Introduction

Sulfur has long been an important component of worldwide industry. The Egyptians used sulfur compounds to bleach fabric as early as 2000 B.C., and sulfur was crucial to create specifically colored pigments used a few hundred years later. The ancient Greeks used sulfur as a disinfectant, and the Romans used it in pharmaceutical applications. When the Chinese developed gunpowder in the 13th century, sulfur was an essential component. The Industrial Revolution expanded demand for sulfur used in the production of sulfuric acid, an essential component of myriad industrial processes (Bodenlos and Nelson, 1979, p. 459). The consumption of sulfuric acid has been considered an indicator of the condition of a nation’s industrial activity (Sander and others, 1984, p. 261). The more sulfuric acid consumed, the greater the industrial activity and, thus, the more robust the economy.

When considering the materials flow of any mineral, the global cycle must be considered. The scope of the global sulfur cycle dwarfs those of most other materials and is illustrated in figure 1. More than 50 million metric tons per year (Mt/yr) of sulfur in all forms is produced worldwide for industrial consumption. The natural sulfur cycle is much harder to quantify but may be comparable in size. In addition, burning fossil fuels, especially coal, liberates tremendous quantities of sulfur dioxide (SO2), only some of which is recovered as byproduct sulfur compounds or waste material through gas-cleaning processes; the rest is released into the atmosphere.

The sulfur industry is different from many other important modern mineral industries in that the disposal of excess supplies of sulfur is becoming a more important issue than that of how to maintain sustainable production. Unlike other industries, which are searching for economical methods to produce a usable product from decreasing reserves and poorer grades of ore, sulfur producers must strive to find innovative uses for the continually growing sulfur supplies. As environmental concerns increase, the trend is to minimize the effects of mining by recycling mineral materials or substituting with more environmentally-friendly products. For the sulfur industry, however, increased environmental awareness results in further increases in the sulfur supply and smaller increases in the demand for sulfur in many industrial processes.

The unusual sulfur situation is a result of the changes of sulfur supply sources over the past 70 years. Whereas many mineral commodities are produced as a primary product from the mining of discrete ore bodies or as desirable byproducts from mineral processing, all the sulfur produced in North America is the result of environmental measures implemented to reduce emissions of SO2 into the atmosphere at petroleum refineries and nonferrous metal smelters and to remove poisonous hydrogen sulfide (H2S) gas from natural gas. Voluntary sulfur production, whether in the form of mined elemental sulfur or pyrites that are produced and burned to recover their sulfur content as sulfuric acid, has become continually less important in the global sulfur supply equation.