This study quantifies the global potential of waste biomass for bioenergy with carbon capture and storage (BECCS) and its carbon dioxide removal (CDR) capacity through anaerobic digestion. Waste biomass, including livestock manure, crop residues, organic municipal solid waste, and wastewater, is a sustainable resource that does not negatively impact land, water, or biodiversity. The study finds that up to 1.5 Gt CO₂ per year, or 3% of global greenhouse gas emissions, can be captured and stored globally through BECCS. Anaerobic digestion of waste biomass can produce up to 10,700 TWh of bioenergy annually, equivalent to 10% of global final energy consumption and 27% of global natural gas supply. The study also highlights that waste biomass can contribute to negative emissions without requiring extensive biomass plantations. The study assesses the technical potential of four waste biomass sources at a 10 km resolution, considering their availability, biogas yields, and carbon dioxide content. It finds that crop residues are the most significant contributor to biogenic CDR, followed by organic municipal solid waste and livestock manure. The study also evaluates the potential of biomethane produced from waste biomass to meet final energy consumption and replace fossil natural gas. It finds that biomethane can offset up to 27% of global natural gas supply and significantly reduce emissions in countries like China, India, and Indonesia. The study also performs a techno-economic analysis of biomethane production, finding that the global average production cost is 66 MWh⁻¹, with lower costs in Eurasia and North America. The study highlights the importance of considering social, economic, and political factors in the deployment of BECCS and the need for institutional support to account for negative emissions. The study concludes that waste biomass can play a crucial role in achieving net-zero emissions by providing a sustainable source of bioenergy and CDR, while also contributing to a circular economy and reducing environmental impacts.This study quantifies the global potential of waste biomass for bioenergy with carbon capture and storage (BECCS) and its carbon dioxide removal (CDR) capacity through anaerobic digestion. Waste biomass, including livestock manure, crop residues, organic municipal solid waste, and wastewater, is a sustainable resource that does not negatively impact land, water, or biodiversity. The study finds that up to 1.5 Gt CO₂ per year, or 3% of global greenhouse gas emissions, can be captured and stored globally through BECCS. Anaerobic digestion of waste biomass can produce up to 10,700 TWh of bioenergy annually, equivalent to 10% of global final energy consumption and 27% of global natural gas supply. The study also highlights that waste biomass can contribute to negative emissions without requiring extensive biomass plantations. The study assesses the technical potential of four waste biomass sources at a 10 km resolution, considering their availability, biogas yields, and carbon dioxide content. It finds that crop residues are the most significant contributor to biogenic CDR, followed by organic municipal solid waste and livestock manure. The study also evaluates the potential of biomethane produced from waste biomass to meet final energy consumption and replace fossil natural gas. It finds that biomethane can offset up to 27% of global natural gas supply and significantly reduce emissions in countries like China, India, and Indonesia. The study also performs a techno-economic analysis of biomethane production, finding that the global average production cost is 66 MWh⁻¹, with lower costs in Eurasia and North America. The study highlights the importance of considering social, economic, and political factors in the deployment of BECCS and the need for institutional support to account for negative emissions. The study concludes that waste biomass can play a crucial role in achieving net-zero emissions by providing a sustainable source of bioenergy and CDR, while also contributing to a circular economy and reducing environmental impacts.