Headline: Can Use of Wood in Future Infrastructure Development Reduce Emissions of CO2? Expertise für das WBGU-Sondergutachten „Entwicklung und Gerechtigkeit durch Transformation: Die vier großen I“

The anticipated growth of urban population will require immense development of housing and other accompanying infrastructures. Production of currently widespread construction materials such as steel, cement, and aluminum is associated with high demands of energy as well as emissions of greenhouse gases (GHG). If the global population to increase to 9.3 billion and the developing countries are to build infrastructures similar to the ones in developed countries, then 350 Gt of carbon dioxide (CO2) will be emitted only from the production of construction materials needed to develop these infrastructures . Using wood materials in construction can reduce net CO2 emissions in several ways: less energy is needed to manufacture wood products compared with alternative materials; non -energy process emissions associated with the alternative materials can be avoided (e.g., CO2 emissions in the calcination reaction used in production of cement); carbon is stored in the wood infrastructures for a long time; and the byproducts of the wood material production can be used as biofuel to replace fossil fuels. In this study, I estimate to what degree CO2 emissions from material production can be reduced, if wood is used to build infrastructures in the future. To calculate how much wood would be needed instead of steel, cement, and aluminum, I first assume the share of steel, cement, and aluminum for building housing out of the total material stock used for infrastructure development. Then, I estimate the wood mass required to replace these infrastructures. Finally, I calculate CO2 emissions from manufacturing the wood materials needed for construction and compare them to the respective CO2 amount emitted from production of steel, cement, and aluminum. This study suggests that the use of natural materials, especially wood, can substantially reduce emissions of GHG associated with future manufacturing of construction materials required to accommodate needs of the growing world’s population. Wooden buildings can also serve as sizable carbon storage with a long carbon residence time. However a substantial share of the world’s forests would have to be harvested to meet the potential demand for wooden construction materials. It remains to be seen if it is possible on a sustainable basis. It is also questionable if full transition from steel and concrete construction materials to alternative materials is possible. New construction materials based on wood as well as other natural products like clay or biochar have to be explored in order to mitigate emissions of CO2 and global warming.