By Ian Palmer, PhD, former BP petroleum engineer Special to The Digest Fossil fuel causes 73% of global greenhouse gas emissions (GHG). Carbon capture and storage (CCS) is an escape hatch, or an offset, to be used if there are “leftover” GHG emissions. If a country is on a pathway to reduce GHG to zero by a certain date, but leftover GHG are still being emitted at that date, an amount equal to the GHG leftover can be buried using CCS. The concept is called “net-zero”. What is carbon capture and storage? Carbon capture and storage means collecting GHG (usually CO2, the dominant component) and burying it deep underground. “Bury” means to inject CO2 down a well where it’s contained by a non-leaking rock layer, and eventually merges chemically with the rock. The rock layer can be a depleted oilfield or a saline aquifer.