The Conservation Conversation: Cleaning Up the Mess We've Made, Part II

Last time, I described the incredible increase in the volume of wastes that we, as individuals and modern societies, create. 

The nature of those wastes has also changed dramatically, and largely, for the worse. In fact, the Industrial Revolution has also been a Chemical Revolution, as we have brought forth a staggering number of compounds that never existed in nature and to which earth’s organisms never had a chance to adapt. The same industries that have contributed so much to our prosperity, comfort and convenience have also left us a bitter toxic legacy.

Among the first industries to experience a massive expansion with the start of the Industrial Revolution were mining and metal smelting operations. The developing industrial society quickly came to depend on large quantities of metal, which had to be extracted from ores, and on coal, which provided the concentrated source of energy required for smelting those metals and fueling the new steam engines that powered the Industrial Revolution.  

Mining and smelting leave behind large quantities of wastes, from overburden and tailings at the mine to slag at the smelter and ash wherever coal is burned. These wastes concentrate and expose chemicals that in nature are usually inaccessible.

For example, coal is laden with bound-up impurities, such as sulfur, mercury and other metals. These are released as air pollutants when the coal is burned or concentrated in the ash. Many ores of desirable metals also contain undesirable substances. As an example, arsenic is commonly found in iron ore and can become concentrated and accessible in mine tailings and smelter slag.

Often, the working of the materials also requires industrial chemicals never seen in nature, such as harsh acids to liberate metals from their ore matrix. These, too, end up as waste products. And many useful metals are themselves hazardous, such as lead, zinc, mercury and certain forms of chromium.

Another frontier in waste generation was crossed in 1792, when the Scottish engineer William Murdock pioneered the process of commercial coal gasification – that is, turning the solid black lumps into gaseous form. Murdock, a colleague of James Watt, of steam engine fame, heated coal in the absence of air, converting most of the coal to gas. This gas is very similar to the natural gas that many of us use today to heat our homes or cook our meals.

Initially, Murdock's technique was employed mainly to produce gas that could be used for lighting. America's first gasification plant opened in 1816. Coal gas soon became the dominant fuel for indoor lighting and streetlights in urban areas. More than 1,500 gasification plants (called manufactured gas plants or MGPs) operated in the U.S. in the past. New York City alone had several dozen. The last MGP in New York State closed as recently as 1972.

Gaslight is beautiful and very romantic, but making coal gas is an extremely messy business. Gasification leaves behind large volumes of coal tar – a thick residue loaded with toxic compounds, such as polyaromatic hydrocarbons that are known or suspected carcinogens. The gooey stuff never really hardens and when dumped on or in the ground, it oozes downwards until it reaches an obstruction like bedrock, then keeps moving sideways. It severely contaminates everything in its path – not only the soil, but also any groundwater or surface water with which it comes into contact.

The MGPs were usually located in urban areas where the gas customers were densely clustered and near waterways, so the coal could be delivered by barge.  Consequently, many of the commercial waterways in older cities are contaminated by coal tar. The mud underneath New York City’s infamous Gowanus Canal, home for over a century to three manufactured gas plants, contains nearly 5 percent coal tar waste.

By the late 19th century, gas was giving way to electricity as a means of producing light. But, for decades, gasification of coal continued to be important for many other industrial purposes. Indeed, we learned how to use portions of the coal tar wastes as raw materials for the predecessors of what today we call the petro-chemical industry.

In 1834, German chemist Friedlieb Runge isolated from coal tar a chemical later called aniline, the basis of the aniline dye industry from which sprang corporate giants like BASF and GAF (the "A" in both stands for aniline). Many other compounds that we now extract from petroleum were first extracted from coal tar. 

Nazi Germany, with plenty of coal but not much oil or natural gas, depended on gasification to create some of the substances on which its chemical, fertilizer and armaments industries depended. During World War II, Britain and France also used the technology, for similar reasons. 

Alas, the same coal tar which spurred much of this chemical ingenuity, also created an enduring legacy of toxic waste sites at which we are now spending billions of dollars for cleanup.  

Next time: Plastics!