- showed that this composite material has the necessary physical, chemical and mechanical properties to render it suitable for producing thermal and acoustic insulation boards for use in RDP and other houses.
- Australian acacia species are among the top 10 worst aliens in South Africa. These trees invade catchments, reduce water runoff, increase the severity of veld fires, and threaten indigenous species.
A new composite material made from invasive Port Jackson trees and recycled low-grade plastic waste could help solve South Africa’s social housing crisis, and some of its environmental problems.
It was developed by Dr Abubakar Sadiq Mohammed, whose recent doctoral studies showed that a combination of these two types of waste may be used to build better low-cost houses.
In December last year, Dr Mohammed, originally from Ghana, received his PhD in wood product science from Stellenbosch University’s (SU’s) Faculty of AgriSciences.
He developed a wood-plastic composite using a mix of biomass from all parts of a Port Jackson tree (Acacia saligna) and recycled, low-density polyethylene. This light polymer is primarily used in packaging such as plastic bags.
Dr Mohammed showed that this composite material has the necessary physical, chemical and mechanical properties to render it suitable for producing thermal and acoustic insulation boards for use in RDP and other houses.
Wood-plastic composites are generally made from recycled plastic and small wood particles or fibres. Typically, manufacturers separate the woody parts of the chosen plants used from the non-woody parts (such as bark, leaves and seeds). Until now, the non-woody parts of alien invasive trees were considered contaminants rather than suitable components from which to produce composite materials.
Dr Mohammed included every part of the Port Jackson tree — from bark to leaves — in his composite mix. The plant material was salvaged from alien invasive clearing operations in the Western Cape. The trees were used in their entirety as received, without any pre-processing.
Having studied industrial art and wood science in Ghana before enrolling for his PhD, his choice of dissertation topic grew from his concern over the amount of waste generated in agricultural processes and the scale of plastic pollution in the environment.
“Plastic waste is a known global menace, so the idea was to transform this waste material into something useful,” he says. “I was also interested in developing affordable, eco-friendly alternatives to existing low-cost building materials.”
His supervisor was Prof Martina Meincken of SU’s Department of Forestry and Wood Science.
Dr Mohammed’s study is part of a bigger project in the department that investigates ways of using alien invasive wood species, including in the building sector.
