Biodiesel is a clean-burning diesel fuel produced from soybean and other vegetable oils instead of petroleum. Biodiesel can be blended at any level with petroleum diesel to create a biodiesel blend.  Biodiesel use in compression ignition (diesel) engines enhances engine combustion performance, improves engine lubrication and reduces air and water pollution caused by the exhaust.

Biodiesel is made from Vegetable Oils through a chemical process called Transesterification

Biodiesel is produced from vegetable oils by converting the triglyceride oils to methyl (or ethyl) esters via a process known as transesterification. The transesterification process reacts alcohol with the oil to release three "ester chains" from the glycerin backbone of each triglyceride. The reaction requires heat and a strong base catalyst (e.g., hydroxide or lye), to achieve complete conversion of the vegetable oil into the separated esters and glycerin. The glycerin can be further purified for sale to the pharmaceutical and cosmetic industries. The mono-alkyl esters become the Biodiesel, with one-eighth the viscosity of the original vegetable oil. Each ester chain, usually 18 carbons in length for soy esters, retains two oxygen atoms forming the "ester" and giving the product its unique combustion qualities as an oxygenated vegetable based fuel. Biodiesel is nearly 10% oxygen by weight.

Petroleum diesel, in contrast, is made up of hundreds of different hydrocarbon chains (roughly in the range of 14-18 carbons in length), with residues of sulfur and crude oil remaining. Diesel fuel sold today, even "low sulfur, low aromatic" diesel, contains 20-24% aromatics (benzene, toluene, xylenes, etc.) that are toxic, volatile compounds responsible for the fire/health hazards and pollution associated with petroleum diesel.

Biodiesel meeting the industry standard ASTM-D6751, in its neat (pure) form, is referred to as B-100.  When blended with petroleum diesel the resulting mixture is identified by the percentage of biodiesel in the mix; e.g. 20 percent biodiesel blended with 80 percent petroleum diesel is referred to as B-20.

ENGINE PERFORMANCE

Biodiesel methyl esters improve the lubrication properties ("lubricity") of the diesel fuel blend. Long term engine wear studies have been conducted in Europe and in the US. Porsche (Germany) determined that neat (100%) Biodiesel reduced long term engine wear in test diesel engines to less than half of what was observed in engines running on current low sulfur diesel fuel. Lubricity properties of fuel are important for reducing friction wear in engine components normally lubricated by the fuel rather than crankcase oil.

Biodiesel has been studied extensively in Europe and the U.S. for its effect on long term engine wear, particularly with respect to those components normally lubricated by the fuel itself. Fuel pumps and injector pumps depend on the operating fuel for lubrication of moving parts and shaft bearings. Initial work on the lubricity of Biodiesel, performed by Mark-IV Group and the Southwest Research Institute in 1994, established a clear advantage to blending Biodiesel with petrodiesel to achieve superior lubrication.

Tests run by Exxon showed that, compared to reference diesel fuel in 1993, a 20% blend of Biodiesel had significant, quantifiable improvements in reducing wear (193 micron scar for B-20 vs. 492 micron scar for petrodiesel) and friction (0.13 micron scar for B-20 vs. 0.24 micron for petrodiesel) while improving film coating ability of the blend (93% film with the B-20 vs. 32% film with the petrodiesel). The B-20 blend compared favorably for lubricity results against Exxon's own lubricity additive.

Heat of Combustion Properties

Relative to petroleum diesel no. 2, Biodiesel has a slightly lower heat of combustion on account of its oxygen content (petroleum diesel hydrocarbons are not oxygenated). The heat of combustion for soy methyl esters is 128,000 BTU (British Thermal Units) per gallon vs. 130,500 BTU/gal. for petrodiesel.  However, with the added oxygen, the net combustion efficiency for the blended fuel is increased, which should compensate for the slight drop in BTU content. The differences would be most noticed at low rpm and high engine load when the engine would most benefit from more oxygen.

Power Differences

Studies conducted in the U.S. and Europe generally indicate that blends of Biodiesel and petrodiesel result in small decreases in overall power output of engines.  In a Volvo marine diesel engine study in Tennessee (110-HP, 2.39 L, 4-cylinder, direct injection engine), a tractor dynamometer was used to measure power outputs under selected loads through an engine-mounted reverse drive gear. Exhaust emissions were also tested along with fuel consumption tests under various loads. The conclusions of these tests were that power produced from 100% soy methyl ester Biodiesel was from 2 to 7 percent less than produced from petrodiesel, depending on the load-speed point. However, at or near maximum throttle (3,800 rpm), the two fuels performed the same. Interestingly, at the lowest engine speed (1855 rpm) at full throttle under heavier load, there was a 13% increase in power with Biodiesel as compared to petrodiesel.

Fuel Consumption Differences

Biodiesel is a mono-alkyl esters containing approximately 10% oxygen by weight. The oxygen improves the efficiency of combustion, but it takes up space in the blend and therefore slightly increases the apparent fuel consumption rate observed while operating an engine with Biodiesel.

Engine Seals, Gaskets and Hoses

The oxygenated methyl esters of vegetable oil cause Biodiesel to have surprisingly strong solvent properties with respect to natural rubber and several soft plastics. As a result, old rubber fuel lines and some seals or gaskets on fuel tanks may slowly deteriorate in the presence of higher concentrations of Biodiesel. Fortunately, few of these solvent effects are noticed at a B-20 blend. When fuel lines or gaskets are affected, they usually get sticky over time and soften or swell, causing fuel to drip from connections. The best solution is to replace affected lines and gaskets with modern synthetic hoses and seals.

Conventional US Coast Guard approved fuel lines are resistant to Biodiesel (neat) and proven in sailboat testing over the past 3 years. In California, an approved fuel hose readily available in marine stores is:

Studies conducted for the National Biodiesel Board on the materials compatibility of Biodiesel concluded that the only hose and gasket material that was truly resistant to the solvent effects of methyl esters was Viton.

The solvent properties of the esters in Biodiesel can loosen old paint on engines or on painted surfaces in the bilge. Besides staining raw wood surfaces, Biodiesel is particularly harmful to teak decks with polysulfide seams (use extra caution when filling tanks via deck ports). Biodiesel could also harm rubber engine mounts if it were spilled and not cleaned up immediately. Use paper towels or absorbant pads to remove spilled Biodiesel and then clean the surfaces thoroughly with warm soapy water.

Warranties and Engine Manufacturer Endorsements

Marine diesel engine manufacturers in United States, Europe and Japan have all recognized the growing role of Biodiesel as a viable fuel additive, and in most cases, as a complete alternative fuel (100%). Two of the sponsors of the SUNRIDER expedition of 1992-1994 were the marine diesel engine manufacturers: Mercruiser (inboard/outboard diesel engine) and Yanmar (outboard diesel engines), endorsing Biodiesel as a suitable alternative fuel to power Bryan Peterson's 28-ft inflatable Zodiac boat around the world. This 35,000 mile adventure remains the most famous and most publicized demonstration of Biodiesel use in marine engines.

Manufacturers warrant their products against defects in materials and workmanship.  In general use of a particular fuel should have no effect on the materials and workmanship warranty.  Use of biodiesel does not "void the warranty"; this is prohibited by the Magnuson-Moss Warranty Act.  As with petroleum diesel, verify that your fuel supplier warrants the quality of their fuel.  In the U.S., diesel engine manufacturers generally endorse Biodiesel fuel meeting the ASTM-D6751 standard when used in a blend with petroleum diesel.  Caterpillar endorses the use of B-100 in many of its engine models.  Contact your engine manufacturer for updates on their acceptance of Biodiesel and Biodiesel blends as an acceptable fuel for use with their particular engine.

SAFETY AND AESTHETIC ADVANTAGES OF BIODIESEL

Boaters can appreciate the user friendliness of handling Biodiesel in their boats. The product has no noxious odors and is considered as harmless to handle as salad oil.  The product smells and feels like cooking oil.

No Noxious or Carcinogenic Fumes

Biodiesel vegetable oil methyl esters contain no volatile organic compounds that would give rise to any poisonous or noxious fumes. Biodiesel does not contain any aromatic hydrocarbons (benzene, toluene, xylene) or chlorinated hydrocarbons. There is no lead or sulfur to react and release harmful or corrosive gases. However, in blends with petrodiesel there will continue to be significant fumes released by the benzene and other aromatics present in the petroleum fraction (80%) of the blend.

No Risk of Explosion from Vapors

Since Biodiesel has no volatile components (vapor pressure of less than 1 mm Hg) and a high flash point (typically over 260 Deg. F), the product poses no risk of explosion caused by fumes accumulated below deck. The only significant fire risk would be from the spontaneous combustion of rags and paper towels soaked in Biodiesel and stored in an area with low ventilation, or high temperatures (like the inside of an engine room).
 
 
LOWER IMPACT ON MARINE ENVIRONMENT

Water pollution is reduced by using Biodiesel in boat engines since there will be more efficient burning of the fuel mixture, less carbon (soot) accumulation and particulate (smoke) emissions. Faster starting and smoother operation also should reduce the discharge of unburned fuel. Any accidental discharges of small amounts of Biodiesel should have relatively little impact on the environment compared to petroleum diesel, which contains more toxic and more water-soluble aromatics. Nonetheless, the methyl esters could still cause harm.

Comparatively Low Toxicity to Marine Plants and Animals

From 1994 through 1996, CytoCulture conducted a series of tests in collaboration with the California Department of Fish & Game (Office of Oil Spill Prevention & Response) to document the impact of vegetable methyl esters on various native species of marsh plants and marine organisms. Because larval forms of fish and shell fish are much more sensitive than the adult forms, all of the marine toxicity studies were performed with larvae of established test species. The studies indicated that the Biodiesel, while not completely harmless to the larvae of crustacea and fish, is much less toxic than petroleum fuels and crude oil.

In research conducted for CytoCulture in 1994, the LC50 (concentration required to kill 50% of the population) for larval test fish (Menidia Beryllina) exposed to soy methyl ester Biodiesel was 578 ppm relative to an LC50 of 27 ppm for reference fuel oil. In larval shrimp (Mysidopsis Bahia) toxicity assays, the LC50 for the soy methyl ester Biodiesel was 122 ppm compared to the LC50 of 2.9 ppm for the reference fuel oil.

Low Solubility and High Biodegradation Rate for Biodiesel in Water

Biodiesel methyl esters are actually quite insoluble in fresh or sea water, with a saturation concentration of 7 ppm (sea) and 14 ppm (fresh) at 17 Deg. C, whereas petroleum diesel can partition aromatics into water in concentrations of hundreds of ppm. The dissolved phase of the Biodiesel methyl esters was shown to breakdown by the biodegradation action of naturally occurring bacteria present in sea water. The half-life for the biodegradation of the vegetable methyl esters in agitated sea water was less than 4 days at 17 Deg. C., about twice as fast as petroleum diesel (reported by others).

Biodegradability of Biodiesel in the Aquatic Environment

A study conducted at the University of Idaho in 1995 determined that rapeseed Biodiesel would biodegrade about twice as fast as petroleum diesel using a standard EPA test protocol based on carbon dioxide evolution and gas chromatography. Further, the Biodiesel was shown to enhance the biodegradation rate for diesel fuel in a blend.

The biodegradation rate of rapeseed biodiesel in shake flasks with fresh water was found to be comparable to dextrose (a test sugar) and about twice as fast as for petroleum diesel. In the Idaho study (Peterson, Reece, et al., 1996), the rapeseed esters were degraded by 95% at the end of 23 days where as the diesel fuel in this test was only about 40% degraded after 23 days.

Spills of Biodiesel Can Still Harm the Environment

For the boating environment, Biodiesel should have less impact to aquatic and marine organisms than petroleum diesel if accidentally spilled or inadvertently discharged over the side. However, the US EPA still considers spills of animal fats and vegetable oils harmful to the environment. In an October, 1997 ruling under the Clean Water Act, as amended by the Oil Pollution Act of 1990, vegetable oils are considered "oil" like petroleum. (In France, Biodiesel is classified as food for transportation purposes.)

Spilling Biodiesel into the water would be as illegal as discharging petroleum fuels overboard. Waterfowl and other birds, mammals and fish that get coated with vegetable oils could die from hypothermia or illness, or fall victim to predators. Even though the Biodiesel is relatively non-toxic and less viscous than vegetable oil, it can still have a serious impact on marine and aquatic organisms in the event of a big spill. We recommend that the Biodiesel always be handled like any other fuel to avoid contamination of our bays and waterways, and that boaters obey all laws governing the handling of engine fuels and oils.
 
STORAGE CONDITIONS FOR BIODIESEL

Biodiesel can be stored for long periods of time in closed containers with little head space. The containers should be protected from weather, direct sunlight and low temperatures. Avoid long term storage in partially filled containers, particularly in damp locations like dock boxes. Condensation in the container can contribute to the long term deterioration of the petroleum diesel or biodiesel (see below). Low temperatures can cause Biodiesel to gel, but Biodiesel will quickly liquefy again as it warms up. In cold weather (near or below freezing), additives can be used to prevent gelling (fuel additives for diesel fuel used in cold weather are available from Exxon, Hammond, and other manufacturers).

Fuel tanks should be kept as filled as possible (regardless of whether they contain Biodiesel), particularly during rainy winter months or periods of inactivity, to minimize the condensation of moisture. Condensed moisture accumulates as water in the bottom of your tank and can contribute to the corrosion of metal fuel tanks, especially with petroleum diesel that also contains sulfur. The condensed water in the fuel tank can also support the growth of bacteria and mold that use the diesel and Biodiesel hydrocarbons as a food source. These hydrocarbon-degrading bacteria and molds will grow as a film or slime in the tank and accumulate as sediment over long periods of time. These hydrocarbon-degrading microbes are frequently referred to incorrectly as "algae" in advertisements for fuel treatments, perhaps because the colonies often have a reddish orange color and tend to form mats.

Petroleum diesel and Biodiesel are both susceptible to microbe growth when water is present in the fuel.  The solvent action of the Biodiesel can also cause microbial slime to detach from the inside of the tank. The accumulation of the newly released slime and sediment can be dangerous if it clogs the fuel filters and causes the engine to suddenly stop. It is very important to monitor the filters on a diesel engine that has been switched over to Biodiesel, particularly if the tank is old and has not been cleaned.

The microbial slime and sediment problem seems to worsen for boats that are used infrequently since the inactivity allows the microbes to accumulate in stable colonies. When the boat is used again, the slime and sediment can break loose and accumulate in the fuel filters. Accumulated sediment in fuel filters can then interrupt the flow of fuel and shut down the engine. As mentioned earlier, the addition of Biodiesel to a dirty fuel tank can accelerate the release of accumulated slime. When the boat is then used after sitting idle for a long period of time, the newly suspended sediment can accumulate and potentially clog the fuel filters. Check fuel filters often and be prepared to change them after introducing Biodiesel to an older fuel tank that may have accumulated slime and sediment.
 

EMISSIONS REDUCTIONS WITH BIODIESEL

Since Biodiesel is made entirely from vegetable oil, it does not contain any sulfur, aromatic hydrocarbons, metals or crude oil residues. The absence of sulfur means a reduction in the formation of acid rain by sulfate emissions that generate sulfuric acid in our atmosphere. The reduced sulfur in the blend will also decrease the levels of corrosive sulfuric acid accumulating in the engine crankcase oil over time. The lack of toxic and carcinogenic aromatics (benzene, toluene and xylene) in Biodiesel means the fuel mixture combustion gases will have reduced impact on human health and the environment. The high cetane rating of Biodiesel (ranges from 49 to 62) is another measure of the additive's ability to improve combustion efficiency.

Smoke and Soot Reductions

Smoke (particulate material) and soot (unburned fuel and carbon residues) are of increasing concern to urban air quality problems that are causing a wide range of adverse health effects for their citizens, especially in terms of respiratory impairment and related illnesses. Boaters always complain of the smoke from their diesel engines as they motor back to port. Soot accumulation on the transoms and decks of their boats is also a problem.  The lack of heavy petroleum oil residues in the vegetable oil esters that are normally found in diesel fuel means that a boat engine operating with Biodiesel will have less smoke, and less soot produced from unburned fuel. Further, since the Biodiesel contains oxygen, there is an increased efficiency of combustion even for the petroleum fraction of the blend. The improved combustion efficiency lowers particulate material and unburned fuel emissions especially in older engines with direct fuel injection systems.

Lower Hydrocarbon Emissions

As an oxygenated vegetable hydrocarbon, Biodiesel itself burns cleanly, but it also improves the efficiency of combustion in blends with petroleum fuel. As a result of cleaner emissions, there will be reduced air and water pollution from boats operated on Biodiesel blends. At a 20% Biodiesel blend, there will be a noticeable change in the odor and smoke in the exhaust. Older engines should also emit less soot under load and less carbon black during startup.

Independent research programs in Europe and the U.S. have shown that Biodiesel in a 20 percent blend (B-20) with petroleum diesel created a significant reduction in visible smoke and odor. The studies documented the reduction in hydrocarbons, carbon monoxide and particulate matter

From field observations with boats and test cars, Biodiesel appears to be even very effective in reducing smoke. The reduction in particulate Matter (PM) when B-20 is used is due to a reduction in insolubles (particles), generally composed of carbon soot. Catalytic converters (used in trucks and cars) can further contribute to the reduction in PM when B-20 is used.

Carbon Monoxide Emissions

Carbon monoxide gas is a toxic byproduct of all hydrocarbon combustion that is also reduced by increasing the oxygen content of the fuel. More complete oxidation of the fuel results in more complete combustion to carbon dioxide rather than leading to the formation of carbon monoxide. In the 1998 report by the Southwest Research Institute on the effects of Biodiesel on truck engine exhaust emissions, the levels of carbon monoxide were shown to be reduced from 8% to 22% with a B-20 blend, depending on the type of engine.

Polyaromatic Hydrocarbon Emissions

Polyaromatic hydrocarbons (PAHs) are a class of heavy oil petroleum hydrocarbons defined by their complex ring structures and unique qualities. They consist of multiple benzene ring structures that make them insoluble, slow to burn and carcinogenic. PAHs are regulated by the EPA in engine emissions. In the 1998 SWRI report, the Cummins N-14 engine had a 12% drop in PAH emissions when operating on B-20 blend relative to petrodiesel, and a 74% drop in PAHs when the fuel was switched to neat Biodiesel. These data suggest major gains in improving the air quality around diesel engines in vehicles and boats operating on Biodiesel.

Nitrogen Oxides

The nitrogen oxides result from the oxidation of atmospheric nitrogen at the high temperatures inside the combustion chamber of the engine, rather than resulting from a contaminant present in the fuel. Although nitrogen oxides (NOx) are considered a major contributor to ozone formation, they are also a reality of operating internal combustion engines. There are consistent reports of slight increases (several percent) in NOx emissions with Biodiesel blends that are attributable, in part, to the higher oxygen content of the fuel mixture. More oxygen and better combustion of the fuel also means more formation of NOx emissions with Biodiesel blends.

In several research studies conducted since 1993 in the U.S. and Europe, EPA-regulated emissions from an unmodified engine operating on a 20% Biodiesel/80% petrodiesel blend (B-20) were shown to be lower than those for petroleum diesel, except for NOx (nitrogen oxides) emissions, which can be 2-5% above baseline emissions.

Biodiesel Helps Reduce Greenhouse Gases

Unlike other "clean fuels" such as compressed natural gas (CNG), Biodiesel and other biofuels are produced from renewable agricultural crops that assimilate carbon dioxide from the atmosphere to become plants and vegetable oil. The carbon dioxide released this year from burning vegetable oil Biodiesels, in effect, will be recaptured next year by crops growing in fields to produce more vegetable oil starting material. Supplementing our dwindling fossil fuel reserves with biomass-based fuels (Biodiesel, for petrodiesel; biomass-based alcohols or hydrogen for gasoline) helps reduce the accumulation of CO2.

To learn more:  http://www.biodiesel.org/

Chad Freckmann
Executive Director
Blue Ridge Clean Fuels
tel: +1 434 996-4473
brcfi@earthlink.net
www.blueridgecleanfuels.org