One kilogram of hemp fibre sequesters 2.1 kg of CO₂, and one cubic metre of hempcrete represents 251.67 kg of CO₂-equivalent stored. A timber-frame house built with hempcrete — including transport, construction and manufacturing — comes out at a net negative 35.5 kg of CO₂-eq per m³ (Jami & Kumar, 2017).
Building materials thereby flip from emission source to carbon store: every wall built captures more carbon than its construction released.