Zero Discharge Manufacturing

Zero discharge manufacturing encompasses all the methods that various industries use to eliminate the wastes—at least all hazardous wastes—they produce. Though each industry differs on how it does this, zero discharge manufacturing always has these things in common:

1. wastewater solid-liquid separation and reuse
2. minimized rinsing or cooling operations to reduce water use
3. nonhazardous solid waste cleanup and reuse
4. hazardous chemical elimination
5. advanced filtration systems to collect hazardous organic compounds or metals
6. heat energy capture and reuse
7. scrubber, afterburner, or electrostatic precipitator for gas emissions

Zero discharge manufacturing is a method of making the industrial process much more sustainable than current practices. Zero discharge procedures usually center on biological methods of production that eliminate hazardous emissions and contaminated soil and water. Zero discharge emphasizes the reuse of materials, energy, and heat.

 Even the dairy industry has attempted zero discharge operations, which represents an important breakthrough because agriculture of almost all types is a major producer of wastes. Zero discharge dairy farms may become more common as more farms adapt to the following practices: (1) capturing wastewaters and mixing with manure wastes; (2) collecting manure and treating in energy-producing on-site digesters; (3) directing rain runoff away from animal areas; (4) fixing all waste transport and feed storage leaks; and (5) building a secondary containment berm around animal and waste areas to hold wastes from accidental spills. Zero discharge agriculture is very difficult to achieve, but, if agriculture can make important headway toward sustainable methods, it will provide an important example for other industries to follow.

 Current zero discharge operations usually begin with wastewater management for two reasons: water is a natural resource that is becoming increasingly scarce, and water carries waste chemicals produced by many different types of manufacturing. Zero discharge facilities have now incorporated one or more of the technologies described in the following table for controlling water pollution.

 Zero discharge has been achieved in wastewater recovery and certain aspects within manufacturing such as production wastes, chemical wastes, and emissions. Manufacturers have found it difficult, however, to incorporate all three methods within one manufacturing plant. Any zero discharge method must consume less energy than the previous waste disposal method, or companies will be reluctant to accept it.

Pollution Control in Manufacturing

Pollution can be controlled during manufacturing by using technologies that filter materials out of wastewater, collect emissions from smokestacks, or burn solid wastes. To control these types of pollution in the future, product teams meet to discuss a process they call “designing out the waste.” The team made up of product developers and manufacturing engineers develops new ways of making a product so that wastes are minimized at three points in the production: pre-production, in-process production, and customer supply. Some of the areas that manufacturers focus on to design out wastes are the following:

1. efficiency in raw material ordering so that only the amount needed is ordered
2. adjusting raw material use-up rate so that raw materials do not pass their expiration date
3. design of assembly line that reduces waste in the form of spills, leaking, or dust
4. collection bins that capture wasted raw materials and return them to the production process
5. reduced final product packaging
6. conversion to biological systems rather than chemical systems to reduce dangerous emissions

 Steps such as these can be difficult to accomplish, expensive, or both. Since pollution control in manufacturing requires that profits do not decline, pollution control technologies must fit into a company’s present operations. For instance, it does not make sense to install a smokestack scrubber on a plant that emits only steam but discharges large amounts of liquid chemicals. The scrubber represents an unnecessary cost and does nothing to address the pollution. Even government regulations, including legal actions and fines, have often been ineffective. The United States and many other countries have manufacturing plants that do not adhere to antipollution laws.

 The World Bank has stated that tying economics to pollution control is the only way to clean up manufacturing wastes: “The new approaches are working because they have a solid economic foundation. Cost-minimizing plant managers will generally tolerate emissions up to the point where the expected penalty for pollution becomes greater than the cost of controlling emissions.” This statement implies that industry will clean up its pollution only if forced to under the threat of severe penalty. Governments must therefore play a part in pushing manufacturers toward cleaner ways of doing things. As an example of this need, rapidly growing economies such as China’s have made business advances faster than they have adopted pollution controls. The China State Environmental Protection Agency estimates that factory pollution accounts for more than 70 percent of the national total, 70 percent of organic compound water pollution, 72 percent sulfur dioxides in the atmosphere, and 75 percent of the dusts that carry particulate matter that damages the respiratory system.

New approaches to pollution control suggested by the World Bank must fit the industry. For example, power plants put emissions into the air, but the food industry is a leading producer of water pollution. The World Bank published a list in order of the top industrial sources of organic compound water pollution in its 2009 publication Greening Industry:

1. food
2. pulp and paper
3. chemicals
4. textiles
5. wood products
6. metal products
7. metal production
8. nonmetallic minerals

 Many of the industries mentioned here have already started on new pollution-control programs. The table on page 98 gives examples of the many new approaches companies have taken to reduce the pollution coming from their manufacturing plants.