Composting Wastes Contaminated with Naphthalene

Recent data show composting as an alternative for treatment of PAHs contaminated wastes. Nevertheless, the presence of highly volatile compounds like naphthalene might compromise the interest of this treatment and thus its careful evaluation is justified. A bench scale composting system was built to evaluate the importance of volatilization in the transformation of naphthalene by composting. Naphthalene concentration was measured in solid, aqueous and gas phases by HPLC and GC. Preliminary results have shown that the presence of microorganisms able to degrade naphthalene reduces naphthalene loss by volatilization.     

Evaluation of Organic Wastes for Composting

Management of organic wastes is essential to reduce environmental pollution and increase resources of plane nutrients for crop production. This study was undertaken to evaluate major organic wastes produced in northwestern Pakistan for characteristics that are useful for composting. Organic wastes such as manures, municipal wastes (MW), crop residues, fruit/vegetable wastes, and yard wastes contained large reserves of nutrients. Manures had high nitrogen (N) and crop residues had low N. Crop residues were relatively dry (7–12% moisture); MW, poultry manure, sheep manure, leaves, and city garbage were moderately moist (27–47% moisture), whereas cattle manure (CM), fruit and vegetable wastes, and grass clippings were wet (62–89% moisture). The compost developed from mixing MW with CM matured early and had low C/N ratio compared with either source alone. These results suggested that MW could be converted into compost when mixed with CM. The inoculation of wastes with effective microbes (EM) was ineffective in expediting the process of composting.     

Composting for the Treatment of Cattle Wastes

? Livestock farming in England and Wales is estimated to produce an annual figure of 200 million tons of animal excreta, half generated by the dairy cattle industry. In the United Kingdom, the structure of the cattle industry has shifted from large numbers of small dairy farms to fewer but larger units. The national average herd size increased from 26 to 42 and finally to 64 animals in 1965, 1975 and 1985, respectively. The latest census revealed that currently there were 2.44 million dairy cows and 9.45 million other cattle and calves in the United Kingdom (total 11.89 million), third place after France (21.50 million) and Germany (19.51 million) in the EEC countries.     

Evolution of Biochemical Parameters During Composting of Urban Wastes

An experiment was performed for evaluating the most suitable biochemical parameters to measure dynamics of substrate transformation during composting of the organic fraction derived from preselected urban wastes and wood bark mixture. Changes of chemical (organic C, hydrosoluble sugars, total and mineral N, humified fraction, volatile acids and phenolic compounds) and biochemical (microbial respiration, biomass C, qCO₂, dehydrogenase, catalase, urease activities, FDA, and BIF) parameters were monitored for 120 days. Limited changes in organic C, total nitrogen, and humification characteristics were observed during composting. Dehydrogenase and catalase activities, BIF and FDA showed small changes during composting. Urease activity and, with some limitations regarding the early stages of composting, microbial respiration and qCO₂, were found to be the most suitable parameters to measure dynamics of substrate transformation during composting of preselected urban wastes.     

Fatty Acid Formation during Composting of Separately Collected Organic Household Wastes

? Recent studies indicate that fatty acids are formed in significant concentrations during the composting of organic household residuals. Their presence may be one major reason for depressed germination and seedling development that often result following application of compost. Experimental results in Sweden indicate that at least five to six months should elapse before low levels of fatty acids for cropping are reached in the composts. Further research on fatty acid formation is recommended.     

The Use of Bacillus Licheniformis HA1 To Accelerate Composting of Organic Wastes

The effect of Bacillus licheniformis HA1 cell density on the acceleration of organic waste composting was tested in a bench-scale composting system utilizing a process limit temperature of 60°C. Variables measured during composting were CO₂ evolution rate, conversion of substrate carbon and pH. When an initial cell density of 2.0×10⁴ cfu/g-dry solid was used, the strain HA1 increased in number and prevented the decrease in pH during the early stage of composting. This resulted in enhanced populations of other thermophiles and increased the rate of organic matter decomposition. By contrast, no effect was observed at a lower cell density of HA1. It was found that the minimum cell density of HA1 to accelerate organic decomposition was around 10⁴-10⁵ cfu/g dry solid of raw material.     

Control of Composting Odor Using Biofiltration

While composting transforms manure wastes into useful fertilizer, it also produces odors during the decomposition process. Biofiltration is a desirable method to control composting odor. This study was conducted to investigate the efficiency of using compost as a biofilter. A mixture of cattle manure and fresh compost was composted in a bin equipped with a suction-type blower. The exhaust gas was filtered through the biofilter of fresh compost. The composting temperature affected the ammonia emission. When the composting temperature was relatively high, the highest ammonia emission appeared in two experiments. The biofiltering properties were investigated according to flow rates and filter depths for two different types of fresh composts (experiment I and II). At the flow rate of 30 L/min, ammonia removal rate was 80.5% for biofilter A(detention time 56.5 s) and 99.9% for biofilter B (detention time 113 s). At the flow rate of 50 L/min, the ammonia removal rate was 82.5% for biofilter A (detention time 33.9 s) and 97.4% for biofilter B (detention time 67.8). The fresh compost could be used as a biofilter medium for odor control during composting process. The moisture content(MC) of the biofilter material increased by absorbing moisture from the exhaust gas, while the pH was decreased due to the degradation of nitrogenous compounds. As the moisture in the exhaust gas increased the MC of the biofilter, there was no need to spray water to the biofilter medium to control moisture content. While the total nitrogen(T-N) of the biofilter increased by absorbing ammonia, the total carbon (T-C) remained unchanged resulting in decrease of the C/N ratio.     

不同来源农业废弃物堆肥进程与产品肥效研究

评价不同来源农业废弃物的堆肥效率与产品肥效,为高品质有机肥生产提供依据.采用室外堆肥的试验方法,选取6种动物源粪便与7种植物源农业废弃物为原料,设置13个堆肥处理,比较不同堆肥原料堆肥过程中温度、pH、C/N、腐殖酸、养分等指标差异及其堆肥产品对小白菜生长的影响.结果表明,动物源和植物源材料质量比7:3,C/N为25:...     

餐厨垃圾与麦秸混合堆肥中碳素物质变化规律研究

餐厨垃圾堆肥是实现营养物质资源良性循环的重要途径,为了研究不同季节环境条件下餐厨垃圾与小麦秸秆混合高温好氧堆肥过程中碳素物质变化规律,试验设定了具有中原地区季节代表性的3种环境温度在15、25、35℃条件下分别进行了为期21d的堆肥。结果表明,餐厨垃圾和麦秸混合堆肥在25。C和35℃条件下,堆体温度能满足堆肥产品无害化要求,而15℃时不能满足;35℃条件下的pH值在前期下降幅度最多,15℃条件下pH值则始终保持在6．0以下;在25℃和35℃条件下,TOC含量明显比15℃条件下下降幅度大,堆肥物料中的糖类物质很容易被微生物分解,经过10d95％以上的糖类物质就被分解,粗纤维降解率均达到60％以上,而在15℃条件下到堆肥结束时,仍有30％多的糖类没有被分解,粗纤维也只分解了27．57％。     

Winter Composting Using the Passively Aerated Windrow System

Field trials demonstrated that agricultural wastes could be successfully composted in the winter with the passively aerated windrow system. Three small windrows were constructed. One pile contained a sheep manure-straw mixture, while the other two piles contained varied amounts of horse manure, cow manure, and bedding materials (straw, wood chips). The piles were constructed on a porous base of wood chips. Standard four-inch (10 cm) perforated pipes were placed approximately three feet apart in the porous base, perpendicular to the length of the windrow. Piles were covered with 15 to 20 centimeters of finished compost. A commercial compost covering fabric permeable to gases and water vapor but impermeable to liquid water was used for additional insulation and protection against high winds. Ambient temperatures ranged from ?27°C to 15°C during the trials. Initially, all three piles froze. Then the ends of the piles began to heat up, with the southern ends which received the most sunlight heating up first. Plugging the pipes seemed to help the piles heat up faster, but did not appear to be necessary. Thermophilic temperatures were attained and the composting cycle took 50 to 80 days after the piles heated up. Oxygen levels were highest at the bottom of the pile, and decreased as one moved to the top of the pile. The biggest practical problem encountered was the snow drifts that periodically formed at the windrow base, covering the pipe openings.     

A Laboratory Method to Investigate Gaseous Emissions And Solids Decomposition During Composting Of Municipal Solid Wastes

A laboratory method was developed to quantify CO₂, NH₃ and VOC yields and to follow solids decomposition during composting of MSW or its components. All organic substrates were shredded, water and nutrients were added to near optimum levels prior to composting, and composting was continued until feed materials reached approximately the full extent of decomposition. Twenty five L stainless steel digesters were used and aluminum packing was mixed with the wastes to facilitate airflow. Thermophilic temperatures were maintained and air supplied in excess. Nutrients were added to reach an initial C/N ratio of approximately 30. CO₂ and NH₃ gases in the exit air stream were captured in alkaline and acidic solutions, respectively, and quantified through titration on a cumulative basis. VOC traps, prior to the gas traps, captured emitted volatile organic compounds, which were quantified on a cumulative basis. Solids were analyzed for hot water soluble matter, fats and lipids, cellulose, hemicellulose and lignin/humus. Food wastes, yard wastes and mixed paper produced approximately 368, 220 and 153 g C-CO₂/dry kg and approximately 40.5, 4.6 and 2.0 g N NH₃/dry kg of starting material, respectively. VOC volatilization profiles had a decreasing trend with composting. Partially composted MSW produced 8.2 mg/dry kg of 8 selected VOCs. CO₂, NH₃ and VOC recovery tests resulted in efficiencies of 98.6%, 97.6% and 94.6% respectively. Reproducibility of the solids decomposition and gaseous emissions measurements was observed. Carbon and nitrogen mass balance closures ranged from 85.5% to 117.1% and 32.2% to 175% respectively.     

Composting of Rhododendron and Bilberry Wastes To Contain Spread of Exotic Plant Pathogens Phytophthora kernoviae and Phytophthora ramorum

Plant material infected with the exotic pathogens Phytophthora kernoviae and Phytophthora ramorum, particularly of the invasive and highly susceptible Rhododendron ponticum, can pose a risk to indigenous host flora in Britain. Areas of infected bilberry (Vaccinium myrtillus) can also threaten surrounding non-infected heathland. Composting was examined as a more environmentally acceptable method of disposal of infected plant material than burning. Three types of low cost composting systems were developed and tested on shredded rhododendron and chopped bilberry wastes: permanent and mobile insulated bays, and insulated cargo containers, located at six different sites. In addition to temperature-time profiles of the composting wastes, the discoloration of the waxy leaves of R. ponticum and Portugal laurel (Prunus lusitanica) was developed as a potential indicator of the sanitising effect of the composting process. The relationship between the mean compost temperature and the percentage of green area of leaves positioned in the compost enabled the sanitising effect of a composting process to be immediately assessed. Mean compost temperatures and exposure times achieved in shredded rhododendron or chopped bilberry wastes in the majority of the compost in the insulated composting systems were above those needed to reduce P. ramorum and P. kernoviae to below detectable limits, and to eliminate any green colour in the indicator leaves. The exception was in the corners of the systems that contained >4 m³ waste, and in the outer surfaces at one site where the volume of waste was only 2.9 m³. Temperature-time profiles of the composts and positioned indicator leaves demonstrated that the main pathogen survival risk was in the corners of the insulated composting systems; pathogen survival risk could be minimised by positioning the corner material into the centre of the composting system during sequential refilling.     

The Fate of Plant Pathogens and Seeds During Anaerobic Digestion and Aerobic Composting of Source Separated Household Wastes

Anaerobic digestion is becoming a more common method for treatment of organic wastes. Little is known, however, about the effects of this process on the fate of plant pathogens and seeds. Therefore, the fates of the plant pathogens Plasmodiophora brassicae, Heterodera schachtii, Meloidogyne incognita, Ralstonia solanacearum, tobacco mosaic virus (TMV) and tomato seeds were followed during anaerobic digestion of source separated household wastes. With the exception of TMV, all test organisms were destroyed to below detectable limits within one day of anaerobic digestion at 52°C. Two days of anaerobic digestion did not reduce the concentration of TMV. However, two days of anaerobic digestion followed by 19 days of high temperature composting at 58°C reduced the concentration of infectious TMV particles by a factor of almost three orders. Anaerobic digestion followed by 12 days of composting at 68°C was even more effective. Although TMV concentrations were not eliminated entirely, we conclude that short-term high temperature anaerobic digestion followed by high temperature composting is a highly efficient process for the eradication of detrimental agents from solid wastes.     

木质纤维降解复合菌剂促进堆肥腐熟研究

利用工厂化高温好氧堆肥方式,探究了具有高效降解木质纤维能力的微生物复合菌剂分别对纯秸秆和秸秆畜禽粪污混合物堆肥效率的影响。以纯秸秆和猪粪秸秆混合物为原料,设置空白对照、单菌处理和复合菌处理,评估堆肥过程中不同堆体温度、含水量、pH、有机质含量、发芽指数和养分等理化指标的变化对堆体腐熟效率的影响。结果表明,无论何种堆肥原料,相比空白和单菌处理,复合菌处理堆体均升温速率最快,高温期温度最高,后熟期降温最快。堆肥过程中,各处理p H无显著差异,变化趋势基本一致;各处理发芽指数(GI)不断提高,纯秸秆和秸秆粪污混合物为原料的接复合菌处理均在第25天高于接单菌处理,至堆肥结束时,接复合菌处理的发芽指数分别为93.45%和98.67%;随堆肥的进行,各处理有机质含量均处于下降趋势,至堆肥结束时,所有处理的有机质含量均高于450 g/kg;各处理的全氮、全磷、全钾含量在堆肥结束时比堆肥初始均有所增加,至堆肥结束时,以纯秸秆和秸秆粪污混合物为原料的接复合菌处理的总氮和总磷含量均显著高于其他处理。综上,相比于不添加外源菌和添加单一菌株,高效木质纤维降解复合菌剂的添加,能够有效促进堆肥的腐熟,提高堆肥效率...     

土工织物透水特性试验研究

土工织物在高速公路护坡、干旱区造林等诸多方面具有重要作用。在阐述土工织物渗透特性及试验方法的基础上,进行了无纺布的垂直渗透试验及水平渗透试验研究,分析结果表明:无纺布的空隙率、孔径大小和覆盖土的颗粒级配是决定织物垂直渗透性能的主要因素;无纺布水平渗透性受垂直压力的影响,随着垂直压力的增加其渗透性略有降低,实际运用时应结合工程土质条件及上层覆盖土层的重量合理选择,确保工程质量。     

Comparative Study of Static Pile Composting Using Natural,Forced and Passive Aeration Methods

Poultry manure slurry amended with sphagnum peat was composted by natural aeration (NA), forced aeration (FA) and passive aeration (PA). Compost piles were built in trapezoidal shape with a volume of 5 m³. A total of nine replicates, three for each treatment method, were built. A total of 231 thermocouples were used to establish a three-dimensional temperature regime in each pile.

The results showed that, for the selected configuration of aeration pipes and aeration schedule, temperature drop occurred almost two weeks sooner in PA and FA process than NA process. Also, temperature inside PA and NA processes stayed above 55°C for a longer time than FA process. Both FA and PA methods were effective in providing more oxygen. Low O₂ concentrations were measured at the bottom and middle of NA pile and middle of PA pile during the early stages of the process which is an indication of anaerobic conditions. A total mass reduction of 32 percent and volumetric reduction of 16 to 22 percent were observed. The mass reduction was mainly due to water evaporation, around 550 liters of water per each pile. C/N ratio dropped from the initial value of 21.9 to 18.9, 19.8 and 20.9 for NA, PA and FA, respectively.

The influence zone of aeration pipes in FA and PA composting was determined using a statistical procedure involving the verage of absolute differences (AAD) of temperature readings and two-way ANOVA. By comparing analogous thermocouple locations between PA with NA as well as FA with NA piles, it could be established whether inclusion of the aeration pipes affected the temperature at that location. A three-dimensional influence zone was mapped for PA and FA composting. Results indicate that for the selected configuration of aeration pipes and aeration schedule, PA pipes influenced temperatures in the bottom half of the PA pile while FA pipes affected the interior part of the pile. Near the pile surface, aeration was predominantly by diffusion, as these positions were not influenced by the aeration pipes. The results obtained were also verified by Cluster analysis.     

堆肥过程中基本条件的控制

概述了堆肥过程中各种基本条件控制因子,包括含水量、通风供氧、温度、挥发性有机物质、C/N比和C/P比、颗粒大小和容积密度、pH值,对其影响作用和如何调控进行综述,为堆肥的顺利进行提供理论基础和实践参考。     

Composting Hog Manure/Sawdust Mixtures Using Intermittent and Continuous Aeration: Ammonia Emissions

Odorous emissions from manures have become a significant problem. Preliminary work on composting hog manure with sawdust had indicated that intermittent aeration could reduce ammonia emissions during this process. This paper presents results from four additional runs with a total of 22 pilot-scale vessels that have confirmed that ammonia emissions are affected by aeration. The pilot-scale vessels consisted of insulated, stainless steel, 205 L drums that either received continuous (high/low rate, thermostatically controlled blowers) or intermittent (5 min on high rate, 55 min off) aeration. Ammonia emissions, air flow rates, carbon dioxide production, oxygen utilization, and temperatures at four locations in each vessel were monitored. Ammonia emissions under intermittent aeration were roughly 50% less than those from the continuously aerated vessels. However, this appeared to result more from total air flow than from the aeration technique used. A linear regression of emissions versus total air flow data for all vessels yielded a fit of y = 0.1309x + 29.385 (y being total ammonia emitted [in g of N] and x being total air flow [in kg]) with an R² = 0.6808. Since air flow termination was relatively arbitrary, this only means basically, that ammonia emissions were doubled for a quadrupling of air flow. Under intermittent aeration, the minimum oxygen level in the exhaust air occasionally dropped to as low as 1%. So the aeration pattern used probably represents the lowest one suitable for maintaining aerobic conditions. Within this constraint, however, lower air flow appears to be suitable for reducing odorous ammonia emissions.     

Measurements of Greenhouse Gas Flux from Composting Green-Waste Using Micrometeorological Mass Balance and Flow-Through Chambers

Greenhouse gases (GHGs) are produced during the composting process, but few studies have measured emissions from a full-scale windrow of composting green-waste. This is important for evaluating composting as a waste management option and for understanding how changes to current composting management practices could help reduce emissions. This study uses micrometeorological mass balance (MMB) and open flow-through chamber techniques to measure emissions of carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) from a windrow of composting green-waste in Northern California. The MMB technique yielded mean upwind–downwind concentration differences over the study period that showed sourcing of all three GHGs. CO₂ showed a stronger signal than CH₄ and N₂O. A strong diel pattern was found in the concentration differences at lower levels and fluxes of CO₂, with substantial noise likely obscuring any possible daily patterns for CH₄ and N₂O. Fluxes normalized by the time since the previous turn event revealed an initial rapid rise in CO₂ concentration differences (at lower levels) and fluxes, peaking close to 13?h after the turn event followed by a gradual decline. The same pattern was not as clear for the other two gases but overall declines in concentration differences and fluxes were apparent with increasing time since the previous turn event. Substantial differences between MMB and chamber calculated fluxes were found, due to both differences in the techniques as well as sampling frequency.