Each year, the paper and pulp industry produces millions of tonnes of sludge in the production of paper. This sludge is typically disposed of in landfill sites or incinerated. Both disposal methods are costly and environmentally undesirable. However, some firms are now transforming undesirable by-products into commercially viable consumer and industrial products. One such firm is Kadant Grantek Inc., based in Wisconsin, USA. Kadant Grantek processes paper mill sludge from local paper mills to make several cellulose-based products.
The sludge is dried and granulated to make an agricultural seed carrier called Biodac, an industrial absorbent called Gran-sorb and a premium cat litter product. The process is clean, releasing only steam into the atmosphere. No waste or further by-products are produced. Kadant Grantek collects the paper mill sludge free of charge from the paper mills. The paper mills in turn do not incur landfill or incineration costs and can portray a greener image. A win–win situation for both parties.
Questions:
1 Assuming paper mills decide to sell their sludge for a small fee, how might they account for the revenue generated?
2 Can you think of any other ‘waste’by-products that are re-used rather than disposed of?