Genetically modified poplar produces more sustainable engineered wood

This is the claim of researchers at the University of Maryland (UMD), whose work was published online on August 12, 2024, in Matter.

Made from traditional wood, engineered wood is often seen as a renewable replacement for traditional building materials. It also has the potential to store carbon for a longer time than traditional wood because it resists deterioration, making it useful in efforts to reduce carbon emissions.

Despite these benefits, engineered wood requires processing with volatile chemicals, a significant amount of energy, and it produces considerable waste. The researchers edited one gene in live poplar trees, which then grew wood ready for engineering without processing. 

In a statement, Yiping Qi, a professor in the Department of Plant Science and Landscape Architecture at UMD and corresponding author, said: “We are very excited to demonstrate an innovative approach that combines genetic engineering and wood engineering, to sustainably sequester and store carbon in a resilient super wood form. Carbon sequestration is critical in our fight against climate change, and such engineered wood may find many uses in the future bioeconomy.”

Before wood can be treated to impart structural properties such as increased strength or UV resistance, it must be stripped of lignin.

Previously, UMD researchers developed methods for removing lignin using various chemicals, and others have explored the use of enzymes and microwave technology.

With this new research, Qi and his colleagues sought to develop a method that does not rely on chemicals, produce chemical wastes or rely on large amounts of energy.

Using base editing to knock out the 4CL1 gene, the researchers were able to grow poplars with 12.8 per cent lower lignin content than wild poplars. According to UMD, this is comparable to the chemical treatments used in processing engineered wood products.

Qi and his collaborators grew their knock-out trees with unmodified trees in a greenhouse for six months. They observed no difference in growth rates and no significant differences in structure between the modified and unmodified trees.

To test the viability of their genetically modified poplar, the team, led by Liangbing Hu, a professor of materials science and engineering, used it to produce small samples of high-strength compressed wood similar to particle board.

Compressed wood is made by soaking wood in water under a vacuum and then hot-pressing it until it is nearly a fifth of its original thickness. The process increases the density of the wood fibres.

In natural wood, lignin helps cells maintain their structure, and prevents them from being compressed. The lower lignin content of chemically treated or genetically modified wood allows the cells to compress to a higher density, increasing the strength of the final product.

To evaluate the performance of their genetically edited trees the team also produced compressed wood from the natural poplar, using untreated wood and wood that they treated with the traditional chemical process to reduce the lignin content.

They found that the compressed genetically modified poplar performed on a par with the chemically processed natural wood. Both were denser and more than 1.5 times stronger than compressed, untreated, natural wood.

The compressed genetically modified wood had a tensile strength comparable to aluminium alloy 6061 and the compressed wood that had been chemically treated.

UMD added that this work could lead to the production of building products in a relatively low-cost, environmentally sustainable way at a scale that can help mitigate against climate change.