Multi-Product Technology Development And Process Research Of Fruit And Vegetable Waste Through Retting Pretreatment

A great quantity of Fruit and vegetable wastes(FVW)are generated in large amounts of planting,improper storage and transportation,by-products of food processing plants and people’s daily life.As the main components of household waste,the harmless and resource treatment of fruit and vegetable waste is a big problem that must be overcome at present.However,because of the high water content,perishable and rich residual value,it is difficult to utilization FVW.If only traditional treatment methods such as landfill,composting and anaerobic fermentation technology are used,it will not only waste resources of residual value of FVW,but also cause mosquitoes and flies all over the sky,serious leachate,odor and other problems,which seriously threaten the ecological environment and human health.Therefore,according to the characteristics and advantages of FVW itself,it is extremely necessary to develop the bio-refining process with full utilization of its resources.Based on this,the solid-liquid separation was used for FVW for it’s classified utilization to obtained Bacterial cellulose(BC),the Hydrogen(H2)and Volatile fatty acids(VFAs)in this study,respectively.At the same time,a simple pretreatment method of FVW-retting pretreatment was put forward,and the ability of producing bacterial cellulose by different retting levels of fruit and vegetable waste was explored.In addition,the effect of retting derivatives including acetic acid,propionic acid,butyric acid,valeric acid,lactic acid,ethanol and nitrite on the biotransformation of BC was also studied.In order to make full use of FVW,a collaborative anaerobic treatment was conducted between FVW solid residue and BC production waste liquid,and the production of hydrogen and volatile fatty acids was evaluated.Finally,Life cycle assessment(LCA)was used to evaluate the environmental and economic benefits of the process.The aim of this study is to improve the BC yield of FVW by simple retting pretreatment and to integrate multi-product processes to achieve a more sustainable and cleaner FVW biorefining process.The main research results are as follows:(1)Different retting time can help release more soluble components from FVW,including sugar(fructose,glucose),organic acid(acetic acid,lactic acid,etc.)and other nutrients(ethanol,etc.),so as to provide more carbon sources and growth factors for BC growth,making BC yield increase by more than 200% compared with pure chemical HS medium.The highest BC yield of 4.09 g/L was obtained in FVW medium after 14 days of retting.At the same time,compared with the BC film obtained from pure chemical medium,the BC film obtained from FVW medium not only has its due structural characteristics,but also has tighter surface morphology,stronger crystallinity and mechanical strength.(2)The derivatives acetic acid,ethanol and lactic acid promote the growth of BC at low concentration and inhibit the growth of BC at high concentration.When the concentrations of acetic acid,ethanol and lactic acid were 3200,5 and 900 mg/L respectively,they had the strongest effect on the growth of BC.However,propionic acid,butyric acid,valerate and nitrite can inhibit the growth of BC,with the inhibition rate reaching more than 90%.The EC50 of the BC bioconversion rate of each retting derivative was ethanol(80 mg/L)< nitrite(212.10 mg/L)<valanoic acid(441.53 mg/L)< butyric acid(1049.45 mg/L)< propionic acid(1187.0 mg/L)<lactic acid(3013.85 mg/L).(3)Collaborative anaerobic digestion technology,the BC culture waste liquid and FVW solid wastes join the digestion into clean energy hydrogen and volatile fatty acids(acetic acid and butyric acid).The process integration of BC production and anaerobic digestion can produce 20.44 kg/t FVW(dry base)BC,23.65 m3/t FVW(dry base)H2 and 29.16 kg/t FVW(dry base)VFAs.(4)The integration of BC production and anaerobic digestion process was named Scene 2,and the traditional anaerobic digestion process was named Scene 1.The results of life cycle assessment(LCA)and economic benefit analysis showed that the reduction of Global warming potential(GWP)and Acidification potential(AP)in scene 2 was 147.6% and 313.51%,respectively.Primary energy demand(PED)increased by 865.81%,indicating that compared with the traditional FVW scene processing process,the environmental sustainability of scene 2was improved.In addition,compared with scene 1,the economic benefit of scene 2 was increased from 129.55 yuan/t FVW(dry base)yuan to 370.85 yuan/t FVW(dry base).