Study On The Performance Of HNO₃-treated Biochar For Enhanced Medium Temperature Anaerobic Digestion Of Kitchen Waste

With garbage classification development,kitchen waste treatment will be one of the significant environmental problems that our country is trying to solve.Due to the mature technical characteristics and high product added value of anaerobic digestion(AD)technology,the AD-based kitchen waste treatment process has been gradually formed in China.However,problems such as ammonia and acid inhibition often occur during AD of food waste.Currently,biochar has drawn much attention because of its ability to improve methane production as well as system stability at low cost.Studies have shown that the redox functional groups on the biochar surface play a key role in the reaction.In this paper,the impact of HNO3-treated biochar on methane production from AD of food waste was investigated.The effects of F/S,HNO3 modification time and biochar addition on methane production were investigated in turn.The influence of biochar addition on acidification and degradation of volatile fatty acids of food waste were further investigated.Finally,a possible pathway for HNO3-treated biochar to promote interspecies electron transfer was proposed in combination with the characterization results of physical and chemical properties of biochar,and the main conclusions were obtained as follows:(1)As the modification time of nitric acid increased,the p H of the biochar decreased,the conductivity dropped sharply,the O/C(molar ratio)increased and C-O,C=O,and COOH contents raised,and its surface redox activity improved.(2)The effect of F/S on methane production was "low promotion and high suppression." When F/S=1,the system had high methane production potential and kitchen waste disposal capacity.(3)The addition of 10 g/L HNO3-treated biochar(treated for 6 hours)increased the biogas and cumulative methane output by 30.11% and 39.54%,respectively.(4)The mechanism of direct interspecies electron transfer was explored to promote direct interspecies electron transfer by modified biochar and raw biochar.It was concluded that BC0 mediated DIET through its conductivity,whereas BC6 accelerated DIET by its surface redox groups.