Saturday, April 13, 1996

Entering the Mainstream: Empty Steel Aerosol Cans, A Part of Many Programs’ Recycling Efforts

The aerosol can is a sealed, airtight container with a unique self-contained delivery system that overcomes atmospheric pressure to dispense its product in a controlled direction and amount. Sounds a bit complex, so it must be difficult to recycle, right?

Wrong. More than 90 percent of aerosol cans are made from steel, North America’s most recycled material. Steel’s recyclability positions the aerosol container for today’s recycling demands.

An entire industry of ferrous scrap processors has been formed around the preparation of steel scrap for steel mills. In 1995, more than 70 million tons of steelmaking, fabrication and post-consumer steel scrap were recycled into new steel products. It is through this very same well-established recycling infrastructure that steel aerosol cans are recycled as a steel scrap.

Steel Can Recycling

Steel food and beverage cans are commonly included in nearly every community’s recycling program: in all, there are more than 14,500 steel can recycling programs.

Empty steel aerosol cans should be a part of each of these programs. But misinformation or misunderstanding initially prevented the immediate inclusion of aerosol cans when many curbside and drop-off municipal recycling programs began collecting steel cans. For example, a large majority of the public wrongly believed or assumed that aerosol cans still contained chlorofluorocarbons (CFCs), which were banned in 1978. Public education and industry outreach have finally begun to turn the tide. Most recently, it appears that one of the major hurdles, regarding the issue of emptiness, has been overcome.

When is an Aerosol Can Empty?

When it comes to recycling, all types of packaging have on ordinary factor in common: the container must be empty before it may be recycled. For aerosol cans, this seems to pose a special challenge. Invariably the question arises, at what point is an aerosol can empty?

There are several ways this can be answered. For those with an exhaustive desire for precision, the federal government has defined exactly when a container, including an aerosol can, is considered empty. The U.S. Code of Federal Regulations 40 CFR, section 261.7 states that emptiness occurs when “No more than 3 percent by weight of the total capacity of the container remains in the container or inner liner . . . “or “when the pressure in the container approaches atmospheric” pressure.

But before gauging how much product is left in the can, you should know that an aerosol can is designed to fully and efficiently dispense virtually all of its contents. The long, thin dip tube that carries the product out of the can reaches into the edge of the can’s domed base to capture the product. In addition, both the aerosol can’s product and propellant are carefully measured to exhaust at virtually the same time.

Finally, common sense says that when an aerosol can’s working nozzle is activated yet does not release any product, the container is empty.

Municipal Recycling Programs

So how much preparation do aerosol cans require for recycling through municipal recycling programs? The answer is simple: none. Before recycling aerosol cans through municipal collection programs, household residents are instructed to simply use up the contents of the containers normally. A 1992 study conducted by the Steel Recycling Institute under the purview of the Texas Water Commission demonstrated that consumers sufficiently empty their aerosol cans before recycling them. The “Houston Aerosol Can Recycling Evaluation” physically evaluated a sample of more than 1,700 consumer-emptied aerosol cans collected through the Houston, Texas curbside program over a six-week period. The results of the study indicated that the mean combined residual product remaining in the cans was 2.69 percent, well
within the three percent “emptiness” criterion established by the U.S. Code of Federal Regulation.

Another study was just recently completed by the Factory Mutual Research Corporation. This study demonstrated that material recovery facilities may safely process aerosol cans collected along with other steel containers and recyclables.
An earlier study on the flammability of aerosols had been conducted by S.C. Johnson Wax at two processing facilities with six different types of equipment. It was determined that the lower flammability limit was never reached with ordinary processing, so concerns about plant safety were answered.

Factories, Plants and Shops

Multiple users, quality of product with intermittent applications and other factors all tend to reduce the chance that an aerosol can’s product will be thoroughly and completely used up at factories, plants and shops. In these cases, special equipment may b employed when required to ensure that the cans are completely emptied for recycling.

To ensure that all steel aerosol cans in the factory, plant or shop are empty before being recycled, preparation may be appropriate. They are collected at one or more preparation sites in the facility, where they are punctured and drained of any remaining product and propellant using appropriate equipment designed for this purpose. Once the cans are emptied and then flattened, they can be picked up by a scrap dealer or waste hauler to be baled along with other steel cans collected in residential programs and shipped to end markets for recycling. Puncturing, draining and flattening provides visual assurance that all of the cans have in fact been properly prepared.

Aerosol Can Fillers and Household Hazardous Waste Processors

Aerosol can fillers and household hazardous waste processors have something in common: aggregate quantities of full or partially full steel aerosol cans. Over time, aerosol can fillers generate filling line rejects, malfunctioning cans and damaged cans. Aerosol cans collected through household hazardous waste collection programs have full or partially full containers that are old or defective or that residents no longer wait.

Aerosol can fillers segregate the reject or otherwise unsalable containers. They also may receive consolidated customer returns from the retail network. The collected cans are taken to the factory’s preparation center, where special equipment is used to decant, degas and flatten them automatically. The steel aerosol cans are then shipped to a secondary processor for baling and shipment to end markets. The contents of the rejected cans are recovered for reuse or prepared for proper disposal.

Household hazardous waste vendors are encouraged to operate in a similar manner. During community household hazardous waste collections, which typically occur once or twice a year, partially full or full aerosol cans (along with many other containers) are taken to a designated collection site by residents. These programs also collect significant quantities of empty aerosol cans which residents should have actually been able to recycle along with other steel cans through their ordinary curbside and drop-off programs. After the aerosol cans are assembled, hazardous waste vendors may use similar specialty equipment to decant, degas, and flatten them. Some operators without appropriate equipment may need to ship the cans to a larger operator in the area. The emptied, flattened aerosol containers are then sent to a secondary processor, such as a ferrous scrap yard, for baling and shipment to end market. They are typically mixed with other empty steel cans, such as paint cans. In some cases, the prepared containers may go to a material recovery facility where they are mixed in with residential cans. By recycling these cans, household hazardous waste management and landfill costs are reduced, in turn reducing the overall cost of the household hazardous waste collection program.

Steel Mills Recycle Aerosols

Less than 15 percent of steel cans were being recycled in 1988, about the time when many municipal recycling programs began to emerge. As steel cans are commonly used to package food, beverages, paint and aerosol products, recycling coordinators were able to divert steel cans from the solid waste stream to secondary processors, including ferrous scrap dealers, for steel mill consumption. The supply of steel cans for recycling began to increase yearly, along with renewed interest by steel melters.

Steel mills purchased increasing amounts of steel can scrap for several reasons. In a steelmaking furnace, molten iron, scrap and varying levels of fluxing agents and other alloying elements are mixed together to create a “heat” of steel with
a specific chemical composition of the scrap being added to the furnace so that the resulting heat meets a desired chemical profile. As a source of steel scrap, steel cans have a highly predictable chemical composition. In addition, they have virtually no contaminants to the steelmaking process, as paper labels or plastic components are vaporized in the face of volcanic temperatures. And, when coupled with the fact that steel cans have been lower in price than other comparable grades of scrap and that appealing public relations is created by helping to reduce the size of a community’s municipal solid waste stream, steel cans are a desirable form of scrap.

Many steelmakers have altered their scrap purchases proving that steel cans are becoming a known and desired commodity. In 1995, more than 80 end markets across the country helped recycle 55.9 percent of the 32 billion steel cans produced in the United States.

Benefits of Empty Steel Aerosol Can Recycling

Municipal solid waste managers and recycling coordinators are adding empty steel aerosol cans to their collection programs, especially at this time when many recycling programs are moving to expand their collection bases in an effort to meet state recycling mandates. Collecting empty steel aerosol cans for recycling requires no further collection or processing equipment, and can add as much as three to five percent to a recycling program’s total steel can diversion rate.

The SRI has a variety of brochures and other information about steel can recycling. For copies of these brochures, please call the SRI at 800-876-7274.