Biodiesel has many beneficial properties and is definetly worth investigating however, it may have some significant drawbacks. Since most information on the product has been presented by organizations promoting it, one has to take a look at the other side of the coin.
(1) The principal issue is that biodiesel is a very aggressive solvent. Even USCG
hose is not completely immune. Some metals are also not recommended including copper alloys, common brass valves and fittings. Any spilled fuel
will rapidly attack paint
on engines, bilges, etc. Rubber engine
mounts will be affected. On deck
it will attack paint
and bedding compounds, gelcoat
hatches and boat shoe soles. It appears that it may also affect fiberglass
tanks if they are not specially coated. It certainly will dissolve and mobilize old scum and deposits in the fuel system.
(2) Newer engines with all Viton seals
and gaskets can probably use it. Older engines are probably questionable. If the fuel causes any problem, the engine manufacturer may not consider it a warranty issue - it is your problem.
(3) Biodiesel is hygroscopic (absorbs water) and perhaps more subject to bacterial action. Biodegradability in the environment
is one of its strong points but not good if it happens in your tank. There is not much information on long term storage
in a typical pleasure boat environment
, i.e. fuel sitting in a hot, humid tank for months and sometimes years. Commercial
users and probably most automobiles do not have this problem.
What The engine Manufacturers have to Say
Detroit Diesel "Lubricating Oil, Fuel and Filters"
5.1.4 BIODIESEL FUELS Biodiesel fuels are alkyl esters of long chain fatty acids derived from renewable resources. Biodiesel fuels must meet ASTM Specification D 6751. Biodiesel meeting the D 6751 specifications can be blended up to 20% maximum by volume in diesel fuel. The resulting mixture must meet the fuel properties listed in Table 5-1. Failures attributed to the use of biodiesel will not be covered by Detroit Diesel product warranty. The following quotation is extracted from World-Wide Fuel Charter
for comments - June 2002, page 46 for reference and guidance:" Based on the technical effects of FAME [Fatty Acid Methyl Esters], it is strongly advised that FAME content be restricted to less than 5%. As a pure fuel, or at higher levels in diesel fuel, the vehicles need to be adapted to the fuel, and particular care is needed to avoid problems."
Cummins: "Biodiesel: Frequently Asked Questions"
Cummins test data on the operating effects of biodiesel fuels indicates that typically smoke, power, and fuel economy are all reduced. However, as there are no firm industry standards on the content and properties for bio fuels, consistency and predictability of biodiesel operation is not well documented. Biodiesel provides approximately 5-7% less energy per gallon of fuel when compared to distillate fuels. To avoid engine problems when the engine is converted back to 100% distillate diesel fuel, do not change the engine rating to compensate for the power loss when operated with biodiesel fuels. Elastomer compatibility with bio diesel is still being monitored. The condition of seals
, hoses, gaskets, and wire coatings should be monitored regularly. Cummins certifies its engines using the prescribed EPA and European Certification
Fuels. Cummins does not certify engines on any other fuel. It is the user's responsibility to use the correct fuel as recommended by the manufacturer and allowed by EPA or other local regulatory agencies. In the United States, the EPA allows use of only registered fuels for on-highway applications. The EPA has additional alternative fuel information at Alternative Fuel Conversion | Cars and Light Trucks | US EPA
Ford Motor Company says
Fuels containing no more than 5% biodiesel may be used in Ford diesel powered vehicles. Consistent with WWFC (World-Wide Fuel Charter) category 1-3, "Fatty Acid Methyl Esters (FAME) used in commercial
fuel must meet both the EN 14214 and ASTM D 6751 specifications". There are still some unresolved technical concerns with the use of biodiesel at concentration greater than 5%. Some of the concerns are: Requires special care at low temperatures to avoid excessive rise in viscosity and loss of fluidity Storage
is a problem due to higher then normal risk of microbial contamination due to water
absorption as well as a higher rate of oxidation stability which creates insoluble gums and sediment deposits, Being hygroscopic, the fuel tends to have increased water
content, which increases the risk of corrosion
. Biodiesel tends to cause higher engine deposit formations The methyl esters in biodiesel fuel may attack the seals and composite materials used in vehicle fuel systems and it may attack certain metals such as zinc, copper based alloys, cast iron, tin, lead, cobalt, and manganese It is an effective solvent, and can act as a paint stripper, whilst it will tend to loosen deposits in the bottom of fuel tanks of vehicles previously run on mineral diesel. Ford believes that it is unlikely that the emission benefits of biodiesel will be sufficient to achieve Tier 2 emission standards with out catalysts and particulate filters.
From - Caterpillar
CAT neither " approves nor prohibits" the use of biodiesel however, any failures that result from the use of any fuel are not covered by any warranty.
And more from a company who sells Biodiesel......
CytoCulture Environmental Biotechnology
(This company sells biodiesel for marine
outlets in California
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, and most of the problems associated with the solvent effects occurred with boats using 100% neat Biodiesel. [ Do "few" and "most" imply that there are some problems ?]
When fuel lines or gaskets are affected, they usually get sticky over time and soften or swell, causing fuel to drip from connections. In one case, the rubber fuel line between the primary filter and the fuel pump
on a Yanmar
sailboat engine became tacky, but did not leak, after 4 years of operating on 100% Biodiesel. The best solution is to replace affected lines and gaskets with modern synthetic hoses and seals.
In bench top studies conducted at CytoCulture, the Trident hose proved to be resistant to neat Biodiesel over a period of months, although the hose did absorb Biodiesel and swell slightly (tightens under hose clamps). With 20% blends, there have been no reports of any problems with these new fuel hoses.
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. Viton fuel hoses (Goodyear) can be special ordered for boats (usually expensive at over $5.00/ft for 5/16" line)
In a survey
, 5% of the boaters reported minor problems with the Biodiesel if they spilled it on decks, on their engine or into their bilges. 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.
Biodiesel can be stored for long periods of time in closed containers with little air space. The containers should be protected from weather
, direct sunlight and low temperatures. Avoid long term storage in partly filled containers, particularly in damp locations like dock
boxes (or boats ?). Condensation
in the container can contribute to the long term deterioration of petroleum diesel or biodiesel.
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.