Technologic Study On Biological Refining Alcohol From Fruit And Vegetable Wastes

Fruit and vegetable wastes mainly come from places for planting, breeding, processing, trading and so on of fruit and vegetables, which are imperfect, decayed or scraps. It will bring not only considerable economic benefits but also alleviation on energy crisis if the wastes are fermented into fuel alcohol production. Whereas, the main processing modes for fruit and vegetable wastes presently are anaerobic fermentation and aerobic compost whose products are methane and fertilizers. The utilization rate is far lower than refining for fuel ethanol. The objective of this study is fermenting fruit and vegetable wastes into alcohol. Effects of pretreatment, sterilization, decay degree, nutrients and related enzymes on the fermentation and alcohol yields were determined based on the characteristics of raw materials. The optimal yeast was screened as well as the optimal fermentation conditions. The economic feasibility was analyzed after the concentration and scale-up trails. The results are presented as follows.The alcoholic fermentation results of different varieties of fruit and vegetable wastes were compared to choose decayed grape and apples as representative materials to investigate technical fermentation method. The wastes were crushed and treated by sulfurous acid (150 mg/L) and sterilized by autoclaving (121℃ at 101 kPa for 30 min). The decay degree and alcohol yield were negatively correlated.Yeast BDX was chosen as the optimal from the eight yeasts K1, KD, EC 1118, SY, RW, TR, CY3097 and BDX by comparing ferment force, residual sugar, alcohol yield and microscopic forms of yeasts. The optimum adding amount was 200 mg/L and the growth curve of BDX was drawn.Effects of temperature, pH, shaking, nutrients, glucoamylase and pectinase on fermentation were studied through single factor tests. The optimal condition was fermented at 25℃, pH 3.5-4.0 and shaking 1-2 times each day. The adding amounts of glucoamylase and pectinase were both 250 mg/L and those of (NH4)2SO4, MgSO4 and KH2PO4 were 1.5, 1.0-1.5 and 2.0-2.5 g/L respectively.The rationality of the optimal fermentation conditions were verified by experiments of simulative fruit and vegetable wastes. The alcoholic degree was 2.31-7.26% and residual sugar was 3.18-3.83 mg/g when the initial sugar content was 24.53-110.37 mg/g. This result was similar to the previous tests. Then the scale-up tests of 20 L and 50 L were taken to investigate the fermentation effects. The alcoholic degrees were 5.76% and 6.12% when the initial reducing sugar contents were 91.75 and 98.26 mg/g for 20 L and 50 L respectively. This will provide reference for industrial amplified production.A real-time detection system for top gas composition using gas chromatography during the alcoholic fermentation was designed. To get alcohol above 95%, the fermentation liquor was filtered before atmospheric distillation for 3 times and a vacuum distillation. The economic feasibility was analyzed to determine that the program is a technology of low energy-consuming, harmless and highly beneficial for processing fruit and vegetable wastes.