SUSTAINABLE

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                                   RESEARCH AND EDUCATION TO PROMOTE CONVERSION
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               Document #2
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                   HOME GROWN FUELS

What are Home Grown Fuels?

          “Home Grown Fuels” is a new name for some very old resources.  Home Grown Fuels are fuels that we can grow within the borders of our own country, within the borders of our own communities, or within the borders of the land that we live on.  As such, they are renewable fuels, as opposed to conventional fossil fuels that we extract from the ground.  Examples are wood, ethanol (made from corn), and vegetable oils.  In particular, the liquid fuels such as ethanol and vegetable oils are useful since they can be burned in internal combustion engines, and therefore serve as a substitute for non- renewable fossil fuels in transportation and many other applications.  

 

 The Carbon Cycle and Global Warming

            When plants grow, they absorb carbon dioxide, water and various materials from the ground, and they give off oxygen.  With sunlight as an energy source, and through the process of photosynthesis, the plants create organic compounds, including hydrocarbons.  In the case of some plants such as sunflowers, safflowers, soybeans, and many others, a hydrocarbon oil is created which can be extracted and burned.  When burned, the oil gives off about the same amount of carbon dioxide as is absorbed when the oil is produced within the plant.  The carbon dioxide therefore follows a full cycle from the atmosphere to the plant and back into the atmosphere. 

             The process of global warming occurs when certain “greenhouse gases”, of which carbon dioxide is one, increase in concentration in the atmosphere.  The effect is to trap heat that would normally escape through the atmosphere, and to raise temperatures here on earth.  The resulting global warming can have serious consequences for life on earth. 

            The burning of fossil fuels releases carbon dioxide that was taken out of the atmosphere millions of years ago when the plant material that created these fuels was growing.  When a gallon of gasoline is burned, it releases 20 pounds of carbon dioxide.  (While this seems implausible since a gallon of gasoline only weighs about 7 pounds, it becomes clear when calculating the effect of substituting of two relatively heavy oxygen atoms for the light hydrogen atoms that had been attached to the carbon atoms before combustion.)  Home Grown Fuels, on the other hand, recycle this carbon dioxide and therefore do not contribute to such an increase in carbon dioxide concentration in the atmosphere.

 Energy Balance

          The process of cultivating, planting, watering, weeding, and harvesting any crop requires energy.  For an oil producing plant that requires 30 units of energy for these activities, and where the oil produced has an energy content of 100 units, the energy balance is 30% or .30.  If fossil fuels are used as the energy for the growing and production activities, this reduces the benefits accordingly.  However, if the renewable fuel itself is used, then the benefits remain, and the effective yield is simply reduced. 

             For vegetable oils, the energy balance is close to .30.  For ethanol, the energy balance can approach 1.0, so it is quite unfavorable from this standpoint.  While ethanol is useful as an additive to gasoline to lessen emissions, it is problematic as a pure source of fuel because of the unfavorable energy balance. 

Practical Aspects - Distribution, Storage, Infrastructure

The three representative examples of Home Grown Fuels mentioned above - wood, ethanol and vegetable oils - have varying degrees of practicality when used for energy production.  Since liquid fuels can be burned in the internal combustion engines that provide power for most of our transportation and for other useful machinery, they are the most practical.  While the poor energy balance of ethanol limits its practicality as a fuel, vegetable oil has very few practical limitations.  Vegetable oil has a relatively high flash point so it can be safely handled and shipped by common carrier.  (For example, one does not consider it dangerous to purchase a container of vegetable oil at the supermarket, carry it home in the passenger compartment of a car, store it in the kitchen, and even heat it in an open  pan to 375 degrees F over an open gas flame in order to make french fries.)  The implications of this are considerable and far reachingThere are numerous other fuels that are being promoted as alternatives to commonly used fuels such as gasoline.  Among these are compressed natural gas, liquid propane and hydrogen.  These fuels are non renewable, or in the case of hydrogen, produced using predominantly non-renewable energy sources.  In each case, these are fuels that are highly flammable and relatively dangerous to transport and handle.  Importantly, in order to make these fuels widely available, it will require a very substantial investment in production, distribution, storage, and dispensing infrastructure.  Vegetable oil, on the other hand, requires no such investment.  Distribution can be built at the grass roots level with virtually no investment.  A distributor can be set up immediately by purchasing a container of vegetable oil fuel which can be shipped by UPS, Fedex, US Postal Service  or similar carrier.  Similarly, an end user can order this fuel and have it shipped in the same method to a home address.   (Of course, purchase at a supermarket or discount warehouse is also an option.)  The result is that this amazingly practical fuel, when used in suitably modified engines, can be brought to market without sponsorship by major oil companies, without government grants or subsidies, and without political obstacles and regulatory hurdles.

 

 Power Conversion

          The most practical Home Grown Fuel, vegetable oil, can be used to power compression ignition (Diesel) engines.  These engines can be used in any conventional application, or used in emerging areas such as hybrid electric vehicles or independent power generation for industrial, commercial or residential applications.  The major difference between vegetable oil and petroleum Diesel fuel is that vegetable oil is more viscous and typically requires heating to be useable.  Modification of fuel injectors may also be necessary to accommodate this difference in viscosity. 

 

Emissions

          Tests of engines using vegetable oil have demonstrated that emissions of most pollutants is reduced, compared to petroleum Diesel fuel, with the emissions of nitric oxides (NOX) to be about equal.  To begin with, the vegetable oil contains virtually no sulfur or benzene compounds that are found in petroleum Diesel fuel, so emissions containing these pollutants are eliminated.   As previously noted, the “carbon neutral” characteristic of vegetable oil results in no net carbon dioxide emissions.  (However, while carbon dioxide is a global warming gas, it is not classified as a pollutant.)  As techniques are developed to lessen the pollutants emitted by engines using petroleum Diesel fuel, these same techniques will prove beneficial for vegetable oil as well.  (Interestingly, the objectionable odor produced from petroleum Diesel fuel is absent when burning vegetable oil, and the odor resembles the aroma produced from cooking french fries or doughnuts.) 

 

Other Renewable Fuels or Power Sources

          A vegetable oil based fuel known as Biodiesel is gaining recognition and popularity as an alternative to petroleum Diesel fuel. Biodiesel is made by mixing vegetable oil (either new or used) with a solution made by mixing methanol and lye.  The resulting fuel has a low viscosity and can be used directly in Diesel engines, without need for heating (except at very low temperatures.)  Biodiesel can, however, cause deterioration of rubberized gasket materials, so should be used only when approved by the engine manufacturer.  Biodiesel can be made on a small scale and is also available commercially.  

 In terms of solar power sources, photovoltaic panels are also an option.  The advantages of noiseless and low maintenance operation for this clean solar power source are well known.   However, the limitation of  sunlight availability, together with high cost (about $8 per watt installed) are formidable obstacles.  Owners of PV panels who are “off the grid,” usually have a backup genset - often a gasoline powered generator which produces considerable emissions.  If a genset powered by vegetable oil were used to replace such a gasoline powered genset and also used to replace a portion of the PV panels, the result would be a power source that is every bit as “solar” as the PV panels themselves, with a considerably reduced per Watt installation cost.  In fact, if the savings in equipment capital outlay were to be invested at a modest rate of return, the interest earned could easily pay for fuel and maintenance for the vegetable oil powered genset. 

 Cost, Availability, and World Wide Production

Vegetable oil can be purchased in bulk (5 gal.) quantities from food warehouse stores such as Costco for about $3.00/gal.  (Used vegetable oil can often be obtained for nothing from fast food restaurants, but the varying consistency of this oil makes it inadvisable to use in engines unless it is first chemically analyzed.)  While our own farmland has the potential for substantial production of oil producing crops, many underdeveloped countries also have climates that are ideal for the growing of abundant, prolific oil producing crops.  There is a great potential for these countries to produce their own Home Grown Fuel and become the new oil producers and exporters for the world. 

 

© 2003 Bruce Colley.  All rights reserved

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Last modified: 05/24/05

© 2003 Sustainable Energy Project.  All rights reserved