THWRC Awarded Proposal 513UHH0034H

Project number:         513UHH0034H

Title:                           Biodiesel Fuels and Groundwater Quality  

Lead PI:                       William Rixey

Awarded amount:      $33,000


Project Abstract

The objective of this research is the assessment of the impact of biodiesel fuels on groundwater contamination.  The use of alternative biofuels is growing and there are concerns about the impact of these fuels on the nation’s drinking water supplies.  A considerable amount of research has been conducted on the impacts of alcohols in gasoline (such as ethanol, which has replaced the important gasoline additive, methyl tertiary butyl ether, MTBE), however there has been limited assessment of the groundwater impacts associated with biodiesel fuels. Biodiesel fuels are widely used in Brazil and Europe, and use in the United States is increasing.  Similar to alcohol gasoline fuels (e.g., gasohol) which can cosolubilize hydrocarbons, diesel fuels containing fatty acid methyl esters (FAME) may have a significant impact on the cosolubility of other fuel components of environmental concern (e.g., benzene, toluene, xylenes, and naphthalene) due to the production of long-chain fatty acids associated with abiotic hydrolysis and bio-transformation processes as well as free fatty acids present as impurities in the unweathered biodiesel fuel.  In addition to cosolubility, another major concern is the redistribution of pre-existing fuel contamination due to lowering of fuel-water interfacial tension associated with the transformation products of FAME.

            The purpose of this proposed research is to investigate the impact of biodiesel fuels over a range of FAME composition in biodiesel (20 to 100 vol.% FAME).  In addition to physical chemical property measurements, experiments will be conducted in a continuous flow, unconfined aquifer, 2-dimensional physical model that simulates spills of these biodiesel fuels.  Another important goal of this research is to quantitatively model the flow characteristics of these processes.  The 2-D experiments will emphasize the behavior of both capillary zone and saturated zone processes for biofuels of different FAME composition.        

            The following activities are expected: (1) measurement of phase equilibria and interfacial tensions for biodiesel fuels containing FAME (C16-C20 methyl esters) including quantification of cosolubilization of BTEX and naphthalene, (2) and spill experiments in 2-dimensional model aquifers, and (3) numerical modeling of the multiphase flow characteristics to both quantitatively analyze the experimental results as well as extend the results to a wide range of spill and aquifer conditions.

            This proposal is for a two-year study.  In Year 1, phase equilibria and interfacial tensions will be quantified; 2-D laboratory experiments and numerical simulations will be initiated for biodiesel fuels.  In Year 2, 2-D laboratory experiments will be continued for biodiesel fuels over a range of FAME composition (from B20 to B100), and numerical modeling studies will continue through Year 2.