Mr. Green Car: Nature’s fuel—part two
By Allen Penticoff
I had a reader contact me about the use of hemp (marijuana) seeds for oil use directly in diesel engines. Like many plants, the hemp seed can be squeezed to produce oil. Like nearly all of them, the oil can be burned in a diesel engine once the oil is warmed up. Depending on the viscosity of the oil, how much you need to warm it up varies greatly. But again, biodiesel is not straight vegetable oil, and thus can be used as though it is ordinary diesel.
The problem in using B100 biodiesel is that its properties as a solvent are far greater than diesel. Thus, soft seals and plastics in a fuel system can suffer. It is generally considered safe to use biodiesel in vehicles manufactured after 1992, but this may not extend to use of B100.
Using straight vegetable oil has its own issues. Having proven feasible, there is no reason systems could not be designed around these issues so engines could run 100 percent on vegetable oils under any conditions. Like a lot of things, it needs a market demand to make it happen.
Another reader questioned using jatropha oil instead of soybeans. I told him that yes, jatropha plants can be grown just for the purpose of producing fuel oil. In fact, the amount of oil per acre is far higher than with soybeans. However, this plant/shrub/tree grows best in tropical and subtropical climates (or in your house). It is a hardy perennial that is drought- and pest-resistant (it is toxic), that can be grown on marginal lands—but has yet to be fully domesticated. Jatropha is considered an invasive weed in Australia.
Rapeseed, or canola, is another high oil-yielding plant (oleaginous) of the 350 or so plants that produce oil. It produces a lot of oil, second only to jatropha, but it likes short, cool seasons of higher latitudes to grow (such as Canada). While it is commonly grown in Europe for fuel oil, very little rapeseed is grown in the U.S. The downside to rapeseed is the amount of nitrogen fertilizer used to spur its growth, the manufacture of which releases a potent greenhouse gas, N2O.
Likewise, sunflowers produce a lot of oil, too, but they like moist, well-drained soil. They are grown commercially from Kansas up into the Dakotas. See the listing of 10 common oil-producing plants* in the table below.
As you can see, jatropha yields oil 323 percent greater than soybeans. If we were growing plants as fuel, our landscape might look much different. But each of these plants has other attractions and uses for its fibers and meals that make them worth growing. As I learned from talking to a farmer at the Renewable Energy Fair—what we see growing in a particular locale is what grows there. As much as a farmer would like to raise a crop with higher cash value, trying to force a plant to grow in an area not suited to it is to court failure.
Another category of oleaginous plant is being researched—plants that are salt or brackish water tolerant (halophytes). Obviously, this opens up great new areas for crop cultivation, particularly in Third-World countries.
A great deal of resources are being directed at algae that produce oil. These algae can grow in tubes or ponds. The U.S. Department of Energy believes algae-based yields may be more than 30 times greater per acre than soybeans. This promising “crop” deserves a Mr. Green Car report all to itself.
Once you have the oil, you can make biodiesel, or design systems to run directly on it. Besides fueling diesel engines, turbine engines can operate on biodiesel, and have flown in tests on jets. Either engine can power an electric generator—so we can get electricity from plants in this fashion. Buses and locomotives are able to run on biodiesel as well, and have been (Disneyland runs their trains on their own in-house waste oil resources). Heating-oil-burning furnaces can operate on biodiesel, as can stoves and lanterns.
Other non-energy uses for biodiesel are as solvents in paints and in cleaning coked or greasy engines. It can be used as a lubricant. Biodiesel can even be used to clean up oil spills on land or water. It has potential as a non-toxic crop adjuvant.
The problem is that we consume an awful lot of diesel, and it would take growing soybeans on every arable acre of land in the U.S. to meet that demand alone, although estimates from University of Idaho research indicate that 24 percent of our diesel fuel could be “grown” without displacing food crops. Reasonable guesses indicate it would take an area the size of the state of Georgia growing algae oil to match 100 percent of diesel demand. Unfortunately, algae fuel is a long way from being cost-competitive with other fuel crops or mineral fuels.
There are a lot of exciting things happening that could keep our farms profitable by growing fuel. The future may be in localized energy production, but it will take the return of higher oil prices to encourage the production and consumption of these much more environmentally- and trade-friendly products.
*Reference: From the Fryer to the Fuel Tank. Yields shown are averages and can vary substantially.
From the Dec. 16-22, 2009 issue
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