatible solvents, like ethyl acetate, that can be produced locally using alcohol and acetic acid, both being products of fermentation of biomass. Considerable work has been done in Brazil and Spain in developing such approaches, using dissolved-vegetable oils.

Indirect use of vegetable oils by converting to biodiesel by trans-esterification.

The commercialized method for using vegetable oils is to convert them to bio-diesel using “esterification”. Here the vegetable oil is treated with a substance, like sodium hydroxide and methyl alcohol (wood alcohol) or ethyl alcohol (spirits of wine), when a layer of glycerol settles to the bottom, and a lighter liquid separates to the top. The top layer is the desired “bio-diesel”. This “trans-esterification” process is highly optimized in industrial production to get optimal yields and reduced costs. However, do-it-yourself conversions of waste cooking oil to bio-diesel is a win-win situation in providing the otherwise unavailable diesel fuel to forex-poor consumers.

A “recipe” for converting castor oil or waste cooking oil (e.g., from cooking oils, like sunflower oil) can be developed using known chemical data for the fatty acids in these oils. We illustrate the method for one litre of waste cooking, giving the rough amounts of ingredients needed, noting that trial and error adjustments are needed for different waste oils.

1. One litre of moisture-free waste cooking oil, filtered to remove frying residues.

2. 3.5-4.0 g sodium hydroxide (not more than 0.1 moles). This is a corrosive substance that should be kept dry.

3. 200 ml (about 4.5 moles) of dry methyl alcohol (wood alcohol) or ethyl alcohol (~ 4.5 moles).

4. Blend (at low speed) the methyl alcohol and the sodium hydroxide until completely dissolution, to be used immediately as it absorbs moisture from the air.

5. Add the filtered cooking oil and blend at low speed for about 1/2 hour. Reaction is facilitated if the blending vessel is kept warm.

6. Let stand until the liquid separates into two layers.

7. The top layer is the bio-diesel, and the bottom layer (glycerol) is drained out.

This is a simple procedure that a cooperative of restaurants or households in a neighbourhood can use to convert their waste cooking oil into diesel fuel. This oil can also be used to fuel an oil-burning cooker or stove instead of using LNG, soot-generating charcoal or wood for cooking.

The biodiesel can be used directly (or mixed with petroleum diesel) as fuel in a standard diesel engine. If the untreated vegetable oil were used (either by using the heated oil, in an engine equipped to heat the input oil held in an auxiliary fuel tank, or by blending with a solvent like ethyl acetate), then (a) the expense for sodium hydroxide and methyl alcohol can be avoided, (b) even the glycerol gets used as a fuel and so the full energy content of the vegetable oil is used in the diesel engine. Otherwise almost half the energy content is lost as waste glycerol. Furthermore, since glycerol is an oxygen-rich chemical, it promotes a cleaner burn in the engine; the exhaust gases contain less soot and less noxious oxides.

Undoubtedly, many owners of high-end diesel cars will hesitate to use artisanal bio-fuels in their cars unless rigorous quality controls are imposed. Private companies, estates, and small entrepreneurs should lead in producing and using bio-diesel or vegetable oils, in diesel engines, without waiting for government action.