One-pot synthesis of digestate-derived biochar for carbon dioxide capture

[Display omitted] •AD digestate was converted into biochar-based sorbents of CO2 easily.•A one-step method of introducing N into biochar was studied.•Adding urea enhanced CO2 uptake ability of biochar.•AD digestate has potential application for carbon capture. Digestate from Anaerobic Digestion (AD) is a very common waste produced by European biogas plants and its current method of reuse is as a fertilizer or as soil amendment. This in turn however gives rise to some other environmental concerns which include greenhouse gas emissions and volatilization of ammonia causing ammonia pollution. Biochar is an environmentally friendly and low-cost product for CO2 capture and sequestration. Thus, we have provided one simple method to convert AD digestate into biochar-based sorbents of CO2. In addition, the nitrogen-functionalised porous carbon has been reported to be effective in improving the uptake of CO2. However, most of them were prepared using multiple steps. In this work, N-doped biochar was prepared by a one-step method of modifying AD digestate by urea. The results show that the addition of N can increase CO2 uptake significantly. Thus, the adsorbent modified by urea with a ratio of 1:1 results in the highest CO2 uptake capacity (1.22 mmol g−1), indicating digestate’s potential application for carbon capture and storage.