Co-pyrolysis of tofu with cellulose, lignin or peach wood: Importance of sugary intermediates in fixing tofu-derived nitrogen species on surface of biochar

N-functionalized biochar has versatile applications, and co-pyrolysis of nitrogen-rich food wastes such as tofu and biomass is a method for production of N-containing biochar (BC). Herein, co-pyrolysis of tofu and cellulose, lignin, or peach wood (PW) was conducted at 400 °C, aiming to probe capability of different components of biomass for retaining tofu-derived nitrogen species in biochar through potential cross-reactions. The results showed that cross-interactions among volatiles or biochar from different sources during the co-pyrolysis did exist, which produced more gases, especially CO 2 from cracking of tofu-derived amino acids. This also enhanced deoxygenation in co-pyrolysis of tofu/cellulose and tofu/peach, producing oxygen-deficient biochar with enhanced aromatic degree and thermal stability. The co-pyrolysis of tofu and cellulose enhanced the retention of N species in the resulting biochar-tofu/cellulose (nitrogen content: 7.1 % versus 4.5 % of calculated value), and similar result was observed in co-pyrolysis of tofu and peach (nitrogen content: 6.2 % versus 4.5 %). The sugary intermediates from degradation of cellulose/peach reacted with tofu-derived nitrogen-containing organics via Maillard reaction to fix nitrogen on/in biochar. In-situ IR measurement confirmed consumption of carbonyl containing intermediates with simultaneous formation of C-N species in the co-pyrolysis. The nitrogen species also acted as “glue” in the co-pyrolysis for binding biochar particles to form cluster morphology and acted as anchoring sites for enhancing adsorption of alkaline fuchsin.