Reducing sulfur content in petroleum and coal-derived fuels remains critical to mitigating air pollution from transportation exhaust on a global basis. The urgency of this challenge is heightened by the fact that the concentration of sulfur continues to grow in petroleum supplies while regulatory standards are growing ever more stringent. Presently, the refining industry employs hydrodesulfurization (HDS) to remove sulfur compounds. This process is energy intensive, expensive and produces 25% of a refinery's carbon output. As sulfur regulations reach into the heavier products (marine fuel, fuel oil, etc.) hydrotreating becomes less efficient and consequently must be run at higher temperatures and pressures which increase a refinery's CO₂ footprint.

Compounding the challenges associated with these sulfur reducing regulations is the fact that crude oil is becoming heavier and more sour. Consequently, the energy required to meet environmental regulations will become exponentially more expensive and has created a regulatory paradox: sulfur levels cannot be reduced without increasing CO₂ emissions.

Additionally, price differentials between light-sweet crudes and heavy-sour crudes will continue to expand as refiners discount for contaminants such as high sulfur, high TAN and low API gravity. Consequently, alternative desulfurization and upgrading technologies remain an industry priority.