Getting to the Source of Hazardous Waste

Hazardous waste in the environment is a national problem that has received a great deal of publicity in recent years. Interpretations differ as to what constitutes a hazardous waste, but it is generally considered to be generated during the production or use of hazardous materials and to include a compound known to harm human health or the environment, even though the concentrations of that compound may be below legal limits. Hazardous waste is generated by industrial producers (in which case the waste is a by-product of production processes) and by commercial and individual users of hazardous compounds. (Such waste is typically a spent chemical.)

In the United States, the organic chemical industry generates the largest volume of hazardous waste, much of it in the form of contaminated water. Over the past several years, the industry has come under increasingly strict regulation that has resulted in improved waste management. Hazardous waste from small industrial and household users, by contrast, remains relatively unregulated and thus has become an increasingly significant environmental issue.

Thus far, much of the remedial work on hazardous waste has been directed toward cleaning up waste already discharged into the environment. Much attention has also been directed toward developing new treatment, containment, and disposal technologies to effectively manage the toxic wastes that are ready to be disposed of. Very little effort, by comparison, has been devoted to "source reduction,"—that is, to reducing, avoiding the production of, or eliminating hazardous waste before it is generated.

Although source reduction is a new and not yet widely used method of dealing with hazardous waste, it has become an increasingly attractive environmental policy for the organic chemical industry because of the high costs of waste disposal and, more importantly, the greater liability that producers now incur for generated wastes. Moreover, public confidence in new waste control and containment technologies such as scrubbers, double liners in landfills, biodegradation, and more efficient incinerators has eroded. Methods such as concentrating the wastes to reduce volume or diluting them to reduce hazardousness are viewed as inadequate solutions to the waste problem.

There appears to be almost universal agreement among policymakers, chemical manufacturers, and users of hazardous chemicals that the amount of hazardous waste generated in the United States each year must be reduced. A June 1987 report to Congress from the Office of Technology Assessment in effect agrees with them in stressing that source reduction is an economically sensible solution to prevent future waste problems.

Prescriptions for an effective source reduction policy, however, still vary widely. Before any policy is implemented, a number of relevant questions must be answered: What are the technical alternatives presently available that will result in the generation of less hazardous waste? How much waste can be reduced with these alternatives? What do these technical alternatives cost? And, finally, what incentives can be designed to encourage the implementation of source reduction? To date, organic chemical manufacturers have made little effort to share specific information on their use of source reduction, although comprehensive evaluations of such waste reduction efforts are needed so that the potential for and economic impact of further waste reduction throughout the industry can be assessed.

Large-scale industrial producers of hazardous compounds are not the only group for which source reduction holds promise. The Massachusetts Department of Environmental Management estimates that 25 percent of that state's hazardous waste comes from users—rather than producers—of hazardous materials, who individually generate relatively small amounts of hazardous waste that become significant in the aggregate. These users for whom source reduction could be very feasible include small businesses such as dry cleaners and jewelry manufacturers, which generate hazardous waste in the form of dry cleaning solvents and toxic metals. (For individual consumers, who generate hazardous waste in forms such as spent motor oil and discarded paint strippers, efficient waste management by means of proper storage and disposal rather than source reduction is viewed as the most viable solution.)

Commercial users of hazardous compounds are numerous and widespread, which has made it difficult to ensure that the wastes they generate are properly disposed of. Recently increased costs for waste treatment and environmental restrictions on the disposal of certain wastes at landfills have resulted in greater interest in source reduction among this group. Thus far, their efforts have been limited mostly to the recycling of chemicals and the adoption of good housekeeping procedures (e.g., distilling dirty solvents and implementing inventory control). Once again, however, there has been no systematic examination of source reduction options or evaluation of efforts to implement them.

Production alternatives

The production and use of chlorinated methanes and ethanes provide a useful framework for examining how hazardous wastes are generated and how source reduction might be implemented. The chemical industry produces large volumes of these compounds, some of which are subsequently used as a raw material for other chemicals, e.g., plastics and freons. These compounds are also widely used as industrial solvents in applications ranging from paint stripping and metal degreasing to dry cleaning. All of the chlorinated methanes and ethanes are considered harmful to humans.

Chlorinated methanes and ethanes are typically manufactured in large plants located in the Gulf Coast states, although there are smaller manufacturing sites in West Virginia, Kansas, and California. In recent years, production of those compounds used as raw materials for plastics and freons has increased, while production of chlorinated solvents has decreased, in part due to stricter environmental regulations and concern over the hazardous nature of the compounds.

Basically, there are five processes by which chlorinated methanes and ethanes can be produced: hydrochlorination of methanol, chlorination of waste chloro-hydrocarbons, balanced oxychlorination of ethylene, oxychlorination of ethylene dichloride, and hydrochlorination of vinyl chloride. Each of these processes generates hazardous waste.

To determine whether there are alternative methods that would generate less waste in the production of chlorinated methanes and ethanes, the production processes must be closely analyzed. Since source reduction seeks to avoid the generation of hazardous waste, it is important to understand where and how the waste is created in the chemical process. This analysis is very difficult, however, if the fundamental chemistry of a process is poorly understood. The amount of waste present in each step of the process must also be determined.

After current production processes have been analyzed, waste reduction alternatives can be considered. These alternatives include using a different sequence of reactions, operating with different process conditions, recycling some waste back into the process, or recycling waste to another process in the plant. Each alternative should be designed to reduce the total amount of hazardous waste emanating from a process or plant.

In producing chlorinated methanes and ethanes, for instance, it is possible to derive the same end product by using any one of several different reaction mechanisms, that is, different sequences of chemical reactions. This may be done by changing the raw materials or the reaction catalyst. The use of different reaction mechanisms results in a different spectrum of by-products, some of which become hazardous waste. Thus, one way for producers of chlorinated solvents to achieve source reduction is by selecting a reaction mechanism that generates a smaller amount of waste.

Substituting different process operating conditions can also change the relative amounts of useful product and useless by-product. For example, the "heavier," more chlorinated by-products that typically end up as waste may be the result of high operating temperatures. Reducing the temperature of the reaction decreases the probability that these heavier compounds will be produced. Other process changes may also be necessary in order for a process to run at a lower temperature. Finally, waste streams can be separated or treated in order to recycle useful components back to the original process or to another process in the plant.

The cost of implementing the alternative versus the savings accrued from later having to treat a smaller amount of hazardous waste shows whether there are cost savings for a particular process alternative. Each alternative involves different process equipment with corresponding differences in capital and operating costs. And for each, there is a maximum amount of waste reduction that is possible, depending on the limitations of the technology used and on the acceptable degree of process degradation (for example, damage that can be caused to a process reactor or to subsequent processing units when compounds are recycled) or on the acceptable reduction of product quality.

By comparing all of the costs for various process alternatives, a producer can determine the most cost-effective method for obtaining a specified amount of waste reduction. Production alternatives with cost savings or relatively low costs and little risk of upsetting the process are likely to be implemented. Those alternatives approaching 100 percent waste reduction—that is, elimination of all hazardous waste—are expensive and tend to compete with known waste treatment technologies such as incineration.

Choices for commercial users

Implementing source reduction alternatives for the spent solvents generated by commercial establishments involves unique problems due in part to these users' limited technical expertise, limited capital, reluctance to accept innovation, and diversity of equipment and operating procedures. Since many commercial users have only recently come under environmental regulation, they may represent the greatest potential for source reduction among all waste generators.

Waste-reducing alternatives for commercial establishments include (1) the use of different operating procedures, (2) simple equipment changes, and (3) recycling or reuse of spent solvents. In the first category, for instance, good housekeeping practices such as eliminating leaks and spills can achieve waste reduction with little or no additional cost. In addition, there should be standard operating procedures to ensure worker safety. Examples of the second type of change—simple equipment modifications that reduce losses and thus waste—include the use of lids and refrigeration units for degreasing operations to trap or condense evaporated solvents.

With regard to the third waste-reducing alternative, the efficiency of recycling is improved if different wastes are kept separate, since the composition of the waste stream is critical in determining the possibilities for recycling. The recycling process can be carried out on or off the production site, although offsite reclamation is considered to be waste management rather than source reduction, and it poses more safety risks. Cleaning and recycling dirty solvent for reuse has been successfully applied in the dry cleaning industry.

Many commercial users who want to eliminate all spent solvents can consider the use of a substitute process or a substitute nonhazardous solvent that adequately meets minimum cleaning or drying specifications. A substitute may have a ripple effect, however, requiring another part of the operation to be changed before the substitute is adequate. Reformulation of a chlorinated solvent may be another workable solution for some establishments. (Such reformulation creates different chemical properties, and it may reduce but not completely eliminate waste.)

As with production alternatives, the cost of each of the options available to commercial users should be compared against the percentage by which the waste would be reduced. The advantages and disadvantages of possible substitutes can be assessed in terms of the amount of waste reduction, the toxicity of the particular type of waste remaining, and safety considerations. (For example, many of the possible substitutes for chlorinated solvents are flammable.)

Efforts to motivate commercial users to adopt source reduction measures have so far originated only at the state level—and in only a few states. They have consisted primarily of advising small commercial users of technical alternatives. Some states, including Massachusetts and North Carolina, have created technical assistance programs that recommend source reduction equipment or process changes. There has been little attempt to educate the unregulated household user.

Within the organic chemical industry, the use of source reduction methods remains limited, with a few exceptions such as the programs at 3M Corporation, Dow Chemical Company, and E. I. du Pont de Nemours & Co. Such programs have tended to be successful when the plant operators work in conjunction with the environmental division to develop waste-reducing production alternatives.

Successful programs in these companies have resulted in greater production efficiency and consequently in higher profits. One of the keys to these successes is the economic incentive given to individual processing units to reduce waste—the most effective being that they, not corporate overhead, are charged for the waste treatment at the end of the production process.

Assessment of waste-reducing alternatives should be considered for all hazardous organic chemicals, not merely chlorinated solvents. Source reduction alternatives for these other chemicals will likely involve methods that are not unlike those available for chlorinated solvents, and similar concerns such as liability and cost should be brought to bear upon decisions about which alternatives to implement.

Economic incentives—e.g., funding for technical assistance, tax relief, increased liability for disposal, or increased costs for waste management and disposal—would speed up the adoption of source reduction measures by both the producers and the users of organic chemicals. At the same time, certain disincentives that result from present environmental regulations—for example, the high cost of obtaining permits for new source reduction technology—should be eliminated. Another type of disincentive that needs to be addressed is that capital which must be spent for pollution control equipment to meet environmental regulations cannot be targeted for source reduction technology. Not until source reduction becomes a top priority among hazardous chemical producers, commercial users, and perhaps most important, national policymakers, will it achieve its potential to address the hazardous waste problem at its origin.