The downstream sector of The petroleum industry is the refining of crude oil and the processing and purifying of raw natural gas,Industry Overview from the website of the Petroleum Services Association of Canada (PSAC) as well as the wholesale and retail marketing and distribution of petroleum products derived from them. It is, along with midstream and upstream, one of three major sectors of the petroleum industry.
The downstream sector produces such consumer petrochemicals as gasoline or petrol, kerosene, jet fuel, diesel oil, heating oil, fuel oils, lubricants, waxes, asphalt, natural gas, and liquefied petroleum gas (LPG) as well as naphtha and hundreds of others.
ISO definition ISO 20815, 3.1.8 downstream, defines downstream as "business process, most commonly in petroleum industry, associated with post-production activities". Example: refining, transportation and marketing of petroleum products.ISO/DIS 20815:2026: Petroleum, petrochemical and natural gas industries - Production assurance and reliability management, accessed 16 September 2026
Sulfur
Elemental sulfur production as a byproduct of crude oil refining is a part of the downstream sector of the petroleum industry.
Crude oil is a mixture of many varieties of hydrocarbons and most usually have many sulfur-containing compounds. The oil refining process commonly includes hydrodesulfurization which converts most of that sulfur into gaseous hydrogen sulfide. Raw natural gas also may contain gaseous hydrogen sulfide and sulfur-containing mercaptans, which are removed in natural-gas processing plants before the gas is distributed to consumers.
The hydrogen sulfide removed in the refining and processing of crude oil and natural gas is subsequently converted into byproduct elemental sulfur. In 2005, the vast majority of the of sulfur produced worldwide was byproduct sulfur from refineries and natural-gas processing plants.Sulfur production report by the United States Geological SurveyDiscussion of recovered byproduct sulfur
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