Timber Biogenic Carbon Stock in the Urban Environment: Santiago City as a Second Forest

Urban environments significantly contribute to carbon emissions, both through operational processes and the embodied emissions of construction materials, thus exacerbating climate change. Nevertheless, urban timber structures offer a viable alternative by acting as carbon sinks, capable of sequestering carbon for decades or even centuries. This study develops and applies a methodology to quantify the biogenic carbon stored in Santiago City's timber-based buildings, conceptualized as a "Second Forest" that transfers and preserves the carbon capture capacity of trees in the built environment. The analysis estimates that Santiago's urban timber constructions have expanded their wood-built surface area by 192,831 m2 over the past eight years, reflecting the growing adoption of timber in urban construction. During the same period, biogenic carbon storage increased from 199.78 kt to 202.73 kt, equivalent to 10.84 kt of CO2 under average conditions. These findings highlight the potential of urban planning strategies, such as promoting taller timber buildings and adopting circular timber practices, to enhance carbon sequestration and reduce reliance on carbon-intensive materials. This research highlights the fundamental role that timber buildings play in urban climate change mitigation, positioning them as active contributors to global carbon management efforts.