Dear Colleagues,All types of biomass, and their waste, comprised one the pillars of the preindustrial,pre-fossil fuel, agriculture-based economies of the past. Traditionalpractices of biomass waste management were applied, but not necessarily in asophisticated and efficient way, and included everything from agricultural activitiesto food production, animal feed, natural fiber separation, and processingof forest wood. The modern bioeconomy sector, however, includes new circulareconomy energy and materials streams of added-value products, such asgaseous, liquid and solid biofuels and bioenergy generation routes, and biocharproduction, along with all the previously mentioned traditional products emergingfrom the bioeconomy.This Special Issue includes some of the latest bioenergy and biochar advancementsand their incorporation into a bioeconomy in transition. It focuses onnature, properties, upgrading, and bioenergy generation processes from all typesof biomass waste and biochars originating from biomass waste. The multidisciplinarityof bioenergy and biochar research is evident throughout the SpecialIssue, highlighting the highly variable and tunable processes involved inbiomass handling, pre-processing, converting to biochar, and recovering energy.Dr. Dimitrios KalderisGuest EditorDr. Vasiliki Skoulouco-Guest Editor