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Residue

The father of modern chemistry, Antoine Lavoisier, used the term residuum to refer to a substance left behind after a chemical reaction took place (1790). Picture the chemical reaction taking place when a reactive substance such as potash or lime is exposed, inside a hermetic glass vessel, to air, a compound gas. Once the reaction occurs, the remaining portion of gas that did not react with the lime or potash is the residue. To determine the nature of that residue, “small trials are to be made of it by experiments” (ibid 325). One might introduce a lighted wick in the jar; if the compound contains some oxygen, the wick will stay lit. The brightness of the flame will indicate whether it contains more or less oxygen than does air. “If, on the contrary, the taper be instantly extinguished, we have strong reason to presume that the residuum is chiefly composed of azotic gaz” (ibid). The chemical industry – indeed, industry in general – brings thousands of ingredients into contact with each other. Reactions are then catalysed to yield the desired products. Each of these reactions churns out residues: the undesired, although not necessarily harmful, outcomes of production. As industry’s bastard progeny, residues first and foremost cause chagrin: here’s ballast to be disposed of, raising production costs without contributing to profits. When industry was in its infancy, factory owners didn’t trouble themselves too much with residues; they were simply discarded. Nineteenth century coal burning plants produced steam to power machines, and their chimneys spewed the resulting smoke straight out in the atmosphere without any thought to its content. Only later did pollution problems arise, forcing operators to take action. It appeared that the fine ash suspended in such exhaust had potential uses. Fly ash contains silicon dioxide and calcium oxide, as well as aluminum oxide and ferrous oxide (Helmuth 1987). These minerals are also the ingredients of cement; reusing the microscopic particles from coal exhaust enables the production of Portland cements less dependent on virgin resources. Once a harmful waste-product, fly ash became a marketable good. Likewise, crude oil refineries were slow in finding a use for their most important residue: asphalt, the stickiest outcome of fractional distillation. A breakthrough occurred in the 1870s, when someone invented a new road-paving material: finely crushed rocks held together by asphalt (Pasetto 2003). The market for this new by-product proved even more gigantic. Such stories of material thoughtfulness sketch the outlines of a utopia: a consumer society that functions as a perfectly balanced ecology, where nothing is lost and nothing is wasted. Unfortunately, just because a product is potentially useful does not make it a necessity. Today, only a fraction of fly ash is used in cement production; the rest is dumped. We no longer build enough roads to use all the asphalt that pours out of oil refineries, but the consumption of coal and oil around the world nevertheless increases inexorably. Carbon dioxide – that other remnant of combustion, that residue of animal life that in turn fuels photosynthesis – now clutters the atmosphere in such quantities that it has become a liability. The accumulation of residue remains one of the main products of the industrial age. R