A recent study has found that using wood for construction instead of concrete and steel can reduce emissions. But Tim Searchinger at Princeton University says many of these studies are based on the false foundation that harvesting wood is carbon neutral (碳中和). "Only a small percentage of the wood gets into a timber (木料) product, and a part of that gets into a timber product that can replace concrete and steel in a building," he says. Efficiencies vary in different countries, but large amounts of a harvested tree are left to be divided into parts, used in short-lived products like paper or burned for energy, all of which generate emissions.
In a report for the World Resources Institute, Searchinger and his colleagues have modelled how using more wood for construction would affect emissions between 2010 and 2050, accounting for the emissions from harvesting the wood. They considered various types of forests and parts of wood going towards construction. They also factored in the emissions savings from replacing concrete and steel.
Under some circumstances, the researchers found significant emissions reductions. But each case required what they considered an unrealistically high portion of the wood going towards construction, as well as rapid growth only seen in warmer places, like Brazil. In general, they found a large increase in global demand for wood would probably lead to rising emissions for decades. Accounting for emissions in this way, the researchers reported in a related paper that increasing forest harvests between 2010 and 2050 would add emissions equal to roughly 10 percent of total annual emissions.
Ali Amiri at Aalto University in Finland says the report's conclusions about emissions from rising demand are probably correct, but the story is different for wood we already harvest. "Boosting the efficiency of current harvests and using more wood for longer lived purposes than paper would cut emissions," he says. "We cannot just say we should stop using wood."
