Chemical Waste Disposal: A Moral, Legal, And Economic Problem

In the laboratory, chemicals are measured by the gram or kilogram rather than by the ton or kiloton as they are in industry. The cost involved with disposal of hazardous chemicals tends to be inversely proportional to the volume of waste, so the disposal cost per pound is usually much higher for laboratory waste than for industrial waste. As a result, laboratories should recognize not only the usual moral and legal reasons for minimizing their waste, but economic reasons as well. Five general principles of waste minimization apply just as well to the smaller-scale operations of research laboratories as they do to industrial settings: Chemicals can be ordered conservatively to avoid disposal of unused materials; by using small-scale equipment and modern analytical techniques, experiments can be run with small amounts of chemicals; hazardous chemicals can be replaced by equivalent, less hazardous ones; some hazardous wastes can be detoxified in the laboratory as part of the experiment and an in-house exchange system can put excess chemicals to use instead of making them part of the waste stream. An estimated 40% of the hazardous waste from labs is in the form of unused chemicals in their original containers. Laboratory scientists have carried their supermarket shopping habits over to their chemical shopping—they tend to order large volumes of chemicals, often in higher quantities than needed, because the cost per unit weight is lower. However, the true cost of a chemical includes the cost of disposing of it, and the disposal cost is often more than half of the true cost of the chemical. Reducing the scale of operation is another way to control laboratory waste. Many laboratory reactions that were normally operated on a scale of grams a decade ago can be operated on a scale of milligrams now. Techniques such as chromatography separate and purify reaction products, and analytical methods such as infrared spectroscopy, mass spectroscopy, and nuclear magnetic resonance identify products and determine their yield. These techniques not only minimize waste, but are usually safer than larger scale reactions. Moreover, because they are faster, the newer techniques generally increase productivity. Replacing hazardous substances by relatively innocuous ones can lower the cost of waste disposal with the bonus of improving laboratory safety. Benzene, for example, when used as a reactant usually cannot be replaced in the research laboratory, but in the teaching laboratory a substitute is available. The Friedel-Crafts reaction can be illustrated to students just as well by the acylation of toluene as by the acylation of benzene. And when used as a solvent rather than a reactant, benzene can usually be replaced by toluene or cyclohexane in both teaching and research labs. A scientist can often detoxify a hazardous byproduct as part of a laboratory experiment. A lot of harmful chemicals can be conveniently destroyed by oxidation with sodium hypochlorite solution, common laundry bleach. Laundry bleach is generally 0.75 molar m hypochlorite, which makes it easy to calculate how much to use. Hypochlorite will convert quite a few easily oxidized toxic chemicals to innocuous substances that can be flushed down the drain with lots of water. Examples include hydrazines, inorganic cyanides, hydrogen sulfide, and mercaptans. Finally, an in-house exchange system that puts excess chemicals to use instead of sending them off to disposal cuts down on waste and saves money. Scientists have understandable prejudices about recycling chemicals that may have deteriorated or become contaminated. However, as mentioned earlier, nearly half of laboratory waste consists of chemicals in their original containers—many of which have never been opened. Many scientists are willing to use such chemicals, especially if they know the person who originally purchased them. Laboratories are increasingly moving to systems that keep track of chemicals from cradle to grave. While the total waste generated by labs is relatively small compared to that generated by industry (in the U.S. it is less than one tenth of a percent of total chemical waste) the number of people generating this waste is sizable. If scientists, engineers, and technicians in research labs; researchers in analytical and medical labs; and students in science-teaching labs in colleges and high schools all follow the five guidelines suggested for minimizing laboratory waste, they will save money and improve safety in their labs while meeting moral and legal waste disposal obligations. Blaine C. McKusick recently retired from his position as assistant director of Du Pont Co.’s Haskell Laboratory for Toxicology Wilmington, Del. This article is based on his presentation at the ACS symposium “Sensible Waste Minimization” during the 3rd Chemical Congress of North America in Toronto last month.

Chemical Waste Disposal: A Moral, Legal, And Economic Problem

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