Biofuels are increasingly used as alternatives for commonly used mineral oils and petrol. The study reported here was aimed at gathering information on the environmental (bio)degradability and toxicity of biofuels. A short literature study was supplemented with model calculation on the biodegradability of the biofuels, using one of the most advanced software packages available for this purpose. Fiscal privileges currently stimulate the use of ethyl-t-butyl ether (ETBE) as additive to biofuels. ETBE is obtained from bio-ethanol. For ETBE too, the biodegradability and toxicity were determined in this study. The general finding of this research is that biofuels are relatively easily degradable in the environment, and that their toxicity is limited. Problems are expected with regard to the additive ETBE. This chemical is less prone to degradation and it is virtually non-degradable in anaerobic environmental compartments. Thereupon, ETBE is highly water soluble, allowing the chemical to migrate freely in the environment.