Technical Handbook for Marine Biodiesel

This handbook has been prepared to provide practical information on Biodiesel to owners of recreational boats powered with diesel engines. The report summarizes research work and field observations collected over the past five years from the U.S. and Europe. The handbook is intended to be relatively comprehensive without being overly detailed. References are cited to guide the reader in pursuing specific topics in more depth. The appendices contain support documentation and articles on marine Biodiesel.

BIODIESEL: Fuel Additive made from Vegetable Oil

Biodiesel is a clean-burning diesel fuel additive produced from soybean and other vegetable oils instead of petroleum. Biodiesel is marketed in California for use in marine compression ignition (diesel) engines to enhance engine combustion performance, improve engine lubrication, and reduce air and water pollution caused by the exhaust. Biodiesel blends operate in diesel engines, from light to heavy-duty, just like petroleum diesel fuel. No engine conversions are required at all, unless an engine has old fuel lines.

Biodiesel and a 20% blend of Biodiesel in petroleum diesel are DOE-designated alternative fuels. Biodiesel is registered as a fuel additive with the Environmental Protection Agency (EPA). Biodiesel and the 20% blend meet clean diesel standards established by the California Air Resources Board (CARB), particularly since the Biodiesel contains no sulfur and no aromatics. The National Biodiesel Board maintains specifications for Biodiesel and has worked with the American Society for Testing and Materials (ASTM) to develop a provisional ASTM standard for Biodiesel production in the U.S.. In 1998, Biodiesel as a 20% blend ("B-20") with petroleum diesel was designated an "alternative fuel" under the Energy Policy Act. This designation allows government fleet services to purchase the B-20 blend for operation in normal diesel vehicles and receive credit for those vehicles equivalent to other DOE-approved multi-fuel vehicles.

As a result, Biodiesel can now compete with other alternative fuels and clean-air options for urban transit fleets and government vehicles across the country. For the marine market, this DOE designation should encourage more Biodiesel production and, eventually, lower prices for consumers.

Biodiesel is Produced from Vegetable Oils by a Process called Transesterification (see Appendix for schematic of process)

Biodiesel is produced from vegetable oils by converting the triglyceride oils to methyl (or ethyl) esters with 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 an 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.) which are toxic, volatile compounds responsible for the fire/health hazards and pollution associated with petroleum diesel.

Niche Market for Biodiesel:

Sailboats with Auxiliary Diesel Engines

Recreational sailboats powered by auxiliary diesel engines have proven to be a reliable and high profile market for Biodiesel. In 1997, CytoCulture surveyed 100 recreational boaters in the San Francisco Bay area and found that 97% of the vessels using Biodiesel from 1993 to 1997 were sailboats. Most of the boats were in the 30 to 50 foot range, and most had smaller diesel engines (12-50 HP) that consumed relatively little fuel. Sailboaters tend to be more conscious of environmental concerns, they are sensitive to smoke and odor from engine exhaust, and they are more inclined than power boaters to pay for premium diesel fuel since they typically consume only 10-50 gallons a year.

Future marine markets in which the benefits of using Biodiesel would outweigh the costs include charter boats, water taxis, dive boats, small ferries, government boats and research vessels.

There should be particular emphasis on using Biodiesel in boats operating on lakes, rivers and confined bays that are more sensitive to air and water pollution.

Aside from sailing with the wind, vegetable oil Biodiesel is the easiest, cleanest and most efficient transformation of solar energy to produce kinetic energy for mechanical power in boats.

Recommended Blending Ratios for Biodiesel in Boat Fuel
Biodiesel mixes easily with diesel as a fuel additive for use in blends of up to 20% with regular petroleum diesel. Add 5 gallons (one 5-gallon container) of Biodiesel to every 20 gallons of petrodiesel to achieve a 20% blend, or use the blending chart printed on the container back label. Biodiesel mixes quickly with petrodiesel once the boat is moving. Biodiesel is a little heavier than the petroleum with has a specific gravity of 0.87 compared to 0.79-0.80 typical of reformulated petrodiesels.

Higher concentrations, up to 100% (neat) Biodiesel, are used in Europe to operate diesel engines in boats and vehicles with good performance results and excellent emissions reductions. However, until new Federal and State laws defining diesel fuel specifications are mandated to accommodate the unique properties of vegetable methyl esters, Biodiesel will only be sold as an additive for use in boat engines at ratios not to exceed 20%. In France, all diesel sold for vehicle fuel in the entire country ranges from 1% up to 5% rapeseed Biodiesel in a blend and some urban buses routinely operate on a 30% blend. In Germany, where the price of Biodiesel (tax exempt) is similar to petroleum diesel (with taxes), over 350 fuel stations offer Biodiesel for sale to motorists and Biodiesel is used in tour boats on their lakes.

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 which 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.

Unfortunately, current "low aromatic, low sulfur" diesel in California still contains 20 to 25% aromatics because the oil companies have been allowed waivers by the state to "reformulate" their diesel fuels and reduce emissions by adding "cetane enhancers" to lower emissions to levels equivalent to 10% aromatics. An engine running on 100% Biodiesel would have NO aromatic emissions and the Biodiesel would be much safer to store and handle. In addition, Biodiesel blends have reduced emissions of polyaromatic hydrocarbons, another group of potentially carcinogenic substances found in petroleum.

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 with petroleum diesel created a significant reduction in visible smoke and odor. The studies documented the reduction in hydrocarbons, carbon monoxide and particulate matter. Biodiesel is comprised of vegetable oil methyl esters, that is, they are hydrocarbon chains of the original vegetable oil that have been chemically split off from the naturally occurring "triglycerides". Biodiesel hydrocarbon chains are generally 16 to 20 carbons in length, and they are all oxygenated at one end, making the product an excellent fuel. As discussed below, several chemical properties of the Biodiesel allow it to burn cleanly and actually improve the combustion of petroleum diesel in blends.

A recent (1997) survey of recreational boaters using Biodiesel on the San Francisco Bay confirmed these findings. Boaters buy Biodiesel for the benefits, and clean emissions from diesel engine exhaust is a major driving force in the marine market. From the survey results among 100 boaters using Biodiesel at various blends over the past 3 years, 98% reported an improvement in the exhaust odor (smells more like french fries), 91% reported a reduction in smoke, and 56% indicated a reduction in soot deposits on the transoms and decks of their boats.

Biodiesel blends should have a beneficial impact on human health by reducing dangerous particulates and enhancing catalyst performance in vehicles. The National Biodiesel Board emphasizes the importance of reductions in EPA-regulated emissions by citing a 1993 study published in the New England Journal of Medicine which concluded that "fine particulate air pollution, or a more complex pollution mixture associated with fine particulate matter, contributes to excess mortality in certain U.S. cities." More recent work (1996-1998) confirmed that Biodiesel contributes to the reduction of heavier (longer chains, C13+) hydrocarbons as well as reducing carcinogenic polyaromatic hydrocarbons (PAHs).

Several emissions reduction studies have been performed by the Southwest Research Institute (SWRI) over the past 5 years. In a 1994 study on light diesel trucks, Biodiesel in a 20% blend (B-20) was shown to reduce particulate matter (PM) by 14% in new engines. However, from our own from field observations with boats and test cars, Biodiesel appears to be even more effective in reducing smoke from the older engines typical of most recreational boats. The reduction in 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.

Subsequent SWRI studies were presented at a Biodiesel Emissions Testing Meeting in Seattle in 1996. The SWRI studies were conducted with the most efficient diesel engine produced by Cummins for pick up trucks: a 1995 5.9 Liter inline 6-cylinder, 4-stroke engine, with direct injection, a turbocharger and an intercooler. The rated horsepower of the test engine was 160 HP at 2500 rpm. Studies were conducted with and without the stock catalytic converter supplied with the engine (unfortunately not available for marine engines). The engine emissions tests were conducted under transient heavy duty loads to simulate road use.

Several types of Biodiesel were tested, including Biodiesel derived from another oil crop, winter rapeseed. Rapeseed is grown extensively in Idaho, Canada and Europe to produce Canola. Biodiesel made from Canola has very similar properties to the Biodiesel made from soybean and other plant oils. In the Idaho study, the Biodiesel test fuels were (100%) rapeseed ethyl esters (REE), rapeseed methyl esters (RME), 50% blends of REE or RME, and 20% blends of REE or RME with petrodiesel. The reference fuel was conventional (Texas) No. 2 petrodiesel ("2D"), a low-sulfur diesel formulation mandated nationally by the EPA since 1993 .

More recent work at the SWRI was presented at a Biodiesel Environmental Workshop in Washington, D.C. (June 4, 1998) by Christopher Sharp, the principal investigator. The newest work provides updates on the effects of Biodiesel on diesel engine exhaust emissions and performance.

The 1998 SWRI report summarized emission studies on three diesel truck engines: a 1997 Cummins 14-L inline 6 cylinder engine, a 1997 Detroit Diesel 8.5-L incline 4 cylinder engine, and a 1995 Cummins 5.9-L inline 6 cyclinder engine. The test fuels were neat (100%) Biodiesel, the B-20 blend of biodiesel with diesel and a standard low-sulfur standard petroleum diesel fuel as a reference.

Exhaust emissions were evaluated over a heavy duty transient cycle with hot and cold starts, with and without a catalyst in some cases.

Total hydrocarbon emissions for the Cummins engines were reduced by 20% for the B-20 blend in the 1997 model and by 31% for the 1995 B-5.9 model. When the same engines were tested with 100% Biodiesel, there was a 94% drop in total hydrocarbons for the 1997 engine and a 72% drop for the 1995 engine relative to No. 2 low sulfur diesel fuel. The Detroit Diesel engine generated less emissions in general, with little change as the test fuel was switched to B-20, but an 82% drop when the test fuel was neat Biodiesel.

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. They also resent the soot accumulation on the transoms and decks of their boats.

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.

In the 1996 study performed by the Southwest Research Institute, the effect of oxygen content (by percent oxygen) on the production of particulates smoke and soot was studied using the same Cummins diesel test engine cited above. The study established, for example, that a B-20 blend (approximately 2% oxygen for RME-20) reduces particulate soot by approximately 30% (from 0.06 for diesel no. 2 to 0.04 G/HP-Hr for rapeseed methyl ester at 20%).

An earlier 1994 EPA Transient Cycle Emissions Test undertaken by the Southwest Research Institute compared emissions from an engine burning No. 2 low-sulfur diesel with those from an engine using the B-20 blend in combination with an oxidation catalyst. Compared with the low-sulfur No. 2 diesel, the B-20 blend with an oxidation catalyst reduced particulate matter by 45%, total hydrocarbons by 65%, and carbon monoxide by 41%.

Pioneering studies performed by the Colorado Institute for Fuels and High Altitude Engine Research used 1991 model series engines. They reported a 13.7% drop in particulate matter and a 12.7% drop in total hydrocarbons when using a B-20 blend.

In the updated 1998 report from the Southwest Research Institute studies, oxygen was shown to be the driving mechanism for soot reduction in truck engines operating on various blends of Biodiesel. The higher the oxygen content of the Biodiesel blend, the greater the reduction in soot emissions. However, not all the particulate emissions is fuel related. With the Cummins B-5.9 test engine, about 22% of the particulate emissions was unburned lubrication oil that did not change significantly when the fuels were switched to B-20 or neat Biodiesel. Carbon soot, in contrast, made up over 50% of the particulate emissions and this carbon soot component was reduced by 20% with the B-20 blend, and reduced with the neat Biodiesel by 66% in the Cummins B5.9 engine and by 71% with the Detroit Diesel engine.

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. When the fuel was switched from low-sulfur petroleum diesel to neat Biodiesel, there was a 28% to 37% drop in the carbon monoxide emissions.

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. The Detroit Diesel engine had a 29% reduction in PAHs operating on B-20 and a 68% reduction when operating on 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 were shown to be lower than those for petroleum diesel, except for NOx (nitrogen oxides) emissions, which can be 2-5% above baseline emissions.

Some reductions in NOx emissions can be attained by retarding the timing of ignition and slowing the burn rate of the fuel in the combustion chamber. In the EPA Transient Cycle Emissions Test (Southwest Research Institute) study with the 1988 DDC 6V-92 engine, there was a 7% increase in NOx emissions that accompanied the 45% reduction in particulate matter and 65% reduction in hydrocarbons (in combination with an oxidation catalyst). Unfortunately, any improvements in NOx emissions are usually offset by increases in hydrocarbon, particulate material and carbon monoxide emissions caused by the mechanical adjustments to the engine. In the case of the Transient Cycle Emissions Test, a one-degree timing change in the diesel engine did result in a net reduction of NOx emissions by 2%, but at the expense of slightly less dramatic reductions in the particulate matter (reduced by 40%), hydrocarbons (reduced by 58%) and carbon monoxide (reduced by 34%). In Europe, the delays in engine ignition timing have been successfully combined with the use of catalytic converters to achieve similar reductions in both NOx emissions and hydrocarbon emissions from transit buses.

In the 1996 Southwest Research Institute study cited above, the use of a catalytic converter improved the reduction of hydrocarbon emissions with a B-20 blend of rapeseed methyl esters from 29% (without converter) to 41% (with converter) for the Cummins test engine without any timing delays. NOx emissions were reduced 3%.

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. The U.S. is under considerable pressure from the international community (for example, at the December 1997 Kyoto Conference) to take seriously its efforts to reduce carbon dioxide, carbon monoxide and other greenhouse gases released, in part, by the combustion of fossil fuels in vehicles. While anthropogenic (man-made) CO2 production accounts for only about 4-5% of the net CO2 emissions, it is sufficient to have caused a net gain over the past 100 years. Fossil fuel combustion accounts for 70% of the total anthropogenic CO2 contribution. 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.

Positive Energy Balance for Solar Energy in Biodiesel

Although it takes fossil energy to produce and transport biofuel, Biodiesel has a very favorable energy balance, especially relative to energy-negative ethanol from corn. Biodiesel production has positive energy balance ratios ranging from 2.5:1 (Institute for Local Self-Reliance) up to 7.4:1 in Europe, depending on oil crop and distance required to transport the raw materials.

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