Zero carbon describes a process that has no greenhouse gas emissions. It differs from net zero carbon in that net zero allows for greenhouse gas emissions but requires that these emissions be offset. Zero carbon emits no greenhouse gas emissions, so there is no need for offsets.
Zero carbon is commonly used in the electricity industry to describe types of electric supply that have no carbon emissions once constructed (it should be noted that during the manufacturing and construction phase there are still emissions). These include wind, solar, hydropower, geothermal, fuel cells or gas plants powered with green hydrogen, and nuclear. In the transport and building sectors, vehicles or buildings powered with green hydrogen or zero carbon electricity sources would also be considered zero carbon.