Life Cycle Assessment

Three management methods are employed to manage the 120 million gallons of used oils collected in California each year: re-refining back to lubricating oils, distillation to clean ship fuels and an asphalt product, and combustion as fuel. In 2005, more than 70 million gallons of used oil were marketed as heavy fuel oil without treatment. Some of this was burned in combustion systems with limited pollution controls. The results of an environmental life cycle assessment show that heavy metal air emissions from used oil fuel far exceed emissions from other used oil management methods. In fact the net zinc, copper, cadmium, and lead emissions to air from used oil combustion may be equal to emissions from all of California's large stationary sources combined (based on EPA-TRI). Because of heavy metal emissions, combustion of used oil as fuel may cause 100 times the environmental impact of used oil re-refining or distillation (see Environmental Assessment of Used Oil Management Methods in Environmental Science and Technology vol. 38, No. 2).

Treatment by re-refining or distillation results in reduced environmental impact primarily from diversion of used oil as fuel, but also from recycling energy-intensive materials back into commerce. This in turn reduces California's net global environmental impact and crude oil imports. Increased domestic use of the products such as re-refined motor oil will help to increase the use of existing treatment capacity and foster the development of additional treatment capacity. Source reduction of used oil generation by extended motor oil change intervals could result in significant crude oil resource savings. A recent report completed by the Federal DOE and EPA reviews the benefits of better used oil management. For more information on this project, use the following links that will exit the DTSC Web site. Environmental Assessment of Used Oil Management Methods Response to Comment on "Environmental Assessment of Used Oil Management Methods" Additional Resources

Re-refining used oil conserves natural resources and reduces air pollution.

Shredder Residue Management Alternatives

At their end of useful life, a majority of automobiles and appliances are shredded to recover iron, steel, and non-ferrous metals. The remaining waste consisting of glass, plastics, carpet, and dirt is called shredder residue. About 360,000 tons of shredder residue are generated each year in California.

Currently the residue is treated with chemical fixatives such as portland cement to reduce the leaching of heavy metals and is then disposed in landfills. The large resource cost of treatment chemicals and the loss of the material resource and energy value when landfilling was studied. A recent study comparing three methods for managing shredder residue to landfilling was published in Resources, Conservation and Recycling. Three material recovery methods were evaluated using LCA methodology, and one alternative, using shredder residues as fuel and mineral feedstock for cement manufacture, proved very beneficial.  Results showed that up to 100,000 tons of coal, 100,000 tons of mineral resources, 150,000 tons of landfill capacity, and 50,000 tons of treatment chemicals could be conserved annually. Additionally, the current practice of chemically treating and landfilling shredder waste may have 4 to 10 times higher environmental and human health impacts. One example of potential savings from recovering this material as fuel instead of coal showed that more than 30,000 tons per year of global-warming gasses could be eliminated (which is equivalent to emissions of 7,000 automobiles).

Crushed auto bodies ready for the shredding process

A follow-up study was initiated with co-funding from USEPA to study separation systems and shredder residue characteristics (the project description can be found here).  The results showed that a fraction constituting about 30 wt% of the total shredder residue with characteristics equivalent to coal could be economically recovered. However, the presence of contaminants lowers the value of SR-derived fuel. Reducing the contamination from components in the shredder feedstocks (e.g., PCB-laden capacitors, lead wheel weights, PVC plastics, and mercury switches) may be the most significant barrier to overcome.  The study, Evaluation of Shredder Residue as Cement Manufacturing Feedstock, has been published in Resources Conservation and Recycling.

For more information on these projects, refer to the following:

Environmental Assessment of Shredder Residue Management

Evaluation of Shredder Residue as Cement Manufacturing Feedstock

Finding Alternatives to Lead Wheel Weights

Life cycle assessment tools were used to evaluate the impacts of alternatives to lead wheel weights currently being used in California. The comparative assessment described in this report evaluates certain impacts associated with lead, steel, and zinc alloy wheel weights to identify regrettable substitutions or burden shifting as a result of the lead wheel weight ban (see http://www.dtsc.ca.gov/PollutionPrevention/ToxicsInProducts/leadwheelweights.cfm for more information). Metal production inventories were used to compare the impacts of the different wheel weight formulations and to understand the processes contributing to adverse impacts. Impacts from weight losses during use were also evaluated to compare the environmental and human health trade-off. Based on the assumptions and considerations outlined in the report, lead or zinc wheel weights lost on the roadway have much higher potential impacts to human health or the environment compared to steel. The substitution of zinc for lead weights poses a burden shift as the losses during use are more harmful to the environment than lead. Considering the assumptions made, the impacts from lead or zinc based wheel weight losses to roadways greatly exceed their manufacturing impacts. Therefore, steel appears to be the preferred alternative for clip-on weights due to its comparatively low toxicity and reasonable manufacturing impacts. The loss rate for adhesive weights (which represent a minor fraction of the current market) is not known but is likely similar across each weight metal type. Nonetheless, the loss rate for zinc adhesive weights would need to be two orders in magnitude lower than that of steel weights for the loss (during use) impacts to become comparable to those of primary metal acquisition and weight manufacturing for steel weights. Lower environmental and human health impacts coupled with the propensity for steel wheel weights to be made from recycled material appears to position steel wheel weights to be the best overall alternative.