碱处理玉米秸秆与超声预处理污泥混合厌氧消化效果研究

以碱处理玉米秸秆和超声预处理污泥为发酵原料,在恒温35±1℃及底物浓度为15 gVS/L的条件下,采用正常运行的大型沼气池沼液作为接种物,研究不同配比(VS污泥:VS秸秆分别为1:0、2:1、1:1、1:2、1:4)对混合厌氧消化效果的影响.研究表明,VS污泥:VS秸秆的比例为1:2时累积产气量最高,VS产气率达到了472.33 mL·g-1,甲烷产量在发酵稳定后达到了60.52%.进一步研究得出,将超声预处理污泥与碱处理玉米秸秆按一定比例混合发酵可以将产气高峰提前.     

闽江口短叶茳芏+芦苇沼泽湿地大、小潮日土壤间隙水溶解性CH4与CO2浓度日动态

研究河口感潮沼泽湿地土壤间隙水溶解性CO_2和CH_4浓度日动态对于揭示河口湿地碳循环过程具有重要作用.于2010年的4月4~5日和9月2~3日(小潮日)和4月14~15日和9月9~10日(大潮日),对闽江河口鳝鱼滩中部中高潮滩过渡区分布的短叶茳芏(Cyperus malaccensis)+芦苇(Phragmites australis)沼泽湿地的土壤间隙水溶解性CO_2和CH_4浓度进行24 h连续监测,并同步测定了原位土壤温度、电导率及NH+4-N等参数.结果表明:14月与9月大、小潮日土壤间隙水溶解性CH_4浓度日变化范围分别介于88.20~190.74、53.42~141.24、16.27~81.89和44.90~88.53μmol·L~(-1),其中4月大、小潮日土壤间隙水溶解性CH_4浓度均呈现昼低夜高特征(P0.05),而9月大、小潮日呈现相反的日变化趋势(P0.05);29月大、小潮日土壤间隙水溶解性CO_2浓度日变化范围分别介于19.33~40.1μmol·L~(-1)和9.69~29.96μmol·L~(-1),均呈现昼低夜高特征(P0.01);3涨潮期间土壤间隙水溶解性CO_2浓度均要低于涨潮前与落潮后,而涨潮期间土壤间隙水溶解性CH_4浓度高于涨潮前和落潮后.     

鄂南棕红壤区不同植茶年限茶园CH4通量特征

于2014年3月—2015年12月,采用静态箱-气相色谱法测定了鄂南棕红壤丘陵区茶园和樟树林地土壤CH_4通量,研究了不同植茶年限茶园及临近林地土壤CH_4通量特征.结果表明,不同植茶年限对茶园土壤CH_4通量有显著影响,中、低龄茶园土壤CH_4以排放为主,植茶20 a和植茶8 a茶园土壤CH_4累积排放量分别为0.26和0.27 kg·hm~(-2),高龄茶园和对照林地土壤CH_4以吸收为主,植茶50 a茶园和林地土壤CH_4累积吸收量分别为0.39和1.95 kg·hm~(-2).降雨促进了鄂南棕红壤丘陵区茶园和林地土壤CH_4排放,除了植茶8 a茶园外,高、中龄茶园和樟树林地土壤CH_4通量均与7 d累积降雨量呈显著的正相关关系.施肥造成了茶园土壤CH_4排放量增加,同时土壤中矿质氮类型对该地区茶园和林地土壤CH_4通量有不同影响,CH_4排放通量与土壤硝态氮含量呈显著正相关关系,而与铵态氮含量相关关系不显著.研究表明,降雨量是影响鄂南红壤丘陵区茶园和林地土壤甲烷通量的主要因素;随着茶园种植年限的延长,土壤CH_4排放通量呈降低的趋势,高龄茶园土壤为大气CH_4汇.     

Sulfate-containing amendments to reduce methane emissions from rice fields: mechanisms,effectiveness and costs

Application of sulfate-containing amendments is oftensuggested as a mitigation option to reduce methane (CH₄) emissionsfrom rice (Oryza) fields. This paper discusses the mechanism andpotential of this mitigation option, reviews the relevant experimental data,and presents first, indicative costs of application. CH₄ emission datafor rice fields with sulfate-containing amendments are compiled toreinterpret the resulting reduction in CH₄ emission and find a generalrelationship between emission reduction and amount of sulfate applied. Thereduction in CH₄ emission depends on the amount of sulfate applied.However, absolute emission reduction is location specific and cannot bederived from the amount of sulfate (SO^2- ₄) applied only. We established alogarithmic relationship, across locations, between SO^2- ₄ application andfractional emission reduction relative to the emission of the non-amendedcontrol field. Recycling of SO^2- ₄ in the rhizosphere was essential to explainthe observed reductions in CH₄ emission for a number of theexperiments. The cost of applying SO^2- _{_4}-containing fertilizers varies acrosscountries and depends on local fertilizer prices. Since a fractional reductionis obtained, the cost-efficiency in terms of CH₄ mitigation per unitof SO^2- ₄ applied will be highest in high-emitting rice production systems.Provided the proper target areas are selected, the cost of SO^2- ₄-containingfertilizer as a mitigation option to reduce CH₄ emissions in rice fieldsis estimated at 5–10 US dollar per Mg CO₂-equivalent.     

Reduction in global habitat loss from fossil-fuel-dependent increases in cropland productivity

Terrestrial biodiversity loss and climate change, driven mainly by loss of habitat to agriculture and fossil fuel (FF) use, respectively, are considered among the world's greatest environmental threats. However, FF-dependent technologies are currently essential for manufacturing synthetic nitrogen fertilizers (SNFs) and synthetic pesticides (SPs) critical to increasing agricultural productivity, which reduces habitat loss. Fossil fuel use increases CO₂ levels, further enhancing agricultural productivity. Based on estimates of global increases in yields from SNFs, SPs, and atmospheric CO₂ fertilization, I estimated that FF-dependent technologies are responsible for at least 62.5% of current global food production (GFP) from cropland. Thus, if FF use is eschewed in the future, maintaining current GFP means croplands would have to increase from 12.2% of global land area (GLA) excluding Antarctica to 32.7%. The additional 20.4% of GLA needed exceeds habitat lost currently to cropland (12.2% of GLA) and cumulative conservation areas globally (14.6% of GLA). Thus, although eliminating FF use could reduce climate change, its unintended consequences may be to significantly exacerbate biodiversity loss and indirectly increase food costs, reducing food security which, moreover, disproportionately affects the poor. Although it may be possible to replace SNFs and SPs with FF-free technologies, such substitutes have not yet been demonstrated to be sufficiently economical or efficient. In the interim, meeting global food demand and keeping food prices affordable would increase habitat conversion and food prices. These trade-offs should be considered in analyses of climate change policies.     

Making carbon sequestration a paying proposition

Atmospheric carbon dioxide (CO₂) has increased from a preindustrial concentration of about 280 ppm to about 367 ppm at present. The increase has closely followed the increase in CO₂ emissions from the use of fossil fuels. Global warming caused by increasing amounts of greenhouse gases in the atmosphere is the major environmental challenge for the 21st century. Reducing worldwide emissions of CO₂ requires multiple mitigation pathways, including reductions in energy consumption, more efficient use of available energy, the application of renewable energy sources, and sequestration. Sequestration is a major tool for managing carbon emissions. In a majority of cases CO₂ is viewed as waste to be disposed; however, with advanced technology, carbon sequestration can become a value-added proposition. There are a number of potential opportunities that render sequestration economically viable. In this study, we review these most economically promising opportunities and pathways of carbon sequestration, including reforestation, best agricultural production, housing and furniture, enhanced oil recovery, coalbed methane (CBM), and CO₂ hydrates. Many of these terrestrial and geological sequestration opportunities are expected to provide a direct economic benefit over that obtained by merely reducing the atmospheric CO₂ loading. Sequestration opportunities in 11 states of the Southeast and South Central United States are discussed. Among the most promising methods for the region include reforestation and CBM. The annual forest carbon sink in this region is estimated to be 76 Tg C/year, which would amount to an expenditure of $11.1–13.9 billion/year. Best management practices could enhance carbon sequestration by 53.9 Tg C/year, accounting for 9.3% of current total annual regional greenhouse gas emission in the next 20 years. Annual carbon storage in housing, furniture, and other wood products in 1998 was estimated to be 13.9 Tg C in the region. Other sequestration options, including the direct injection of CO₂ in deep saline aquifers, mineralization, and biomineralization, are not expected to lead to direct economic gain. More detailed studies are needed for assessing the ultimate changes to the environment and the associated indirect cost savings for carbon sequestration.     

氧化铁催化甲烷脱硝的实验研究

文章使用固定床反应器在350℃~850℃范围内对氧化铁催化甲烷脱硝进行了实验研究。研究结果发现在有2%氧气存在条件下,氧化铁催化甲烷脱硝的效果最高只有20%,而且在350℃~750℃范围的氧化铁催化甲烷脱硝反应机理与850℃时的脱硝反应机理并不相同。在高温的850℃~950℃范围无氧气条件下,NOx转化率随着温度升高而单调增加,随CH4/NO摩尔比的增加而升高,氧化铁催化甲烷脱硝的最佳效果可以达到将近100%。通过进一步分析发现高温850℃~950℃无氧气条件下的脱硝反应机理是在催化剂表面进行了氧化还原反应,即首先发生了CH4与Fe2O3的气固反应,将Fe2O3还原为Fe3O4,而后Fe3O4再与NO反应将其还原为N2。     

煤层气开发环境污染特征及防治对策研究

煤层气开发是一个时短、线长、面广的工程活动,具有单井产气量低、井网密度大、降压排水等独特特征,对生态环境有一定的影响。文中分析了煤层气开发过程中钻井废液、排采水等污染物的性质,结果表明,钻井废液中COD浓度较高,为1 985.5 mg/L,As、Cr、Cu、Zn、Mn、Fe、Pb等重金属含量均在污水综合排放二级标准之内;排采水中含有较高的COD、重金属、盐浓度,经自然沉降后,COD、重金属浓度有所降低,而盐浓度变化不大;考察了煤层气开发对土壤环境质量的影响,发现钻井过程对土壤盐渍化没有影响,但土壤中As含量有所增加。在此基础上,提出钻井废液、排采水及污染土壤的具体防治对策,为煤层气开发污染治理提供理论依据与技术支持。     

接种对厌氧消化产气的影响研究进展

厌氧消化是一种高效的废物处理方法,接种是影响厌氧消化能否成功启动的重要因素。文章从接种物的种类、接种量两方面讨论了接种对厌氧消化产气的影响,包括对厌氧产气量、产气速率和产甲烷速率的影响,指出以猪粪为底物时,一定接种量范围内,厌氧消化的产气率和甲烷产率随接种量的增加而增大,而当接种量过大时,产气率和甲烷产率反而随着接种量的增大而减小。最后,对接种对厌氧消化影响的研究作了展望。     

造纸污泥和餐厨垃圾混合发酵联产氢气和甲烷试验

采用联产氢气和甲烷复合工艺,对造纸污泥和餐厨垃圾进行中温-高温混合厌氧消化,通过设计两种物料的不同配比(质量比,以VS计),研究了不同比例混合的物料联产氢气和甲烷的性能.试验结果表明,造纸污泥和餐厨垃圾混合比例为2:2的反应器总气体产率最高,达496.78mL·g-1(其中,氢气64.48mL·g-1,甲烷432.3mL·g-1,均以VSfed计,下同),其VS去除率也最高,达41.33%,在反应30h后和产甲烷18d后分别完成了80%的氢气产量和甲烷产量,而单纯造纸污泥总气体产率为144.99mL·g-1,单纯餐厨垃圾总气体产率为80.4mL·g-1.综合氢气和甲烷产率、产气速率、VS去除率等指标发现,造纸污泥和餐厨垃圾混合发酵联产氢气和甲烷的最佳配比为2:2.