The Question

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Diesel generators are still used for various tasks and from a renewable perspective as back up on the grid and as the fossil fuel component with off grid systems. But what if you don’t want to use diesel. Are there viable alternatives?

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Let’s look at diesel

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In a book titled Diesel Engines for Land and Marine Work, Diesel said that "In 1900 a small Diesel engine was exhibited by the Otto company which, on the suggestion of the French Government, was run on arachide [peanut] oil, and operated so well that very few people were aware of the fact. The motor was built for ordinary oils, and without any modification was run on vegetable oil. I have recently repeated these experiments on a large scale with full success and entire confirmation of the results formerly obtained."

Basically diesel designed his engines to run on a variety of fuels!

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Fuels used historically: WW2

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During WW2 the troops fighting in the Pacific experienced issues with fuel supplies and were forced to look at diesel alternatives to run their machinery. 

One of the obvious options was coconut oil and this fuel was employed successfully until diesel supplies were resumed.

Fast forward nearly 70 years and a large number of people are experimenting with other non diesel fuel options.

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Fuels used historically: WW2

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During WW2 the troops fighting in the Pacific experienced issues with fuel supplies and were forced to look at diesel alternatives to run their machinery. 

One of the obvious options was coconut oil and this fuel was employed successfully until diesel supplies were resumed.

Fast forward nearly 70 years and a large number of people are experimenting with other non diesel fuel options.

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Coconut oil as fuel today

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Coconut trees are found everywhere in the Pacific's tropical islands and the dried white flesh, known as copra, from six to 10 coconuts,  produces one litre of oil.

In the Marshall Islands there’s a company that has used 100% coconut oil in ships with 1,000 horsepower engines all the way down to five horse power generators

The rising cost of oil, worries that oil will run out and increasing concerns about the environmental impact of fossil fuels have all boosted attempts to find alternative energy sources.

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Potential issues with coconut oil

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With oils,  viscosity is of concern. The more viscous, in other words, sticky and gluey, the more potential issues using oils as a fuel.

With coconut oil issues are as follows:

• One problem is that coconut oil starts to solidify below 25 degrees Celsius 
• But that is not a problem on many tropical islands
• By carefully filtering coconut oil with excess moisture removed worked perfectly in many diesel engines.

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Blending and heating

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Coconut oil can be blended with diesel, used straight in an adapted engine or turned into biodiesel:

• Because of higher specific density and  slightly lower energy content, specific fuel consumption using coconut oil is generally 8% higher.
• Some say that using more than 20% coconut oil in a motor is potentially detrimental to the engine but this is not proven.
• Coconut oil is up to 30 times more viscous than regular diesel so requires some kind of heating element and this applies to other vegetable oils with the use of a pre heater being essential.

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Coconut oil: Start/Stop on Diesel

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Most adaption include a start and stop on regular diesel:

• When engine gets up to operating temperature the fuel switches to coconut oil
• Just before shutting down switches back to diesel
• It is also possible to adapt the fuel system to to start and stop on pure vegetable/coconut oil

And these systems feature adapted injectors, dedicated fuel pumps and extra filters.

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What about Biodiesel?

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Biodiesel is a standardized fuel that consists of vegetable oil Methyl Ester

It is a product of vegetable oil that reacts with an alcohol ( methanol) and a catalyst ( sodium hydroxide).

Generates two products, glycerin for soap and biodiesel 

There is a standard for biodiesel which is ASTM-D 6751 in the US and EN14214 in the EU

Positive impacts on the engine include increased lubricity and a reduction of visible particles in the exhaust but the problem ATM is that biodiesel is expensive to make!

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Production of Fuel ethanols

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So instead of using waste oils, vegetable oils such as coconut oil, can use ethanol that is produced by the fermentation of carbohydrates from various feedstocks  such as:

• Sugar cane
• Cassava or corn
• Wood and agricultural waste

Over time various farm communities around the world have looked at community stills where waste crop materials are fermented and alcohol is produced to run their farm machinery.

https://www.researchgate.net/profile/Ca-Rotz-2/publication/317342405_Ethanol_as_a_tractor_fuel/links/59349844aca272fc554fa7c2/Ethanol-as-a-tractor-fuel.pdf

https://www.farmshow.com/view_articles.php?a_id=768

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Hydro diesel

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Hydro diesel is classed as an emulsified fuel which are emulsions composed of water and diesel.

The main advantages to using emulsified fuels instead of the fuel itself are: 

• Environmental and economic benefits.
• Addition of water to the diesel process decreases combustion temperatures and lowers NO emissions
• Emulsified fuels are singularly effective in simultaneously reducing NO, nitrogen oxide and PM, particulate matter  emissions.

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Conclusion 

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While internal combustion engines are still used it is of paramount importance to explore the viability of using non polluting fossil fuels or at the very least reducing our reliance on these products by mixing with other oils, creating biodiesel or ethanol based products or replacing completely with something like straight coconut oil. The issues with ICE are many and no matter what fuel is used particulate matter and pollution are of concern but the ability for the farmer or similar to produce their own fuel has a certain attractiveness not only from a sustainability point of view but also from an economic one.

If you’d like to see what Greenwood Solutions get up to in the real world of renewable energy, solar, battery storage and grid protection check out our industry and commercial pages:

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https://www.greenwoodsolutions.com.au/industry 

https://www.greenwoodsolutions.com.au/commercial

https://www.greenwoodsolutions.com.au/news

https://www.greenwoodsolutions.com.au/commercial/customer-stories