Waste from hydrocarbon production mosaic
These photos show sulfur, a waste product resulting from the extraction of hydrocarbons from crude oil.
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HYDROCARBONS
Hydrocarbons are valuable and versatile molecules, used in manufacturing and as fuel.
Hydrocarbons can be used to make plastics, rubbers, solvents, and fibres. In addition, hydrocarbons like diesel, petrol, and kerosene are used to power cars, planes, and trains.
Hydrocarbons can be solids, liquids, or gases, but they all have one thing in common — their molecules are made up entirely of hydrogen and carbon.
The size and structure of hydrocarbon molecules determine their properties. For instance, diesel is made up of larger hydrocarbons than petrol. This means that diesel stores more energy per litre and so can be used to power larger vehicles over long distances.
Photo by Dawn McDonald on Unsplash
Photo by Taylor Heery on Unsplash
Hydrocarbons occur naturally in the form of crude oil, also known as petroleum.
Crude oils contain mixtures of different hydrocarbons, which are separated out during the refining process. The refining of crude oils also involves the removal of impurities, like sulfur.
CRUDE OIL
Crude oil is found in geological deposits all over the world, from the oil reserves of Saudi Arabia to the tar sands of Canada.
Crude oil is made up of the remains of ancient marine organisms, like algae and zooplankton. After being buried under sediment for millions of years, these organic remains are exposed to limited oxygen, and high temperatures and pressures.
Altogether, these conditions create the perfect environment for transforming marine organisms into crude oil.
Scraping the bottom of the barrel
The increasing demand for hydrocarbons is leading to a rapid depletion of our crude oil reserves. This means we are having to turn to less desirable sources of hydrocarbons to keep up with demands. These "sour" crudes include the tar sands found in Alberta, Canada.
Compared to their "sweet" counterparts, sour crudes contain lower proportions of the most valuable hydrocarbons, like petrol and diesel.
In addition, sour crudes have higher levels of impurities.
Whereas sweet crudes contain less than 1% sulfur by weight, the sulfur content of sour crudes can reach up to 14%.
SULFUR
The sulfur impurities found in hydrocarbons are a cause for environmental concern, especially those found in fuels.
When hydrocarbons are burnt to release energy, any sulfur impurities they contain will be converted into sulfur dioxide.
Sulfur dioxide is a respiratory irritant and contributes to acid rain.
Oil refineries are therefore forced to store large deposits of waste sulfur, like those photographed by J Henry Fair.
These deposits of sulfur waste must be carefully managed to prevent them from contaminating the local environment.
Any rainwater that runs off the deposits will be acidic and so must be treated to prevent it from damaging local habitats.
Furthermore, the sheer amount of sulfur waste that is produced by oil refineries means that large stretches of land must be repurposed for its storage.
As of 2014, the mining of tar sands in Canada has resulted in the disturbance of 300 square miles of forest and peat marsh, including land earmarked for Indigenous communities.
The dangers of sulfur pollution are well-established, and most governments now place stringent restrictions on the sulfur content of petrol and diesel.
These regulations require petrochemical companies to remove sulfur from crude oils at the source, preventing it from reaching car engines.
These restrictions have proven effective in the UK, where overall sulfur emissions have dropped 91% between 1990 and 2019.
But the sulfur that is extracted from crude oil does not simply disappear.
In some cases, it can be sold on for secondary purposes, like the manufacture of industrial chemicals. But our thirst for hydrocarbons means that crude oil is refined at an astonishing rate, and the by-production of sulfur is rapidly outstripping demand.
Photo by Seadil Hakim on Unsplash
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