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There is a growing demand for sustainable forms of waste management due to both legislative pressures (e.g. the European Union Landfill Directive (99/31/EC)) and increasing public awareness of environmental issues. Composting of biodegradable waste materials to produce a stabilized beneficial multi-functional product (compost) is being widely promoted. Currently, the most popular method of composting is the open windrow method, whereby the mixed and shredded feedstocks are arranged in long rows termed windrows and turned on a regular basis. During the process the waste material is subject to aerobic exothermic microbial decomposition. Commercial composting operations suffer from the problem that much of the processing is performed using empirical approaches. Improved understanding of the composting process based on scientific methodology is required to allow composting to develop its potential as an economic, safe and reliable method of sustainable waste management. This study used a series of large scale windrow-based seasonal field trials employing urban green waste as a feedstock, to investigate in unprecedented detail the temperature trends and patterns of behaviour within such structures. In addition physical-chemical profiling was undertaken. It demonstrated that windrow temperature development is not uniform in either a spatial or temporal sense. Temperature variation is a key feature of composting. All regions of typical windrows exhibited thermophilic and mesophilic temperature zones throughout the composting process. There was little seasonal variation. Sustained high temperatures were most widespread in the core regions at a height of around lm. Thus, these areas should not be favoured during temperature assessment to avoid bias results. It was demonstrated that current methods of temperature assessment are inadequate. It is suggested that greater numbers of data points are collected at varying positions and instead of simply calculating overall mean temperature that individual trends are plotted. The use of temperature frequency distribution histograms and cumulative temperature plots is additionally advised. Increased windspeed (greater than approximately 15MPH) was demonstrated to be a major factor preventing the development and sustaining of thermophilic temperatures within windrows. It is recommended that commercial composters routinely assess windspeed and direction. Changes in organic matter content, bulk density and pH provided an indication of the composting process in the long term but lacked the sensitivity of temperature measurement. Surveying using electronic tacheometry allowed changes in windrow shape and volume to be assessed. The field trial data allowed a novel physical compost model to be developed, based upon open windrow composting of urban green waste. Existing models are based on in-vessel composting systems and are technically flawed in certain key aspects. The model successfully simulated the initial stages of windrow composting, which was proven by experimentation and comparison with field trial data. The use of low level internal feedstock heating was demonstrated to be a viable method of stimulating natural enhanced microbial activity. A non- insulated model windrow and the employment of an environmental simulation system allowed the natural relationship between windrow and external environment to be modelled. The importance of such a model to the compost scientist and waste manager is highlighted. The study showed that it is possible to successfully physically model the open windrow composting process.

The research presented in this thesis can be split into two well-defined areas. Firstly, the effects of the addition of lime (either 2%, 4%, 6% or 8% Ca(OH)2 or 1.5%, 3%, 4.5% or 6% CaO) on various engineering properties of a sulphide (pyrites) rich, naturally occurring clay - Lower Oxford Clay (LOC) - were studied. Experimental tests representing, or relating to, tests outlined in the Design and Construction of Lime Stabilised Capping Specification (DoT, 1995) were utilised and consisted of Atterberg (consistency) tests, compaction tests, unconfined compressive strength tests, linear expansion measurements and durability tests. Also, sulphate (S03) analyses, pH measurements, differential thermogravinietric (DTG) analyses and X-ray diffraction (XRD) tests were employed to confirm experimental data. Environmental conditions were chosen to reflect temperatures experienced in the UK - between 5°C, 10°C and 20°C. The majority of samples were mellowed (the time delay between initial mixing and compaction) for 3 days at 20°C prior to testing. The results show that small additions of lime (i. e. 2% Ca(OH)2 or 1.5% CaO) modify the engineering properties of LOC by causing flocculation, and also increase S03 levels due to increased gypsum levels via pyrites oxidation. However, strength development is poor as little cementitious bonding is formed. Mellowing further modifies the engineering properties as the increased time allows greater flocculation leading to a less dense, more porous material. Also ettringite forms during mellowing allowing expansive reactions to occur prior to compaction, consuming both calcium and sulphate in the process and leading to slightly reduced pH levels compared to similar unmellowed samples. Further additions of lime give further change to the engineering properties of the LOC, up to an addition of 6% Ca(OH)2 or 4.5% CaO. Further additions result only in supplying an excess of calcium. Strength development is improved with increasing lime additions, especially after 4 weeks of curing at higher curing temperatures (20°C); however linear expansion increases and durability worsens. However, a period of mellowing prior to compaction reduces linear expansion and improves durability. Sulphate (S03) levels are also increased with increasing additions of lime due to pyrites oxidation. In samples containing >2% Ca(OH)2 or 1.5% CaO, pH levels are maintained to a level where ettringite formation is sustained rather than gypsum formation. Secondly, the effects of a secondary stabilising agent (ground granulated blast furnace slag - GGBS - incorporated at various percentage additions (2%, 4%, 6% or 8%)) on the strength development, linear expansion and durability of mellowed, lime-modified LOC is presented. For comparative purposes, Portland cement (PC) is also used. The results show that although LOC-lime-PC samples exhibit greater strengths (especially when cured for long periods at 20"C), linear expansion is lower and durability is higher in similar LOClime- GGBS samples. As the hydration process of PC produces lime, and as lime is usually consumed during GGBS hydration, then samples containing the former stabiliser will maintain pH levels well above samples containing the latter. Therefore, on soaking disruption and expansion due to the formation of ettringite (which is unstable at pH levels <10.5) is common to LOC-lime-PC samples but not in similar GGBS samples. In conclusion, the findings from this thesis indicate that soil stabilisation with lime and GGBS is particularly effective for naturally occurring sulphide rich clay soils (such as the LOC) and is an environmentally friendly alternative to PC-stabilised soils.

Se estudia el contenido de semillas viables del suelo de varias comunidades pratenses demontaña, sometidas a distintos niveles de intensificacón agrí­cola, en la zona de Fragen (PirineosCentrales) y en Kaserstattalm (Alpes Orientales). Para ello, en distintos momentos, se tomaronmuestras de suelo, que tras un proceso de reducción, fueron puestas a germinar en un ambientecontrolado. La composición de los bancos se estimó mediante la identificación y el conteo de lasplántulas germinadas en estas fracciones.Los suelos han presentado importantes cantidades de semillas viables enterradas, queoscilan entre las 6.029 y las 54.517 semillas/m según el manejo agrí­cola al que está sometido lacomunidad: los bancos de los prados más intensivos poseen menores cantidades de semillas y deespecies que los extensivos. La composición taxonómica de los bancos se ha caracterizado por lapresencia en cada comunidad de una o dos especies claramente dominantes, entre las quedestacan: Plantago major, Verbena officinalis, Medi­cago lupulina y Stellaria media en losprados pirenaicos y Calluna vulgaris, Erica herbácea y Poa alpina en los alpinos.Sobre la misma red muestral del banco, se recolectó la biomasa para el análisis de lavegetación aérea, en los momentos de máximo desarrollo vegetativo de cada comunidad. Lacomparación entre las semillas enterradas y las plantas adultas arroja grandes diferenciasflorísticas, sobre todo en los prados con régimen de explotación intensivo, donde se producensemillas que no se incorporan al banco. Con los resultados obtenidos, se analizó cómo variaronentre las distintas comunidades: la riqueza especí­fica, la diversidad, la calidad forrajera, lapersistencia de las semillas en el suelo, el tipo de dispersión, y la forma de vida de las especiesdel banco y de la vegetación aérea.Con el objetivo de conocer la variación estacional de los bancos pirenaicos, semuestrearon en dos fases muy significativas en su dinámica: la parada invernal y el primer cortede la hierba. Mientras que en la época estival, las parcelas intensivas aumentan sus reservas desemilla en el suelo, los bancos de los prados extensivos no presentan diferencias.Para averiguar la capacidad regenerativa del banco de semillas, se efectuó un seguimientode las plántulas germinadas en el campo, durante dos periodos vegetativos. Se hizo un inventariodel establecimiento de las especies bajo la cubierta inalterada de la vegetación y tras la alteraciónde la misma, diferenciándose las germinaciones procedentes de las semillas recién dispersadas,con las del suelo. De los resultados se concluye la necesidad de la alteración para que seproduzca el establecimiento de plántulas. El recubrimiento, se efectúo en las comunidades demanejo intensivo, principalmente a partir de la lluvia de semillas local. En las parcelas extensivaséste concierne más a las semillas enterradas en el suelo. Las máximas densidades de plántulas secensaron cuando el suelo estaba a una temperatura media en torno a los 15°C y con contenidos dehumedad a capacidad de campo.Por último, se examinó sobre una malla de 10 m x 10 m, los modelos de distribuciónespacial de las especies de los bancos pirenaicos y de su vegetación aérea. Para ello se hautilizado el í­ndice de autocorrelación (I) de Moran, estimador del grado de agrupamiento de lasespecies en función de la localización geográfica exacta de cada punto de muestreo. Losresultados indican que tanto las plantas adultas, como las semillas enterradas se distribuyenpreferentemente al azar. El reparto agregado se detectó en el 20% de los taxones, y en ningunacomunidad se observaron distribuciones uniformes.

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This thesis examines soil fertility management strategies in dry season irrigated vegetable production (DSIVP) in peri-urban areas of Jos, Nigeria. Farmers have developed a complex strategy of mixing inorganic fertilisers with organic manure and town refuse ash (produced by open burning, and sorting for non-combustible components). The thesis aimed to gain insights into the sustainability (in terms of nutrient supply) of the local agricultural system, acquire an understanding of past and present fertiliser practices and the rationale behind them, provide an appreciation of the role played by urban waste ash and the risks attached to its use, and place the problem of soil fertility in a wider context of farming problems. An inter-disciplinary approach was adopted so the methods used are: chemical analysis of soil and inputs (i.e. refuse ash), questionnaire surveys, semi-structured interviews (with farmers and PADP, JMDB, FUA etc.) and participant observation. The thesis observed that farmers have in-depth, but informal, empirically-derived knowledge about fertiliser application, which explains their past success in soil fertility maintenance. The tremendous increase in DSIVP in the last decade, though, has brought about a scarcity of organic amendments; farmers are increasingly reliant on inorganic fertilisers, probably over-applying them. Although this is not an immediate threat to the stability of the system, it may lead to soil acidification in the near future. Urban waste ash can counteract soil acidification (high pH and base cations), but certain batches can be contaminated by heavy metals, and indeed there is some indication of accumulation in the crops of the study farms. The problem of soil fertility needs to be addressed, however, farmers' short-term concerns (particularly access to credit facilities) need to be solved first. It is imperative that the Nigerian Government should take note of these issues and rapidly take steps to solve them.

La introducció de noves tecnologies en l'àmbit agroalimentari ha revolucionat la eficiència pel que fa al sector productiu, si bé també ha tingut efectes rellevants pel que fa a la demanda, que cal analitzar amb profunditat. Aquest és el cas dels productes modificats genèticament, que solen ser productes de consum habitual, per la qual cosa han creat una important polèmica.Hi ha diferents agents del mercat que participen en aquest debat, com és el cas dels productors, els quals en poden obtenir benefici pel que fa a millores en eficiència i reducció de costos. Tanmateix, és essencial tenir en compte l'opinió dels consumidors alhora d'analitzar els límits comercials de les noves tecnologies.Per a conèixer l'opinió dels consumidors cal entendre el seu procés d'elecció i de valoració dels productes agroalimentaris, com també el seu comportament a l'hora de prendre decisions en el mercat alimentari.Aquesta tesis comença amb una extensa revisió bibliogràfica en relació a les actituds dels consumidors vers els productes modificats genèticament.Seguidament s'analitza la intenció de compra dels consumidors utilitzant experiments d'elecció. L'objectiu principal d'aquesta tesi s'ha assolit amb els subsegüents capítols on s'han analitzat els diferents elements cognitius que porten a l'individu a la intenció final de compra. La metodologia emprada ha estat principalment equacions estructurals i experiments d'elecció. S'han emprat diferents bases de dades per a poder contrastar totes les hipòtesis plantejades en l'estudi.La principal contribució d'aquesta tesi ha estat determinar quins son els elements que cal considerar per entendre el procés de decisió del consumidors vers els aliments modificats genèticament, com també determinar que existeix un clar escepticisme en la societat pel que fa a aquests productes. Les conclusions d'aquesta tesi posen en manifest la necessitat de una millor estratègia de comunicació que permeti als consumidors una percepció de millor i major qualitat d'informació en relació a aquests productes. / The introduction of new technologies in food production not only has revolutioned its productive efficiency but has exerted important demand side effects that cannot be dismissed and require careful analysis. This is especially the case of genetically modified (GM) food, typical daily consumed products (e.g. GM milk, tomato, maize, etc) given its considerable interest and worldwide public controversy. Several stakeholders are place, on the one hand, farmers and manufactures perceive potential benefits from efficiency improvements as well as costs, mainly resulting from the need to reimburse intellectual property rights for new foods. From a demand side, GM food brings new products in the food chain and ultimately fulfils to an extent a latent consumer's preference for diversity. Hence, in order to determine the limits of technology dissemination and transfer it becomes a key issue to examine and disentangle which demand side factors stand behind technology acceptance. This calls for a better understanding of consumer choice, its valuation and the behavioural decision making process.The valuation of a new technology good implies the provision of information from several sources - public and private, formal and informal, etc - while conditioning on the credibility and trustworthiness of each relevant information source. Given the information available, a further issue concerns attitude expression and formation, which ultimately leads to the final question regarding product valuation and consumer preference. Interestingly, attitude formation for the case of new food generations is found to be explained by a combination of risk and benefit perceptions, based on different elements such as a general attitude towards science, knowledge, trust, education and values, among others.This thesis begins with an extensive review of the literature on attitudes towards GM agro-food products- chapter 2- by means of a literature review. Next it conducts a study on consumers' final intentions towards agro - food products, entailing the application of choice experiments - chapter 3. moreover, the main core of this dissertation is aiming at examining what gives rise to the final choice (chapters 4 to 6). The methodologically employed relies on structural equation modelling, although in each chapter different databases have been used. The relative strengths of each database allow us taking into account the information required to test specific hypotheses. Finally, some conclusions are drawn in chapter 7 which summarises the main findings of each chapter and put them in context of the main discussion questions examined in this thesis.The main contribution of this thesis has been to point out a set of features that condition choice, intentions and revealed purchase intentions regarding GM food. Our wok is innovative in that: 1) it contains an innovative literature review; 2) develops choice modelling of scenarios that includes, apart from methodological features, the choice between GM processed and organic food; and 3) unlike most of behavioural analysis it exploits using structural equation modelling, several theoretical structures that explain decision making and, particularly, the role of broader attitudes towards science and technology in influencing purchase intentions alongside the effect of both risks attitudes and risk perceptions in determining consumer acceptance.The sequence and findings of the thesis can be summarized as follows: drawing from an exhaustive review of published finding regarding public intentions towards GM food we conclude that there is consumer's scepticism explaining a negative valuation towards GM food. However, the most important outcome has been to find that final purchasing intention is the result of a complex decision process which only has been partially explained in the literature. Therefore, upon the definition of a general theoretical model this thesis has tried to explain in the different chapters some specific issues of such model as well as to validate it in a croos - country exercise in the last chapter. Results from this study rises a key policy implication: the need of a well defined communication stralegy to provide information in such a way that allows individuals to feel adequately informed.

To assess the availability of bracken and the factors influencing frond yields, this thesis investigated the growth and phenology of bracken populations across Scotland in relation to site characteristics.  The change in elements in fronds and litter from April to November was analysed, along with the concentrations of the carcinogen Ptaquiloside (Pta).  Frond dry matter yields increased to maximum in August/September, falling to those in November.  In September/October, frond yields ranged from 4.70-15.9 DM t ha^-1.  Frond concentrations of phosphorus and potassium reduced, and concentrations of calcium and magnesium increased from May to November.  Frond Pta concentrations reduced during this period also, with the highest concentration recorded of 5792 mg kg^-1 in May 2002 at Loch Grannoch, SW Scotland. This thesis also investigated the effects of harvesting of fronds, and the burning and clearing of litter on the yield of frond dry matter, yield and content of ash and on Pta concentrations in fronds.  The concentration of twenty-one elements, the CaCO₃ equivalence and pH of this ash were determined, and the effect of harvesting of fronds on subsequent yields was assessed.  Harvesting during the growing season reduced the preceding yield of fronds, but not if harvested after senescence.  A positive regression was found between frond DM and ash yields.  The maximum yield of K in ash was harvested in August/September, at around 180 kg ha^-1.  Calculations of the value of bracken ash using August 2001 K concentrations and the cost of other organic K sources came to between £219-£980 t^-1.  The ash produced had a mean pH of 11.9, and mean calcium carbonate equivalence of 52%.  Lifting litter increased the density of fronds, and burning litter increased the soil available Mg concentrations and Ca concentrations in the ash.  Pta concentrations in fronds that emerged in reaction to harvesting were higher compared to those fronds first harvested at the same time.