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. Ethanol is a versatile starting material that finds diverse application in the production of industrial chemicals, bio-based plastics and sustainable aviation fuel.
The solution was announced in April by the Paper Manufacturers Association of SA (PAMSA), in collaboration with Stellenbosch University (SU), Sappi Southern Africa and Mpact at the demonstration plant, co-funded by the Department of Science and Innovation (DSI) and PAMSA, at Sappi Tugela mill in Mandini, KZN.
Credentials
Paper sludge is a solid waste with a high moisture content. It comes from the production of paper using virgin wood fibre and/or recycled paper and collected from the paper mill wastewater treatment systems.
“This technology started as a research project and thesis by one of our Masters in Engineering students and now we have a South African first. Bioethanol comes with many environmental credentials and further contributes to the circularity of the pulp and paper sector,” explains Jane Molony, PAMSA executive director.
Fermentation process
Driven by the vast potential of this feedstock, the research by SU has shown that paper sludge, as well as food and textile waste, does not require pre-treatment before hydrolysis-fermentation. The plant aims to demonstrate the commercial readiness of the fermentation technology under industrial conditions.
“This is a culmination of 10 years of research by our Bioresource Engineering group at the Department of Chemical Engineering where we have explored various beneficiation routes to create application for this by-product of pulp, paper making and recycling processes,” says Prof. Eugene van Rensburg, project lead at SU, adding that the same fermentation process can be used to address food waste and clothing/textile waste.
Demonstration plant
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-litre bioreactor and key utilities with the specific aim of fermenting approximately 100kg paper sludge per day to ethanol.
The current demonstration plant has been deployed for a nine-month period at Sappi’s Tugela mill in northern KZN with a follow-up project planned at Mpact’s mill in Springs, Gauteng.
Waste into worth
“Turning waste into worth is key for our sector as it aligns with the principles of a circular economy,” says Neil Hunt, group risk and sustainability manager at Mpact, which recycles around 500 000 tonnes of recovered paper and plastic packaging.”
There is global recognition in local and international markets for the environmental benefits of waste-derived bioethanol due to attractive greenhouse gas (GHG) reduction credits from the avoided emissions through diversion from landfilling, as well as the benefits from fossil-fuel replacement.
