Cleanup for urban gasworks, usually smaller Victorian sites, has usually consisted of removing the worst material en masse to a landfill site away from town.
Remediation of larger sites, such as industrial cokeworks, has required a more selective approach as the volumes and site values involved have been too large to justify simply carrying it away elsewhere. 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. Billy residues may require small-scale identification across the site and their separation. By such screening it has been possible to separate the worst of the wastes as one-thirtieth of the total, then to stabilise that within a cementitious matrix and produce a stable form which could be re-used on site.