Waste Oil As A Fuel Alternitive
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Waste Vegetable Oil As A Diesel Replacement Fuel
Phillip Calais* and AR (Tony) Clark**
* Environmental Science, Murdoch University, Perth, Australia, [email protected]
** Western Australian Renewable Fuels Association Inc, [email protected]
Abstract
In the past, waste edible oils and fats were often used in the production of animal feeds. However due to links between BSE and this practice, the use of waste fats for animal feed is not as common as it once was and this has resulted in surplus quantities becoming available. This has led to significant disposal problems.
Waste oils and fats can be used as renewable fuel resources. Conversion of waste oils and fats to biodiesel fuel is one possibility but poses some difficulties such as in the use of toxic or caustic materials and by-product disposal. Conversion to biodiesel may also decrease the economic attractiveness of using waste oils as fuels.
An alternative to the use of biodiesel is the use of vegetable oils or rendered animal fats as a fuel.
Using relatively unmodified oils or fats eliminates the problems associated with toxic and caustic precursor chemicals and residual biodiesel alkalinity as the oil is used without altering its chemical properties.
This paper discusses the use of waste vegetable and animal oils and fats as unmodified fuels in compression ignition engines.
Introduction
Waste edible oils and fats pose significant disposal problems in many parts of the world. In the past much of these waste products have been used in the production of animal feeds. However due to possible links between BSE and this practice, the use of waste edible animal fats for animal feed is not as common as it once was, resulting in disposal problems. As it is often difficult to prevent the contamination of waste vegetable oil with animal products during cooking, waste vegetable oil often must be treated in a similar manner as is waste animal fats.
One possibility for the disposal of these products is as a fuel for transport or other uses. Conversion of waste oils and fats to biodiesel fuel has many environmental advantages over petroleum based diesel fuel. However it is not commercially available in Australia and the �back-yard’ production of biodiesel may present serious risks as the process uses methanol, a toxic and flammable liquid, and sodium or potassium hydroxide, both of which are caustic. By-product disposal may present further difficulties and environmental considerations may preclude production in sensitive areas.
An alternative to the use of biodiesel is the use of vegetable oil or rendered animal fats as fuel.
Using unmodified oils not only eliminates problems such as residual biodiesel alkalinity by-product disposal, but also increases the economic viability of using the oil or fat.
While the use of vegetable or animal oils and fats as fuels may be somewhat surprising at first, when examined in an historical context we can see that the compression ignition engine, first developed to a usable level of functionality by the French-born Rudolf Diesel near the end of the 19th century, was originally designed to operate on vegetable oil.
In 1900, Rudolf Diesel demonstrated his new compression ignition engine at the World Exhibition in Paris running on peanut oil. In 1911 he wrote “The engine can be fed with vegetable oils and would help considerably in the development of agriculture in the countries that use it.” [1]
It was about this time that new drilling technology and exploration techniques were developed and together these ushered in the age of cheap and plentiful fossil fuels. Consequently, the use of vegetable and animal oils and fats as fuels has only been used for a few special purposes such as in racing fuels or in environmentally sensitive areas where petroleum spills tend to cause more serious problems than do spills of animal and/or vegetable derived fuels.
After some one hundred years of using liquid petroleum fuels, we are now finding that there are unforeseen side effects, the foremost perhaps being the so-called Enhanced Greenhouse Effect.
In Australia, transport use contributes some 16% of Australia’s greenhouse gas emissions. Of this, diesel fuel contributed about 17% or 11,705,000 tonnes of CO2 equivalent. An additional 1,622,000 tonnes is released from diesel fuel used for electricity generation. [2] On top of greenhouse gas emissions is the vexing question of how little — or much — is left.
However oils of vegetable and animal origin, unlike fossil fuels, have to potential to be produced not only on a sustainable basis but also could be greenhouse gas neutral, or at the very least, emit substantially less greenhouse gases per unit energy than do any of the fossil fuels.
Properties of Triglycerides as Fuels
A large amount of research has gone into examining Diesel’s dream of using raw vegetable oils as fuels and when one speaks of growing crops for liquid fuels it is often assumed that the oil will be used after only basic extraction and filtering. [3,4,5]
Work has been conducted to examine these oils as fuel replacements or additives. For example in the late 1970’s and early 1980’s, research was undertaken at Murdoch University (Perth, Australia) into the use of eucalyptus and other plant oils as a fuel component. [6] In New Zealand, there are considerable problems with the disposal of surplus tallow from the processed meat industry and a large amount of work was conducted in the early 1980’s on the use of tallow as a fuel. [7]
Experience has shown that the use of unsaturated triglyceride oils as a fuel may cause significant problems that can affect the viability of their fuel use. [8] But this is not always the case and in many circumstances these problems can either be dealt with or are acceptable to the user.
While power output and tailpipe emissions using plant or animal oils are in most cases comparable with those when running on petroleum diesel fuel, the main problem encountered has due to the higher viscosity of the