De-inking sludge contains wood fibre and a significant quantity of clays from the de-inked paper.

Paper industry de-inking sludge, a by-product of recycled paper, was also a suitable raw material, the companies said.

These other waste fuels include primary and secondary wastewater treatment sludge, de-inking sludge from the recycling of paper, and tall oil soaps, crude tall oil, and turpentine.

Stack dioxin emissions increased significantly in power boilers burning de-inking sludge (compare test results for mills C and E in Table 3.3 and for Mill O on page C-10).

The mill conducted one stack test when there was no de-inking sludge fired (5.6 pg TEQ/dscm) and two tests when firing deinking sludge (average emission- 22.3 pg TEQ/dscm).

The aided investments aim at reducing energy consumption in newsprint production, producing energy by combusting de-inking sludge in a combined heat and power installation, and transporting waste paper and finished product by rail instead of truck.

This is consistent with reports that while mechanical dewatering can reduce the moisture content of de-inking sludge to 40 - 60 %, the high inert content of these materials make them difficult to burn on conventional stoker grates [Douglas, 1997].

Chematur's Super Critical Fluids technology was acquired by SCFI Group (Cork, Ireland) who are actively commercializing the Aqua Critox SCWO process for treatment of sludge, e.g. de-inking sludge and sewage sludge.

Many long duration trials on these applications have been made and thanks to the high destruction efficiency of 99.9%+ the solid residue after the SCWO process is well suited for recycling - in the case of de-inking sludge as paper filler and in the case of sewage sludge as phosphorus and coagulant.