The wood products industry is massively undercounting its impact on the climate, according to a new study published in Nature.
“For the most part, people treat wood harvests as though they’re not causing emissions,” said study co-author Timothy Searchinger, who splits his time between Princeton and the World Resources Institute. However, the study findings show that wood harvests exert “a really, really big carbon cost,” he said. “And we’re not paying attention to it.”
Through its production of paper, pulp, pellets and lumber, the industry releases at least 3.5 billion tons of carbon dioxide every year, according to the study. That is a large number in its own right: more than three times the annual emissions from aviation and nearly twice the carbon burned off by fossil fuel-dependent Russia.
It is particularly dramatic when compared to the carbon cost claimed by the wood products industry itself — which is often calculated to be less than zero.
On the surface, the idea that wood harvests release carbon dioxide is intuitive, Searchinger said. Wood is mostly made of carbon, and every aspect of the process of harvesting it, whether for pulp, housing or furniture, dumps carbon into the atmosphere.
The biggest portion of wood’s carbon emissions comes from simply burning it. About half of the volume of wood that enters saw, pellet and paper mills — like bark and small branches — is stripped off and burned up to power the factories.
Much of what remains is sold as firewood — to be burned in homes — or wood pellets, which largely go to power plants.
While this energy is renewable — trees grow back — it isn’t carbon-free, unlike potential replacements like solar or wind power, Searchinger noted.
The industry has operated under the assumption that wood harvests offer only benefits in the fight to slow climate change. It assumes any trees that are harvested to create wood products will be replaced by new trees that grow in their place, replacing the carbon that was lost in the products’ creation. “Harvested wood products … represent a common widespread and cost-efficient opportunity for negative emissions,” according to a 2018 study in Carbon Balance and Management.
And a study by the U.S. government agency charged with promoting timber products found “notable carbon emissions savings when wood products are used in constructing buildings in place of non-wood alternatives.”
Additionally, the wood industry argues that a freshly logged and rapidly regrowing plantation forest grows far faster — and therefore stores more carbon — than the more sedate carbon sequestration offered by an older one.