With the global population increasing, it can only be expected that the demand for housing and fuel will increase. As pressure on natural resources are on the rise, we urgently need more sustainable alternatives to protect and preserve our environment for future generations. One such alternative has recently been investigated in the form of using vine cuttings as an additive in the manufacturing of pine core particle board.
Why consider crop waste?
Global crop waste is estimated to be approximately 3.7 x 109 tonnes per year. The majority of it is used as mulch, or burned – contributing to greenhouse gas emissions. Any innovator would consider this scenario ample opportunity for upcycling, which is why valorisation of crop waste into higher value products is currently researched worldwide.
What crops are currently used to produce particle board?
Sorghum straws, kenaf stalks, flax shives, bagasse, canola straws, wheat straws and oat hulls are currently utilised in particle board production. However, these crops are also garnering attention as raw materials for biofuel production, urging manufacturers to seek alternative crops for particle board production.
Looking into wood alternatives
Grapevines need to be pruned annually. Researchers from the Department of Engineering at Melbourne University in Australia figured that the wood from grapevine-pruning cuttings has the potential to be added as an alternative to woodchips in the manufacture of wood-based composites, such as pine core particle board.
Has this been done before?
Particle board has been manufactured using 100% vine cuttings in previous research. Although it met the minimum required standards for particle board, the mechanical properties and durability needed more attention. Pine contains more cellulose than vine cuttings do. Cellulose contributes to structural integrity and less cellulose means less mechanical properties, which is why using 100% vine cuttings is not suitable.
Rising to the challenge
The team from Melbourne University considered producing a hybrid particle board using a combination of vine cuttings and pine. Particle board consists of three layers, two outer surface layers and a middle/core layer. They tested these two raw materials (pine and vine cuttings) in varying ratios for the core layer and concluded that 10% vine cuttings to 90% pine was the magic number to produce particle board that met all the required industry standards. Adding up to 25% vine cuttings worked, but to make up for the reduced strength, bigger grapevine particles needed to be used. Even though most standards were met with the larger percentage of grapevine cuttings, it didn’t tick all the boxes.
What makes vine cuttings the ideal additive?
A high lignin percentage and satisfactory pH and grit values of grapevine particles contribute to delivering a product with desirable qualities. In particle board manufacturing, the pH has to be within specific limits to ensure that the chemical-bonding processes can be adequately completed. If a crop with a high grit value is used, there is more wear and tear on the tools used during fabrication. Grapevine cuttings have a lower grit value than other crop alternatives. There was no significant difference in the lignin content of vine cuttings versus pine.
Furthermore, by adding a small fraction of finer grapevine particles, improved hot pressing is achieved in these hybrid boards. This means that its surface density and steeper vertical density is improved, compared to a 100% pine core board. Grapevine particles fill the gaps between the pine particles and hence improve the mechanical properties of hybrid boards.
Bringing it home
This research proved that grapevine cuttings can contribute to making the manufacturing of particle board more sustainable, while improving the final product. At the same time, greenhouse gas emissions from burning of crop waste is reduced and the forests get a bit of a breather.
South Africa is the seventh largest wine-producing country in the world. Add the table and raisin grape industries, then you have a substantial amount of vineyards producing vine cuttings. While some producers keep their vine cuttings for mulch, others remove it from the vineyards to decrease the risk of grapevine trunk disease spread. Does everyone have a purpose for these cuttings?
In a country where more affordable housing and construction solutions will surely benefit the growing population, could there be a partnership between construction and agricultural industries to introduce more innovative, affordable and sustainable alternatives? As they say, one man’s trash is another man’s treasure.
Wong, Marcus C., Hendrikse, Simone I.S., Sherrell, Peter C. & Ellis, Amanda V., 2020. Grapevine waste in sustainable hybrid particleboard production. Waste Management 118: 501 – 509.
– For more information, contact Lucinda Heyns at email@example.com.