An assessment of the feasibility of using vegetable oil fuels in light of the impending post fossil fuel dilemma
Creators: name: Thomas, Ian
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 300202
subject: Agricultural land management
classificationCode: 400201
subject: Automotive combustion and fuel engineering

description: This work reviews the use of compression ignition engines fuelled by a range of vegetable oil fuels, conducts a 45,000 km on-road trial using a 50/50 blend of waste vegetable oil and diesel fuel, reviews available plant species, availability of land for growing fuel crops and conducts a detailed study of Australia's prospects for growing fuel crops. It finds that diluted vegetable oil is a viable fuel in conventional diesel engines, that there are some 2500 non-food oil-producing ground-crop and tree species available, and that there is nowhere near enough land in the world to feed the growing human population and to provide fuel when fossil-fuels run out. The most promising class of plant species is shown to be halophytes in particular, those which grow in arid and semi-arid areas. <br><br>The literature review and on-road trials were conducted simultaneously. The review studied 65 publications covering the period 1980-2014 on the use of vegetable oil fuels in automotive and some other compression ignition engines either as straight oils or as blends. Exhaust emission and engine performance findings are tabulated and assessed. Vegetable oil fuel is found from the literature review, to be viable provided that measures are taken to reduce viscosity such as dilution or dual-fuelling and provided that greater ignition-advance is incorporated to allow longer burning time.<br><br>The on-road trial used mostly 50/50 decanted and sieved waste vegetable oil and diesel fuel with and without homogenising additives in a 1996 IDI diesel engine powered utility vehicle. Difficulties were experienced but they were able to be addressed. Some statistically significant improvements in fuel consumption are reported when performing repeatable, long country runs. While the work demonstrated that this pre-Euro 2 low-pressure mechanically injected vehicle could be operated on the 50/50 blend, this may not necessarily be the case for modern high-pressure, common-rail engines. Upon completion, trial findings were compared with findings by others. <br><br>The oil-producing species appraisal lists 341 non-food species and 73 food-related species describing a selection of 26 of these in more detail. It is evident that availability of species will not limit use of biofuels and that there should be no need to deplete food oils or fertile food-producing land in order to provide for our fuel needs. Rather with care, the broad range of salt-tolerant saltwater irrigated species such as sea asparagus, sea rocket and sea radish are considered capable of development in coastal margins in an environmentally and socially acceptable manner. Many other, arid area growing species show promise but only if care is taken to avoid the often associated adverse sociological and environmental impacts. The author  delves more deeply into the potential for halophyte species to provide both fuel and food by being grown in coastal margins, arid areas, deserts and salt-affected farmlands. It quickly becomes clear that the 400 Mha of world farmland nominally available for biofuel production is insufficient against the present need for at least 2500 Mha for producing fuel.<br><br>The current alternative fuel situation in Australia is presented as well as the potential to produce vegetable oil and other biofuels. Available native species, where they grow and how and where they may be cropped for fuel production are addressed. A detailed biogeographical appraisal of Australia estimates that 500,000 km2 are available provided that for each selected location, the correct species is chosen and due consideration is given to existing peoples and land uses. <br><br>The author concludes that vegetable oils and indeed biofuels as a whole, can presently only be part of the solution to the impending world energy crisis. The full solution is therefore likely to be a combination of vegetable oil and other biofuels together with other sustainable/renewable energy forms such as solar photovoltaic, solar thermal, geothermal, hydroelectric, wind, wave, tidal and salinity-gradient power. At the same time, as much waste vegetable oil and new non-food oils should be used as is physically, morally and environmentally practicable.