Biodiesel contamination?

The question is a bit open ended as there are a lot of ways that biodiesel can be inadequately processed. But ...

If the reaction process is not done properly then the oil will still have glycerine bound up in it. This will mean that the viscosity of the oil is too high. This may or may not cause a problem with your fuel injection system. Typically one tankful is not going to cause a problem, it will take months or years for this sort of bad fuel to cause issues.

If the fuel has not been washed properly then you will have methanol and free glycerin in it. Despite what some people say I have personally seen a fleet of vehicles ruined with badly washed fuel.

The free glycerin and soaps are an issue. They do not clean the injection system. Instead because of the high pressures in the injection system they polymerize (turn into plastic) and totally stuff everything up. Soaps also do not burn in an engines cylinders, they carbonize and can bung up your valves and rings leading to catastrophic engine failure.

The other more long term problem with inadequate washing is that there are still caustic chemicals in the biodiesel, this will corrode the injectors and pump and over a long period this will lead to failure.

So the answer to the question is yes, if there is free glycerin and soap in the biodiesel it will cause carbon deposits in your engine similar to sugar. Glycerin is in fact a sugar itself so I suppose it makes sense that it has a similar effect.

The glycerol is a byproduct of transesterfication.

Transesterfication is the process of reacting animal fats or certain oils and alcohol (usually methanol) with a catalyst (lye). The result is biodiesel and glycerol. They naturally separate, with the biodiesel rising to the top of the solution. After they are separated, you have completely usable biodiesel and glycerol, and a little bit of excess methanol. The glycerol is around 1/11th of the final solution.

If the bio-diesel was produced by transesterification, there may be residual glycerin and methanol dissolved in the bio-diesel if the washing procedure was not sufficiently thorough.

Glycerine is soap, detergents in fuels are nothing new and are actually added to the gasoline that you buy at the pump, the trace amounts will just help keep your engine clean.

Methanol is corrosive to brass and dissolves natural rubber. If your fuel lines haven't been hardened with stainless steel and nickel coated parts and the hoses and seals replaced with synthetics then the methanol could do some damage to your fuel system much as ethanol would to a pre 1980's car. Otherwise, methanol is oxygenated and will help the combustion be more complete.

Depending on where the original oil is from, there can be any number of other products in it that could cause problems. The best bio-diesel is made from unused vegetable oil not waste vegetable oil.

If the concentration of NaOH used to reduce the average hydrocarbon chain lengths down to suitable lengths isn't high enough, some of the polymers would still be too long to combust in the engine and will further polymerize into longer chain lengths inside the engine. This is why bio-diesel from unused vegetable oil is much better than from waste vegetable oil as WVO can have chain lengths as long as 35 carbon atoms (the target is about 10 to 12). NaOH are like knives, they react with a portion of the hydrocarbon chain resulting in glycerin which precipitates out and hopefully the two resulting esters will have chain lengths of the appropriate size. It is still these hydrocarbon chains that turns to plastic in the engine if they are too long, not the glycerins themselves, this is why running engines on unprocessed vegetable oil (greasers) are bad for the engine. Most of the glycerins should precipitate out but if a lot is suspended which I don't believe should be an issue, there could be problems, otherwise it will have a tendency to loosen polymerized hydrocarbons as a solvent. Glycerin is actually called Glycerol and is an alcohol, technically a sugar alcohol and can have effects similar to sugar as it is easily converted to a sugar or it can be a beneficial fuel additive as in glycerin acetate. It can also easily be converted into ethanol. There is a wide range of properties for glycerin from a solvent through being used as an emulsifier and thickener, however it should've precipitated out and the polymerization danger is from not having enough NaOH to chop up the hydrocarbon chains enough. The usage of NaOH is a matter of probability as you can't control exactly where along the hydrocarbon chain the NaOH will encounter the oil so you want enough so that the probability of long chains are kept to a minimum but too much and you'll change entire oil molecules into soap.

If the reaction to produce the glycerin were for some strange reason truly not to complete as in the presence of an acid then you would have glycerin acetate, a fuel additive, glycerin acetate is an ester which is what you're trying to turn the oil into anyways. The typical comment of an "incomplete reaction" refers to not having enough NaOH to ensure that no hydrocarbon chains are longer than about 18 atoms (the chain length of pure peanut oil).

Measuring the specific gravity (density) is how the average chain length of the resulting bio-diesel is estimated. The longer you allow the bio-diesel to settle and stratify, the more likely you will be able to skim off only the portion with the appropriate chain lengths.

Residual water from the washing, at the temperatures and pressures within the cylinder should react with any carbon in the cylinders to produce carbon monoxide and hydrogen. Another reason for thorough washing and not to attempt "boiling" the water out though it would be wise to allow the water to separate out as much as possible.

It's the methanol that corrodes and the hydrocarbons with chain lengths longer than 18 carbon atoms that polymerize. As to glycerol, well best not to have any of that either but it's not the major polymerization risk unless you haven't allowed the bio-diesel to settle.

Compare the fates of biodiesel fuel in soil to petroleum diesel and determine if biodiesels are more, less, or similar in toxicity in soil and determine the potential of using bioremediation and phytoremediation to clean biodiesel contaminated soil. Research will ascertain (1) the influence of biodiesel on microbial populations, (2) the influence of biodiesel on plant survival.

Outcomes and Impact

Research showed that biodiesel fuel is less phytotoxic than petroleum diesel. Evidence included a higher rate of soybean seedling emergence, plant height, root and shoot biomass, and nitrogen fixation rates in biodiesel contaminated soil compared to petroleum diesel contaminated soil.

Yes this can happen, thats why I produce my own