• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 127
  • 82
  • 22
  • 12
  • 12
  • 4
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 294
  • 129
  • 107
  • 73
  • 56
  • 53
  • 50
  • 43
  • 39
  • 30
  • 28
  • 27
  • 27
  • 26
  • 24
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Municipal Solid Waste Management in an urban area of China: Case studies of Shanghai, China and Linköping, Sweden.

Yang, Cha January 2011 (has links)
With the rapid and large increase of waste quantities, China, surpassed the USA as the world’s largest municipal solid waste (MSW) generator since 2004. The phenomena and critical issues of MSWM in China inspired this paper to investigate and analyse the MSWM in an urban area of China. Comparing with the increasing rates of MSW generation, little has been done concerning the municipal solid waste management (MSWM). Not only the local government and authorities are responsible for the MSWM, but also the individuals are playing a significant role in MSWM. An integrated waste management system should be built in order to improve the holistic MSW system and reduce the waste production. The aim of the study is to investigate and analyse the current status and problems of MSWM in an urban area of China and to analyse to what extent a viable reduction of the MSW can be implemented and management systems to be improved in the near future. In this study, two case studies of Shanghai and Linköping are employed and compared to explore the challenges and potentials for improving the MSWM system in China. The result indicated that inadequate facilities and infrastructure, less advanced technology, insufficient public participation, low awareness of environmental protection, problems in policy and laws are the major barriers for the improvement of MSWM. Involving international environmental cooperation activities, planning a sustainable and comprehensive policy and framework for MSWM, introducing economic incentive approaches, promoting the capacities of waste management technologies, raising public environmental awareness are believed to be viable solutions to improve the MSWM system in China.
52

Preventive control of ammonia and odor emissions during the active phase of poultry manure composting

Zhang, Wenxiu 05 1900 (has links)
Traditional measures used in the composting industry for ammonia and odor emissions control are those involving collection and treatment such as thermal oxidation, adsorption, wet scrubbing and biofiltration. However, these methods do not address the source of the odor generation problem. The primary objective of this thesis research was to develop preventive means to minimize ammonia and odor emissions, and maximize nitrogen conservation to increase the agronomic value of compost. Laboratory-scale experiments were performed to examine the effectiveness of various technologies to minimize these emissions during the active phase of composting. These techniques included precipitating ammonium into struvite in composting matrix before it release to outside environment; the use of chemical and biological additives in the form of yeast, zeolite and alum; and the manipulation of key operational parameters during the composting process. The fact that struvite crystals were formed in manure composting media, as verified by both XRD and SEM-EDS analyses, represents novel findings from this study. This technique was able to reduce ammonia emission by 40-84%, while nitrogen content in the finished compost was increased by 37-105%. The application of yeast and zeolite with dosages of 5-10% enhanced the thermal performance of composting and the degree of degradation, and ammonia emission was reduced by up to 50%. Alum was found to be the most effective additive for both ammonia and odor emission control; ammonia emission decreased by 45-90% depending on the dosage, and odor emission assessed via an dynamic dilution olfactometer was reduced by 44% with dosages above 2.5%. This study reaffirmed that aeration is the most influential factor to odor emission. An optimal airflow rate for odor control would be 0.6 L/min.kg dry matter with an intermittent aeration system. Quantitative relationships between odor emission and key operational parameters were determined, which would enable “best management practices” to be devised and implemented for composting. An empirical odor predictive model was developed to provide a simple and direct means for simulation of composting odor emissions. The effects of operating conditions were incorporated into the model with multiplicative algorithm and linearization approximation approach. The model was validated with experimental observations.
53

Bioskaidžių atliekų kompostavimo technologinių procesų parmetrų tyrimai / Research of Process Parameters in the Composting of Biodegradable Waste

Mačiulskas, Robertas 21 June 2013 (has links)
Biologiškai skaidžių atliekų kompostavimui didelę įtaką turi anglies ir azoto santykis, priklausantis nuo kompostuojamų medžiagų rūšies. Kokybiškam kompostui pagaminti būtinos trys pagrindinės fazės: temperatūros kilimo, aukštos temperatūros ir temperatūros kritimo. Oro temperatūra buvo palanki kompostavimo procesui – vidutinė mėnesio temperatūra buvo aukštesnė arba artima daugemiačiams vidurkiams, o kritulių kiekis kompostavimo metu buvo permainingas. Komposto temperatūra priklausė nuo kompostavimo procesui būdingos fazės ir matavimo vietos – aukščiausia temperatūra (nuo 63 iki 82oC) nustatyta termofilinio proceso metu aukščiausios komposto vietos giliuosiuose sluoksniuose. Rūgštingumas komposto krūvoje kito nuo neutralaus (pH 7) kompostavimo pradžioje, termofilinės kompostavimo fazės metu tapo šarminės reakcijos (pH 8,0–8,3), temperatūros kritimo fazėje komposto rūgštingumas mažėjo iki neutralių reikšmių (pH 7,0–7,1). Optimalus kompostavimui drėgnumas (50–60%) buvo pasiektas trečią kompostavimo savaitę. Kompostavimo aikštelėse gaminant kompostą po atviru dangumi būtina atsižvelgti į meteorologines sąlygas, kurias vertinant galima parinkti tinkamą komposto krūvos vartymo dažnumą bei dirbtinio laistymo poreikį. / The carbon to nitrogen ratio, depending on the type of compostable materials, has a great impact on the composting of biodegradable waste. The three main phases necessary for obtaining the high-quality compost: temperature rise, high temperature and temperature drop. The air temperature was favourable to the composting process – the average monthly temperature was above or close to the multi-annual average, and the rainfall has been erratic during composting. The compost temperature depended on the phase and the measurement location characterized by the composting process – the highest temperature (from 63 to 82 °C) was determined during the thermophilic process in the deep layers of the highest composting place. The acidity of the compost pile varied from neutral (pH 7) at the beginning of composting, became alkaline (pH 8,0–8,3) during the thermophilic composting phase, the compost acidity decreased to neutral values (pH 7,0–7,1) during the temperature drop phase. The optimum composting humidity (50–60%) was achieved on the third week of composting. When the compost is produced in the open air composting sites, it is necessary to take account of the meteorological conditions. According to these evaluated conditions, the proper moving procedure frequency and the need for artificial irrigation can be selected for the compost pile.
54

A Study of Sustainable Compost Micro-Enterprise In Chimaltenango, Guatemala: Profitability and Employee Characteristics

Silberg, Timothy 2011 December 1900 (has links)
Over 13 million people live in Guatemala, and among this population more than 50% live below the poverty line. One proposed solution to mitigate the large percentage of poverty in the country is micro-entrepreneurship. A compost micro-enterprise is a small business, which collects organic raw material and processes it into stable humus material for the purpose of applying to soils to increase crop yields. Developing such micro-enterprises could not only indirectly improve current soil nutrient deficiencies specific to the region, but also provide alternative incomes for the already agriculturally involved community. The success or failure of enterprises practicing composting may be measured by a plethora of figures or outcomes. Employee characteristics are one variable that should be taken into consideration when estimating the efficiency of an agricultural enterprise's operations and productivity. While a variable, such as an employee characteristic, may not be able to be quantified exactly it should be argued that this variable can have a structural impact on productivity. Another crucial variable considered when developing such a micro-enterprise is accounting for its input and output. It is explained the issue of costs within micro-enterprises is complex and should be considered not only in terms of fees but also in terms of payments in any kind, such as entry and exit presence, and the duration of the apprenticeship. When an enterprise has failed to account for its various inputs and consequent output, it has become unsustainable because it has not satisfied basic economic, social and security needs presently and for its future. This study identified and described employee characteristics and documented the inputs and outputs of compost micro-enterprises in Chimaltenango, Guatemala. The study found that employee characteristics, particularly gender, age, and occupation affected a micro-enterprise's access to markets as well as row materials, and how efficiently tasks were completed. Costs of labor, raw material, transport, packaging, energy and the location the micro-enterprise itself heavily influenced profitability. The production of any product on a large scale must anticipate how positive financial outcomes will occur because profitability may not arrive as planned. If the revenue cannot be determined and/or made, compost micro-enterprise may fail to be a sustainable, much less a viable option for alternative income streams.
55

A study of power, kinetics, and modelling in the composting process

Mason, Ian George January 2007 (has links)
This thesis explores the roles of physical and mathematical modelling in the prediction of temperature profiles in the composting process. A literature-based evaluation of the performance of laboratory- and pilot scale composting reactors, showed that physical models used in composting research frequently do not properly simulate the full-scale composting environment, and may therefore produce results which are not applicable at full scale. In particular, self-heating, laboratory-scale, reactors typically involve significant convective/conductive/radiative losses, even with insulation present. This problem can be overcome by using controlled temperature difference or controlled heat flux laboratory reactors, which allow convective/conductive/radiative heat fluxes to be controlled to levels close to those occurring in full-scale systems. A new method of assessing the simulation performance of composting systems is presented. This utilises the areas bounded by the temperature-time profile and reference temperatures of 40 and 55 ℃ (A₄₀ and A₅₅), the times for which these temperatures are exceeded (t₄₀ and t₅₅), and times to peak temperature. An evaluation of published temperature profiles showed a marked difference in these parameters when comparing many laboratory- and full-scale reactors. The impact of aeration is illustrated, and laboratory- and pilot-scale reactors able to provide good temperature profile simulation, both qualitatively and quantitatively, are identified. Mathematical models of the composting process are reviewed and their ability to predict temperature profiles assessed. The most successful models in predicting temperature profiles have incorporated either empirical kinetic expressions, or utilised a first-order model, with empirical corrections for temperature and moisture. However, no temperature models have been able to predict maximum, average and peak temperatures to within 5, 2 and 2 ℃ respectively, or to predict the times to reach peak temperatures to within 8 h, although many models were able to successfully predict temperature profile shape characteristics. An evaluation of published constant-temperature and varying-temperature substrate degradation profiles revealed very limited evidence to support the application of single exponential, double exponential or non-logarithmic Gompertz functions in modelling substrate degradation kinetics, and this was identified as a potential weakness in the temperature prediction model. A new procedure for correcting substrate degradation profiles generated at varying temperature to a constant temperature of 40 ℃ was developed and applied in this analysis, and on experimental data generated in the present work. A new approach to the estimation of substrate degradation profiles in the composting process, based on a re-arrangement of the heat balance around a reactor, was developed, and implemented with both a simulated data set, and data from composting experiments conducted in a laboratory-scale constant temperature difference (CTD) reactor. A new simulated composting feedstock for use in these experiments was prepared from ostrich feed pellets, office paper, finished compost and woodchips. The new modelling approach successfully predicted the generic shape of experimental substrate degradation profiles obtained from CO2 measurements, but under the conditions and assumptions of the experiment, the profiles were quantitatively different. Both measured CO2-carbon (CO2-C) and predicted biodegradable volatile solids carbon (BVS-C) profiles were moderately to well fitted by single exponential functions with similar rate coefficients. When corrected to a constant temperature of 40 ℃, these profiles gave either multi-phase or double exponential profiles, depending upon the cardinal temperatures used in the temperature correction procedure. If it is assumed that the double exponential model generated is correct, this work provides strong evidence that a substrate degradation curve generated under appropriate laboratory conditions at 40 ℃ would, given the correct cardinal temperatures, generate a correct substrate degradation profile under varying temperature conditions, and that this in turn would enable an accurate and precise prediction of the temperature profile using a heat and mass balance approach. This finding opens the door for the development of a simple laboratory test for composting raw material characterisation, but underlines the need for accurate estimates of the physical cardinal temperatures. Experimental factors appear to be the likely cause of the dysfunction between previously reported substrate degradation patterns and existing substrate degradation models, and suggestions for further research are provided in order to more precisely and accurately quantify these factors.
56

Minska matsvinnet i landets alla skolor som ett led i arbete med hållbar utveckling. : " ett roligt sättför er skola att nå kunskapskraven"

Åteg Vandell, Nickolina, Gustavsson, Pia January 2013 (has links)
Syftet med detta arbete är att vi ville göra ettfärdigt material till skolor som de kan använda praktiskt i klasserna. Detta påett sätt som inspirerar eleverna till de naturvetenskapliga ämnena och hållbarutveckling. Vi började prata om denna inriktning redan för någon termin sedanom hur vi kan göra ett arbete på ett roligt sätt som engagerar eleverna. Vibeslutade oss för att göra ett arbete som kan användas av andra som vårtexamensarbete. När vi började med arbetet insåg vi begränsningarna som fanns ibokhyllorna och fick då istället använda oss av internets resurser för att letaupp information som var användbar för oss. Vi höll samtidigt kontakten med vårapartnerskolor och kontrollerade så detta arbete skulle vara användbart för demi praktiken. De svar som vi kunde samla in från skolorna visade på att vi varpå rätt väg. Vi tror att klasserna som använder sig av temaarbetet kommer attminska sina matrester och ha en större kunskap om hållbar utveckling. / Summary The purpose of this essay was that we wanted to make a finished material for schools that they can practically use in the classes in a way that inspires the students to the scientific topics in school and for sustainable development. We started to talk about this kind of work a few semesters ago and how we could make the lessons more interesting for the students. We also wanted to make a specialty work that the teachers could take home from the internet and use immediately. At the start of our work we discovered the limitations of the bookshelves and made the decision of using the internet instead.  At the same time we stayed connected to our partner schools to make sure that our work could be used in the classes. The answer that we collected from the teachers showed that we were on the right track and so we continued working and the finished results were a student brochure and a teacher's guide. We believe these will help the classes that are going to use this specialty work to reduce their leftovers and get a bigger knowledge about sustainable development.
57

Human excreta treatment technologies : prerequisites, constraints and performance /

Niwagaba, Charles, January 2007 (has links) (PDF)
Licentiatavhandling (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2007. / Härtill 3 uppsatser.
58

EVALUATING THE EFFECTIVENESS OF WEEP BERM SYSTEMS FOR TREATING RUNOFF FROM A HORSE MUCK COMPOSTING OPERATION

Guffey, Ross L 01 January 2012 (has links)
Two contour weep berms systems were designed and implemented to evaluate their performance at mitigating water quantity problems from a horse muck composting operation. The field-scale study focused on the hydrologic response of a standard contour weep berm and a modified contour weep berm. The modified contour weep berm incorporated a woodchip trench upgradient of a typical standard contour weep design. Monitoring occurred from July 2011 through spring 2012. Eight storm events produced measureable runoff for the standard contour weep berm; however, only five storm events produced measurable runoff for the modified contour weep berm. The largest storm event occurred on November 27, 2012 with rainfall depth of 49.0 mm. This storm event generated a total runoff volume of 183.1 m3 and 188.5 m3 for the standard and modified contour weep berms, respectively. All runoff produced from the storm events during the monitoring period was completely detained and infiltrated. No runoff was released from the horse muck composting facility through the passive dewatering system to down-gradient vegetative filter strips during the monitoring period.
59

Zjišťování a porovnávání stability kompostu pomocí respirometru pro různé typy zakládek / Detection and comparison of stability of compost with respirometer for different types of piles.

ONDRÁČEK, Vojtěch January 2014 (has links)
The aim of this work was to verify the suitability of the device Ramko 2 for measuring the biological stability during the composting in terms of the Department of Agricultural Engineering. For this purpose were based four piles four piles with a similar composition and on which were measured temperature and DRI during all stages of composting. From the recorded data was created graphs both processes individual piles and compared with each other. From results assess the suitability for the authentication of biological stability.
60

Investigação do potencial celulolítico de bactérias oriundas de processo de compostagem / Investigation of the cellulolytic potential of bacteria from the composting process

Kimura, Giselle Kobata, 1985- 24 August 2018 (has links)
Orientadores: Fabiana Fantinatti Garboggini, Suzan Pantaroto de Vasconcellos / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-24T14:10:34Z (GMT). No. of bitstreams: 1 Kimura_GiselleKobata_M.pdf: 1372257 bytes, checksum: 0fad6fec65eb0d479d24daeddec4aeef (MD5) Previous issue date: 2014 / Resumo: Bactérias e fungos têm sido largamente explorados devido às suas habilidades em produzir uma grande variedade de enzimas, entre elas, as celulases que se destacam devido ao seu potencial em degradar materiais lignocelulósicos em açúcares fermentáveis, que podem então ser convertidos, por exemplo, em biocombustíveis. O presente trabalho visou a bioprospecção de bactérias isoladas a partir do processo de compostagem realizado pela Fundação Parque Zoológico de São Paulo (FPZSP), quanto à produção de enzimas celulolíticas, além da caracterização taxonômica das linhagens de interesse. Para tanto, os micro-organismos oriundos do processo de compostagem da FPZSP foram isolados, preservados e caracterizados macroscopicamente. Dentre as linhagens isoladas, 168 foram testadas numa triagem qualitativa para a produção de celulases, obtendo-se 135 micro-organismos com potencial celulolítico evidenciado pela formação de halos de hidrólise em meio de cultura contendo carboximetilcelulose. Destes, 10 linhagens apresentaram halos translúcidos com diâmetros entre 1,3 cm e 1,9 cm, as quais foram avaliadas quanto a atividade celulotíca em ensaios quantitativos monitorados durante 7 dias, em duas condições de pH distintas: 4,8 e 7,4. Os melhores tempos de incubação verificados foram de sete e cinco dias para os valores de pH 4,8 e 7,4, respectivamente. Em seguida, foram selecionados linhagens para os ensaios de delineamento experimental e otimização das atividades enzimáticas. No planejamento P&B, a melhor atividade celulolítica verificada foi de 3,6392 FPU/mL obtida a partir da linhagem FPZSP 143, no pH 4,8. Esta linhagem foi então selecionada e o planejamento do tipo Delineamento Composto Central Rotacional ¿ DCCR aplicado, promovendo dessa maneira, um aumento 0,4574 FPU/mL em relação ao experimento do planejamento anterior. Posteriormente, o experimento foi validado e o resultado máximo alcançado para atividade celulolítica da linhagem FPZSP 143 foi de 4,6435 FPU/mL. Cinco linhagens selecionadas com atividade celulolítica foram identificadas por análise de sequências do gene RNA ribossomal 16S como membros do gênero Bacillus, bactérias frequentemente encontradas em ambientes da compostagem e que tem sido largamente reportada como produtoras de enzimas celulolíticas. O processo de compostagem demonstrou ser um ambiente em potencial para a produção de celulases de interesse para diversos ramos da indústria, sendo os representantes do gênero Bacillus os melhores produtores de enzimas celulolíticas. Embora as bactérias tenham sido isoladas de um ambiente com pH em torno de 7,4, há um potencial para a produção de celulases em pH mais ácidos, evidenciando sua aplicabilidade em diferentes condições. Essa característica torna-se relevante quando se leva em consideração os processos industriais, onde uma condição diferente e específica é exigida em cada processo, tornando as enzimas celulolíticas oriundas de processo de compostagem grandes aliadas no desenvolvimento e otimização de processos industriais / Abstract: Bacteria and fungi have been extensively explored due to their ability to produce a variety of enzymes, including the cellulases that stand out because of their potential to degrade lignocellulosic materials to fermentable sugars, which can then be converted, for example, in biofuels. The present work aimed bioprospecting of bacteria isolated from the composting process conducted by Fundação Parque Zoológico de São Paulo (FPZSP), for the production of cellulolytic enzymes and the taxonomic characterization of strains of interest. For both, the microorganisms derived from the composting process of FPZSP were isolated, preserved and characterized macroscopically. Among the isolates, 168 were tested for production in a qualitative screening of cellulases, obtaining 135 cellulolytic microorganisms with potential evidenced by the formation of halos of hydrolysis in culture medium containing carboxymethylcellulose. These, 10 strains showed translucent halos with diameters between 1.3 cm and 1.9 cm, which were evaluated for activity in cellulolytic quantitative assays monitored for 7 days under two different pH conditions: 4.8 and 7.4. The best times of incubation recorded were seven and five days to pH 4.8 and 7.4, respectively. Then, strains for testing experimental design and optimization of enzymatic activities were selected. In Planning P&B, the best cellulolytic activity verified was 3.6392 FPU/mL obtained from FPZSP 143, at pH 4.8. This strain was selected and the DCCR applied, thus promoting an increase of 0.4574 FPU/mL compared to the previous experiment planning. Subsequently, the experiment was validated and the maximum score achieved for cellulolytic activity FPZSP 143 strain was 4.6435 FPU/mL. Five strains with cellulolytic activity were identified by sequence analysis of the 16S ribosomal RNA gene as members of the genus Bacillus, bacteria frequently encountered in composting environments and has been widely reported as producing cellulolytic enzymes. The composting process proved to be a potential environment for the production of cellulases of interest for various branches of industry, being the representatives of the genus Bacillus the best producers of cellulolytic enzymes. Although bacteria have been isolated from an environment with a pH around 7.4, there is a potential for the production of cellulases in more acidic pH, indicating their applicability in different conditions. This feature becomes important when one takes into account the industrial processes, where a different and specific condition is required in each case, making the cellulolytic enzymes derived from composting process a good allied in developing and industrial process optimization / Mestrado / Microbiologia / Mestra em Genética e Biologia Molecular

Page generated in 0.0854 seconds