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Direct emissions from the process of making recycled paper
Emissions to air:
Direct emissions from the process of making recycled paper itself are minimal and considered to be relatively insignificant, although little research has been done in this field.
Those gaseous and particulate emissions to air that are produced, primarily come from the incineration of de-inking sludges and fuel combustion during the production process. Typical emissions from incineration of sludge and fuel combustion include methane (CH4) ; sulphur dioxide (SO2); nitrogen dioxide (NOx); carbon monoxide (CO); carbon dioxide (CO2).
According to Waste Watch, who are part-funded by the UK Government,“recycled paper produces fewer polluting emissions to air and water” [20].
Solid wastes
As noted, processed waste paper produces a sludge. This contains 30-50% solids made up of short fibres, fillers1 and ink from the de-inking process [21]. The amount of waste is dependent on paper source and product type. Traditionally, this waste has been consigned to landfill. However, incineration is becoming increasingly popular. This too produces solid waste as ash which then goes to landfill. Other disposal options include composting and techniques to remove clay and other fillers for reuse. However, these are still only at the early stages of development and have yet to be proved.
De-inking sludges may contain low concentrations of heavy
metals - cadmium, lead, chromium and nickel. Heavy metal contamination is of concern with respect to direct landfill, incinerator ash disposal and composting while incineration produces emissions of CO2, NOx, CO and SO2, hydrocarbon and dioxins2.
However, as noted above, the toxicity of the sludge is a matter of debate within the industry. Comparisons with sludge from the public sewer have shown levels of heavy metals to be lower in de-inking sludge [22].
The volume of waste is no more than that created in mechanical pulping of roundwood (which produces bark and rejects) and much less than from chemical pulping (which produces bark rejects, spent liquor, sludges, and requires effluent treatment) [23]. But because of the heterogeneous composition of sludges from recycled pulp, and rejects such as staples and glue, disposal is difficult. Cleaner raw materials, processes and products are still needed.
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