Ford's answers to the NHTSA 6.7 Investigation

Prior research suggests that, while the anaerobic metabolismof
hydrocarbons in fuels is fairly restricted and requires
“specialist organisms”,the ability of bacteria, archaea, and
even eukaryotes to hydrolyze the component esters of biodiesel
is common. Such bioconversions result in the formation of
fatty acid intermediates, the metabolism of which has been
extensively documented.In fact, syntrophic microbial
partnerships based on fatty acid metabolism are widespread
and obligate for the turnover of many forms of organic matter
in anaerobic environments.
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The microorganisms originated from fresh and marine environments with differing histories of exposure to hydrocarbons, biodiesel, and oxygen. All inocula were able to biodegrade biodiesel within 1 month.Biodiesel metabolism accelerated the rate of both sulfate reduction and methanogenesis above biodiesel-unamended controls. Metabolite profiling indicated that the methyl esters of biodiesel were readily hydrolyzed to the corresponding suite of fatty acids, and the latter were also metabolized. Electrochemical/corrosion experiments showed that the anaerobic microbial metabolism of biodiesel in coastal seawater samples accelerated the rate of pitting corrosion in carbon steel. The susceptibility of biodiesel to anaerobic biodegradation and its propensity to stimulate biocorrosion suggest caution when integrating this alternate fuel with the existing infrastructure.

The increasing world reliance on biodiesel has important
environmental and financial consequences. Our studies suggest
that biodiesel can be quite easily hydrolyzed and converted to a
variety of fatty acid intermediates by anaerobic microorganisms,
regardless of their previous hydrocarbon- or biodieselexposure
history. The acidic nature of these intermediates
accelerates the pitting corrosion process of the most common
metal alloy used throughout the fuel infrastructure.
The
corrosion of pipelines, tanks, storage units, and associated
equipment increases the risk of the release of hazardous
materials to the environment, with concomitant pollution
issues. With the widespread use of biodiesel as an additive to
fuel supplies, it is at least prudent to consider how best to avoid
the negative consequences associated with the microbial metabolism
of these labile fuel components.
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