Research on Using Vegetable Oils based Fuels
BioDiesel versus Straight Vegetable Oil and Diesel
Biodiesel usually refers to using a vegetable oil modified by a chemical process (such as transeterification, which involves an alcohol) to produce fuel for a diesel engine.
The advantage of biodiesel over normal diesel is that biodiesel uses either less fossil fuel or no fossil fuel at all. The advantage of using biodiesel over straight vegetable oil (SVO) is that biodiesel can be used in an unmodified diesel engine, without additional fuel tanks or warming of the secondary fuel source.
The major disadvantage of biodiesel is its cost. Biodiesel fuels are more expensive than petroleum diesel and harder to make than vegetable oil. Also, they are difficult and potentially dangerous to manufacture (methanol is toxic).
The main advantage of using vegetable oil based fuels instead of fossil fuels is that vegetable oil is better for the environment. Specifically, vegetable oil fuels are sustainable and carbon neutral.
The sources for vegetable oils are, obviously, vegetables – soy beans, canola seeds, etc. The energy to grow the crops comes from the sun, and does not use fossil fuels.
Vegetable oil fuels, do emit greenhouse gases when burned, but they are considered carbon neutral because any carbon dioxide emitted was absorbed by the plant during its growing process and counterbalances the emitted CO2.
Sustainability issues come into play when considering the ability of the world to farm enough raw products for the mass use of vegetable oil-based fuels while using sustainable farming methods. One source claims that through recycling and using currently fallow land, the US could produce up to 25% of its oil needs without major farming changes, but this figure is probably very optimistic. Increasing farming efficiency or using algae farms (which are still experimental) are other possibilities for the production of vegetable oil.
Performance Data for Vegetable-based Fuels
Most sources claim that engines perform equitably whether running straight vegetable oil or biodiesel, with the possible exception of long term wear and tear on the engine.
All studies generally agree that there is a negligible performance difference between vegetable oils and diesel, an approximately 5% loss. An engine specifically designed for vegetable oil would run at least as well as normal diesel engine running diesel, but such engines are very expensive as they are not currently mass produced.
Feasibility, Economics of Vegetable-based Fuels
Economically, things don’t look very good for the mass production of biodiesel and waste vegetable oil fuels in the short term or the long. Vegetable oil is more expensive than gasoline, and there is only so much waste oil available. A survey of 12 economic analyses of biodiesel fuels concluded that biodiesel is not currently economically feasible because it is more expensive than diesel. In other words, the price of diesel would have to increase significantly or be heavily taxed, or other price factors would have to change.
However, producing fuel domestically would also create jobs in the US, reduce the trade deficit, and reduce the US’s reliance on the volatile Middle East. Additionally, fossil fuel oil is subsidized, both directly and militarily, while farmers are subsidized to keep vegetable oil prices high, meaning the apparent price difference is not necessarily the real difference in production cost. Nevertheless, by the time oil runs out, there is likely to be a better solution than biodiesel available on a mass scale.
Emissions of Vegetable-based Fuels
In general, the emissions from vegetable oil fuels are similar to those from diesel engines, but somewhat lower (again, the major difference is that SVO is carbon neutral). For straight vegetable oil, particulate matter emissions are higher but NO2 emissions are lower. For biodiesel, NOx emissions are higher, but sulfur, CO2, and particulate emissions are slightly lower. Also, “upstream emissions,” the emissions from the making and transporting the fuel, are much lower for biodiesel than for diesel fuels.
Appendix: Net energy loss/gain for fuels (losses in parenthesis) from http://www.mda.state.mn.us/ethanol/yield#yield
* Life cycle yield in liquid fuel BTUs for each BTU of fossil fuel energy consumed.
Summary of Energy Balance/Energy Life Cycle Inventory
||* Energy yield
||Net Energy (loss)/gain