芦苇酶解对氢气-甲烷联产过程微生物群落演替规律的影响

采用10 mg/g纤维素酶R-10预处理芦苇秸秆,研究了酶解预处理对芦苇厌氧产气潜力的影响,分析了氢气-甲烷联产过程中微生物群落结构演替规律. 结果表明:酶解预处理后,芦苇秸秆在产氢阶段的累积产气量和φ(H₂)分别达到42.5 mL/g和52.1%;在产甲烷阶段,累积产气量稳定上升,最高值可达137.5 mL/g,是对照组产气量的5倍. 由扫描电镜(SEM)观察可知,产氢阶段以短杆状和梭状菌为主,产甲烷阶段以长杆菌为主. PCR-DGGE(聚合酶链式反应-变性梯度凝胶电泳)分析表明,芦苇在酶解预处理后,其厌氧联产过程中微生物群落呈规律性演替,产氢阶段的优势微生物分别为具有降解纤维素产氢气功能的嗜热纤维素菌Clostridium thermocellum(条带B20)、具有高效产氢潜力的兼性厌氧产气肠杆菌Enterobacter aerogenes(条带B28);在产甲烷阶段,其优势微生物为可利用氢营养途径合成甲烷的产甲烷古菌Methanoculleus bourgensis(条带A3)、Methanoculleus horonobensis(条带A13). 经纤维素酶预处理后,芦苇秸秆厌氧联产的累积产气量、φ(H₂) 提高显著,具有纤维素降解功能的细菌和可利用氢营养途径合成甲烷的古菌为主要优势微生物.      

剩余污泥厌氧消化过程产甲烷抑制技术研究进展

剩余污泥厌氧发酵过程中产生的挥发性脂肪酸（VFA）相比甲烷具有更高的应用价值,因而受到广泛关注。研究发现,通过产甲烷抑制剂可以将厌氧发酵控制在产酸阶段,阻断产甲烷过程,从而实现VFA的大量积累。然而,目前产甲烷抑制剂存在分类不明确、部分产甲烷抑制剂机理研究不够完善等问题。因此,根据抑制产甲烷菌物质的来源和特性,将剩余污泥厌氧消化过程中产甲烷抑制剂分为内源抑制、外源抑制和生物抑制3类,分别阐述了其抑制机理及其对厌氧发酵产酸过程的影响,分析了各种抑制剂的研究现状及不足之处,指出抑制剂的毒性抑制研究和水解机理研究将是今后的研究重点,同时应进一步研究了厌氧发酵系统中微生物之间的竞争关系,明确微生物在剩余污泥厌氧发酵产酸和抑制产甲烷过程中的作用机制。     

生物炭介导鸡粪厌氧消化性能研究

为探究生物炭介导的鸡粪厌氧消化产甲烷的较优添加比例,在发酵温度[(35±1)℃]、接种率30%的条件下,进行了以鸡粪为底物,生物炭为外源添加剂的厌氧消化试验,研究生物炭不同添加量(20%、15%、10%、5%和不添加)对鸡粪厌氧消化产气特性的影响,确定了生物炭介导的鸡粪厌氧消化的较优添加比例;同时,用扫描电子显微镜对厌氧消化前后生物炭颗粒和附着在生物炭颗粒上的微生物进行了观察.结果表明:生物炭的添加提高了鸡粪单位VS产甲烷量,添加20%、15%、10%和5%生物炭的处理鸡粪VS产甲烷量分别为223mL/g、228mL/g、230mL/g和281mL/g,均高于对照组的202mL/g;添加生物炭提高了产气中的甲烷含量,降低了二氧化碳和硫化氢含量,提高了沼气品质;电镜扫描结果表明,厌氧消化后生物炭表面及内部附着了大量厌氧微生物,主要为杆菌、微粒菌和球菌;本研究中,生物炭介导鸡粪厌氧消化最优的添加比例约为5%.     

外加氨氮对玉米秸秆厌氧发酵的影响

以玉米秸秆为例,研究了氨氮浓度对农业废弃物厌氧发酵产甲烷性能以及沼渣特性的影响,并利用Gompertz方程对沼气及甲烷产生过程进行了数学拟合。实验结果表明:外加氯化铵浓度(1¹0 g/L)对秸秆厌氧产累计产气量影响不显著;但对累计甲烷产量、玉米秸秆中挥发性组分(volatile solid,VS)的去除率、沼渣组分等有显著影响。在外加氯化铵浓度为5 g/L时,即碳氮比(C/N)为15∶1时,产气组分中甲烷含量最高为1 039 mL,当外加氯化铵浓度为10 g/L时,产气组分中甲烷量最低仅为833 mL。此外,用修正的Gompertz方程能够很好地拟合各反应器的厌氧发酵产气产甲烷过程。高浓度氯化铵(10 g/L)对产甲烷量、VS去除率有抑制作用。氯化铵浓度对沼渣中纤维素含量影响不显著,对半纤维素及木质素含量影响显著。     

生物炭强化苯酚厌氧降解产甲烷特性

通过批次实验探究生物炭对苯酚厌氧降解产甲烷过程的促进机制,并考察了300,500,700℃下制备的生物炭对苯酚甲烷化过程延滞期、最大产甲烷速率和微生物群落结构的影响.结果表明：生物炭的电子交换能力与苯酚甲烷化过程具有显著关系（R²=0.997）.与对照组相比,投加15g/L的生物炭可将苯酚甲烷化的延滞期从15.0d缩短至1.1~3.2d,最大产甲烷速率由4.0mL/d提高到10.4~13.9mL/d.其中在热解温度500℃下制备的生物炭由于含有丰富的电化学活性类醌结构,对苯酚甲烷化过程促进效果最优.此外,生物炭投加促进了典型产电细菌Geobacter及产甲烷菌Methanosaeta的富集.进一步说明生物炭投加通过促进种间电子传递加速了苯酚甲烷化过程.     

不同填埋龄垃圾甲烷和恶臭物质产生潜势

针对甲烷和恶臭物质产生潜势与垃圾填埋龄的关系,利用全自动甲烷潜能测试系统进行厌氧发酵实验,监测累积产甲烷量和速率,使用气相色谱/质谱联用仪分析恶臭物质种类和浓度.结果表明：填埋龄较短的垃圾产气量高于填埋龄较长的垃圾,填埋龄3a的垃圾产气量最大,单位质量垃圾甲烷累计产生量为29.81mL/g,填埋龄7a的垃圾产气量最小,为6.16mL/g,填埋龄3a的垃圾产甲烷速率最大,最高值达112.3mL/d;共检出40种恶臭物质,芳香族和脂肪烃种类最多、浓度最高,芳香族、卤代烃和含硫化合物浓度比例随垃圾填埋龄增加而增加;脂肪烃浓度比例随垃圾填埋龄增加而减小.     

厌氧分步生物反应器系统处理城市生活垃圾的试验研究

以生活垃圾中COD溶出量为研究参数,试验研究了厌氧分步生物反应器系统和渗滤液直接回灌填埋场中的有机物降解规律与产甲烷特征.结果表明:厌氧分步生物反应器系统可显著促进生活垃圾及渗滤液中有机污染物的降解,加速填埋垃圾稳定化,其COD溶出总量与填埋时间的对数呈极显著的线性相关性.厌氧分步生物反应器中产甲烷反应器的产气量占总产气量的80%,甲烷含量55%～69%,较适容积COD负荷为6.5～7.5g/(L·d).     

煤层气资源及利用进展

煤层气为非常规天然气，即煤层中的甲烷，是一种极易爆炸的气体，需要在采煤作业中先行排出，以保证煤矿生产安全。而且，甲烷的温室效应是二氧化碳的21倍，综合利用煤层气将降低温室气体排放。煤层气（煤层甲烷，CBM）开发对弥补天然气的供应不足具有重要意义。加拿大和印度等国正在加快煤层气的开发利用。     

雌激素污染对水体微生物产甲烷功能的影响

针对目前水体环境雌激素的污染形势严峻,且其对水体功能性微生物群落影响规律及机理不明等问题,选择典型天然雌激素——17β-雌二醇(E2)为主要研究对象,构建实验室厌氧水体微生态系统,分析E2污染对厌氧水体微生物活性和产甲烷功能的影响规律。结果表明,在厌氧条件下,E2污染对水体微生物群体的活性存在显著的抑制效应,对水体甲烷的产生速率亦存在规律性的影响。当水体E2浓度≤0.5 ng/L时,对水体微生物的产甲烷活性存在促进作用。当E2浓度≥1.0 ng/L时,E2污染对水体微生物的产甲烷活性存在明显的抑制效应,且随着E2浓度的升高抑制作用增强。因此,厌氧条件下,微量E2污染会影响水体微生物活性和产甲烷效应的变化,从而对水体自净功能和甲烷释放产生影响。     

海洋油气田沉积物产甲烷活性及微生物生态

海洋产甲烷古菌是与海洋中甲烷的产生、释放及天然气水合物的形成等密切相关的微生物类群.以产甲烷菌可能利用的底物为碳源,评价了海洋油气田沉积物的产甲烷活性.结果表明,海洋油气田沉积物对于H2/CO2、甲醇、一甲胺、三甲胺,在25℃和37℃两种温度条件下都具有较高的产甲烷活性,少数样品只在37℃对乙酸有产甲烷活性,说明在海洋油气田环境下,主要有氢营养型及甲基营养型发酵途径产生天然气甲烷.利用厌氧培养法对产甲烷菌进行了多样性解析,16S rRNA基因测序显示,优势产甲烷菌主要属于Methanosarcinales目的 Methanosarcinaceae科及Methanomicrobiales目的 Methanomicrobiaceae科,其中Methanococcoides、Methanogenium和Methanosarcina为油气田沉积物的主要菌属.     

中国油气系统甲烷逸散排放估算

为实现碳达峰碳中和目标,中国正致力于推动能源低碳化转型,这促进能源由煤炭向油气资源的转变.因此,中国石油和天然气系统（油气系统）的甲烷（CH₄）排放日益受到关注.逸散排放包括设备泄漏、排空和火炬燃烧,涉及油气资源的开发、生产、运输、储存和分配等过程.但目前油气系统CH₄逸散排放缺乏统一的核算方法,逸散排放量亦未被纳入国家温室气体清单统计之中.基于相关方法,评估了1980~2020年中国油气系统的CH₄逸散排放.结果表明,油气系统的CH₄逸散排放随着油气资源的生产和消费增长而快速增加,由1980年不足60万t增长至2020年的超过260万t.石油系统和天然气系统在2020年的CH₄逸散排放分别达到约60万t和200万t,是1980年的1.38倍和16.6倍.油气系统的CH₄逸散主要源于天然气生产、石油生产、天然气分配、天然气运输和储存,分别占总排放的41%、20%、18%和13%.天然气管道是主要的逸散设施.相比于常规油气资源开发,非常规油气资源开发的排放强度更高.研究完善了CH₄逸散排放清单,可为CH₄减排提供重要科学数据支持.     

天然和水热合成针铁矿对有机物厌氧分解释放CH4的影响

以乙酸钠为碳源,通过序批式实验研究了天然和水热合成针铁矿对铁还原菌-甲烷菌厌氧微生物生化系统中CH4释放量的影响.通过对实验过程中气体组分、溶液中总有机碳(TOC)、总无机碳(TIC)、Fe2+等主要组分的分析测定和固体产物的X-射线衍射(XRD)分析,结合对矿物的比表面(BET)、XRD、X-射线荧光光谱(XRF)分析表征,探讨了针铁矿在铁还原菌存在下对有机物厌氧消化产CH4的影响和作用机制.利用修正Gompertz方程对累计产CH4和CO2量进行拟合.结果表明,与对照实验组相比,添加针铁矿能使CH4累计释放量提前60～78 d达到最大值,并且能有效降低CO2释放量达30%～67%,添加水热合成针铁矿较之天然针铁矿更能促进CH4释放和减少CO2释放;固体产物分析表明添加针铁矿促使菱铁矿形成固定部分CO2.     

Der atmosphärische Kreislauf von Methan

Present methane concentrations in the northern troposphere average 1.65 ppm. Most CH₄ is of recent biogenic origin. ¹⁴C analyses indicate that no more than 10% is released by fossil sources. The various CH₄-producing ecosystems are described and the total annual production is estimated to lie between 5.9×10¹⁴ and 9.3×10¹⁴ g/y. CH₄ is destroyed through photochemical oxidation mainly in the troposphere. In this process CH₂O, H₂, and CO are produced as intermediates. Tropospheric CH₄ provides an important source of stratospheric water vapor.     

Climate impact from peat utilisation in Sweden

The climate impact from the useof peat for energy production in Sweden hasbeen evaluated in terms of contribution toatmospheric radiative forcing. This wasdone by attempting to answer the question`What will be the climate impact if onewould use 1 m<sup>2</sup> of mire for peatextraction during 20 years?'. Two differentmethods of after-treatment were studied:afforestation and restoration of wetland.The climate impact from a peatland –wetland scenario and a peatland –forestation – bioenergy scenario wascompared to the climate impact from coal,natural gas and forest residues.Sensitivity analyses were performed toevaluate which parameters that areimportant to take into consideration inorder to minimize the climate impact frompeat utilisation. In a `multiple generationscenario' we investigate the climate impactif 1 Mega Joule (MJ) of energy is produced every yearfor 300 years from peat compared to otherenergy sources.The main conclusions from the study are:?The accumulated radiative forcing from the peatland – forestation – bioenergy scenario over a long time perspective (300 years) is estimated to be 1.35 mJ/m²/m² extraction area assuming a medium-high forest growth rate and medium original methane emissions from the virgin mire. This is below the corresponding values for coal 3.13 mJ/ m²/ m² extraction area and natural gas, 1.71 mJ/ m²/ m² extraction area, but higher than the value for forest residues, 0.42 mJ/ m²/ m² extraction area. A `best-best-case' scenario, i.e. with high forest growth rate combined with high `avoided' methane (CH₄) emissions, will generate accumulated radiative forcing comparable to using forest residues for energy production. A `worst-worst-case' scenario, with low growth rate and low `avoided' CH₄ emissions, will generate radiative forcing somewhere in between natural gas and coal.?The accumulated radiative forcing from the peatland – wetland scenario over a 300-year perspective is estimated to be 0.73 –1.80 mJ/ m²/ m² extraction area depending on the assumed carbon (C) uptake rates for the wetland and assuming a medium-high methane emissions from a restored wetland. The corresponding values for coal is 1.88 mJ/ m²/ m² extraction area, for natural gas 1.06 mJ/ m²/ m² extraction area and for forest residues 0.10 mJ/ m²/ m² extraction area. A `best-best-case' scenario (i.e. with high carbon dioxide CO<sub>2</sub>-uptake combined with high `avoided' CH₄ emissions and low methane emissions from the restored wetland) will generate accumulated radiative forcing that decreases and reaches zero after 240 years. A `worst-worst-case' (i.e. with low CO<sub>2</sub>-uptake combined with low `avoided' CH₄ emissions and high methane emissions from the restored wetland) will generate radiative forcing higher than coal over the entire time period.?The accumulated radiative forcing in the `multiple generations' – scenarios over a 300-year perspective producing 1 MJ/year is estimated to be 0.089 mJ/ m<sup>2</sup> for the scenario `Peat forestation – bioenergy', 0.097 mJ/ m² for the scenario `Peat wetland with high CO<sub>2</sub>-uptake' and 0.140 mJ/ m<sup>2</sup> for the scenario `Peat wetland with low CO₂-uptake'. Corresponding values for coal is 0.160 mJ/ m², for natural gas 0.083 mJ/ m² and for forest residues 0.015 mJ/ m². Using a longer time perspective than 300 years will result in lower accumulated radiative forcing from the scenario `Peat wetland with high CO₂-uptake'. This is due to the negative instantaneous forcing that occurs after 200 years for each added generation.?It is important to consider CH₄ emissions from the virgin mire when choosing mires for utilization. Low original methane emissions give significantly higher total climate impact than high original emissions do.?Afforestation on areas previously used for peat extraction should be performed in a way that gives a high forest growth rate, both for the extraction area and the surrounding area. A high forest growth rate gives lower climate impact than a low forest growth rate.?There are great uncertainties related to the data used for emissions and uptake of greenhouse gases in restored wetlands. The mechanisms affecting these emissions and uptake should be studied further.     

Modeling the impact of mitigation options on methane abatement from rice fields

The enhanced concentration of methane (CH₄) in the atmosphere is significantly responsible for the ominous threat of global warming. Rice (Oryza) paddies are one of the largest anthropogenic sources of atmospheric CH₄. Abatement strategies for mitigating CH₄ emissions from rice fields offer an avenue to reduce the global atmospheric burden of methane and hence the associated menace of climate change. Projections on population growth suggest that world rice production must increase to meet the population’s food energy demand. In this scenario, those mitigation options are advocated which address both the objectives of methane mitigation and increased production of rice simultaneously. In this paper, we have formulated a nonlinear mathematical model to investigate the effectiveness and limitations of such options in reducing and stabilizing the atmospheric concentration of CH₄ while increasing rice yield. In modeling process, it is assumed that implementation rate of mitigation options is proportional to the enhanced concentration of atmospheric CH₄ due to rice fields. Model analysis reveals that implementation of mitigation options not always provides “win-win” outcome. Conditions under which these options reduce and stabilize CH₄ emission from rice fields have been derived. These conditions are useful in devising strategies for effective abatement of CH₄ emission from rice fields along with sustainable increase in rice yield. The analysis also shows that CH₄ abatement highly depends on efficiencies of mitigation options to mitigate CH₄ emission and improve rice production as well as on the implementation rate of mitigation options. Numerical simulation is carried out to verify theoretical findings.     

Quantification of carbon dioxide and methane emissions in urban areas: source apportionment based on atmospheric observations

Anthropogenic emissions of carbon dioxide (CO₂) and methane (CH₄) in the atmosphere constitute an important component of the related carbon budget. The main source of anthropogenic CO₂ is burning of fossil fuels, especially in densely populated areas. Similar emissions of CH₄ are associated with the agricultural sector, coal mining, and other human activities, such as waste management and storage and natural gas networks supplying methane to large urban, industrial centers. We discuss several methods aimed at characterizing and quantifying atmospheric loads and fluxes of CO₂ and CH₄ in Krakow, the second largest city in Poland. The methods are based on atmospheric observations of mixing ratios as well as isotopic composition of the investigated gases. Atmospheric mixing ratios of CO₂ and CH₄ were measured using gas chromatography (GC) and cavity ring-down spectroscopy (CRDS). The isotopic composition of CO₂ and CH₄ was analyzed using isotope ratio mass spectrometry (IRMS), accelerator mass spectrometry (AMS), and CRDS techniques. These data, combined with auxiliary information characterizing the intensity of vertical mixing in the lower atmosphere (height of the nocturnal boundary layer [NBL] and atmospheric ²²²Rn concentration), were further used to quantify emission rates of CO₂ and CH₄ in the urban atmosphere of Krakow. These methods provide an efficient way of quantifying surface emissions of major greenhouse gases originating from distributed sources, thus complementing the widely used bottom-up methodology based on emission statistics.

     

酸性冲击对微生物电解产氢阳极菌群影响及功能基因变化解析

微生物电解产氢工艺是借助能够直接与电极传递电子的功能菌在阳极降解有机质并将产生的电子在阴极与质子结合回收氢气能源的新技术.采用市政废水在固定外加电压相同条件下直接启动15个反应器,以葡萄糖为碳源驯化获得电极功能菌群,稳定运行1个月获得反应器稳定产氢和伴随产甲烷效能.初始稳定时采用pH为7的磷酸盐缓冲液可以获得稳定的产气量,平行反应器表现出不同的氢气和甲烷产量.最高产氢反应器的氢气转化率为32.2%,氢气产率为(3.9±0.6)mol·mol-1(以每mol葡萄糖产生的H2量(mol)计,下同);相同条件下最低产氢效率反应器的甲烷转化率则可达到48.4%.通过48 h阳极生物膜的酸性冲击试验对阳极菌群功能恢复效果进行分析,发现消除冲击10~15 d反应器的电子传递效率得到恢复,但功能菌群多样性增加,氢气与甲烷比例发生变化.最高产氢反应器氢气产率降低1.8 mol·mol-1,而甲烷增量为0.4 mol·mol-1(以每mol葡萄糖产生的CH4量(mol)计,下同).通过关键功能基因分析发现,初始产氢效能高的反应器功能菌群中电子传递功能菌优势较大;阳极功能菌群受到短暂酸性冲击后,基于细胞色素C基因的相关菌群能够较快恢复,其电子传递能力恢复更快;与碳源降解和产甲烷相关基因群落受酸性冲击后变化较为显著,甲烷增量与氢气减少量基本符合反应计量关系.     

不同污水处理工艺非二氧化碳温室气体的释放

甲烷和氧化亚氮是两种重要的非二氧化碳温室气体.城市污水处理厂是甲烷和氧化亚氮的重要释放源.因此,为探究不同污水处理工艺甲烷和氧化亚氮的释放现状和变化规律,通过浮流式表面集气罩对西安市第三污水处理厂（Orbal氧化沟工艺）和第四污水处理厂（A/A/O工艺）生物处理过程中甲烷和氧化亚氮的排放情况进行测定,比较不同污水处理工艺中非二氧化碳温室气体的释放情况,并以第四污水处理厂为例研究溶解氧、温度对非二氧化碳温室气体释放量的影响.结果表明,西安市第三污水处理厂每m³进水释放甲烷1181 mg（以CH₄计）、氧化亚氮36.20 mg（以N₂O计）,西安市第四污水处理厂每m³进水释放甲烷209 mg（以CH₄计）、氧化亚氮54.64 mg（以N₂O计）.温度、曝气方式、溶解氧浓度、亚硝酸盐氧化速率和最大产甲烷活性是甲烷和氧化亚氮释放量的重要影响因素.     

瓦里关气相色谱法大气CO_2和CH_4在线观测数据处理分析

加强我国本底站温室气体数据资源的科学管理与共享,首先应保证观测全流程的标准化和规范化,确立数据处理和质量控制方法.我国青海瓦里关全球本底站自1994年开始了气相色谱-氢火焰离子化检测器法(GC-FID)大气CO2和CH4在线观测,本文详细讨论了该系统原始资料采集、数据信息合并、时间序列检查、观测员级质量控制和专家级质量控制等流程.利用局部近似回归法对大气CO2和CH4数据进行本底值筛分,获得CO2本底数据百分比约占有效数据的72%、CH4占44%.在线观测的CO2和CH4月平均浓度与同期瓶采样分析结果基本一致,相对偏差均在±0.5%以内.经流程化处理和质控的瓦里关大气CO2和CH4本底浓度变化资料已进入全球同化数据库(Globalview-CO2、Globalview-CH4),报送世界温室气体数据中心(WDCGG)并应用于世界气象组织(WMO)温室气体公报和联合国政府间气候变化专门委员会(IPCC)评估.     

Biochar addition to agricultural soil increased CH4 uptake and water holding capacity – Results from a short-term pilot field study

Biochar addition to agricultural soil has been suggested to mitigate climate change through increased biogenic carbon storage and reduction of greenhouse gas emissions. We measured the fluxes of N₂O, CO₂, and CH₄ after adding 9 t ha^?1 biochar on an agricultural soil in Southern Finland in May 2009. We conducted these measurements twice a week for 1.5 months, between sowing and canopy closure, to capture the period of highest N₂O emissions, where the potential for mitigation would also be highest. Biochar addition increased CH₄ uptake (96% increase in the average cumulative CH₄ uptake), but no statistically significant differences were observed in the CO₂ and N₂O emissions between the biochar amended and control plots. Added biochar increased soil water holding capacity by 11%. Further studies are needed to clarify whether this may help balance fluctuations in water availability to plants in the future climate with more frequent drought periods.