[4] These could be arranged as either a wet or dry process, where the gas produced was bubbled through water or passed through a box of a dampened absorber material such as wood shavings.
Waste tips where they were dumped, or even storage areas where they remained for a time and released leachates, are all common places to find billy deposits forming.
[5] Early gasworks, from 1812, used Samuel Clegg's 'wet lime' purification process which produced large quantities of blue billy.
[4] Bog iron wastes were also weathered in open piles, which allowed them to be regenerated for use four or five times, until they reached a final sulfur content of 50–60%.
This ferrous sulphate was commercially saleable for acid production, and although the economics of this were only marginally profitable, it avoided disposal costs.
Bio-remediation, mechanically working the soil to expose it to air, sunlight and bacterial action, is a process which can be effective against tars, but not blue billy.
By such screening it has been possible to separate the worst of the wastes as one-thirtieth of the total,[iii] then to stabilise that within a cementitious matrix and produce a stable form which could be re-used on site.