Research into Recycling

Paper recycling is the process of recovering waste paper and remaking it into new paper products. It has become a recognised component of the pulp and paper sector, with a growing world trend towards recycling. In 1970, 23% of the total paper manufactured in the world was made from recovered paper. Today the figure is around 50%. In South Africa, of the 2.3 million tons of paper consumed annually, approximately 1.8 million tons is suitable for recovery, of which just over 58% is recovered. According to the Paper Recycling Association of South Africa (PRASA), for every ton of waste paper that is diverted from landfill and recycled, 3m³ of landfill space and 17 trees are saved. Recycling of recovered paper requires 40% less energy to manufacture new paper products, and reduces air emissions by as much as 70%. Paper recycling also leads to job creation and reduced collection and landfill costs for local municipalities.

The social and environmental benefits of paper recycling are thus evident and research into the recycling of recovered paper has been identified by the CSIR as a high priority in South Africa. Despite the many advantages of recycling paper, the use of recovered paper poses many challenges for the paper recycling industry. This is because recycled fibre processing systems are significantly more complex than systems for virgin fibres, owing to the various fibre types and significant proportion of contaminants found in recovered paper. However, similar to virgin fibres, recycled fibre must meet defined quality criteria in terms of fibre quality and cleanliness. Since its inception in 2007, the ffp ’s Paper Recycling section has been involved in various projects indentified by industry, such as:

Process solutions for specialised grades
A considerable amount of specialised paper grades such as wet strength, tetrapak, sack-kraft and polylined grades are either being landfilled or exported due to the lack of technologies to process these grades in South Africa. Successful implementation of technologies to process these grades will increase the amount of fibres available to the recycling sector in South Africa to meet rising demands. This will also have important implications for the country from an environmental point of view (reduction of landfill space, reduction in CO² and SO² emissions, etc.).

Methods for measurement and removal of stickies
Contaminants from adhesives and waxes remain one of the biggest concerns of papermakers involved in recycling. These contaminants are called “stickies” by papermakers because they stick to the paper machine felts and wires, leading to operating problems, reduced productivity, and defects such as holes and dark spots in the paper. Although there are no official figures available in South Africa, it has been estimated that stickies related problems are costing the United States paper industry alone several hundred million US dollars per year. Quick, accurate and reliable methods for routine monitoring of stickies, and procedures for efficient removal of stickies from the pulp needs improvement. Development of simple, quick and reliable methods for measurement of total stickies concentration would enable mill personnel to monitor the quality of their pulp and process waters on a regular basis and allow for a proactive approach to dealing with potential stickies outbreaks, optimise efficiency of the various unit operations such as re-pulping, screening, cleaning, washing, and optimise process conditions in terms of additive dosages, pH, temperature etc., to remove/control the level of stickies throughout the process and in the final product.


			Measurement dyed macrostickies in pulp handsheets


			Microstickies concentration measured on pulp samples taken at various stages in a newsprint mill recycling old newspapers and sorted books and magazines. Microstickies were measured using a modified method developed by the CSIR () and the results were compared to turbidity measurements of the filtrates ()

Flotation de-inking chemistry and technology
Flotation de-inking is a selective separation process in which hydrophobic ink particles are removed from a wastepaper suspension by adhesion to air bubbles which then rise to the surface to form a foam layer. It is an active area of research, and current efforts are directed at finding combinations of economical operating conditions and chemistries that improve the efficiency of ink removal from the fiber and allows for a wide range in paper product qualities. Development of predictive feed-forward control models are underway which would enable mill personnel to adapt to changing waste conditions in a proactive manner. Better process control and final product quality would provide economic benefits to South African producers as they seek to compete in a globally, very competitive industry.

RECYCLING EQUIPMENT:

			Low Consistency (LC) Repulper	Top view: LC Repulper

			High Consistency (HC) Repulper	Top view of HC Repulper

			Flotation Deinking	Example of Flotation Experiment

Publications in recycling area:

Pauck, W. J., Venditti, R. A., Pocock, J. and Andrew, J.E. (2012). Using Statistical Experimental Design Techniques to Determine the Most Effective Variables for the Control of the Flotation Deinking of Mixed Recycled Paper Grades. Tappsa J. 2: 28-41

Andrew, J., Hanuman, A. and Sithole, B. (2011). Measurement of stickies (macro, micro and potential secondary stickies. Tappsa J. 1: 10-12.

Andrew, J., Hanuman, A. and Sithole, B. (2011). Stickies monitoring at a newsprint and packaging mill. Tappsa J. 4: 16-25.

Andrew, J. and Hanuman, A. (2010). Measurement of total stickies. Tappsa National Conference and Exhibition, 19-20 October, Durban, South Africa.