A pioneering solution has been developed to convert cellulose fibre-rich waste from pulp and paper mill operations into ethanol using a specialised fermentation process.

The solution was announced by the Paper Manufacturers Association of South Africa (Pamsa), in collaboration with Stellenbosch University (SU), Sappi Southern Africa and Mpact.

A demonstration plant, co-funded by the Department of Science and Innovation (DSI) and Pamsa, was shown to government officials, media and industry partners at the Sappi Tugela mill in Mandini, KwaZulu-Natal on April 24.

Paper sludge was a solid waste with a high moisture content. It came from the production of paper using virgin wood fibre and/or recycled paper and collected from the paper mill wastewater treatment systems, Pamsa explained in a statement.

“This technology started as a research project and thesis by one of our master’s in engineering students and, today, we have a South African first. Bioethanol comes with many environmental credentials and further contributes to the circularity of the pulp and paper sector,” said Pamsa executive director Jane Molony.

The research by SU has shown that paper sludge, as well as food and textile waste, does not require pretreatment before hydrolysis-fermentation.

This solution would help to reduce the amount of waste disposed to landfill and the associated greenhouse-gas emissions and improve water reclamation for reuse, further contributing to the circular economic and industrial decarbonisation, Pamsa highlighted.

It posited that the solution held considerable economic promise, as waste-derived bioethanol attracted premium prices in global markets, and added that the project had the potential to generate sustainable employment and upskilling opportunities and stimulate regional economic development.

The plant aims to demonstrate the commercial readiness of the fermentation technology under industrial conditions.

“This is a culmination of ten years of research by our Bioresource Engineering group at the Department of Chemical Engineering where we have explored various beneficiation routes to create applications for this by-product of pulp, paper making and recycling processes,” says SU project lead Professor Eugene van Rensburg, adding that the same fermentation process can be used to address food waste and clothing or textile waste.

“It was important to validate this technology, which can only be achieved through technology demonstration under real industrial conditions,” explains Professor Johann Görgens, also from the Chemical Engineering Department at SU and the main driver behind this initiative.

Given that the process had only been tested and proven under laboratory conditions, the Stellenbosch team designed and built a containerised demonstration plant housing a 1 000 ℓ bioreactor and key utilities with the specific aim of fermenting about 100 kg paper sludge daily to ethanol, Pamsa pointed out.

The current demonstration plant has been deployed for a nine-month period at Sappi’s Tugela mill in northern KwaZulu-Natal with a follow-up project planned at Mpact’s mill in Springs, Gauteng.