The influence of structural components of alkyl esters on their anaerobic biodegradation in marine sediment

Abstract

Ester-based organic compounds are one type of synthetic base fluid added to drilling mud used during off-shore oil-drilling operations in the Gulf of Mexico. Concern over the environmental impact of synthetic base fluid (SBF) contaminated rock cuttings discharged into the Gulf of Mexico has prompted the promulgation of EPA regulations requiring that all SBF be tested for biodegradability in marine sediment prior to their use in the Gulf. In order to allow the design or selection of suitably biodegradable esters, the anaerobic biodegradability of a variety of ester compounds was tested using a marine sediment inoculum to reveal the effect of: (a) increasing the chain length of the acid moiety, (b) increasing the chain length of the alcohol moiety; (c) alternating the relative size of the alcohol and acid moieties, (d) branching in the alcohol moiety, and (e) the presence of an unsaturated bond in the acidic moiety. The chemical structure of esters was found to affect the completeness and rate of anaerobic biodegradation, and would affect their ability to be certified for use as an SBF in the Gulf of Mexico. Recommendations for ester usage include using esters that have a total carbon number of between 12 and 18 and avoiding the use of branched alcohols (or acids by inference). The presence of an unsaturated bond in the acid (or alcohol by inference) increased biodegradability of the ester.

High resolution depth distribution of Bacteria, Archaea, methanotrophs, and methanogens in the bulk and rhizosphere soils of a flooded rice paddy

“…To measure methane concentrations along a depth gradient in the rice paddy, the 10-ml serum bottles containing the soil samples were warmed to 25°C and shaken for 1 min after injection of 1 ml of distilled water (DW). Headspace gas samples (0.5 ml) were taken from the serum bottles using a gas-tight syringe (Hamilton, USA) and methane concentrations were measured with a 6890N gas chromatograph (GC, Agilent Technologies, USA) equipped with a flame-ionization detector and an HP-5 capillary column (0.32 mm × 30 m, 0.25 μm film thickness, J & W Scientific, USA) as described previously (Herman and Roberts, 2006 ). The methane concentrations in the rice paddy soil were calculated on a fresh weight basis by measuring the weights of the soil subsamples used for methane analysis.…”

Designing Small Molecules for Biodegradability

“…Detailed study of a series of esters yielded a set of rules for selecting a specific structure or structures with maximum anaerobic biodegradability. 36 Norman et al 37 studied aerobic biodegradation of SBFs in soil and found that the ester and linear C 12-17 paraffins degraded at much higher rates than branched paraffins and diesel. Available biodegradation data for SBFs thus yield a picture of SBF biodegradability that is consistent with rules of thumb: esters and linear hydrocarbons degrade appreciably faster than branched compounds and diesel (which is a mixture containing branched and unbranched, aliphatic and cyclic hydrocarbons varying in biodegradability).…”

“…The esters, LAO, and IO degrade 2−3 times faster than mineral oil and diesel. Detailed study of a series of esters yielded a set of rules for selecting a specific structure or structures with maximum anaerobic biodegradability 4 Chemical structures of some drilling base fluids, vegetable oil-based functional fluids, and other functional fluids.…”

Review of synthesis, characteristics and technical challenges of biodiesel based drilling fluids

“…Additionally, Herman & Roberts studied the relationship between the biodegradability of commercial esters and their chemical structure ( such as chain length, branching, and the unsaturation level) (David Herman and Roberts 2006). These studies conducted an anaerobic closed bottle test on marine sediment samples from Galveston Bay in Texas.…”