The direct conversion of biorenewable alcohols into value‐added graphene and pure hydrogen (H2) at benign conditions is an important challenge, especially, considering the open carbon‐reduced cycle. In this study, it is demonstrated that inexpensive calcium oxide (CaO, from eggshells) can transform alcohols into bulky nanoporous graphene and pure hydrogen (≈99%) with robust selectivity at the temperature as low as 500 °C. Consequently, the growth of graphene can follow the direction of alcohol flow and uniformly penetrate into bulky nanoporous CaO platelets longer than 1 m without clogging. The experimental results and density functional theory calculations demonstrate that alcohol molecules can be catalytically carbonized on the surface of CaO at low temperature. The concept of the comprehensive utilization of biomass‐derived alcohols offers a carbon‐negative cycle for mitigating global warming and the energy demand. The cheaply available CaO can simultaneously transform renewable alcohols into pure hydrogen (≈99%) and high‐value graphene at a temperature as low as 500 °C. The concept on the comprehensive utilization of biomass with a carbon‐negative cycle offers a new way to mitigate global warming and the world's energy demands.