Study On The Methane Production Performance Of Facilities Vegetable Wastes During Anaerobic Digestion

With the improvement of living standard,the consumption of vegetables is fast increasing.Inevitably,in the process of vegetable planting,growth and harvest,large amounts of inedible vegetable wastes(VWs),rich in organic matters,are produced.These VWs are abandoned indiscriminately in the fields,causing serious pollution to the environment and also a waste of resources.Therefore,this study focused on managing the facilities VWs abandoned in the field through anaerobic digestion(AD).And then,cucumber vine waste(CVW)was adopted as a representative to further explore the method of enhancing its methane production potential.Firstly,the properties and methane potential of 25 kinds of common facilities VWs were systematically analyzed.Most samples showed the high methane production performance of more than 100 mL/g VS,and cucumber leaves performed the highest cumulative methane production(CMP)of 281.6 ml/g volatile solids(VS).And then,a correlation between CMP and organic components(OC)was established based on the determination of OC,which could be used to simply and quickly predict the methane production performance of similar VWs through OC analysis.In addition,results of kinetic analysis showed that the modified Gompertz model and Cone model were better than the first-order model to simulate the AD process for such VWs.Secondly,CVW with low biodegradability(BD)and high lignocellulosic content was selected as experimental materials to investigate methane production performance of CVW during AD after nine pretreatment methods,including H2SO4,HCl,H3PO4,NaOH,KOH,Ca(OH)2,CaO,H2O2,and alkaline hydrogen peroxide(AHP).Results showed CMP and BD of untreated CVW were 142.0 mL/g VS and 34.77%,respectively.After pretreatments with 3%NaOH,2%KOH and 3%AHP,the CMP of CVW was significantly promoted to 241.5?217.0 and 210.5 mL/g VS(p<0.01),and the BD was increased to 59.16%?53.16%and 51.55%,respectively.The determination results of lignocellulose as well as the characterization analysis of CVW showed that alkali pretreatment,causing more efficient removal of hemicellulose and lignin,could more significantly destroy the lignocellulosic structure of CVW,compared to other pretreatment.Finally,KOH and Ca(OH)2 were used together to investigate the combined pretreatment of CVW,due to some pollution to the environment might be caused by Na+residues after NaOH pretreatment,no pollution of K+but KOH is too expensive,and the cheap price of Ca(OH)2 but with slightly lower effect.Results showed that the effects of 1.5%KOH+1.0%Ca(OH)2 and 2.0%KOH+2.0%Ca(OH)2 were much better than other conditions,as they could promote the CMP of CVW to 207.1 and 210.5 mL/g VS,respectively;and no significant difference was found between these two combined pretreatments.In order to save the cost,pretreatment with 1.5%KOH+1.0%Ca(OH)2 was considered as the optimal condition for combined pretreatment,which was close to the effect of mono-pretreatment with 2.0%KOH.It suggested that KOH could be partly replaced by Ca(OH)2 to achieve the similar pretreatment effect and save the cost effectively.This study contributed a large number of basic data for the research of facilities VWs during AD and also presented scientific management for VWs with high lignocellulosic structure that is difficult to be digested,which provided important reference for application of facilities VWs in future.