Robust quantification of carbon dioxide removals (CDR) lies at the heart of any certification mechanism and is central for their functionality and environmental integrity. For the establishment of a Carbon Removal Certification Framework (CRCF) that was recently adopted, the EU Commission is currently conducting an inventory of the existing knowledge base. The objective of most certification mechanisms is to turn greenhouse gas emission reductions or removals into tradable commodities. To achieve this, each certificate issued by a mechanism must reliably represent the same amount of greenhouse gas reduced or removed from the atmosphere. The report compares selected standards to work out advantages and disadvantages of existing monitoring methods for an EU certification of carbon removals.