This filtering and curing treatment of waste to energy bottom ash results in a beneficial composite that can be mixed with cement to form environmentally safe concrete. Waste to energy bottom ash or incinerator ash is a portion of the non-combustible residue that remains after waste combustion. Municipal waste combustion generates 7-8 million tons of waste in the United States annually and, because it has the potential to leach concentrations of heavy metals, it currently requires disposal in secure landfills. The construction, permitting, compliance and operating costs of a landfill are significant; recycling bottom ash for beneficial use instead of storing it in a landfill would be a significant cost savings for ash generators. Researchers at the University of Florida have developed a filtering and curing treatment that immobilizes contaminants in the bottom ash and creates a properly graded and usable aggregate product for use in asphalt and concrete or as a roadway base.
Immobilizes contaminants from waste to energy bottom ash allowing use as a construction aggregate
Bottom ash from municipal waste is processed through physical processes to use as an aggregate for a road base, or in Portland cement concrete and hot mix asphalt. The bottom ash moves through gradation screenings to remove metals, elements, alloys and other contaminants. The ash is then cured by selective exposure to water and atmospheric CO2, effectively lowering the pH of the ash and creating an environment that washes heavy metals and trace elements from the ash. The resulting composite has few negative health and environmental effects while maintaining similar structural properties to alternative composites.
