November 11, 2019

Circular economy can bring major cost savings to the water and energy-intensive forest industry

The pulp and paper industry is very energy-intensive and consumes high volumes of water. The industry would therefore gain considerable benefits from more efficient water and energy solutions. Companies operating in the industry can achieve significant cost savings using various circular economy solutions.

Pulp and paper industry processes traditionally consume high volumes of energy and water. A comprehensive and objective examination of the industry’s production processes would enable major savings through circular economy solutions. Such solutions include water recycling, heat recovery and reuse, and the utilisation of previously unused production sidestreams and raw material.

Closed cycles bring savings

“In terms of savings, the best result is often achieved with a combination of water and energy solutions. With today’s technology, industrial process water can even be purified into drinking water, and at the same time, chemicals, for instance, can be recovered from the water and reused. Similarly, heat can be recovered from wastewater,” explains Adven’s Recovery Engineer, Elina Isokangas, who holds a PhD in environmental engineering.

The pulp and paper industry’s traditional water solutions often involve considerable use of chemicals and produce high volumes of sludge, and the water purification criteria are not always met. Water purification can, however, be developed: the water cycle can be closed using a semi-permeable membrane and evaporation methods, which allows the same water to be cost-effectively reused again and again. In practice, cost savings arise thanks to the reduced need for water and chemicals, and the lower volume of sludge that is produced.

“A current example of the integration of energy and water solutions is the use of hydrothermal carbonisation (HTC) technology to produce carbon from the biosludge generated during water treatment: the carbon can then be used as a fuel in energy production. In addition, renewable energy can be obtained from the biogas produced from wastewater,” says Isokangas.

Often room for improvement in energy production and raw material processing

The energy-production and raw-material-processing tools used by the pulp and paper industry are often aged, and investing in them comes at a high cost. For that reason, major improvements can be achieved by developing energy production and raw material processing. For example, debarking trees when they are dry instead of wet can directly improve the quality of the water generated by the mill.

“Although the chemicals from the pulp industry’s core processes are already being recycled from the recovery boiler, the cycle’s energy efficiency can be improved, for example, by renewing the black liquor evaporation process. Using an evaporation system that is based on a closed-loop heat cycle, raw material can be recovered and reused with greater efficiency than before,” Isokangas points out.

Pulp production is largely self-sufficient for its energy, but combined with paper production, there may be energy shortages. This is when energy-efficiency projects begin to pay off. Waste heat, for example, can be recovered and recycled, which brings major cost savings and reduces the need for energy. On the other hand, climate change and political controls may result in a situation where it will be profitable in the future to also invest in energy efficiency projects for pulp production plants and to also produce, e.g. district heating.

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