Proper Disposal or Reuse of Old Laboratory Chemicals

Laboratories frequently accumulate bottles of old chemicals, often toxic or hazardous, that are no longer used. Laboratory managers can use several strategies to properly reuse or dispose of these chemicals. These strategies are not mutually exclusive. Laboratory managers can apply more than one to meet the requirements of maintaining laboratory safety and environmental protection. These strategies are discussed in the individual sections below.

Proper disposal can be expensive. So it is essential to minimize the need for proper disposal, by minimizing chemical purchases. Even if yours is a small laboratory, centralizing chemical purchasing is an effective way to do this. Having a single person assigned to purchase all chemicals for the entire laboratory will help ensure that duplicate orders are not made by different members of the laboratory staff. More people may be assigned to do this in larger laboratories, and departments may be set up to manage chemical purchasing, storage and waste disposal.

Maintaining a computer-searchable chemical database

The first step in proper recycling or disposal of chemicals is to know what you have. The best way to do this is by maintaining an inventory of all the chemicals in use or stored in your laboratory. Supply room personnel should record the receipt of all purchased chemicals. Among the data that should be recorded are the supplier, the amount of chemical purchased, its purity, its amount, the person ordering the chemical and the laboratory room number to which it was delivered.

New chemicals should be added to the database as they are purchased and old ones deleted as they are consumed. This last requirement means that laboratory personnel and not just stockroom personnel should be able to access the database to update information. Laboratory personnel should record when samples are completely consumed or transferred from one laboratory to another.

This inventory can be used to tell laboratory managers and staff members when samples become so old that disposal is necessary. This database can also be a moneysaver by enabling lab personnel to learn from whom they can obtain a needed chemical without purchasing a new sample. Should it be necessary to purchase a fresh sample of a particular chemical, the purchaser can review the chemical inventory to identify a supplier and the chemical purity of previously purchased samples of the same chemical.

Several firms offer commercially available chemical inventory database software. Using an Internet search engine and keyword phrases such as “chemical inventory management software” can identify software suppliers and retrieve a description of their products.

These computer programs vary in sophistication and features. Software search features can include one or more of the following search options: searching by chemical name, chemical supplier, the storage location, and the laboratory department and/or individual who purchased the chemical. The chemical name can be the proper IUPAC (International Union of Pure and Applied Chemistry) systematic name designation or one or more common names of the chemical. Other search options include the CAS (Chemical Abstracts Service) number of the chemical and the date of purchase. Some programs provide storage of MSDS information.

More sophisticated software can print barcode labels for chemicals that can be affixed to the chemical sample container and used to track movement of chemicals within the laboratory and their consumption. Should supply of a chemical be recorded as falling below a specified level, some software can automatically issue an alert informing the user of that particular chemical and that it needs to be reordered. Some chemicals may arrive with an expiration data beyond which the chemical should not be used. Some software offer features that include issuing an alert when a particular chemical sample usage date is due to expire.

Some software suppliers such as Chemoventory offer limited capability versions of their software for free (www.chemoventory.com) to educational and other nonprofit institutions. Other software provides more features but must be paid for. One example is Nexxis Chemical Inventory Manager (www.labtronics.com/chemical_inventory_management.htm).

Holding periodic lab cleanup days

Having periodic cleanup days during which old chemical samples and unused/nonfunctional equipment is collected and disposed of can be a useful way of putting labs in clean, tidy and safe operating condition. These cleanup days are most effective in achieving these goals if lab managers insist that all routine work stop for the day to focus on cleanup.

Sometimes only an individual laboratory rather than the entire facility needs to have a laboratory cleanup day. This situation can arise if a laboratory is being relocated from one location to another either within the facility or from one facility to another. Alternatively, the termination of a project or its relocation from one laboratory to another may be facilitated by a lab cleanup day.

If an individual laboratory rather than the entire facility is cleaning up and disposing of old chemicals, have the appropriate lab staff members advertise their lack of availability to coworkers before this process begins. Interruptions can greatly reduce the efficiency of the cleanup process and increase the time required for it.

Once old chemical samples are identified and selected for disposal, proper procedures must be followed. Lab managers can have samples packed properly by lab personnel for pickup and disposal by a qualified chemical disposal firm. Some disposal firms will perform all the work themselves. This approach may be more appropriate for large laboratories.

While any chemical to be discarded is chemical waste, hazardous chemical waste is defined by the Environmental Protection Agency (EPA) or a relevant state authority as waste that presents a danger to human health and/or the environment. The EPA defines four key properties that determine whether a chemical is hazardous waste: ignitability, corrosivity, reactivity and toxicity.

Potentially hazardous chemicals must be disposed of in accordance with federal and state regulations and procedures. EPA regulations are summarized at www.epa.gov/epaoswer/osw/conserve/clusters/schools/index.htm.

While state requirements vary somewhat by locality, the basics remain the same. However, it is best to consult with your relevant state agency or the EPA to determine whether particular chemicals are defined as hazardous and what the requirements are for storage and disposal. These requirements should be defined on the chemical’s MSDS. However, if the chemical was purchased some time ago, the available MSDS sheet may be out of date and you should consult the current version of the MSDS.

Many labs use one or more large containers labeled “chemical waste” for solvents and other chemical wastes. Extreme care must be used in combining chemicals in such containers, as some chemicals may be incompatible. For example, addition of a strong oxidizing agent may result in oxidizing another chemical in the container and leading to heat evolution and an explosion or fire.

Because of the dangers of such chemical incompatibilities and the hazards of chemical spills occurring in a busy work area, chemical waste containers should be stored away from normal work areas and away from sinks and floor drains. Every addition of a chemical waste to a storage container should be noted in a permanent record such as an online file or a laboratory notebook.

Do not completely fill waste containers, particularly waste storage bottles. While the amount of empty headspace at the top of the container can vary with the size of the container, it is usually best to allow about 20 percent vacant headspace at the top of the container for possible vapor formation or liquid expansion due to heat evolution.

To remove chemical wastes from your laboratory site, contact professional, licensed hazardous waste haulers and transporters. Trained personnel from these firms will package waste chemicals properly for transport and disposal.

Training lab personnel

Training lab personnel in proper disposal and storage procedures is essential. This is a particular issue in academic laboratories because the students using a laboratory can change from semester to semester. Larger laboratories often have a Health, Safety & Environment Department whose personnel are qualified to conduct such training. If your laboratory does not, there are consultants who offer training programs in proper chemical storage and disposal.

When supervising students working in laboratories, professors and teaching assistants should review the safety concerns and required safety procedures associated with each laboratory exercise or experiment.

Solvents and glassware cleaning

Solvents produced as waste in laboratory equipment such as rotary evaporators and distillation apparatus are often as clean as what initially comes from a fresh solvent bottle. Do not dispose of these solvents; reuse them instead for routine laboratory operations such as glassware cleaning. Often one can filter and reuse solvents for at least initial cleaning of glassware. Laboratory personnel should limit the use of solvents and other chemicals in routine operations such as cleaning laboratory glassware.

Chromium-containing cleaning agents can be highly effective but should be used only as a last resort. Evaluate the use of enzyme-based or detergent-based cleaners before resorting to chromium-based cleaners. Chromium- based cleaners are highly toxic, as the Julia Roberts film Erin Brockovich makes clear in a fairly accurate recital of a major California pollution case in which chromiumcontaining toxic wastes leached into a town’s water supply and apparently led to birth defects in children and severe illnesses in adults.

Volatile solvents such as isopropyl alcohol routinely used for sterilizing equipment should be replaced by quaternary amine-based detergents. Replace highly toxic solvents such as benzene or carbon tetrachloride with less toxic ones whenever possible. For example, cyclohexane is often used as a substitute for carbon tetrachloride.

Mechanical cleaning methods should be used instead of solvents whenever possible. These may be as simple as using cleaning brushes in good condition or ultrasonicators instead of solvents. Large laboratories often use industrial dishwashers instead of solvents for cleaning glassware.

Keeping an adequate supply of clean glassware on hand will reduce the tendency to rinse glassware with volatile solvents such as acetone to quickly dry glassware for reuse. So will the use of a glassware drying oven.

Neutralize aqueous acids and bases. Pour only nontoxic, pH 4 to 9 aqueous fluids down drains. Neutralize and clean up spills so that all or most of the waste can be disposed of properly.

Distill used solvents to purify them. For example, scale-up laboratories and pilot plants can accumulate large volumes of used solvents. If distillation removes all reactive compounds and impurities, distillation can both purify solvents for reuse and reduce volumes released to the environment. After all, production plants frequently distill solvents for these reasons as well as economic ones.

Dr. John K. Borchardt is a consultant and technical writer. He is the author of Career Management for Scientists and Engineers and often writes on career-related subjects. He can be reached at jkborchardt@hotmail.com.