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