The Effect Of Vermiculite And Bio-carbon Additives On The Anaerobic Co-fermentation

Anaerobic fermentation(AF)is an effective waste treatment method.It can produce clean fuel(biogas)while realizing the resource utilization of waste.Because of some shortcomings of AF,such as low biogas production,incomplete degradation rate of organic matter,and poor utilization rate of digestate,the wide application of AF is limited.These shortcomings can be significantly improved by co-fermentation and adding accelerants.Honeycomb-like porous bio-carbon derived from aloe peel waste was prepared by hydrothermal carbonization combined with potassium hydroxide activation,and the effect of bio-carbon on co-digestion systems was investigated.In the co-digestion system that added bio-carbon,the cumulative biogas production(279.6–297.9 m L/g VS),chemical oxygen demand(COD)removal rate(55.20%–63.11%)and volatile solids(VS)removal rate(49.32%–53.78%)was increased by 18.17%–25.91%,18.94%–35.98% and 26.73%–35.50%,respectively,after adding bio-carbon(0.1 wt.%,0.2 wt.% and 0.3 wt.%)as compared with the control check(CK).Vermiculite containing rich-phosphorus was used as a co-fermentation additive to investigate the effect of different concentrations(0.1 wt.%,0.3 wt.%,0.6 wt.%,and 0.9wt.%)on the co-fermentation performance.Compared with the CK group(234.08 m L/g VS,39.38%),the cumulative biogas production(295.14–353.96 m L/g VS)and COD removal rate(45.53%–71.03%)was increased by 26.09%–51.21% and 15.62%–80.37%,respectively,after adding vermiculite.After co-fermentation,the stability and fertilizer value(5.97%–6.81% vs.5.76%)of the digestate with vermiculite were improved.The total phosphorus(11.44–13.29 g/kg),and water soluble phosphorus content(6.06–9.79g/kg)were superior to the CK(10.37 g/kg,7.94 g/kg).In addition,the potential mechanism of vermiculite in anaerobic co-fermentation system was proposed.Based on the optimum addition of bio-carbon(0.2 wt.%)and vermiculite(0.3 wt.%),these two additives were mixed and added to the co-fermentation systems.The cumulative biogas production(201.1–247.4 m L/g VS)and COD removal rate(47.29%–54.32%)were less than or close to CK(237.1 m L/g VS,49.39%)when the vermiculite content was low(0.1 wt.% and 0.3 wt.%).The cumulative biogas production(280.11–332.22 m L/g VS)and COD removal rate(52.32%–66.63%)were higher than CK(237.1 m L/g VS,49.39%)after increasing vermiculite content(0.6wt.% and 0.9 wt.%).In a word,the addition of vermiculite and bio-carbon improves the biogas production,COD removal rate,digestate stability,fertilizer value and phosphorus content,which opens up a new way for the future utilization of digestate.