Optimization of the methane production in batch anaerobic digestion of maize straw by adjustment of total solid and substrate-to-inoculum ratio based on kinetics

Anaerobic digestion(AD)operating under conditions of organic overload stress typically exacerbates the potential for process instability,thereby resulting in significant economic and ecological ramifications.In this investigation,an augmented substrate-to-inoculum ratio(S/I)along with varying total solid content(TS)levels was employed to replicate diverse organic loadings,utilizing maize straw and cattle manure.The findings reveal that a moderate augmentation in S/I and TS proves advantageous in augmenting methane yield,while an excessive substrate loading diminishes methane yield,hampers the kinetics of methane production,and even induces severe process instability.Kinetic study also displayed the variation of the model parameters for the first-order model,the modified Gompertze model,and the transfer function model.Both the modified Gompertze model and transfer function model exhibited the same environmental stress trend.Thus,both the increase in particulate content and the increase in S/I had a substantial effect on the substrate conversion rate to methane.Microbial analysis demonstrates the dominant influence of Firmicutes and Methanosarcina under different organic loading stresses.From both a kinetic and a microbiological point of view,this work provides novel insights into the fundamental processes that regulate anaerobic digestion(AD)under varying loading stress.Furthermore,it has significant implications for improving the operating efficiency of AD,which is a significant benefit.

Combined pretreatment using CaO and liquid fraction of digestate of rice straw: Anaerobic digestion performance and electron transfer

To improve anaerobic digestion(AD)efficiency of rice straw,solid alkaline CaO and the liquid fraction of digestate(LFD)were used as pretreatment agents of rice straw.The results showed that AD performance of rice straw with CaOLFD pretreatment was optimal in different pretreatment methods of the CaO+LFD,CaOLFD,LFD+CaO,CaO,and LFD.The maximum methane yield(314 ml(g VS)^(-1))and the highest VFAs concentration(14851 mg·L^(-1) on day 3)of the CaOLFD pretreatment group were 81%and 118%higher than that of the control group,respectively.Under the action of solid alkaline CaO,the bacteria of Clostridium,Atopostipes,Sphaerochaeta,Tissierella,Thiopseudomonas,Rikenellaceae,and Sedimentibacter could build up co-cultures with the archaeal of Methanosaeta,Methanobacterium,and Methanosarcina performing direct interspecies electron transfer(DIET)and improving AD performance of rice straw.Therefore,the combined pretreatment using CaO and LFD could not only pretreat rice straw but also stimulate co-cultures of microorganism to establish DIET enhancing AD efficiency.

Effects of Different States of Fe on Anaerobic Digestion:A Review

Anaerobic digestion is widely used in the treatment of industrial wastewater,excess activated sludge,municipal waste,crop straw and livestock manure,with the functions of environmental protection and energy recovery. This review summarizes and evaluates the present knowledge of effects of different states of Fe( ZVI,Fe( II),Fe( III)) on hydrogen and methane production in anaerobic digestion process. The potential promotion effects of iron oxides nanoparticles( IONPs),especially magnetite nanoparticles on anaerobic digestion are also mentioned. Fe plays important role in transporting electron,stimulating bacterial growth and increasing hydrogen and methane production rate by promoting enzyme activity. Adding Fe with different morphologies and valence states in anaerobic digestion to increase biogas( hydrogen and methane) production and enhance organic matter degradation simultaneously,which has attracted many scientists' attention in recent years. Rapid progress in this area has been made over the last few years,since Fe is essential to the fermentative hydrogen and methane production,while few is known about how Fe affects the fermentative biogas production. This review is significant to maintain the stable operation of the biogas project.

Anaerobic co-digestion of rice straw and digested swine manure with different total solid concentration for methane production

This study aimed to investigate potential methane production through anaerobic co-digestion of rice straw and digested swine manure with different total solids.The research was carried out in bench scale with utilizing batch system.To evaluate the stability of anaerobic co-digestion process,the experiment was run in triplicate.The anaerobic co-digestion process was operated in 500 mL batch digesters under constant agitation speed and temperature.The agitation speed was maintained at 270 r/min.Temperature of the batch system was set and maintained at 35℃.Digested swine manure utilized in this experiment was obtained from semi-continuous digesters run at steady state condition,with 25 days of hydraulic retention time under mesophilic condition.Rice straw(RS)generated the highest methane production at 3% total solids(TS)which was around(1814±47.43)mL,where in this concentration,it had C:N ratio at 10.6:1.Rice straw obtained the highest methane yield at 3% TS,which was around(141.4±3.70)mL CH_(4)/g volatile solids(VS)added.Rice straw also had the highest chemical oxygen demand(COD)removal and VS reduction at 3% TS which were around(52.97%±1.46%)and(61.81%±1.04%),respectively.

Oxidative chemical pretreatment by piranha solution for enhanced methane yield of wheat straw:mechanism and kinetic study

The present research work aims to explore the potency of piranha solutions at the best-optimized concentrations,i.e.,40%and 30%to reduce the recalcitrant and heterogeneous structure of wheat straw,and the treated wheat straw was denoted as WS40 and WS30.The effect of pretreatment on wheat straw was determined by anaerobic digestion(AD)in a batch mode,followed by the analysis of soluble chemical oxygen demand(sCOD)and volatile fatty acids(VFAs).After pretreatment,the surface fibers shattered and detached,showing a distorted surface of wheat straw.An increase in the crystallinity of wheat straw after pretreatment was also observed due to the removal of amorphous cellulose and lignin.Enhancement in methane yield was obtained on the 9th day,which was 103±6.92 and 99.33±0.57 mL/d for WS40 and WS30,respectively.Displaced water measurement revealed that the pretreatment of wheat straw minimized the hydrolysis period by 14 days.It also improved the methane yield by 2.65(WS40)and 2.45(WS30)fold in comparison with the control which yielded 35.66 mL/d methane on the 23rd day.The modified Gompertz model(MGM),logistic function model(LFM)and transference function model(TFM)adequately described the degradation process and explained the kinetic behavior of the cumulative methane yield.Among the three models,MGM was found to fit best for the methane yield of WS40 and WS30.

发酵助剂配方优化对小麦秸秆厌氧消化产甲烷的研究

试验旨在研究不同种类及不同复配方式的添加剂对小麦秸秆厌氧消化(anaerobic diges⁃tion,AD)的影响。研究了四氧化三铁纳米颗粒(Fe_(3)O_(4)nanoparticles,NPS-Fe_(3)O_(4))、三氧化二铁纳米颗粒(Fe_(2)O_(3)nanoparticles,NPS-Fe_(2)O_(3))、四氧化三铁(Fe_(3)O_(4))、三氧化二铁(Fe_(2)O_(3))、氯化亚铁(FeCl_(2))、血晶素(hemin)、皂苷(Ginsenoside Rg1,Rg1)七种外源添加剂在不同添加浓度及搭配方式对AD产甲烷的影响。结果表明:单独添加各发酵助剂均可显著提高AD的累计甲烷产量,混合添加后提升效果反而降低。其中单独添加100 mg/L Fe_(2)O_(3)的提升效果最好,累计甲烷产量达到207 mL/g,比空白组提高了86%。通过不同复配方式添加发酵助剂的试验结果显示,混合添加100 mg/L FeCl_(2)+1 mg/L hemin的提升效果最好,累计甲烷产量达到192 mL/g,比空白组高出了70%。试验所用的发酵助剂提高了小麦秸秆厌氧消化效率,为农业废弃物厌氧处理提供进一步技术支撑。

微量元素Fe^(2+)、Co^(2+)、Ni^(2+)对麦秸与鸡粪混合厌氧发酵的影响

以麦秸与鸡粪为原料,采用批次式中温厌氧发酵方式,探究微量元素Fe^(2+)、Co^(2+)、Ni^(2+)对混合厌氧发酵的影响。实验结果表明:Fe^(2+)、Co^(2+)、Ni^(2+)最佳浓度分别为210、32、32 mg/L,当Fe^(2+)、Co^(2+)、Ni^(2+)的添加浓度在适宜范围内时,可显著(p<0.05)提高发酵系统产CH4潜力及CODs去除率;当Fe^(2+)浓度为210 mg/L、Co^(2+)浓度为32 mg/L、Ni^(2+)浓度为32 mg/L时,其CH4累积产量分别为322.21、331.19、357.10 mL/(g VS),相比于对照组为245.35 mL/(g VS)显著(p<0.05)提高31.33%、34.99%、45.54%,CODs去除率依次为61.83%、57.01%、63.63%,提高CH4产量的排序为Ni^(2+)>Co^(2+)>Fe^(2+),Ni^(2+)对CH4累积产量的提高最明显,同时也有最高的CODs去除率,且各实验组pH值均稳定在适宜范围内,厌氧发酵稳定运行,可为麦秸与家禽粪便的沼气工程提供技术参考。

纳米Fe强化污泥厌氧消化产甲烷的研究

介绍了利用纳米Fe强化污泥高效产甲烷的方法。实验结果表明,纳米Fe最佳投放量为6 g/L,相应的甲烷产量(以VSS计)为198 m L/g。机理研究表明,纳米Fe能够促进污泥水解、酸化,进而促进甲烷的积累。

HCl预处理对蔬菜秸秆厌氧消化性能的影响

以黄瓜秸秆、番茄秸秆和茄子秸秆3种蔬菜秸秆为原料,采用不同浓度的HCl(0.2、0.4、0.6、0.8 mol·L^(-1))作为预处理试剂,探讨HCl预处理在蔬菜秸秆厌氧消化应用中的可行性。结果表明:HCl预处理均能显著提高3种蔬菜秸秆的累积甲烷产量,且以0.6 mol·L^(-1)HCl处理更经济适宜,黄瓜秸秆、番茄秸秆和茄子秸秆累积甲烷产量分别为167.88、169.94m L·g^(-1)和146.81 m L·g^(-1),较各自未经预处理的对照分别提高了12.58%、30.97%和18.68%。HCl预处理能有效降解蔬菜秸秆中的纤维素和半纤维素,且浓度越大,降解率越高,尤其对半纤维素降解效果最明显,降解率为14.08%~43.68%。

微波-Fe(Ⅱ)/S_(2)O_(8)^(2-)耦合强化污泥溶胞与定向甲烷转化

本研究探讨了微波-Fe(Ⅱ)/S_(2)O_(8)^(2-)耦合预处理对污泥溶裂、甲烷转化以及有机物降解的影响,结果表明,单一微波预处理可促进污泥厌氧消化,而微波-Fe(Ⅱ)/S_(2)O_(8)^(2-)耦合预处理则有利于强化污泥细胞溶裂,缩短厌氧停留时间,提高有机质去除率,处理效果与微波瓦数和氧化剂投加量成正比.其中,微波辐射640 W,Fe(Ⅱ)/S_(2)O_(8)^(2-)=0.8/1.0 mmol·g^(-1)-TS为最佳预处理条件,此时污泥溶解性多糖(soluble polysaccharides,SPS)增溶量较对照组高7.5倍,厌氧产气率仅在4 d即可达到峰值,厌氧停留时间较其他预处理污泥缩短约75.7%,且SPS去除率达到98.6%.一级动力学模型模拟揭示,污泥水解速率与产甲烷性能无必然联系,基质本身的产甲烷潜力则是影响和决定其最终甲烷产量的关键制约因子.能量评估结果进一步表明,尽管耦合预处理未能获得明显的能量输出,但单位干基污泥的处理能耗节约20.1 kWh·kg^(-1),仅为原来的45%—60%.

HCl和NaOH预处理对菊芋秸秆产甲烷潜力的影响

为资源化利用菊芋秸秆,以菊芋秸秆为底物进行了中温批式厌氧消化实验,通过对比不同浓度HCl和NaOH(0.2~0.8 mol/L)预处理对菊芋秸秆产甲烷潜力的影响,研究了HCl和NaOH预处理在菊芋秸秆厌氧消化中应用的可行性。研究结果表明:HCl处理效果优于NaOH处理,0.4 mol/L HCl处理后菊芋秸秆的产甲烷潜力达到了(229.57±13.77)mL/g,较未经处理的菊芋秸秆提高了71.17%;NaOH和HCl预处理均能够有效打开菊芋秸秆内部结构,其中HCl处理后,半纤维素降解率最大,为17.26%~31.75%,NaOH处理后,木质素降解率最大,为6.87%~16.87%;NaOH处理可以缩短菊芋秸秆的厌氧消化周期(T_(50),T_(80)和T_(90)分别缩短了5~6,9~14,5~11d),但要获得更大的甲烷产量可能需要更高浓度的NaOH进行预处理。综合考虑经济效益和对环境的污染等因素,低浓度的HCl更适于菊芋秸秆厌氧消化的预处理。

生物处理对稻草秸秆厌氧发酵产甲烷的影响及动力学分析

厌氧发酵制沼气是农作物秸秆能源化利用的有效途径,但产气效率低是其规模化应用的制约因素之一。本实验通过外源添加微生物的方式对稻草秸秆进行处理,研究其对厌氧发酵产甲烷的影响,并采用Gompertz模型对发酵过程进行拟合分析。结果表明:生物处理可有效促进稻草秸秆厌氧发酵产甲烷,且复合菌种具有协同促进作用。单种添加纤维素降解菌后,稻秆单位挥发性固体(VS)甲烷产量达203.52~213.52 mL/g,比未添加菌种的对照组提升了0.42%~5.35%;添加复合菌种的甲烷产量达217.33~245.52 mL/g,比对照组提升5.90%~19.64%。动力学分析表明Gompertz模型对稻秆厌氧发酵产甲烷过程拟合效果佳,模型相关系数R2达0.9999,产气预测值与实测值的绝对百分偏差小。研究表明,生物处理是提高稻草秸秆厌氧发酵产气率的有效手段。

厨余垃圾残渣与芦笋秸秆协同干式厌氧消化产甲烷研究

针对上海市湿垃圾处理厂厨余垃圾残渣及当地芦笋秸秆资源化利用率低的问题,对厨余垃圾残渣与芦笋秸秆协同干式厌氧消化产甲烷进行了批式实验研究。结果表明:当设置40 g/L有机负荷(以VS计)且各实验组的C/N分别为10.3、13.4、16.5、19.6、22.7进行厨余垃圾残渣与芦笋秸秆协同干式厌氧实验时,C/N为13.4的实验组获得的最大比产甲烷速率(以VS计)最高,为18.01 mL/(g·d),这时芦笋秸秆占整个进料原料的干基质量比为44.44%。微生物群落结构分析结果表明:各实验组在属水平上主要细菌为norank_f_norank_o_norank_c_norank_p_Firmicutes、norank_f_ST-12K33、Fastidiosipila、norank_f_Dethiobacteraceae等;在属水平上主要古菌为产甲烷菌Methanobacterium和Methanosaeta,且C/N为10.3的纯厨余实验组的氢型产甲烷菌Methanobacterium的丰度明显低于其他协同干式厌氧实验组。

复合菌系MC1预处理对玉米秸秆厌氧发酵产甲烷效率的提高

采用高效纤维素分解菌复合系MC1对玉米秸秆进行预处理,以提高玉米秸秆厌氧甲烷发酵的效率和产气量。复合菌系预处理的结果表明,预处理发酵液的pH值呈先下降后升高的趋势,与以往的复合菌系发酵产物pH值特性相似。在14 d的预处理过程中,秸秆质量减少了59.0%,其中纤维素减少了53.1%,半纤维素减少了76.4%。发酵液中的可溶性糖含量最大值出现在第2 d,为1.44 g/L。化学需氧量(COD)和挥发性产物最大值均出现在第4 d,监测到的5种挥发性产物的量分别为乙醇2.38 g/L、乙酸0.57 g/L、丙酸0.11 g/L、丁酸0.62 g/L和甘油0.22 g/L,因此,处理4 d后最适合甲烷发酵。厌氧发酵的结果表明,与未处理的玉米秸秆的厌氧发酵相比,预处理后的秸秆总产气量和总甲烷量分别了提高了33.0%和58.1%。结果表明,MC1对玉米秸秆预处理后,可明显提高甲烷产量,具有较高的利用潜力。

三价铁离子促进玉米秸秆厌氧发酵

厌氧消化是农业废弃物资源化利用的有效途径之一。微量元素是影响有机废弃物厌氧产沼气性能的重要生态因子,其中铁对有机废弃物的厌氧发酵过程的效率和稳定性作用最为显著,而通常秸秆的含铁量很低。因此,该试验以玉米秸秆为例,研究了初始FeCl3加入量分别为0.1%、0.2%、0.5%、1.5%、3%、6%(基于秸秆的挥发性组分)时秸秆厌氧发酵产沼气、产甲烷过程以及沼液沼渣特征。结果表明初始FeCl3加入量为3%,秸秆的厌氧产甲烷效率相对于对照(加入量0%)提高了14%。X射线衍射分析结果表明FeCl3存在时,沼渣中纤维素的结晶度显著降低。沼渣的组分分析结果表明FeCl3的存在有助于提高玉米秸秆中纤维素及半纤维素的分解效率,从而提高了秸秆产甲烷效率。该研究可为农业废弃物甲烷化利用提供参考。

稻草与鸡粪配比对混合厌氧消化产气率的影响

为获得稻草与鸡粪混合厌氧消化较佳的原料配比,以稻草和鸡粪为原料,在初始挥发性固体(VS)负荷为6%和中温(37℃)条件下,考察不同的稻草与鸡粪VS配比(0:1、1:2、1:1、2:1、1:0)对混合厌氧消化过程的影响。结果表明,不同配比条件下厌氧消化均没有出现挥发性有机酸或氨氮抑制,整个发酵过程的pH值稳定在6.8～8.2;与稻草和鸡粪单独厌氧消化相比,混合厌氧消化能够显著提高原料产气率;在稻草与鸡粪VS比分别为0:1、1:2、1:1、2:1、1:0时,实际挥发性固体甲烷产率分别为212.43、240.45、250.28、206.09和178.03mL/g,实际平均甲烷体积分数分别为58.8%、50.5%、50.8%、49.2%和50.1%;C/N在11.2～47.5,甲烷产率和沼气产率的实际值与理论值之比(Ya/Ym)呈现先上升后下降趋势,在C/N为17.8时,Ya/Ym达最大值。在中温厌氧消化工程应用中,建议稻草与鸡粪VS比为1:1,或控制配比后混合原料的C/N约为17.8,设计发酵停留时间为23d,挥发性固体产气率为446mL/g。

秸秆厌氧消化产甲烷的研究进展

近年来,随着国际能源紧缺与环境污染的日趋严重,秸秆厌氧消化产甲烷技术再次成为国内外学者研究生物质固废处理的热点之一。农作物秸秆厌氧消化产甲烷为大量廉价易得的生物资源转化为可再生能源提供了一个新机会。通过厌氧消化,不仅改善农村生态环境质量,还产生了清洁能源沼气,真正实现变废为宝,对解决农村用能和种植业污染问题有重要意义,也是目前中国最有希望实现产业化的生物质能源之一。然而,由于秸秆的特殊物理化学结构,使得微生物与酶很难对其吸附、降解,并因此限制了秸秆厌氧消化的推广、应用。尽管在当前中国的鼓励政策下,许多秸秆沼气示范工程建成并投入生产,但实际运行中依旧有些问题亟待解决。该文根据国内外关于秸秆厌氧消化产甲烷技术的最新研究成果,基于厌氧消化原理和原料特性分析的基础上,分析了影响秸秆产甲烷的因素及不足,总结了产气优化的方法,展望了秸秆厌氧消化产甲烷的发展方向。该项研究结果对推广秸秆厌氧消化产甲烷、加快生物质固废的资源化成果转化具有积极的推动意义。

玉米秸秆固态和液态厌氧发酵产气性能与微生物种类比较研究

厌氧发酵产沼气是中国绿色农业发展过程处理农业废弃物的重要手段,该文以玉米秸秆为研究对象,开展液态、固态厌氧发酵产气性能、微生物系统多样性及演替规律的比较研究,得出如下结论:固态发酵总固体(TS)产气率及甲烷转化率略低于液态发酵,发酵结束后,前者沼液中N、P、C的含量要低于后者;乙酸是两发酵体系挥发性脂肪酸(VFAs)的主要组成,占总VFAs的70%以上。高通量测序结果发现,2个发酵系统中细菌主要以Bacteroidetes、Firmicutes、Proteobacteria、Cloacimonetes、Synergistetes及Verrucomicrobia为主,这6类菌群占总克隆数的80%以上。而Methanosaeta,Methanospirillum,Methanocorpusculum以及Methanoculleus是两系统优势古菌,并且随消化过程的进行,古菌群落呈现由乙酸型向氢营养型转变的趋势。发酵结束后,上述2类古菌在群落中的占比基本持平。对微生物多样性的聚类分析结果显示,在发酵第4天和第8天后,2个系统中细菌与古菌群落结构的差异逐渐明显。进一步分析表明,影响玉米秸秆液态发酵微生态结构的主要环境因子为乙酸,秸秆纤维素水解可能是制约物能转化率的关键过程;总磷(TP)是影响固态发酵系统微生态结构的关键环境因子,而如何增加产甲烷古菌的生物量是提高原料产气率的关键。该研究结果为调控玉米秸秆厌氧发酵过程、提高其生物降解效率提供了科学依据。

不同温度下氢氧化钠预处理对玉米秸秆甲烷产量的影响(英文)

利用农作物秸秆进行厌氧发酵生产沼气是解决我国农村能源紧张的重要途径，然而秸秆中难以降解的木质纤维结构导致在发酵过程中甲烷转化率较低。利用自行设计的可控性恒温发酵装置，以玉米秸秆为发酵原料，分析了在不同温度条件下氢氧化钠（NaOH）预处理对秸秆木质纤维结构以及厌氧发酵产气效率的影响。结果表明， NaOH预处理能够显著降低玉米秸秆的木质纤维素含量，与未预处理的秸秆相比，经NaOH处理后的秸秆纤维素含量降低了24.4%～33.2%，半纤维素含量降低了14.2%～52.4%，木质素含量降低了9.3%～29.3%。在6%、8%和10%浓度中，经8%NaOH处理的秸秆在55℃下的甲烷产量最高，达到188.7 ml CH4·（gVS）-1，较未处理的增加了84.2%，因此可作为提高秸秆厌氧发酵产气效率的预处理方法。

高含固率秸秆和牛粪混合物料发酵产甲烷工艺

该研究针对高含固率纤维质物料难以连续厌氧发酵、甲烷产率低的问题，利用所研制的一套能连续进出料、具有高有机负荷承载力的新型反应器，以玉米秸秆和牛粪为原料，通过调控搅拌强度和投料强度在反应器内建立了“分区发酵”体系，比较了3种高含固率（10%、15%和20%）物料在不同有机负荷下的甲烷容积产率，系统研究了物料含固率、搅拌强度和投料强度对“分区发酵”体系形成功能分区的高度、各功能区的pH值和甲烷容积产率的影响，旨在为纤维质物料产甲烷提供高效的发酵工艺和可靠的运行参数。结果表明，含固率为10%和15%的反应器，甲烷容积产率随有机负荷的增加而增加，平均甲烷体积分数稳定在52%左右，二者在有机负荷分别为13.44和20.17 kg/（m3·d）时，甲烷容积产率最高，分别为1.62和1.66 m3/（m3·d），在有机负荷分别为20.17和30.0 kg/（m3·d）时，甲烷产量明显下降；含固率为20%的反应器，甲烷容积产率随有机负荷的增加基本保持不变且较低（0.98 m3/（m3·d）），当有机负荷达到30.0 kg/（m3·d）时，发酵体系酸败，甲烷产量明显下降。双因素优化结果表明，当物料含固率为10%和15%、搅拌强度为6～12 h/d、投料强度为6.5～10 d时，发酵体系可形成高效的酸化区和产甲烷区，二者的高度之比为1.1～1.6：1，甲烷容积产率可达1.63～1.69 m3/（m3·d）。综上，该反应器可实现含固率为10%～20%的纤维质物料连续进出料，并在含固率为10%和15%时能高效、稳定地产甲烷，通过调控搅拌强度和进料强度能提高其甲烷容积产率。该发酵工艺有规模化应用的前景。