Mazut

Mazut (Russian: Мазут, romanized: Mazut) is a very high-sulfur, low-quality heavy fuel oil that is typically produced as a residual product of petroleum refining after gasoline, diesel, and other light distillates are removed from crude oil. Similar to Bunker C (No. 6 fuel oil), mazut has high viscosity and sulfur content and is generally used as a fuel for large industrial boilers and power plants. However, unlike Bunker C, mazut is produced from lower grade source crude oil with higher sulfur content. Mazut is produced primarily in Azerbaijan, Iran, Kazakhstan, Russia, and Turkmenistan. In some regions, mazut is burned directly as fuel, including in Iran and North Korea, where it has been used in power plants to compensate for shortages of higher-quality fuels. Its combustion is associated with significant air pollution due to its high sulfur content. Mazut is also used as a heating oil in some parts of the former Soviet Union and Far East that lack facilities to further refine or blend it into lighter petroleum products. Marine oil spills involving mazut can have especially harmful environmental effects. The fuel solidifies at under 25 °C (77 °F), allowing it to sink to the seabed, making chemical remediation difficult. On 15 December 2024, two oil tankers collided in the Kerch Strait, releasing about 5,000 tonnes of mazut in the 2024 Black Sea oil spill. A similar spill occurred in the same strait during a November 2007 storm. The commercial grading is Mazut-100, produced to GOST specifications such as GOST 10585-75 or GOST 10585-2013.