Assessing the Biological Stability of a Terpene-Based Advanced Biofuel and Its Relationship to the Corrosion of Carbon Steel

Abstract

Energy-dense terpene biofuels have recently been recognized as renewable alternatives for high-density petroleum-derived fuels. While the physicochemical properties of terpene dimer fuel (TDF) have been well-documented, the propensity of these mixtures to undergo biodegradation and exacerbate the corrosion of the fuel infrastructure remains unknown. Coastal seawater/sediment incubations were amended with TDF or a blend of petroleum-derived hydrocarbons and incubated under strict anaerobic conditions. In some incubations, a model hydrocarbon-degrading sulfate-reducing bacterium (Desulfoglaeba alkanexedens, strain ALDC) was inoculated as a positive control. No increase in sulfate reduction or corrosion was observed in long-term experiments (300 days) relative to TDF-free controls when only seawater/sediment served as the inoculum. However, inoculation with the positive control organism and a mixture of C 6 −C 12 n-alkanes increased both the sulfate reduction rate (95.2 ± 5.2 μM/day) and general corrosion, as determined by both coupon weight loss (27.9 ± 1.6 mg) and the number of pits (495 ± 62). The ratio of manganese (Mn)/weight loss (0.34) in incubations exhibiting coupon pitting was lower than those (0.53−0.68) showing only generalized coupon corrosion. Despite no indication for TDF biodegradation under all test conditions, the detection of a suite of alkylsuccinate metabolites attested to the anaerobic metabolism of the suite of n-alkanes when strain ALDC and the hydrocarbons served as amendments. These findings suggest that TDF is resistant to biodegradation and will not exacerbate the corrosion of carbon steel. If used in combination with petroleum hydrocarbons, the degree of metal corrosion would be that expected as a result of labile fuel components. However, the relatively recalcitrant nature of TDF might pose other risks if released to the environment and, thus, warrants further study.

Anaerobic Biodegradation of Alternative Fuels and Associated Biocorrosion of Carbon Steel in Marine Environments

“…36 Presumably, D. alkanexedens strain ALDC T27 was primarily responsible for oxidizing these hydrocarbons. However, the prospect of indigenous microorganisms contributing to the overall metabolism of these substrates, via the same or by different mechanisms, 11 cannot be ruled out. Since the exogenously added n-alkanes in the fuel were certainly in excess, quantification of microbial metabolism by substrate utilization against the large background signal was not possible.…”

“…Coastal seawaters that are typically used to fill carbon-steel ballast tanks were used as both medium and inoculum sources. Given the potential differences in microbial community composition and water chemistry, three geographically distinct seawaters from Key West (KW), Florida; the Gulf of Mexico (GoM), Alabama; and San Diego Bay (SDB), California, were collected as previously described and shipped to the University of Oklahoma . Sediment from SDB was also used in some experiments since it is routinely introduced into ship ballast systems and serves as a source of anaerobic microorganisms. , The seawater and sediment samples were stored at 4 °C until use.…”

“…The headspace of the bottles was exchanged three times with N 2 /CO 2 (80:20). The pH of the incubations was initially slightly alkaline (7.46–7.80), and other chemical parameters of the three seawaters (e.g., the content of Cl – and SO 4 2– ) were reported previously . Fuels (0.1 mL, ∼2 g/L) were aseptically added to 40 mL of seawater by sterile syringe.…”

“…Numerous challenges are associated with adopting alternative fuels to augment or replace petroleum-derived fuels . Typically, fungible biofuels require various tests to ensure that they have physicochemical properties comparable to their petroleum-based counterparts. − However, even though fuel performance might meet both explicit and implicit requirements, the biological stability of the emerging alternative fuels , and their compatibility with the mainly carbon steel energy infrastructure, such as storage tanks and transportation pipelines, should not be overlooked. Fuel biodeterioration and the biocorrosion (or microbiologically influenced corrosion) of the carbon steel infrastructure can lead to serious economic and environmental problems .…”

Sources of Active Ingredients for Sustainable Corrosion Inhibitors

“…For the high-density petroleum resulting fuels, Liang et al, 2015 reported renewable substitutes as energy-dense terpene biofuels. Coastal sediment/seawater developments incubated underneath simple anaerobic circumstances and were revised with TDF or a mixture of consequential petroleum hydrocarbons [37].…”