**Abstract**

The circular economy is considered as an alternative model to the unsustainable linear "take–make–waste" approach that characterizes contemporary economic systems. It aims to achieve sustainable development by promoting the responsible and cyclical use of resources to maintain their value in the economy and minimize pressures on the environment. Biochar systems offer opportunities for operationalizing the CE model. They are multifunctional systems that can be used for bioenergy and biochar production using an extensive range of biomass feedstocks, including biowaste. They can contribute to climate change mitigation, as producing biochar and mixing it with soil is a means for sequestering atmospheric CO2. Moreover, the produced biochar has a wide range of applications, including its use for agricultural soil amendment, wastewater treatment, manufacturing of cement, and remediation of contaminated soils. This versatility of biochar systems creates great opportunities for developing circular models of waste management that can valorize different waste streams. This chapter provides an overview of the CE concept and describes biochar systems, focusing on systems for the synergistic valorization of wood waste and contaminated soils. It also discusses the role of these systems in the CE indicating that they can contribute to the transition toward the CE.

**Keywords:** circular economy, sustainable development, biochar systems, wood waste, contaminated soil
