Emission reductions generally relate to projects that reduce carbon emissions by taking a specified action compared to a reference scenario, whereas greenhouse gas removals take greenhouse gases from the atmosphere and permanently sequester them.
This area has been beset with controversy since there are a wide variety of schemes, largely unregulated which vary in quality and some of them have very questionable greenhouse gas benefits. There are several verification and certification schemes which attempt to address this. Carbon offsets can be used to achieve the standard PAS 2060 - Carbon Neutrality. To achieve net-zero, any remaining emissions should be balanced with an appropriate amount of carbon removals using certified greenhouse gas removals. Possible greenhouse gas removal options include largescale afforestation and bioenergy with carbon capture and storage.