Study on the comprehensive utilization of nutrients in the anaerobic digestion process of kitchen waste

The output of kitchen waste is large, the recycling value is high, the harm is great, and it is urgent to rationally utilize the value of its phosphorus resources to avoid its pollution risk. Scenario analysis and material flow analysis methods were comprehensively used and, based on the scenario analysis concept model and nutrient flow concept model, the material flow analysis of total phosphorus (TP) was conducted for three by-product treatment scenarios of anaerobic digestion of kitchen waste in southern Jiangsu Province. Among the scenarios, Scenario 1 (S1) was water treatment of biogas slurry and biogas residue incineration, Scenario 2 (S2) was biogas slurry returned to the field and biogas residue to organic fertilizer, and Scenario 3 (S3) was water treatment of biogas slurry and biogas residue to organic fertilizer. Taking the 100 t scale of kitchen waste treatment as a reference, the results showed that for S1, 0.99 kg of TP in the kitchen waste was returned to the field, and finally 0.96 kg TP entered the rice. For S2, 64.05 kg of TP was returned to the field in the kitchen waste, and 62.10 kg TP eventually entered the rice. For S3, 8.67 kg of TP was returned to the field in the kitchen waste, and eventually 8.49 kg TP entered the rice. Combined with the economic performance, the three scenarios were comprehensively evaluated, and it was found that S2 was the optimal mode of kitchen waste resource utilization, and the resource utilization rate of TP was 91.53%, which was much higher than that of S1 and S3.