Carbon Dioxide Removal (CDR) is a mitigation activity that captures carbon dioxide from the atmosphere and stores it in reservoirs or products, and proof of storage is given through carbon accounting methodologies embodied in standards. We review nature- and engineering-based terrestrial CDR activities, certifications and standards and explore their expected durations. Using a mapping exercise, we find a complex ecosystem with 23 standard developing organizations certifying carbon removal from 15 different terrestrial CDR activities resulting in the availability of 17 different certification instruments. More standards exist for nature-based compared to engineering-based activities. The process revealed ambiguity on what constitutes CDR and highlights potential reforms to CDR certification. Furthermore, we conducted a literature review of the expected storage durations, risks, and process times for mineral and geologic formations, long-lived products, soil carbon, and above & belowground biomass carbon reservoir types (13 terrestrial CDR activities). We find variations in the expected storage durations that span multiple orders of magnitude between reservoir types and within estimates for the same reservoir type. We discuss the implications of the scaling of terrestrial CDR, of different durations, in relation to the Exponential Roadmap for Natural Climate Solutions and perspectives for future terrestrial carbon storage.