For every 100 tons burned in an incinerator, about 30 tons of toxic ash are produced.
This is evidenced by the data from various incinerators. Below is data from trash incinerators in Pennsylvania, Maryland, and Virginia, where state waste disposal databases provide the tonnages burned and tons of ash disposed. Pennsylvania now provides this raw data online.
|1991-2020||PA||Delaware||Covanta Delaware Valley||32,837,620||9,685,859||29%|
|1991-2020||PA||Montgomery||Covanta Plymouth Renewable Energy||11,895,753||3,142,549||26%|
|1988-2020||PA||Dauphin||Susquehanna Resource Management Complex (Harrisburg Incinerator)||6,382,799||1,922,622||30%|
|1990-2020||PA||Lancaster||LCSWMA Resource Recovery Facility||11,252,432||2,825,722||25%|
|2016-2019||MD||Montgomery||Montgomery County Resource Recovery Facility||2,352,579||700,724||30%|
|2016-2019||MD||Baltimore City||Wheelabrator Baltimore||2,810,737||779,121||28%|
|2015-2016||VA||Portsmouth City||Wheelabrator Portsmouth||1,346,729||359,165||27%|
Note: A sixth incinerator in Pennsylvania was left out of the analysis above because some of the ash went to an ash recycling scheme for years, and due to impossibly low ash numbers, more may have been disposed of out-of-state, which goes untracked by Pennsylvania's reporting system. The numbers above may be slightly low, as Covanta now has an ash "recycling" plant in Bucks County, Pennsylvania where some ash goes, escaping reporting.
There is also a certain portion of the municipal solid waste stream that cannot be burned in an incinerator and which is bypassed and sent directly to landfills, so these numbers are also conservative in the sense that they do not cover this bypassed waste.