An industry group committee will release a report next month on waste-to-energy (WTE) ash management. The research finds that ash recovery plays a significant role in recycling.
The report, scheduled to be released in September 2016, focuses on “Innovations in Waste-To-Energy Ash Management.”
In 2000, the Solid Waste Association of North America (SWANA) created the Applied Research Foundation (ARF) to conduct collectively-funded and defined applied research projects that address pressing solid waste issues. The group of nine subscribing organizations determine what research topics should be addressed and participate in the research.
Jeremy O’Brien, director of applied research for SWANA, says one of the most surprising finds in the research is that the recovery of metals from WTE bottom ash can play a significant role in a community's recycling program.
“About two thirds of metals generated by residential households end up in the mixed waste mainly because they are not targeted for recovery in source-separation recycling programs,” he says. “When metals are processed through a WTE facility, about a third are oxidized and can no longer be recovered. Only metals in their pure or native form can be economically recycled.”
Some of the most promising new developments in ash recovery are the new technologies being used to enhance the recovery of ferrous and non-ferrous metals—as well as enable the recovery of precious metals and rare earth metals—from WTE ash, according to O’Brien.
“A new method of WTE ash management is being tried in the U.S. —namely, the controlled mixing of WTE bottom ash with fly ash to render the mixture non-hazardous and the processing of the remaining bottom ash for metals and minerals recovery,” he says.
The research findings presented in the report document the important role that WTE facilities can play in recovering materials and energy from the non-recycled waste stream.
“By separately managing bottom ash and recovering construction aggregates and metals from the ash, communities can divert more than 90 percent of their wastes from landfill disposal,” says O’Brien. “WTE facilities should more properly be referred to as resource recovery facilities due to the significant role that they can play in a community's metal and aggregates recycling programs.”
According to O’Brien, the top five pieces of information gathered in the findings include:
- New technologies are being used to enhance the recovery of ferrous and non-ferrous metals: These technologies will enable WTE facilities to achieve higher diversion rates and receive new revenues.
- New method of WTE ash management is being tried in the U.S.: The controlled mixing of WTE bottom ash with fly ash to render the mixture non-hazardous and the processing of the remaining bottom ash for metals and minerals recovery. Bottom ash has been processed for the recovery of aggregates for road construction for over 20 years. This new approach allows WTE facilities in North America to do the same.
- Recovering ferrous and non-ferrous metals from products and packaging discards: A fact that is often overlooked regarding WTE facilities is their ability to recover ferrous and non-ferrous metals from products and packaging discards that are not collected in source-separation recycling programs. In this regard, WTE facilities can play a significant role in the recovery and recycling of metals from MSW. For example, it is estimated that, despite a strong and established commitment to curbside recycling programs, approximately two-thirds of all metals discarded by households in Switzerland end up in the municipal waste processed through WTE facilities. These metals can be recovered from the bottom ash of WTE facilities. The recovery of metals from WTE bottom ash can result in more metal recycling than is typically achieved through source separation recycling programs. By implementing WTE systems, communities can significantly increase their metals recycling rates.
- Improved metal recovery rates: Advanced metal recovery systems improve the metal recovery rates from WTE bottom ash by targeting metals that are less than 12 millimeters (0.47 inches) in size and utilizing new technologies that have been recently developed. These systems can increase the metals recovery rate from 11 percent to more than 15 percent of the bottom ash. In this regard, a contract has just been signed between the LCSWMA and Inashco for the implementation of an ash processing facility at the LCSWMA's Frey Farm Landfill. This facility will increase the ash metals recovery rate from 10.5 to 15.3 percent and will provide additional revenues to the LCSWMA of more than $600,000 per year over the 10-year contract period. Implementing this approach can provide new revenue sources to WTE facilities.
- Case study: A WTE facility in Pasco County, Fla., has implemented a new approach to WTE ash management that enables the recovery of most of the bottom ash for beneficial reuse while avoiding the need to manage fly ash as a hazardous waste. This approach involves mixing a portion of the bottom ash with fly ash to render the mixture non-hazardous and then processing the remaining bottom ash for the recovery of metals and aggregates. Following the conduct of a successful pilot test program, on Dec. 5, 2014, Pasco County received the first permit ever issued by a state government authorizing the use of WTE bottom as an aggregate in road construction. The issuance of a WTE bottom ash reuse permit by the State of Florida is a watershed moment regarding WTE ash management in North America. By only mixing enough bottom ash with fly ash to render the mixture non-hazardous, the majority of WTE bottom ash that is currently disposed in landfills in North America can be diverted and reused as has been done in Europe for many years. The WTE bottom ash reuse project in Pasco County has the potential to divert an additional 52,000 tons of waste from landfill disposal each year. If this ash is used in road construction, it would mean that almost 94 percent of the waste processed through the county's WTE facility would be diverted from landfill disposal and recovered in the form of energy or reusable materials and metals. With the implementation of this approach, WTE facilities can now offer communities a proven, reliable and cost-effective method of implementing a zero waste to landfill system.