Biochar is currently one of the dominant topics in soil research, despite the fact that it is not a new discovery. It has the potential to address some of the most pressing questions humanity is currently facing, that is climate change, food security, energy security and environmental pollution. However, a soil system is very complex and together with the multitude of biochar production settings and nearly infinite number of potential feedstock resources it becomes evident that there is no single solution for these challenges available. This is specifically an issue when addressing the potential of biochar for climate change mitigation via reduction of greenhouse gases (GHG). Systems approaches are needed, covering the entire supply chain and backed up with life cycle assessments to ensure a positive impact by using biochar as a tool for environmental management.

This chapter provides a summary and brief introduction of the subsequent chapters of this book, with a focus on biochar for climate change mitigation, including an economic assessment of GHG abatement costs. The FOREBIOM project will be briefly introduced and results on biochar erosion after amendment of a forest floor are presented.

Biochar as a boon for soil fertility in the tropics still has to show that it is able to provide the same benefits to soils in temperate regions. Here an Austrian study with the objective to analyze the extent of benefits that biochar application offers to agricultural soils in Europe beyond its role as a carbon sequestration strategy is presented. Based on hypothesis testing, several potential benefits of biochar were examined in a series of lab analyses, greenhouse and field experiments. Three hypotheses could be confirmed: biochar can protect groundwater by reducing the nitrate migration in seepage water; biochar can mitigate atmospheric greenhouse gas accumulation by reducing soil N2O emissions; and biochar can improve soil physical properties by increasing water storage capacity. One hypothesis was only partly confirmed: biochar supports the thriving of soil microorganisms only in specific soil and climate settings. Two hypotheses were refuted: biochar does not generally provide nutrients to plants except when produced from specific feedstocks or by combining it with mineral or organic fertilizers; the cost-effectiveness of biochar application is not given under current production costs if the existing benefits of biochar are not transferable to financial value.