Northwestern Office for Research


Specific Methods of Laboratory Waste Minimization

Hazardous waste minimization is the EPA's first-choice method of pollution prevention. Waste minimization means a reduction in both the volume and the physical hazards or toxicity of the material. The University, as a generator of hazardous waste, must do its best to integrate pollution prevention into experimental design and laboratory management.

Waste minimization has many advantages. Smaller quantities of waste mean less impact on the environment at the time of disposal. Waste minimization leads to safer conditions in the lab and in handling and transporting the waste. It also lessens disposal costs, benefiting everyone in the University community. Waste minimization activities can be grouped into four broad categories:

  • Treatment to reduce hazards
  • Substitutions of less hazardous materials
  • Procedural changes to minimize generation
  • Improved laboratory management practices

Treatment to reduce hazards

The last step of an experimental procedure should include treatment methods to reduce or eliminate the hazardous of experimental byproducts. Eliminate corrosives from wastes through neutralization. Small quantities of inorganic acids - hydrochloric, sulfuric, phosphoric, nitric - can be neutralized and flushed down the drain. Never release chromic acid to the drain, however, even if neutralized. Chromium is a carcinogen and must be given to ORS for disposal. Bases such as sodium, ammonium, and potassium hydroxide can also be neutralized and flushed down the drain. Laboratory quantities of oxidizers can be treated in the laboratory as can small quantities of water-reactive or pyrophoric materials.

The toxicity of some compounds can be reduced. Sodium cyanide can be treated to yield sodium cyanate; ethidium bromide can be reacted to a non-mutagenic waste; waste epoxy monomers can be polymerized to a safe solid. The final step of an experiment should include detoxification, if possible.

Other techniques include treating organosulfur wastes with bleach to reduce odors, deactivating organometallic compounds, and reclaiming metals, especially silver from photographic solutions. ORS can help identify treatment methods for the minimization of experimental byproducts.

Substitutions and Elimination

Minimize hazardous wastes by substituting less hazardous materials in your experiment. This has the collateral advantage of improving worker safety. The following substitutions are recommended by ORS:

  • For glassware, use biodegradable detergents or other nonchromium-containing cleaners.
  • Use biodegradable detergents such as Alconox in place of ethanol-base baths.
  • Use non-mercury based preservatives.
  • Use red liquid (alcohol), metal, or digital thermometers.
  • Substitute sodium hypochlorite for sodium dichromate.
  • Substitute alcohols forbenzene.
  • Substitute cyclohexane for carbon tetrachloride.
  • Substitute ethanol for formaldehyde in biological specimen preservation.
  • Use water-based paints instead of oil-based paints.
  • Eliminate the use of pigments containing heavy metals in art practices.
  • In photography labs, eliminate silver from waste streams through recovery.
  • In teaching labs, eliminate experiments using heavy metals.
  • Replace with iron, cobalt, copper, etc.
  • Substitute biodegradable liquid scintillation cocktails for xylene- or toluene-based cocktails.
  • Try to substitute nonchlorinated solvents for chlorinated solvents.

Procedural changes

Wastes can be minimized by implementing procedural changes such as:

  • Use microscale procedures or simply scale down the magnitude of experiments.
  • Distill spent solvents for reuse.
  • Segregate halogenated waste from nonhalogenated wastes.
  • Segregate organic liquids from inorganic wastes.
  • Segregate very toxic wastes (potassium cyanide, acrolein, etc.) from less toxic wastes.
  • Do not mix chemical waste with normal office trash or food waste. All waste contaminated with hazardous materials is considered a hazardous waste.
  • Avoid reagents or paints containing heavy metals.
  • Use spent solvent for the initial glassware rinse and fresh solvent for the final rinse only.
  • Purchase lecture bottles only from companies who will accept their return when empty.
  • Reuse developers in photography labs.
  • Recover metals for recycling or reuse by precipitation.

Management Practices

Good laboratory management can go a long way towards avoiding unnecessary waste generation. Order only the quantity of material which you anticipate using. Many chemicals have a limited shelf-life. For example, diethyl ether may begin to form peroxides within several months after opening. If you do have leftover material, dispose of it promptly through ORS instead of storing it for future use. This is especially important for peroxide-formers and reactive material. It is much safer and less expensive to dispose of a flammable liquid than it is to dispose of a flammable liquid that contains peroxides. One person should order chemicals for a research group, thereby minimizing duplicate orders. Keep an updated inventory of all the chemicals that are in the lab so that unnecessary orders are not placed. This is a highly recommended practice and a legal requirement for some groups. Share excess and unexpired chemicals with other groups. Keep containers labeled so they do not later become unknowns which require costly analysis. Finally, remember that waste minimization begins when planning an experiment. Consider the kind and quantity of waste which will be generated and adjust the experimental design to minimize it.
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