Iranian Clarified Spurry Oil (CSO), also known as Carbon Black Feedstock (CBFS), is a high-aromatic residual stream characterised by a specific gravity of approximately 1.065, sulphur content around 3 wt %, and controlled viscosity and ash levels. It is the preferred feedstock for carbon-black production and is also used in selected industrial fuel and binder applications.

Primary destination markets are Iraq, the Kurdistan Region, Afghanistan, Uzbekistan, Jordan, Oman, Syria, Russia, Georgia, Armenia and the Persian Gulf countries, where carbon-black manufacturers and specialised fuel users require a stable, high-aromatic residual oil from Iran.