Biochar Development in the Urban Environment: A Case Study of Sludge Char Production in Finland

Biochar, as one of the most prominent carbon drawdown technologies to emerge over the past few years, is intensely researched and tested. By no means a new creation, biochar has a rich history as a soil amendment in agriculture across the globe. However, the interest it raises now focuses more on its carbon sequestration potential and beneficial applications in the urban environment. This chapter offers an overview of the material, a literature review of its physical and chemical properties, production technologies, and uses in the urban context. It concentrates on biochar as a component in manufactured soils, water filtering systems, contaminated soil remediation methods, and construction material additives. Additionally, it investigates sewage sludge as an innovative feedstock for biochar production. Sewage sludge disposal is both environmentally and economically costly for wastewater treatment facilities, and biochar represents a viable way of upcycling. A case study of the largest sludge char pilot plant in Europe (in Finland) has been included, providing insights into its technical developments and operations.