CRISPR-edited poplar trees (left) and unedited poplars (right)
Chenmin Yang
Using CRISPR to genetically edit trees could dramatically cut the energy footprint of the paper industry.
Making paper is both energy and water intensive, says Jack Wang at North Carolina State University. In 2021, the industry’s global carbon footprint was estimated to be 190 million tonnes – a figure that is expected to rise until 2030, when paper production is projected to peak.
One of the biggest energy drains in the paper-making process is the removal of the polymer lignin from wood, says Wang. Within wood’s structure, lignin is linked with cellulose, the molecule that makes up paper. Separating the two requires high temperature and pressure, as well as a lot of water, says Wang. But lignin also “contributes to the structure, integrity and resilience of trees”, says Rodolphe Barrangou also at North Carolina State University.
Wang, Barrangou and their colleagues wondered if they could genetically edit poplar trees, which are widely used to make paper, to have a lower concentration of lignin while maintaining their structure.
To do this, they used machine learning to analyse the genome of the poplar tree and highlight combinations of genes they could edit using CRISPR, with the program identifying 69,123 ways to edit 21 genes.
The researchers analysed this data to determine which combinations had the best chance of reducing a tree’s lignin content while ensuring it remained strong, finding that just 0.5 per cent of these editing methods fit the bill. They chose seven that they deemed to be particularly robust, from which they grew 174 different variants of CRISPR-edited poplar trees.
After six months of growth, the team found that the lignin content in the edited trees was up to 49 per cent lower than in the unedited trees.
“At a time when climate change is so important, coming up with tangible, potential real-world solutions to substantially reduce the carbon emissions of pulp and paper production is very exciting,” says Wang.
The trees have been growing for about a year and show no major adverse effects to their structure, says Barrangou. The researchers plan to plant several of them in a forest to study the long-term effects of genetic editing and are exploring the technique for other tree types that are used to make paper.
“This could be the start of a whole new era of sustainable forestry,” says Barrangou. Wang says he hopes these trees may be in large-scale commercial use by the 2040s.
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