Preliminary techno-economic analysis of three typical decentralized composting technologies treating rural kitchen waste: a case study in China

● Decentralized composting (DC) is a profitable KW treating technology. ● SAC and BEC were economically attractive in rural area, while HDC was unprofitable. ● KW handling subsidy plays a vital role in making DC profitable. ● SAC and BEC have great potential in promoting rural KW treatment. This study was designed to evaluate whether the decentralized rural kitchen waste (KW) composting technologies used in China can be widely applied. To this end, we completed a techno-economic analysis of three typical types of KW compositing, namely solar-assisted (SAC), bio-enhanced (BEC), and heat-dewatering composting (HDC). These evaluations revealed that all three technologies produce composting products that meet China’s organic fertilizer standard and that both SAC and BEC are economically self-sustaining and generate net profits (18824.94 and 17791.52 US$/a) and positive net present values (32133.11 and 25035.93 US$). Subsequent sensitivity analysis demonstrated that the KW-handling subsidy plays a critical role in making decentralized composting economically attractive. Based on these analyses, we believe that reducing the coverage area of SAC, reducing the operating cost of BEC and HDC, upgrading composting products, and strengthening secondary pollution control would aid in supporting the technological improvement of these processes. Moreover, providing appropriate subsidies and promulgating specific standards and policies for KW fertilizer are key strategies for decentralized rural KW composting management.     

小球藻强化餐厨废水处理效果及机理

利用小球藻对混凝出水进行处理,考察小球藻接种量对COD、DTP和TN去除率的影响,通过扫描电子显微镜(SEM)、红外光谱、比表面积微孔分析仪分析小球藻形貌和组成结构的变化,采用紫外可见光谱和三维荧光光谱研究餐厨废水中有机物成分的变化,探究小球藻降解餐厨废水的机理.结果表明:当小球藻接种量为25%时,COD和TN去除率最高(分别为79.73%和78.28%);当小球藻接种量为35%时,DTP去除率最高(85.55%).反应前的小球藻细胞表面相对光滑,反应后的小球藻细胞表面粗糙,比表面积增大,并粘附大量颗粒态物质;小球藻细胞表面的羧基、氨基和磷酸基团等官能团参与污染物的吸附沉淀;小球藻破坏了腐殖质结构,降低了腐殖质芳香性;小球藻在降解可溶性微生物副产物和类腐殖酸的同时,产生芳香类蛋白物质.     

耐酸厌氧消化污泥处理餐厨垃圾

采用耐酸驯化的厌氧消化污泥处理餐厨垃圾，在酸性条件下（pH=4．5），对实验装置容积负荷从1．0kgVS／（m3·d）分9次逐级增加到5．0kgVS／（m3·d）的过程进行了跟踪监测，并较深入地研究了驯化污泥代谢活性和处理效果。实验结果表明，pH4．5的耐酸厌氧消化污泥，最佳投加负荷约为4．5kgVS／（m3·d），此负荷下容积产气率，CH4含量平均值均达最大，分别为1．68m3／（m3·d），75．0％。耐酸厌氧消化装置持续增料运行46d，产甲烷菌仍能保持较高的活性，其COD去除率范围为40．4％-75．0％，仍能保持pH7．2时处理效果的65．0％-91．8％，表明在低pH、低碱度下实现稳定的产甲烷过程是可行的。     

Direct utilization of kitchen waste for bioethanol production by separate hydrolysis and fermentation (SHF) using locally isolated yeast

Kitchen wastes containing high amounts of carbohydrates have potential as low-cost substrates for fermentable sugar production. In this study, enzymatic saccharification of kitchen waste was carried out. Response surface methodology (RSM) was applied to optimize the enzymatic saccharification conditions of kitchen waste. This paper presents analysis of RSM in a predictive model of the combined effects of independent variables (pH, temperature, glucoamylase activity, kitchen waste loading, and hydrolysis time) as the most significant parameters for fermentable sugar production and degree of saccharification. A 100 mL of kitchen waste was hydrolyzed in 250 mL of shake flasks. Quadratic RSM predicted maximum fermentable sugar production of 62.79 g/L and degree of saccharification (59.90%) at the following optimal conditions: pH 5, temperature 60°C, glucoamylase activity of 85 U/mL, and utilized 60 g/L of kitchen waste as a substrate at 10 h hydrolysis time. The verification experiments successfully produced 62.71 ± 0.7 g/L of fermentable sugar with 54.93 ± 0.4% degree of saccharification within 10 h of incubation, indicating that the developed model was successfully used to predict fermentable sugar production at more than 90% accuracy. The sugars produced after hydrolysis of kitchen waste were mainly attributed to monosaccharide: glucose (80%) and fructose (20%). The fermentable sugars obtained were subsequently used as carbon source for bioethanol production by locally isolated yeasts: Saccharomyces cerevisiae, Candida parasilosis, and Lanchancea fermentati. The yeasts were successfully consumed as sugars hydrolysate, and produced the highest ethanol yield ranging from 0.45 to 0.5 g/g and productivity between 0.44 g L^–1 h^–1 and 0.47 g L^–1 h^–1 after 24-h incubation, which was equivalent to 82.06–98.19% of conversion based on theoretical yield.     

不同氧浓度下脱脂餐厨垃圾燃烧特性及动力学研究

利用热重分析法和Coats-Redfern积分法,对不同氧浓度下脱脂餐厨垃圾的燃烧特性进行研究,得到了各试样的着火温度、燃烬温度及综合燃烧特性指数,并通过燃烧动力学分析得到各试样的活化能。实验结果表明,燃烧温度从室温升至1 000℃时,脱脂餐厨垃圾燃烧过程可分为3个失重阶段:水分析出阶段、挥发分析出及燃烧阶段和固定碳燃烧阶段;随着氧浓度的升高,脱脂餐厨垃圾最大失重率以及燃烧特性指数等燃烧特性参数都有显著变化。根据Coats-Redfern积分法计算得低温和高温阶段的活化能分别为83.76~91.2 k J/mol和95.25~141.7 k J/mol。     

不同调理剂对微生物降解餐厨垃圾的影响

为了探索不同调理剂对微生物降解餐厨垃圾效果的影响,本实验选取了木屑(桦木)、米糠、泥炭、花生壳、稻壳等材料分别作为主要调理剂,以餐厨垃圾的重量减量率作为评价降解效果指标,测定实验过程中的温度、含水率、pH值、微生物生物量及重量的变化。实验结果表明,影响餐厨垃圾降解效果主要因素有温度和含水率;以木屑和米糠为主要调理剂的保温性能最优,其余材料热量散失较快;以50%木屑处理的调理剂含水率适宜,能达到最适含水率要求(50%);同时,以50%木屑(桦木)为主要调理剂处理的减量率最高。     

微波联合酸预处理对厨余垃圾酶水解糖化的影响

酶水解糖化是厨余垃圾制造燃料乙醇的关键步骤,对厨余垃圾进行预处理以促进糖化过程,具有重要意义.以学生食堂厨余垃圾为原料,以常规、微波为加热手段,比较不同预处理方式对厨余垃圾酶水解的影响.结果表明,微波加热结合酸性溶剂的预处理方式最有利于厨余垃圾酶水解糖化.考察微波联合酸预处理的影响因素,得到最佳的预处理条件为:溶剂为H2SO4、溶剂浓度3％、微波功率80 W,预处理时间40 min,固液比1∶8,该条件预处理后,与未经预处理的厨余垃圾酶水解糖产量相比,提高46.1％.     

耐酸厌氧消化污泥处理餐厨垃圾简

采用耐酸驯化的厌氧消化污泥处理餐厨垃圾，在酸性条件下（pH=4.5），对实验装置容积负荷从1.0 kg VS/（m³·d）分9次逐级增加到5.0 kg VS/（m³·d）的过程进行了跟踪监测，并较深入地研究了驯化污泥代谢活性和处理效果。实验结果表明，pH 4.5的耐酸厌氧消化污泥，最佳投加负荷约为4.5 kg VS/（m³·d），此负荷下容积产气率，CH₄含量平均值均达最大，分别为1.68 m³/（m³·d），75.0%。耐酸厌氧消化装置持续增料运行46 d，产甲烷菌仍能保持较高的活性，其COD去除率范围为40.4%~75.0%，仍能保持pH 7.2时处理效果的65.0%~91.8%，表明在低pH、低碱度下实现稳定的产甲烷过程是可行的。     

餐厨废油捕收剂浮选高炭粉煤灰

通过对餐厨废油进行处理,制备餐厨废油捕收剂用以处理高炭粉煤灰.分别采用机械活化试验确定高炭粉煤灰原灰的最佳机械活化时间,通过不同温度工况的浮选试验获得餐厨废油捕收剂的脱炭性能规律并同常规捕收剂煤油对比,通过FTIR、SEM、TG等技术对餐厨废油捕收剂和脱炭产物进行系统分析.结果表明：最佳机械活化时间为30min,最佳温度工况下,浮选炭热值可达到中高热值燃料要求,产物脱炭粉煤灰矿物成分可达到Ⅰ级粉煤灰标准.真正实现了"以废治废"和"变废为宝",对环境保护、节能减排和资源的综合利用有着重要意义.     

餐厨垃圾与水葫芦联合好氧堆肥生物质组分分类表征

为解决农村生活垃圾处理实践中存在的问题,并对水葫芦的堆肥化处理进行探索.利用自行设计的能量输入式高温好氧堆肥系统,以农村生活垃圾主要组成——餐厨垃圾及餐厨垃圾+水葫芦混合物料为堆肥化对象,测定与分析了堆肥化过程中温度、有机质的变化规律,并分类表征了总糖、还原糖、淀粉、脂肪、蛋白质5种生物质组分的演变趋势.同时,借助C/N比值、CEC/TOC比值的变化及GI指数评估了堆肥的腐熟度.研究表明,在外界环境温度小于8℃的情况下,与单一餐厨垃圾堆肥化处理相比,混合物料堆肥化升温更快(ld即达40℃,3d达52℃),处于高温堆肥化时间更长(8 d),堆肥无害化程度更高,有机质降解更迅速且降解程度高;而且,混合物料有助于提高总糖、还原糖、淀粉、脂肪与蛋白质5种生物质组分的降解水平.腐熟度评估结果表明,在约11d的堆肥化时间内,能量输入式好氧堆肥系统能够使单一餐厨垃圾堆肥达到基本腐熟,餐厨垃圾与水葫芦混合物堆肥达到完全腐熟.