Academic literature on the topic 'Composting science'

AbstractThis review investigates the significant challenges of the process of livestock manure composting in cold regions and assesses the critical features related to the quality of the final compost product. Recently, the composting process has grasped more attention because of environmental pollution concerns and seeks for environmentally-sound approaches for managing livestock manure. Despite recent progress in crucial areas like the microbiology of compost, further improvement is needed in composting process monitoring. Therefore, specific obstacles related to livestock manure composting in cold regions, such as the generation and preservation of temperature, and the solution of obstacles such as inoculation of coldadapted microorganisms, and the role of biochar in prolonging the thermophilic stage of composting were reviewed. Also, the challenges were adequately addressed, and promising strategies to improve composting of livestock manure under harsh conditions were proposed. Still, there is a need for more investigation to get a better understanding of the role of microbial inoculants and biochar amendment regarding the start-up of the composting process in cold regions.

Recently, composting has been gaining increased attention as an alternative means of handling manure generated by the livestock industry. Composting is not a new technology, it merely controls what is a natural decomposition process. A major advantage of composting is reduced mass, volume and water content compared with fresh manure which in turn reduces transportation requirements. Concomitant benefits include elimination of pathogens, parasites, weed seeds and odour emissions on land application. However, carbon (C) and nitrogen (N) losses and greenhouse gas (GHG) emissions are associated with composting. Nutrients are stabilized during composting which slows their release once soil-applied. Compost also enhances soil physical and biological properties and has a disease suppression effect. Where the supply of manure currently exceeds land availability for application, or in some future scenario, if producers need to comply with stricter manure application rate regulations, composting may be an option to encourage nutrient export from high-loading watersheds to soils that may benefit from nutrient and organic matter inputs. Composting may be seen as a means of maximizing the potential for recycling manure nutrients by soils and crops while protecting surface and groundwater resources from manure-related contamination. Key words: Manure, compost, nutrients, cropping systems, soil quality

The organic wastes of plant origin and, in particular, those coming from sources related to tourism activities, such as those generated from golf courses and touristic coasts, constitute an increasing concern due to the rise in their production and their unsuitable management. Thus, this work aimed to assess the use of different composting strategies to manage these specific green wastes, such as grass clippings and pruning waste from a golf course and marine plant debris, mainly from posidonia (Posidonia oceanica L.). To this end, two composting scenarios were established: the first only considered green wastes in the composition of the composting mixtures, and the second used sewage sludge as a co-composting agent. The temperature of the piles was monitored, and physicochemical and chemical parameters were also studied throughout the process. The results obtained showed that composting is a feasible method to manage and recycle this type of green waste, obtaining end products with suitable physicochemical and chemical characteristics. However, proportions of sea plant wastes in the composting mixture higher than 30% can compromise the fertilizing value of the final compost. Moreover, the use of an additional co-composting agent (sewage sludge) improved the characteristics of the end products obtained, provided that this co-composting agent had suitable initial characteristics.

We measured nitrogen components during composting process of feces in a batch test in which sawdust was used as a matrix. Further decomposition rates of fecal nitrogen and carbon were obtained in the batch tests of different feces loading. In composting material that was a mixture of sawdust and fresh feces, fecal organic matter decomposed to CO2 and fecal nitrogen mineralized to ammonia during the composting process. The biological response of organic matter and nitrogen in the composting material was evaluated by oxygen consumption (OUR) and ammonia production that was a sum of volatilized ammonia gas and ammonia remaining in the composting material. Since composting material contains two different sources of organic matter from feces and sawdust, the OUR by using the sawdust matrix only was evaluated in preliminary tests. The fecal contribution to the OUR in the composting material was therefore calculated by subtraction of the result in the preliminary tests from the one in the composting material. The ammonia production from the fecal nitrogen was obtained by the same procedure. The decomposition rates of input organic matter in feces were approximately 83 and 70% respectively, whereas ammonia production rates were approximately 73 and 58% of input fecal nitrogen. There was an interesting time lag of the peak time between volatilisation rates of ammonia and CO2 during the composting process while fecal carbon and nitrogen simultaneously decomposed to ammonia and CO2 in the composting material.

This paper is an overview of the potential use of composting technology in programmes aimed at organic waste recycling (product-oriented perspective) or decomposition of hazardous materials (process-oriented perspective). This latter approach includes composting as a tool for bioremediation of environmental matrices, such as contaminated soils and sediments. In all above-mentioned cases, biological reactions that characterize composting must be managed carefully to allow putrescible residues to become a humified agricultural fertilizer with no phytotoxic effects, or the degradation of organic pollutants (e.g., aliphatic and aromatic hydrocarbons or halogenated solvents) to proceed to the highest extent with formation of innocuous end products. Thus, the fundamental aspects of controlling the microbial environment in composting matrices are singled out as a means for better evaluating the range of adverse conditions possibly responsible for hindering the correct evolution of the process within different applications. Key words: biopiles, bioremediation, composting, ex situ soil biotreatments, in-vessel systems, open systems, organo-nitro explosives, organic waste reclamation, polycyclic aromatic hydrocarbons, soil composting windrows.

Composting could be a suitable solution to the correct treatment and hygienization of several organic waste, producing compost that can be used in agriculture. The evolution and maturity of this process has been studied using a variety of techniques. One very promising technique for these studies is thermogravimetric analysis. On the other hand, the compost can be used for a variety of purposes different to the agricultural one, such as direct energy by combustion or energy and products by pyrolysis and its suitability can be measured by thermogravimetric techniques. With these goals, a bibliographic analysis has been done, applying Preferred Reporting Items for Systematic Reviews and Meta-Analyses PRISMA methodology, to the use of thermogravimetric equipment applied to the study of composting and compost uses. According to the methodology for PRISMA systematic reviews, the following databases have been searched Google Scholar, Web of Science, Mendeley, Microsoft Academic, World Wide Science, Science Direct, IEEE Xplore, Springer Link, Scopus, and PubMed by using the terms “thermogravimetry AND (compost OR composting) AND NOT plastic”.

A comparative composting trial with wood shavings (WS), sawdust (SD) and peat moss (PM) was carried out under field conditions. In each, fresh material was mixed with cattle manure in a 2:1 ratio by volume. The initial pH of the WS, SD and PM composts (CST) were 6.2, 5.1 and 5.3, respectively. The chemical and biological changes in CST related to maturity were determined. Samples taken at 0, 12 and 24 mo of composting were also mixed with soil and increasing rates of N and tested as growing media for faba beans (Vicia faba L.) and corn (Zea mays L.) under greenhouse conditions. During composting, the C/N and E4/E6 values decreased in all cases but much more rapidly in WS pile. Thus, after 36 mo of composting, the C/N value decreased from 43 to 17 in WS pile and from 48 to only 35 in PM pile. As indicated by a low C/N ratio (17) and lower humic absorbance values (E4/E6 = 6.4), WS material was practically mature after 24 mo, more rapidly than SD and PM composts which presented initial lowest pH values. The microbial respiration rate (CO2), the pH and N–NO3 values increased during composting in all materials but much more in WS than in SD or PM pile. All composts were not harmful to plant growth even after a short time of composting (12 mo), but yields increased with the duration of composting. These data showed that it was possible to obtain, in field conditions, a compost from ligneous materials in 24 mo. Key words: Compost, composting, corn (Zea mays L.), faba beans (Vicia faba L.), microflora, peat moss, sawdust, wood shavings

In a large agricultural operation, such as the one at Cal Poly San Luis Obispo, disposal of deceased animals is an immense issue. The cost of transporting and rendering every dead animal is inhibitory to the general function of the agricultural operations and their thin budget. Therefore, we propose that composting mortalities could be an economical alternative. Composting is a recognized method for taking animal waste products along with carbon waste and turning it into a pathogen-free, nutrient-rich topsoil. Carcass composting is in fact performed in other countries and states to varying degrees of success. However, the California EPA limits carcass composing to only private land. Therefore, the purpose of this work was to determine the efficacy of killing pathogens by composting using bench top composting models. Ultimately, our goal is to provide “proof of concept” data in order to gain permission for a full-scale carcass compost pile to be set up at Cal Poly San Luis Obispo. Using thermo tolerant Salmonella senftenberg as an indicator organism, we performed bench top trials of traditional and carcass compost in the lab. Samples were inoculated with S. senftenberg and kept at 55°C for 15 days in accordance with the California EPA and Test Method for the Examination of Composting and Compost (TMECC). Samples were then plated and processed for multiple tube analysis and most probable number. Samples were also partitioned for a viability qPCR with propidium monoazide (PMA) to compare to the classic techniques. Using these methods we were then able to track and produce thermal death time data for S. senftenberg in both traditional and carcass compost. By comparing the types of compost, we were able to determine that the composting method presented by the California EPA and the TMECC produces safe, pathogen free compost, even when inoculated carcasses were introduced. However, even with removal of dead cells by PMA, qPCR did not outperform the classical microbiological methods for as tracking pathogen killing.

Thesis (PhD)--Stellenbosch University, 2012.
ENGLISH ABSTRACT: The use of cowdung as an organic fertilizer in Asian and African agriculture is an ancient practice. This explains its renewed interest, partly due to the financial inability of most farmers to purchase agrochemicals but also the ever increasing need to adopt greener technologies that do not adversely affect soil health, water quality, biodiversity and promote sustained or even increased food production. In this context, many innovative farmers have developed their own novel technologies based on the use of local resources. One such innovation is Sanjeevak (a mix of cow dung, cow urine, water and a handful of sugar); which showed very promising boosting effect on crop productivity. However, very little scientific work has so far been conducted to evaluate its effect as an organic product for soil amendments. The present study was subdivided into three main objectives. (i) To assess the fertilizing value, human health and ecological risk profiles of Sanjeevak; (ii) To screen Sanjeevak for phytohormones content using Salkowski colorimetric method and liquid chromatography – mass spectrometry (LC-MS) (iii) To evaluate Sanjeevak application at various rates on growth parameters and yield of various crops cultivated in glasshouse and field conditions. Sanjeevak was assessed for its micro and macro nutrients contents. The analysis showed the presence of micronutrients such as Mg, Na, Ca and Zn at variable concentrations and phosphorus (P) (0.007%) and potassium (K) (0.063%). However, Sanjeevak content in total nitrogen (TN) (0.11%), and total organic carbon (TOC) (0.71%) was very low; suggesting that it may be a viable source of nutrients only if applied at higher and consistent rates or alternatively by improving its formulation. Also, Sanjeevak was analysed for its microbiological characteristics and level of heavy metals content in comparison to the strictest legislations that regulate the use and application of wastewater sludge to agricultural land in South Africa. The findings showed that heavy metals, which averaged from 0.03±0.01 for Arsenic (As) to 4.74±0.92 mg/kg for Zinc (Zn) and feacal coliform was estimated at 1.2×102 CFU/g dry matter measured were considerably below the threshold (for Arsenic between 40 to 75 mg/kg dry weight; for Zinc between 2800 to 7500 mg/kg dry weight) and faecal coliform bacteria between 1000 to 1×107 CFU/g dry weight for application as a source of soil amendments. Studies investigating the detection and concentration of phytohormones in Sanjeevak were carried out. In using the Salkowski colorimetric method to detect and quantify auxins from Sanjeevak and its composites (cow urine and dung), the results showed the presence of indole-3-acetic acid (IAA) at variable concentrations ranging from 20.38±2.1 ppm in cow urine, 20.1±6.6 ppm in cow dung, Sanjeevak 17.90±1.1 ppm to up to 138.31±12.6 ppm when LTRP was added to Sanjeevak bacterial cultures and by varying parameters such as incubaton time and temperature. Screening of the above mentioned samples for IAA using LC-MS analysis validated earlier findings. Further analysis of these results strongly emphasized the influence of bacteria in Sanjeevak in producing IAA. Trials were carried out both in the glasshouse and the field. In the greenhouse, different Sanjeevak application rates consistently confirmed its root promoting effect on crops such as tomato, cucumber and grapevine and increased wheat yield independent of the nutrients it contains. Marginal increases were recorded between treatments under field conditions; for example compost and compost + Sanjeevak 20.35 and 20.61 t/ha; and 2.46 and 2.60 t/ha compared to the control 11.67 t/ha and 1.29 t/ha respectively for tomato and maize. However, statistical analysis of the results obtained, revealed that there was no difference between treatments (control, compost, Sanjeevak and compost + Sanjeevak) for the same crop tested due to the high coefficient of variation of the data. Therefore, the use of Sanjeevak as an organic source of soil amendments may be considered as a cheaper alternative to effective microorganisms (EM) technology made up of local and natural resources. As observed in the study, it may be best used in combination with a reliable source of plant nutrients.
RESUMEE: L'utilisation des excréments de vaches comme engrais organique dans l'agriculture asiatique et africaine est une pratique très ancienne. Ceci explique son intérêt renouvelé, en partie due à aux restrictions monétaires de la plupart des agriculteurs d'acheter des produits agrochimiques, mais aussi la nécessité croissante d'adopter des technologies vertes qui ne nuissent pas à la qualité des sols, des eaux, la biodiversité et qui permettent d’améliorer la production agricole. C’est dans ce contexte que de nombreux paysans ont développé des techniques nouvelles dépendant des ressources naturelles et locales. L’utilisation de Sanjeevak (un mélange d’excréments de vaches, d’urine de vaches, l'eau et du sucre), a démontré sa capacité à accroître la productivité des plantes vivrières. Cependant, très peu de travaux scientifiques ont jusqu'à présent été menée pour étudier ce produit organique. La présente étude a été subdivisée en trois objectifs principaux. (i) Evaluation de la valeur fertilisante, et les profils de risques écologiques et sanitaires de Sanjeevak, (ii) Etudes de détection des phytohormones et leurs concentrations en utilisant une méthode colorimétrique adaptée de celle de Salkowski et la chromatographie liquide - spectrométrie de masse (LC-MS) (iii) Etude des effets de l’utilisation de Sanjeevak a différents taux d’applications sur la croissance et le développement des plants. Sanjeevak a été évaluée pour son contenu en micro et macro nutriments. L'analyse a montré la présence d'oligo-éléments tels que Mg, Na, Ca et Zn à des concentrations variables. De plus, son contenu en éléments majors tels que le phosphore (P) (0.007%), le potassium (K) (0.063%), l’azote (N) (0.11%), et carbone (C) (0.71%) est très faible; suggérant qu'il pourrait être une source viable de nutriments que si elle est appliquée à des taux plus élevés et répétés ou alternativement en améliorant sa formulation. En outre, Sanjeevak a été analysé pour ses caractéristiques microbiologiques et sa concentration en métaux lourds en comparaison a la législation qui réglemente l'utilisation et l'application de déchets liquide d’origines domestiques sur les terres agricoles en Afrique du Sud. Les résultats ont révélé que des métaux lourds et le niveau de coliformes fécaux mesuré était inférieur aux seuils d'application en tant que source d'amendements de sols agricoles. Les études portant sur la détection et la concentration d’hormones végétales ont été effectuées. En utilisant la méthode colorimétrique de Salkowski pour détecter et quantifier les auxines de Sanjeevak, les urines et les excréments de vaches; les résultats ont révélé la présence d'acide indole-3-acétique (AIA) à des concentrations variables dans les urines, les excréments et Sanjeevak. Une autre analyse des échantillons mentionnés ci-dessus pour les AIA en utilisant LC-MS a validé les résultats obtenus au préalable. L’étude détaillée de ces résultats confirme l'influence des micro-organismes dans la production des hormones végétales. Concernant les expériences sous serre, les différents taux d'application de Sanjeevak ont confirmé son effet stimulant à la croissance accélérée des racines des plantes telles que la tomate et les raisins et augmenté le rendement du blé indépendamment des nutriments qu'il contient. L'analyse statistique des résultats obtenus dans des conditions de terrain, a révélé qu'il n'y avait pas de différence entre les traitements (contrôle, compost, compost + Sanjeevak et Sanjeevak) pour la même plantes testées. Par conséquent, l'utilisation de Sanjeevak comme un produit organique qui améliore la qualité des sols et le rendement des cultures vivrières; peu être considéré comme un inoculum contenant des microorganismes constitué de ressources locales et naturelles. Comme l'a observé dans l'étude, il pourrait être mieux utilisé en combinaison avec une source fiable de nutriments végétaux.
AFRIKAANSE OPSOMMING: Die gebruik van beesmis as 'n organiese kunsmis in Asië en Afrika is' n eeu-oue landbou praktyk. Dit verklaar die hernude belangstelling, deels vanweë die finansiële onvermoë van meeste boere om landbouchemikalieë aan te koop, maar ook as gevolg van die toenemende behoefte vir groener tegnologie wat nie nadelig is vir grond gesondheid, waterkwaliteit, biodiversiteit en wat volhoubaarheid of selfs verhoogde voedselproduksie bevorder. In hierdie konteks het baie vindingryke boere hul eie nuwe tegnologie, gebaseer op die gebruik van plaaslik verkrygde hulpbronne, ontwikkel. `n Voorbeeld hiervan is Sanjeevak ('n mengsel van beesmis, beesurine, water en die handvol melasse), wat belowende bevorderende effekte op gewas produktiwiteit en grond mikroflora getoon het. Tot dusver was daar egter baie min wetenskaplike werk gedoen om die effek daarvan as 'n organiese produkte vir grond wysigings te evalueer. Hierdie studie was verdeel in vier belangrike doelwitte. (i) Om die bemestingswaarde, menslike gesondheid en ekologiese risiko-profiele van Sanjeevak te evalueer; (ii) Om Sanjeevak vir fitohormone inhoud en vlakke met behulp van 'n kolorimetriese metode afgelei van dié van Salkowski en vloeistofchromatografie – massaspektrometrie (LC-MS) te besigtig; (iii) Glashuis en veld waarneming reaksies met betrekking tot groei parameters en opbrengs van verskeie gewasse na die toediening van Sanjeevak by verskillende tempos; (iv) Laastens, om die effek van die Sanjeevak voorbehandeling op saad ontkieming en voortplanting te toets in vergelyking met die metodes en tegnieke wat gereeld gebruik word. Sanjeevak is geassesseer vir die mikro-en makro voedingstowwe inhoud. Die analise het die teenwoordigheid van mikrovoedingstowwe soos Mg, Na, Ca en Zn by wisselende konsentrasies, asook fosfor (P) (0.007%) en kalium (K) (0.063%), getoon. Sanjeevak inhoud van totale stikstof (TN) (0.11%), en die totale organiese koolstof (TOC) (0.71%) was egter baie laag, wat daarop dui dat dit slegs 'n lewensvatbare bron van voedingstowwe is indien dit by hoër en konsekwente tempos toegedien word of alternatiewelik wanneer formulering daarvan verbeter word. Sanjeevak was ook ontleed vir die mikrobiologiese eienskappe en die vlakke van swaar metale in vergelyking met die streng wetgewing wat die gebruik en toediening van afvalwater slyk op landbougrond in Suid-Afrika reguleer. Die bevindinge het getoon dat swaar metale en fekalieë kolivorm vlakke hier gemeet, aan die drumpel vereistes voldoen vir die toediening as ‘n grondverbeteringsmiddel. Studies wat die opsporing en die konsentrasie van fitohormone in Sanjeevak ondersoek is uitgevoer. In die gebruik van die Salkowski kolorimetrise metode om die ouksiene op te spoor en te kwantifiseer uit Sanjeevak en sy mengsel (beesurine en mis), het die resultate die teenwoordigheid van indol-3-asynsuur (IAA) by wisselende konsentrasies wat wissel van 20 tot 140 ppm in beesurine, beesmis en Sanjeevak getoon. Evaluering van die bogenoemde monsters vir IAA met behulp van LC-MSanalise bevestig vroeër bevindings. Verdere ontleding van hierdie resultate beklemtoon sterk die invloed van Sanjeevak mikrobiota in fitohormone produksie. Proewe is uitgevoer in die glashuis en die veld. In die glashuis eksperimente, is het die verskeie toedieningstempo van Sanjeevak herhalend die wortelbevorderende effekte bevestig op gewasse soos tamaties, komkommer en wingerdstok en dit het opbrengs van koring verhoog, onafhanklik van die voedingstowwe wat dit bevat. Statistiese analise van die resultate verkry onder veldtoestande, het getoon dat daar geen verskil tussen die behandelings (kontrole, kompos, Sanjeevak en kompos + Sanjeevak) was nie, gegee dat dieselfde gewas getoets was. Ten slotte, laboratorium-eksperimente op Sanjeevak as voor-behandeling om die beworteling te verbeter van die wingerdstok (Ramsey) onderstok steggies, het baie belowende resultate getoon in vergelyking met naftaleen asynsuur (NAA) voorbehandeling en die kontrole. Dit beklemtoon die feit dat Sanjeevak 'n alternatief kan wees en wat verdere studie verdien, hoofsaaklik as gevolg van sy lae-koste en omgewingsvriendelike prosedures. Die gebruik van Sanjeevak as 'n organiese grondverbeteringsmiddel vir gewasproduksie en voortplanting kan beskou word as' n goedkoper alternatief tot effektiewe mikro-organisme (EM) tegnologie wat uit plaaslike en natuurlike hulpbronne saamgestel is. Soos waargeneem in die studie, kan dit die beste gebruik word in kombinasie met 'n betroubare bron van plantvoedingstowwe. Dus, moet die gebruik daarvan vir die produksie van gewasse en voortplanting aangemoedig word.

Um dos grandes problemas ambientais da atualidade é o gerenciamento dos resíduos sólidos. Para a preservação do ambiente o tratamento dos resíduos deve ser considerado como uma questão de toda a sociedade. O presente estudo teve o objetivo analisar os impactos da implementação da metodologia CAT - Conhecer, Analisar e Transformar - como estratégia/ ferramenta para o ensino de Ciências, englobando temas relacionados aos resíduos sólidos. A metodologia de pesquisa utilizada foi de natureza qualitativa, do tipo pesquisa- ação. Participaram da pesquisa sete alunos da 5ª série/6º ano do Ensino Fundamental II de uma escola estadual campesina. Em relação aos impactos promovidos pelo projeto, têm-se como principais considerações o aumento do domínio dos conteúdos trabalhados durante a execução da metodologia proposta, a grande participação e o envolvimento dos alunos e o crescimento de assiduidade dos discentes. Considerou-se também que os sujeitos da pesquisa são influenciados por fatores de ordem micro e macrossocial. Os resultados anunciaram outras possibilidades para o currículo e o ensino de Ciências em escola campesinas. Por fim, ressalta-se que execução do projeto possibilitou quantificar o grau de influência de projetos como este na aprendizagem significativa de alunos camponeses.
One of the major environmental problems of today is the management of solid waste. For the preservation of the environment waste treatment must be considered as a matter of the whole society. The present study had the objective of analyzing the impacts of the implementation of the methodology CAT - Knowing, Analyzing and Transforming - as a strategy / tool for the Teaching of Sciences, encompassing themes related to solid waste. The research methodology used was qualitative, of the research- action type. Seven students from the 5th grade / 6th year of Elementary School II participated in a rural state school. In relation to the impacts promoted by the project, we have as main considerations the increase of the content domain worked during the execution of the proposed methodology, the great participation and the involvement of the students and the student growth of attendance. It was also considered that the subjects of the research are influenced by factors of micro and macrossocial order. The results announced other possibilities for curriculum and science education in peasant schools. Finally, it is emphasized that project execution made it possible to quantify the degree of influence of projects such as this on meaningful learning of peasant students.

Understanding the fundamentals of composting science from a pragmatic perspective of necessity involves mixtures of different sizes and types of particles in constantly changing environmental conditions, in particular temperature. The complexity of composting is affected by this environmental variation. With so much "noise" in the system, a question arises as to the need to understand the detail of this complexity as understanding any part of composting with more precision than this level of noise is not likely to result in greater understanding of the system. Yet some compost piles generate offensive odours while others don‟t and science should be able to explain this difference. A driver for this research was greater understanding of potential odour, which is assumed to arise from the anaerobic core of a composting particle. It follows that the size of this anaerobic core could be used as an indicator of odour potential. A first step in this understanding is the need to determine which parts of a composting particle are aerobic, from which the anaerobic proportion can be determined by difference. To this end, this thesis uses a finite volume method of analysis to determine the distribution of oxygen at sub-particle scales. Diffusion laws were used to determine the thickness of each finite volume. The resulting model, called micro-environment analysis, was applied to a composting particle to enable determination of onion ring type volumes of compost (called micro-environments) containing substrates (further subdivided into substrate fractions) whose concentrations could be determined to high precision by the application of first-order degradation kinetics to each of these finite volumes. Determination of the oxygen concentration at a micro-environment's inner boundary was achieved by using the Stępniewski equation. The Stępniewski model was derived originally for application to soil aeration and enables each micro-environment to have its own oxygen uptake rate and diffusion coefficient. This first version of micro-environment analysis was derived from the simpler solution to diffusion laws, based on the assumption of non-diffusible substrate. It was tested against three sets of experimental data with two different substrates: Particle size trials using dog sausage as substrate – where the peak composting rate was successfully predicted, as a function of particle size. Temperature trials using pig faeces and a range of particle sizes – the results showed the potential of micro-environment analysis to identify intriguing temperature effects, in particular, a different temperature effect (Q10) and fraction proportion was indicated for each substrate fraction. Smaller particle sizes, and possibly outward diffusion of substrate confounded a clear experimental signal. Diffusion into a pile trials which showed that the time course of particles deeper in the pile could be predicted by the physics of oxygen distribution. A fully computed prediction would need an added level of computational complexity in micro-environment analysis, arising from there being two intertwined phases, gas phase and substrate (particle) phase. Each phase needs its own micro-environment calculations which can not be done in isolation from each other. Unexplainable parts of the composting time course are likely to be partly explained by the outward diffusion of substrate towards the inward-moving oxygen front. Although the possibility of alternative electron acceptors can not be discounted as a partial explanation. To test the theory, a new experimental reactor was developed using calorimetry. With an absolute sensitivity of 0.132 J hr-1 L-1 and a measurement frequency of 30 minutes, the reactor was able to detect the energy required to humidify the input air, and "see" when composting begins to decline as oxygen is consumed. Optimisation of the aeration pumping frequency using the evidence from the data was strikingly apparent immediately after setting the optimum frequency. Micro-environment analysis provides a framework by which several physical effects can be incorporated into compost science.

Composting is one element of waste management. It allows waste to be transformed into a valuable product. The processes involved and the final product, however, may vary in terms of quality, efficiency or security. Models have been established to represent some features of the composting process, but never all of them together. We hypothesized that all the key features from the literature could be gathered in one model. This model should be qualitatively faithful, reliable, and easily adapted to any situation. We used COMSOL TM, software that uses proven algorithms and the finite element method to solve partial differential equations in high spatial resolution in up to three dimensions. The behavior of this model was studied through parameter variations and sensitivity analysis. Patterns in temperature, biomass, substrate, oxygen and water concentration curves were consistent with the typical curves found in literature about composting. Initial water concentration and airflow were found to have an important impact on the composting process, while inlet air temperature did not. The resolution of the mathematical problem in a two-dimensional, longitudinal cross-section of the rectangular vessel allowed the observation of spatial patterns. This model can be used as a basis for further studies as new features are easy to implement. It can likewise be adapted to any apparatus, which makes it useful for comparative analysis. The suggested model, however, has yet to be validated against a physical system and this should be the next step.
Le compostage est un composant de la gestion des déchets et permet de les transformer en un produit à valeur ajouté. Les procédés en jeu, ainsi que les produits finis peuvent cependant varier au niveau de la qualité, de l'efficacité, et de la sécurité. Des modèles ont été mis au point pour prendre en compte certaines caractéritiques du compostage, mais jamais de façon exhaustive. Notre hypothèse était que toutes les caractéristiques clés décrites dans la littérature peuvent être réunies en un seul modèle. Ce modèle doit être qualitativement fidèle, fiable, et facilement adaptable à toutes les situations. Nous avons utilisé COMSOL TM, un logiciel qui utilise des algorithmes établis et se base sur la méthode des éléments finis pour résoudre les systèmes d'équations différentielles partielles avec une bonne résolution spatiale en deux ou trois dimensions. La réponse de ce modèle face à des variations paramètriques et à une analyse de sensitivité a été étudiée. Les comportements de la température, de la biomasse, du substrat, de l'oxygène, et de la quantité d'eau ont été cohérents avec ceux trouvés dans la littérature sur le compostage. La concentration initiale en eau, ainsi que l'aération, ont été prouvés avoir un impact important sur le compostage, contrairement à la température de l'air entrant. La résolution du problème mathématique dans une coupe bidimensionnelle longitudinale du container rectangulaire permet l'observation de comportements spatiaux. Ce modèle pourra être utilisé comme un fondement pour de futures études car l'ajout de nouvelles caractéristiques y est aisé. Le modèle peut aussi être facilement adapté à différentes conditions expérimentales, ce qui en fait un bon outil comparatif. Cependant, le modèle suggéré doit d'abord être validé par des données expérimentales.

On-site treatment (home and community composting) of organic waste (OW) reduces cost and environmental issues as opposed to centralized facilities and landfilling. By 2025, such on-site practices could reduce costs and greenhouse gas emissions (GGE) by 50 and 40 %, respectively, and save land as compared to maintaining landfilling practices. However, the shift of municipal solid waste (MSW) management systems from landfill disposal to resource recovery requires technological input, population participation and compost quality assurance. The composting process and quality of composted product depends on the initial compost mixture formulation, design type and management practices of home composting systems (HC). A project was therefore conducted both in the laboratory and in the field, to establish a home composter design and compost formula, which favours the best organic waste decomposition. The results indicated that home composter design is important: perforations must be concentrated at the top and bottom to provide an aeration level equivalent to that of a ground pile. Such home composters can reach thermophilic temperatures when fed at least 10 kg (week)-1 of organic waste with a dry matter content over 15 % (half yard trimmings and half food waste). The compost produced generally offers acceptable levels of polycyclic aromatic hydrocarbons (PAHs) and heavy metals, but residents must be careful in applying the right amount of garden herbicides. The total GGE from home composters were found to be equivalent to that of centralized composting facilities but eliminate the need to spend energy equivalent to 50 kg CO2-eq (tonne wet waste)-1 for handling and processing.
Le traitement des matières résiduelles organiques (MRO) sur place (centres communautaires de compostage et composteurs maison) est une approche qui réduit les coûts de manipulation et de procédé associés aux centres régionaux de compostage et à l'enfouissement. D'ici 2025 et comparativement à l'enfouissement, cette approche pourrait diminuer les coûts de traitement et les émissions de gaz à effet de serre (GES) de 50 et 40 %, respectivement. D'autre part, la diversion et le recyclage des MRO exigent des connaissances techniques et la participation des gens pour assurer la qualité sanitaire du produit, qui dépend du mélange initial, et de la conception du composteur maison ainsi que de sa gestion. Un projet fut donc réalisé en laboratoire et sur le terrain, dans le but de déterminer les critères de conception des composteurs maison et la formulation du mélange initial qui favorisent la décomposition et la stabilisation des MRO traitées. Les résultats ont démontré que la conception du composteur maison est importante, surtout en ce qui concerne l'emplacement des ouvertures qui, quand concentrées dans le haut et le bas, favorisent l'aération par convection. Cette configuration d'ouvertures fait en sorte que le composteur peut atteindre des température thermophiles, semblables aux amas au sol, s'il est chargé de plus de 10 kg (semaine)-1 de MRO possédant une matière sèche de plus de 15 % (moitié résidus de jardin et résidus de table). Le compost produit par résident est généralement propre, avec de faibles teneurs en hydrocarbures aromatique polycyclique (HAP) et en métaux lourds, à la condition d'appliquer des herbicides jardins en quantités raisonnables. Comparativement aux centres régionaux de compostage, les composteurs maison générent la même quantité de gaz à effet de serre (GES) mais font économiser 50 kg de CO2-équ. (tonne de matières résiduelles humides compostées)-1 en tant qu'énergie de manipulation et de procédé.

Ettsyfte med denna uppsats är jämförelsen mellan två behandlingsalternativ för matavfall, hemkompostering eller biogasproducering sett från klimatperspektivet. Koldioxidekvivalenter har beräknats för de två alternativen. Ett annat syfte har varit att studera den politiska processen för att förstå varför det först under 90-talet uppmuntras till att hushållen ska hemkompostera för att sen under början av 2000-talet förespråka rötning av matavfallet. Mina uträkningar och jämförelser visar att det är mer fördelaktigt för klimatet att röta matavfallet, koldioxidutsläppet blir mindre än vid hemkompostering. Mitt andra syfte visar att det kan finnas en klimatvinst genom att låta politiken fatta besluten men det kan även finnas en risk att det egentliga syftet med hemkompostering glöms bort och att hushållen måste betala för något som de egentligen inte behöver (matkärl) eller som inte kanske finns (tillsynen).
One purpose of this study is to compare two treatment options for food waste. Home composting or biofuel production, seen from the climate perspective. The carbon dioxide equivalent has been calculated for the two options. The second purpose was to study the political process with regard to food waste to understand why Swedish households were encouraged to home compost food waste during the nineties only to early twenties advocate biofuel production. My calculations and comparisons shows that it is more beneficial for the climate to digest the food waste then composting since the carbon dioxide emissions is less. My second analysis indicates that while the political reorientation has led to environmental improvements, the effect has also been that to gain control of the food waste stream, waste management organisations effectively provide customers with no choice and economically punish households that have no food waste to collect since they have effective home composting.