SMES - Sulfur Cycle (Lesson)

Sulfur Cycle 

An important component of protein and vitamins, sulfur is essential for plant and animal health. Naturally, most sulfur is located in rocks and ocean sediments, but some is also found in the atmosphere.

The natural sulfur cycle is described by the following path:

• Sulfur is naturally released into the atmosphere from rocks and sediment in the forms of hydrogen sulfide (H₂S) and sulfur dioxide (SO₂) through weathering, volcanic eruptions, and the decay of dead organisms.
• Once in the atmosphere, SO₂ reacts with oxygen to form sulfur trioxide (SO₃) and with water to form sulfuric acid (H₂SO₄)
• Sulfur particles are deposited back into the soil and water, or they combine with water and fall in the form of acid precipitation.
• Plants absorb sulfate ions (SO₄^2-) through their roots, and animals receive sulfur by consuming plants.
  

How are human activities affecting the sulfur cycle?

We intervene in the atmospheric phase of the earth's sulfur cycle by:

• Burning sulfur-containing coal and oil to produce electric power, producing about two-thirds of the human inputs of sulfur dioxide.
• Refining sulfur-containing petroleum to make gasoline, heating oil, and other useful products.
• Using smelting to convert sulfur compounds of metallic minerals into free metals such as copper, lead, and zinc.

The Future of Sulfur

The U.S. is no longer the top energy consumer according to the International Energy Agency. This occurred in 2009 when China rose to the global energy apex, consuming 2,252 billion tons of oil equivalent energy from sources such as coal, nuclear power, natural gas, and hydroelectric power—about 4 percent more than the United States. In 2000, China only consumed half of the energy of the USA. Demand for energy is soaring as the Chinese are buying more cars, moving into bigger houses that need more heat, purchasing more televisions, refrigerators, and other appliances, and starting new businesses and factories.

Sulfur is different than other minerals with respect to mining issues and supply concerns. As long as the world economy is petroleum-driven, the sustainable production of necessary sulfur supplies is not in question. Instead of relying on sulfur mining, it is possible to recover enough sulfur for the global demand using the natural byproducts at natural gas plants and petroleum refineries. Byproduct H₂SO₄ from metal smelters contributes additional supplies.

While the production of recovered sulfur has been increasing around the world as a result of growing environmental awareness and concerns, the use of sulfur in a multitude of end uses has increased at a slower pace. Huge quantities of sulfur and H₂SO₄ are consumed in many industries, but not as much as is produced. Expansive world trade transfers large quantities of sulfur from the large producing areas to the large consumers. Stocks, however, are accumulating at recovery operations in remote locations where the distances to the market make its transportation prohibitively expensive. In such countries as Kazakhstan, the infrastructure is inadequate for transporting the large volumes of sulfur produced.

The cumulative effects of sulfur production also differ from the results of other mineral production. Modern sulfur production actually results in improved environmental conditions rather than mining processes and outcomes that must be repaired. Sulfur recovery prevents the emissions of SO₂ and other harmful compounds into the atmosphere, avoiding the detrimental effects of those emissions.

The challenges facing the sulfur industry are unique. In other mineral industries, the major concerns are how to continue to produce necessary materials and protect the environment as much as possible at the same time. The sulfur industry is confronting the question of what to do with all the sulfur it produces. Current production exceeds consumption by a relatively small percentage, but environmental regulations continue to increase with little growth in sulfur use. The 21st-century sulfur industry will need to expand sulfur consumption in nontraditional markets and find acceptable ways to dispose of unneeded sulfur without compromising environmental protection.

 

RESOURCES IN THIS MODULE ARE OPEN EDUCATIONAL RESOURCES (OER) OR CREATED BY GAVS UNLESS OTHERWISE NOTED. SOME IMAGES USED UNDER SUBSCRIPTION.