Biodegradability assessment of complex, hydrophobic substances: Insights from gas-to-liquid (GTL) fuel and solvent...

The assessment of substances of Unknown or Variable composition, Complex reaction products or Biological materials (UVCBs) presents significant challenges when determining biodegradation potential and environmental persistence for regulatory purposes. An example of UVCBs is the gas-to-liquid (GTL) products, which are synthetic hydrocarbons produced from natural gas using a catalytic process known as the Fischer-Tropsch process. These synthetic hydrocarbons are fractionated into a wide array of products equivalent in function to their petroleum-derived analogues. Here we summarise the results of an extensive testing program to assess the biodegradability of several GTL products. This program highlights the challenges associated with UVCBs and provides a case study for the assessment of such substances that are also poorly soluble and volatile. When tested with the appropriate methods, all the GTL products assessed in this study were found to be readily biodegradable indicating they are not likely to be persistent in the environment.