This document discusses the quality issues associated with increasing biofuel requirements in transportation fuels. It notes that legislative mandates in the US and EU will require more biofuels usage. Both ethanol and biodiesel can cause problems like phase separation, corrosion, cold flow issues, stability problems, and microbial growth. Refiners can overcome these issues through good supplier sourcing, robust hygiene practices, additive programs, and a complete predictive maintenance program.