High-solid Anaerobic Co-digestion of Food Waste and Rice Straw for Biogas Production

Anaerobic co-digestion of food waste（FW） and rice straw（RS） in continuously stirred tank reactor（CSTR） at high organic loading rate（OLR） was investigated. Co-digestion studies of FW and RS with six different mixing ratios were conducted at an initial volatile solid（VS） concentration of more than 3 g VS · L-1. The biogas production, methane contents, degradation efficiency of VS, chemical oxygen demand（COD） and volatile fatty acids（VFAs） were determined to evaluate the stability and performance of the system. The results showed that the co-digestion process had higher system stability and higher volumetric biogas production than mono-digestions. Increase in FW content in the feedstock could increase the methane yield and shorten retention time. The efficiency of co-digestion systems mainly relied on the mixing ratios of FW and RS to some extent. The highest methane yield was 60.55 m L· g V· S-1 · d-1 at a mass ratio（FW/RS） of 3 ： 1, which was 178% and 70% higher than that of mono-digestions of FW and RS, respectively. Consequently, the anaerobic co-digestion of FW and RS could have superior stability and better performance than monodigestions in higher organic loading system.

Coupling System for Food Wastes Anaerobic Digestion and Polyhydroxyalkanoates Production with Ralstonia eutropha

A new technology was developed to couple the anaerobic digestion of food wastes with production of polyhydroxyalkanoates (PHAs). Acetic, propionic, butyric and lactic acids were produced during food wastes anaerobic digestion and their concentrations reached 5.5, 1.8, 27.4 and 32.7 g/L, respectively under appropriate digestion conditions. The fermentative acids were transferred through a dialysis membrane to an air-lift reactor for PHA synthesis by Ralstonia eutropha. Dry cell concentration and PHA content reached 22.7 g/L and 72.6%, respectively. The obtained PHA was a copolymer of b-hydroxybutyrate (HB) and b-hydroxyvalerate (HV) with 2.8% (mole ratio) of HV units in polymer.

Biogas Production from Co-Digestion of Grass with Food Waste

Management of grasslands in Ghana has become so poor that most rural communities result in bushfires that cause a lot of environmental challenges. Grass could be used for biogas generation. This study investigated the effect of grass and food waste co-digestion on the biogas yield and clarified how the addition of grass enhances the AD performance. Grass (GR) mixed with the co-substrate food waste (FW) was then evaluated under anaerobic conditions for the production of biogas (methane). Five laboratory-scale reactors, R1 (100% FW, 0% GR), R2 (75% FW, 25% GR), R3 (50% FW, 50% GR), R4 (25% FW, 75% GR) and R5 (0% FW, 100% GR) were set up with different proportions of grass and food waste which had 8% total solid concentration. Digestion was carried out for twenty (20) days at room temperature, 35&#176C ± 2&#176C. The biogas yield in the R1, R2, R3, R4, R5 was 805, 840, 485, 243 and 418 mL respectively. Food waste only produced 805 mL and grass only produced 418 mL of biogas. Food waste only produced 50% more biogas than grass. However, co-digestion at 75% FW, 25% resulted in 6% more biogas than food waste only.

Biohythane production from two-stage anaerobic digestion of food waste:A review

The biotransformation of food waste(FW)to bioenergy has attracted considerable research attention as a means to address the energy crisis and waste disposal problems.To this end,a promising technique is two-stage anaerobic digestion(TSAD),in which the FW is transformed to biohythane,a gaseous mixture of biomethane and biohydrogen.This review summarises the main characteristics of FW and describes the basic principle of TSAD.Moreover,the factors influencing the TSAD performance are identified,and an overview of the research status;economic aspects;and strategies such as pre-treatment,co-digestion,and regulation of microbial consortia to increase the biohythane yield from TSAD is provided.Additionally,the challenges and future considerations associated with the treatment of FW by TSAD are highlighted.This paper can provide valuable reference for the improvement and widespread implementation of TSAD-based FW treatment.

Impact on Acidification Characteristics of Anaerobic Digestion of Kitchen Waste by F/M

The effect of F/M on acidification characteristics during anaerobic digestion of kitchen waste was investigated. Under different F/M,p H,alkalinity,ethyl alcohol,volatile fatty acids(VFAs),and biogas production status of acidification effluent in 96 h were observed. The study results showed that the content of propionic acid + acetic acid reached 56%-80% when F/M≤1. 0,which was mainly known as propionic acid type of fermentation and was accompanied by methane. The value of alkalinity was only 3 000-4 000 mg/L,which indicated that the stability was weak in the system. When 1. 0 < F/M≤2. 5,the concentration of butyric acid + acetic acid was in the range of 77%-85%,and acid production rate per unit load was more than 250 mg VFAs/g VS,which was known as butyric acid type of fermentation. The fermentation type was stable and could provide more available VFAs for subsequent methanation processes because the value of alkalinity reached 5 650 mg/L. When F/M≥2. 5,the content of ethanol + acetic acid was 80%-92%,which was known as ethanol type of fermentation. And p H of 96 h was only 5. 0( F/M = 3. 0) and 4. 3(F/M =4.0),and acidification was serious and the stability was weak in the system,which would hinder the subsequent methanation process.Therefore,F/M influenced fermentation type,and it can provide a target product for subsequent methanation process by controlling F/M in a reasonable range.

Ultrasonication as anaerobic digestion pretreatment to improve sewage sludge methane production:Performance and microbial characterization

A large amount of sludge is inevitably produced during sewage treatment.Ultrasonication(US)as anaerobic digestion(AD)pretreatment was implemented on different sludges and its effects on batch and semi-continuous AD performance were investigated.US was ef-fective in sludge SCOD increase,size decrease,and CH_(4)production in the subsequent AD,and these effects were enhanced with an elevated specific energy input.As indicated by semi-continuous AD experiments,the mean daily CH_(4)production of US-pretreated A^(2)O-,A^(2)O-MBR-,and AO-AO-sludgewere 176.9,119.8,and 141.7 NmL/g-VSadded,whichwere 35.1%,32.1%and 78.2%higher than methane production of their respective raw sludge.The US of A^(2)O-sludge achieved preferable US effects and CH_(4)production due to its high organic con-tent andweak sludge structure stability.In response to US-pretreated sludge,amore diverse microbial community was observed in AD.The US-AD system showed negative net energy;however,it exhibited other positive effects,e.g.,lower required sludge retention time and less residual total solids for disposal.US is a feasible option prior to AD to improve anaer-obic bioconversion and CH_(4)yield although further studies are necessary to advance it in practice.

Anaerobic digestion of food wastes for biogas production

Five types of food wastes were investigated as feedstock for a potential centralized anaerobic digester system in the area of Sacramento,California to produce biogas energy.The wastes were from a soup processing plant,a cafeteria,a commercial kitchen,a fish farm,and grease trap collection service.Digestibilities of the food wastes,individually and in mixtures,were conducted at mesophilic(35℃)and thermophilic(50℃)temperatures and at two food to microorganism ratios(F/M)of 0.5 and 1.0,for 28 days.A continuously fed mesophilic single-stage anaerobic digester was evaluated using a mixture of the five food wastes at organic loading rates of 0.5 to 1.0 g VS/L/d.In the batch digestion tests,fish and grease trap wastes required longer time to complete the digestion and had higher biogas yields than the other wastes.The continuously-fed digester required the addition of sodium hydroxide to maintain pH at proper levels in the digester.Alkalinity of about 2,500 mg CaCO3/L and pH above 7 was maintained by adding 0.2 g NaOH/g VS.The results of this study indicated that it was necessary to use the chemicals,such as NaOH,to control the pH of the single-stage anaerobic digester treating the food waste.For commercial applications,the cost of chemicals and proper management of additional salts in the digester effluent need to be carefully considered.

温度转换对厌氧消化系统连续运行及微生物群落的影响

通过210d的连续厌氧消化试验,实现了以餐厨垃圾为发酵底物的同一厌氧消化系统内发酵温度从中温到高温的转换.试验结果显示,中温阶段,最高有机负荷(OLR)为6.5kg COD/(m^(3)·d),平均沼气产率658L/(kg COD·d);产甲烷优势菌属包括Methanosaeta(57.0%)、Methanospirillum(10.0%)、Methanomethylovorans(9.2%)和Methanobacterium(19.7%),其与水解酸化类细菌、同型产乙酸菌等形成互营关系,实现高效产甲烷过程.经35d升温过程后,中温发酵系统平稳转换为高温发酵系统.高温系统稳定运行时OLR为5.0kg COD/(m^(3)·d),平均沼气产率480L/(kg COD·d);产甲烷优势菌属主要为Methanoculleus(96.2%),其与互养产氢类细菌和互营乙酸氧化细菌等形成互营关系,共同推动H_(2)利用和产甲烷过程.但高温系统在试验后期呈现明显酸化趋势,产气效率大幅下降,推断是因为该阶段产甲烷菌活性受到抑制,而水解产酸菌大量富集,使得有机酸生成与利用过程失衡,最终导致系统崩溃.综上说明厌氧发酵系统在线温度转换具有技术可行性,但高温系统的运行性能和稳定性较中温系统偏低.

发酵罐内通入空气去除H_(2)S同步提升产甲烷效率研究

餐厨垃圾高温厌氧消化沼气中含有高浓度的H_(2)S,在使用前需要将其去除。对连续运行了230d的高温厌氧消化反应器进行研究,考察了不同有机负荷、通入空气量和沼气顶空循环对H_(2)S去除效果的影响,并分析了向反应器顶空通入空气后厌氧消化性能的提升效果。实验发现,在水力停留时间15d和沼气顶空停留时间2.8h的条件下,恒流量连续通入3倍理论空气量可去除78%的H_(2)S。进一步采用沼气顶空循环,H_(2)S体积分数从平均0.2%下降至0.01%以下,去除率达到95%。在通入空气的工况下,餐厨垃圾高温厌氧消化的甲烷产率提高了8.5%,达到310mL/g(以COD质量计);沼气容积产气率提高了10.5%,达到4.2L/(L∙d)。乙酸和丙酸的浓度与对照反应器相比没有显著变化,均维持在较低浓度水平。总体而言,在反应器内脱除H_(2)S的工艺方法操作简便,成本低廉,具有广阔的工程应用前景。

厨余垃圾厌氧发酵定向产酸的影响因素

随着垃圾分类工作不断推进落实,厨余垃圾的分出量急剧增长。由于其极易变质,在收集、运输和储存过程中可能会对环境造成二次污染,厨余垃圾的处理问题逐渐成为人们的研究热点。现有的主要处理技术有填埋、焚烧、好氧堆肥、厌氧发酵等,由于焚烧和填埋的方式是非常不环保的,好氧堆肥和厌氧发酵具有良好的资源化属性,水解产酸是厌氧发酵技术的一个研究方向,厨余垃圾是产酸的合适原料。因此,本文针对水解产酸技术发展进行了梳理和分析,基于厨余垃圾水解产酸的代谢机理,重点介绍了影响厨余垃圾产酸效果的两种因素,即水解微生物和水解条件。针对挥发性脂肪酸的不同应用场合,分别讨论了其所需的酸类组成,分析总结了不同产酸微生物的类别及其产酸效果,在不同pH、温度、有机负荷以及投加试剂的条件下其对产酸的影响,并针对定向产酸需求提出解决方案,希望为未来研究提供支持。

纳米气泡的特性及其在有机固体废物厌氧消化中的应用

基于国内外研究现状,分析了纳米气泡(NBs)的基本性质和产生方式,以及改善厌氧消化性能的作用机理,综述了NBs在有机固体废物厌氧消化中的研究进展,以及在增强厌氧消化稳定性、加快水解速率、提高甲烷产量等3个方面的应用,提出了加强不同气体NBs理化性质研究、开发多种气源、提升检测能力、降低能耗和成本等后续研究展望。

餐厨垃圾压榨液厌氧发酵的温度效应及微生物

近几年餐厨垃圾资源化日益受到重视,用餐厨垃圾生产生物质燃料棒以及保水疏松介质是一种新的全量资源化技术,但会产生一种新型废水即餐厨垃圾压榨液。该研究主要探究温度对餐厨垃圾压榨液厌氧发酵过程中产甲烷的影响,分析了压榨液厌氧发酵过程中微生物群落变化。在最佳发酵温度47℃下发酵53 d后,总产气量达17220 m L,日产甲烷量的峰值占日产气量峰值的70%~75%,较37℃日产甲烷量峰值高2.5倍,27、57、67℃在发酵的第5天后不再产生甲烷。通过16S r DNA高通量测序,发现在发酵过程中微氧环境下的优势菌群unclassified_d_Bacteria的相对丰度从83.92%下降到24.16%,在严格厌氧环境下优势菌群Clostridium的相对丰度从0.93%上升到44.75%,在发酵实验结束时Clostridium的相对丰度从44.75%下降到5.40%,unclassified_d_Bacteria的相对丰度从24.16%上升到68.12%。研究结果可为实际工程中餐厨垃圾压榨液厌氧发酵温度和菌种的选择提供参考。

沼渣水热炭与沼渣热解炭强化餐厨垃圾厌氧消化对比研究

餐厨垃圾厌氧消化产生大量沼渣,亟需得到妥善处理。采用水热与热解将沼渣分别制备为水热炭与热解炭,并对比研究了其对餐厨垃圾厌氧消化的影响。结果表明:与对照组(23.8 mL/g)相比,水热炭组(投加量1、5、10 g/L)甲烷产量分别为24.0、38.9、34.9 mL/g,分别提高了0.8%、63.4%、46.6%;热解炭组(投加量1、5、10 g/L)甲烷产量分别为29.7、35.7、31.1 mL/g,分别提高了24.8%、50.0%、30.7%。投加水热炭和热解炭促进了有机物溶出,且水解产酸菌包括Fastidiosipila、 W5053、 Propioniciclava、 Actinomyces (放线菌属)、Norank_f__ST-12K33的总相对丰度由73.0%分别提升至84.6%和82.0%。投加水热炭和热解炭后,Methanosaeta(鬃毛甲烷菌属)相对丰度分别高达60.3%和50.6%,Methanobacterium (甲烷杆菌属)相对丰度仅为26.5%和36.9%。沼渣生物炭可以强化餐厨垃圾厌氧消化,随着投加量的增加,甲烷产量先上升后下降,最优投加量为5 g/L,且水热炭效果优于热解炭。

餐厨垃圾厌氧处理技术研究进展

餐厨垃圾是城市生活垃圾中有机固体废弃物的主要来源,厌氧消化技术是目前餐厨垃圾资源化的主流处理工艺,文章分析了我国餐厨垃圾的处理技术现状,其中厌氧消化技术作为目前的主流处理工艺,从厌氧反应器类型、厌氧消化工艺等方面着重分析了目前国内外餐厨垃圾厌氧处理技术的发展现状,为提高我国餐厨垃圾资源化水平提供参考。

餐厨垃圾淀粉类代表组分生熟大米中温厌氧发酵产氢性能

餐厨垃圾中淀粉类组分的性质是影响产氢效率的重要因素.为探究淀粉类代表组分——大米在生、熟性状下(RR、CR)的产氢效能,本文通过中温批式小瓶试验,研究不同接种比条件下生、熟大米的厌氧发酵混合体系(RR-F、CR-F)产氢及底物变化情况.结果表明,无论RR-F或CR-F产氢效能均随基质与种泥比(S/I)比的增大而增大,最佳S/I比为1∶1;CR产氢效能更佳,RR-F和CR-F的最大累积产氢量分别为59.62 mL·g^(−1)VS和166.97 mL·g^(−1)VS.发酵副产物以乙酸和正丁酸为主,属于丁酸型发酵;正丁酸/乙酸比值越大,累积产氢量越大.发酵过程中,可溶糖、可溶蛋白浓度和pH快速降低,总挥发酸(TVFA)浓度快速增加并逐趋于稳定.Pearson相关性分析表明,累积产氢量主要受可溶糖降解量、乙酸浓度的影响.蒸煮使CR的可溶糖析出更多,导致CR-F产氢效能明显高于RR-F.

餐厨垃圾厌氧消化快速启动特性的研究

为明确餐厨垃圾快速启动过程的厌氧消化特性,通过半连续搅拌反应器系统,监测了有机负荷(Organic Loading Rate,OLR)为1.5、2.0、2.5和3.0 gVS·L^(-1)d^(-1)运行过程中沼气产量和甲烷含量、沼液pH值、挥发性脂肪酸(VFA)、碱度和氨氮等参数的变化情况。研究结果表明:OLR从1.5 gVS·L^(-1)d^(-1)提高至3.0 gVS·L^(-1)d^(-1)时,容积产气率提高到2.12±0.05 L·L^(-1)d^(-1),比甲烷产量稳定在273.2±7.8 mLCH_(4)·g^(-1)VS,系统产气性能良好且稳定;挥发性脂肪酸浓度维持较低水平(650 mg·L^(-1)左右),主要成分是乙酸。氨氮含量随着OLR的提升不断增加,最高达到4171 mg·L^(-1),游离氨增加至300~350 mg·L^(-1),对产气性能产生轻微抑制作用;微生物群落分析表明厌氧消化过程主要细菌菌群是Firmicutes、Bacteroidota和Synergistota,优势产甲烷菌群主要以Methanosarcina、Methanobacterium和Methanosaeta为主。厌氧消化启动阶段在有机负荷达到3.0 gVS·L^(-1)d^(-1)时可以稳定运行,反应器成功启动。

白菜废弃物与玫瑰秸秆混合发酵的产气性能研究

以白菜废弃物和玫瑰秸秆为原料,采用批量厌氧消化工艺,在水浴恒温(35±1)℃的条件下进行混合发酵,探究不同配比的白菜废弃物与玫瑰秸秆混合发酵的产气潜力和产气特性。结果表明,经过33 d的发酵周期,白菜废弃物与玫瑰秸秆以质量比0∶3、1∶2、2∶1、3∶0不同配比混合发酵,对应的总固体产气率分别为254、248、213、191 mL/g。单一玫瑰秸秆发酵的产气潜力最优,单一白菜废弃物发酵的产气潜力最差。添加花卉秸秆能够有效提升蔬菜废弃物的产气效果,白菜废弃物与玫瑰秸秆为1∶2配比组的产气潜力优于2∶1配比组。

餐厨垃圾水力制浆耦合厌氧消化的效果分析

根据餐厨垃圾高含水的特点,从水力模拟、浆化物料特性、设备运行关键指标及项目运行效果等方面对餐厨垃圾水力浆化预处理技术进行综合评价。计算流体力学(CFD)的水力模拟结果表明,浆化过程中流体质点螺旋式汇聚至转叶,形成三股内旋状涡流,在流体内部产生明显的流速差和正负压分区现象,水力作用下可快速实现餐厨垃圾的浆化。浆料和杂质特征分析表明,浆化产物颗粒细小,有机质损失率低,杂质去除率高,可与后端不同资源化技术(如厌氧消化、好氧堆肥等)高度融合。以水力浆化与厌氧消化技术相结合的餐厨垃圾资源化项目为例,餐厨垃圾经水力浆化预处理后,有机质损失率约为8.5%;不可生物降解杂质分选率约94%;粗油脂提取率约91%,吨餐厨垃圾平均产油率为3.76%,产气率为85.57 m^(3)(以标态计)。该处理方式较机械式预处理具有更高的资源化利用率,可大幅提升项目的经济效益。

不同浓度餐厨垃圾高温厌氧消化研究

为探索餐厨垃圾高温厌氧消化的可行性,研究不同浓度餐厨垃圾高温厌氧消化过程中厌氧罐内参数的变化。通过餐厨垃圾连续厌氧发酵的进料负荷变化试验,试验结果表明,低浓度的餐厨垃圾浆料较高浓度的餐厨垃圾浆料厌氧发酵过程更加稳定,餐厨垃圾沥水浆料在7.5 kg·m^(-3)d^(-1)的COD负荷和6 kg·m^(-3)d^(-1)的TS负荷下可以长时间稳定运行,系统的容积产气率可达4 m^3·m^(-3)d^(-1)并可长期稳定运行。相较餐厨垃圾中温厌氧发酵,高温厌氧发酵能显著提升厌氧罐的进料负荷,从而有效降低厌氧罐体的大小,降低工程投资和运行费用。

生物炭强化厨余垃圾厌氧消化研究进展

厨余垃圾资源化利用是固废处理领域的研究热点。厌氧消化技术具有工艺成熟和产物附加值高等优点,是最常见的厨余垃圾处理技术之一。但其存在反应速率慢、抗冲击能力弱等问题。生物炭作为一种生物质衍生的碳基材料,凭借其独特的理化特性在强化厌氧消化过程中发挥重要作用。通过分析生物炭理化特性和系统梳理生物炭对厨余垃圾厌氧消化过程的影响,阐述了生物炭强化厨余垃圾厌氧消化的作用机制。同时提出生物炭强化厌氧消化领域的重点研究方向,以期为厨余垃圾处理提供理论指导和科学依据。