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Bio-diesel

Diesel Fuel, Made from vegetable oil, in a process called transesterification.

Background Information on Biodiesel

Agriculture and industry utilize the diesel-powered engine for a multitude of purpose, but the supply of petroleum derived diesel fuel is limited. The depletion in world petroleum reserves and uncertainty in petroleum supply due to political and economical reasons stimulated the search for alternative sources for petroleum based fuels especially for diesel fuels. Vegetable Oils are the best candidates for diesel fuels in diesel engines.

Several vegetable oils have been tried as substitutes, but continued use of triglyceride fuels in the diesel engine has presented problems in fuel injector coking and crankcase lubricant polymerization. Both of these problems have been attributed to high viscosity of vegetable oil, which is approximately 10-20 times higher than petrodiesel. Higher viscosity causes the poor atomization of fuel in the injector system and poor spray pattern. Viscosity can be reduced by following four ways
(a) By blending,
(b)By transesterification,
(c) By microemulsification, and
(d) By pyrolysis.
By using any of these procedures, appreciable amount of viscosity reduction and improved spray pattern can be achieved.

http://www.exicom.org/cew/oct97/sinha.htm (dead link)

What is Biodiesel?

Biodiesel is a diesel fuel substitute produced from renewable sources such as vegetable oils, animal fats, and recycled cooking oils. Chemically, it is defined as the mono alkyl esters of long chain fatty acids derived from renewable lipid sources. Biodiesel is typically produced through the reaction of a vegetable oil or animal fat with methanol or ethanol in the presence of a catalyst to yield glycerin and biodiesel (chemically called methyl or ethyl esters). Biodiesel can be used in neat form, or blended with petroleum diesel for use in diesel engines. Its physical and chemical properties as it relates to operation of diesel engines are similar to petroleum based diesel fuel. Non-Hazardous, Biodegradable.

How much land is needed to replace fossil fuels used for transportation?

by Michael S. Briggs

First, we need to understand exactly how much biodiesel would be needed to replace all petroleum transportation fuels. So, we need to start with how much petroleum is currently used for that purpose. Per the Department of Energy's statistics, each year the US consumes roughly 60 billion gallons of petroleum diesel and 120 billion gallons of gasoline.

First, we need to realize that spark-ignition engines that run on gasoline are generally about 40% less efficient than diesel engines. So, if all spark-ignition engines are gradually replaced with compression-ignition (Diesel) engines for running biodiesel, we wouldn't need 120 billion gallons of biodiesel to replace that 120 billion gallons of gasoline. To be conservative, we will assume that the average Diesel engine is 35% more efficient, so we'd need 35% less diesel fuel to replace that gasoline.

That would work out to 78 billion gallons of diesel fuel. Combine that with the 60 billion gallons of diesel already used, for a total of 138 billion gallons. Now, biodiesel is about 5-8% less energy dense than petroleum diesel, but its greater lubricity and more complete combustion offset that somewhat, leading to an overall fuel efficiency about 2% less than petroleum diesel.

So, we'd need about 2% more than that 138 billion gallons, or 140.8 billion gallons of biodiesel. So, this figure is based on vehicles equivalent to those in use today, but with compression-ignition (Diesel) engines running on biodiesel, rather than a mix of petroleum diesel and gasoline. Combined diesel-electric hybrids in wide use would of course bring this number down considerably, but for now we'll just stick with this figure.

One of the biggest advantages of biodiesel compared to other alternative transportation fuels is that it can be used in existing diesel engines. This completely eliminates the "chicken-and-egg" dilemma that other alternatives have, such as hydrogen powered fuel cells. For fuel cells, even when (and if) vehicle manufacturers eventually have production stage vehicles ready, nobody would buy them unless there was already a wide scale hydrogen fuel production and distribution system in place. But, no companies would be interested in building that wide scale hydrogen fuel production and distribution system until a significant number of fuel cell vehicles are on the road, so that consumers are ready to start using it.

However, with biodiesel, since the same engines can run on conventional petroleum diesel, manufacturers can comfortably produce diesel vehicles before biodiesel is available on a wide scale. As biodiesel production continues to ramp up, it can just go into the same fuel distribution infrastructure, just replacing petroleum diesel. Not only does this eliminate the chicken-and-egg problem, making biodiesel a much more feasible alternative than fuel cells, but also eliminates the huge cost of revamping the nationwide fuel distribution infrastructure.

II. Large scale production

There are two steps that would need to be taken for producing biodiesel on a large scale - growing the feedstocks, and processing them into biodiesel. The latter step would perhaps be best accomplished by existing oil refineries within the US being converted to biodiesel refineries, but could also be accomplished by new companies building new plants. The main issue that is often contested is whether or not we would be able to grow enough crops to provide the oil for producing the amount of biodiesel that would be required to completely replace petroleum as a transportation fuel. So, that is the main issue that will be addressed here.

The Office of Fuels Development, a division of the Department of Energy, funded a program from 1978 through 1996 under the National Renewable Energy Laboratory known as the "Aquatic Species Program". The focus of this program was to investigate high oil yield algaes that could be grown specifically for the purpose of wide scale biodiesel production1. Some species of algae are ideally suited to biodiesel production due to their high oil content (some as much as 50% oil), and extremely fast growth rates. From the results of the Aquatic Species Program2, algae farms would let us supply enough biodiesel to completely replace petroleum as a transportation fuel in the US (as well as its other main use - home heating oil).

One of the important concerns about wide scale development of biodiesel is if it would displace croplands currently used for food crops. With algae, that concern is completely eliminated, as algae grows ideally in either hot desert climates or off of waste streams. NREL's research focused on the development of algae farms in desert regions, using shallow salt water pools for growing the algae. Another nice benefit of using algae as a food stock is that in addition to using considerably less water than traditional oilseed crops, algae also grows best in salt water, so farms could be built near the ocean with no need to desalinate the seawater as it is used to fill the ponds.

NREL's research showed that one quad (ten billion gallons) of biodiesel could be produced from 200,000 hectares of desert land (200,000 hectares is equivalent to 780 square miles). In the previous section, we found that to replace all transportation fuels in the US, we would need 140.8 billion gallons of biodiesel, or roughly 14 quads. To produce that amount would require a land mass of almost 11,000 square miles.

To put that in perspective, consider that the Sonora desert in the southwestern US comprises 120,000 square miles. As can be seen in Figure 1 below, the Sonora desert is located along the Pacific ocean, making it an ideal location for algae farms. The arid climate of the desert is very supportive of algae growth, and the nearby ocean could supply saltwater for the algae ponds. Enough biodiesel to replace all petroleum transportation fuels could be grown in 11,000 square miles, or roughly nine percent of the area of the Sonora desert.

http://www.unh.edu/p2/biodiesel/article_alge.html

http://www.chemsoc.org/networks/learnnet/green/biodiesel/home.htm

http://www.ott.doe.gov/biofuels/pdfs/biodiesel_from_algae_ps.pdf

 

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