Study On Improvement Of Anaerobic Digestion Of Food Waste By Addition Of Synthesized Allophane And Safety Evaluation Of Digestate

Food waste is a kind of organic waste produced in the process of food processing and transportation.With the development of economy,a large quantity of food waste will be produced every year in our country,which is not only a huge waste of resources,but also will bring a series of problems in environmental pollution.The use of food waste for anaerobic digestion can not only realize the resource utilization of food waste,but also produce methane rich biogas and bio-organic fertilizer,which is a multi-win treatment method.However,the application of kitchen waste in anaerobic digestion still confronts the challenges of poor process stability and low methane production.It has been proved that additional additives can be added to improve the performance of anaerobic digestion.Allophane with desirable physicochemical properties,such as high p H buffer and organic adsorption capacity,as well as high porosity and specific surface area,which shows great potential in improvement of anaerobic digestion.Based on the above situation,this article studies from the following aspects:(1)The synthetic allophane was selected as the research object to evaluate its application potential in anaerobic digestion from the aspects of physicochemical properties,buffering ability to four typical volatile fatty acids and biological toxicity.The results show that the physical and chemical properties of the allophane are consistent with those reported in the literature,it can be widely used.The synthesis method of allophane is stable and mature.Through acid titration experiment,it was found that allophane significantly slowed down the decline trend of p H and showed good buffering performance for volatile fatty acids produced in the anaerobic digestion process of food waste.It mainly promoted the consumption of H~+and reduced the content of VFAs to improve the acid buffering capacity of the anaerobic digestion system.Through the cytotoxicity test and seed germination test,it was found that allophane did not show any negative effects and showed high environmental safety.(2)Synthetic allophane was selected as the exogenous additive,the anaerobic digestion of food waste was carried out under the condition of different loads of allophane.The strengthening effect of allophane on anaerobic digestion was explored from its biogas production,anaerobic digestion environment and changes of anaerobic microbial community.The results showed that the cumulative biogas production increased from409.69±20.77 m L/g TS to 624.06±6.63 m L/g TS by adding allophane(0-10 g total solid(TS)),the cumulative methane production increased from 224.12±9.26 m L/g TS to391.52±0.87 m L/g TS.The improvement of anaerobic digestion performance was mainly because allophane alleviated excessive acidification during the start-up period and created an environment conducive to the growth of microorganisms,especially promoted the growth of Methanosarcina,indicating that the addition of allophane enhanced the acetoclastic methanogenic pathway.The results provide a reference mechanism for improving the performance of anaerobic digestion and a potential strategy for stabilizing the application of food waste in anaerobic digestion.(3)Wheat seeds were selected as the evaluation object,and the germination rate of wheat seeds,seedling growth,peroxidase activity and MDA content in roots and leaves after the action of digestate were determined and used as the investigation index to evaluate the safety of digestate produced after anaerobic digestion.The results showed that the germination rate and germination index of all the experimental groups were above 90%.The plant height,root length and weight of wheat seedlings in all the experimental groups showed no inhibition phenomenon.The contents of TOD,POD,CAT and MDA in the root and leaf of wheat seedlings were at the same level as those in the blank group.This showed that the addition of allophane did not have a negative effect on the seed germination and seedling growth of wheat,and digestate showed a high safety.In addition,the detection of heavy metal content in digestate showed that the digestate produced in this experiment was in line with the national preparation standards for marsh fertilizer and had the potential to be applied to farmland soil.