Effect of locally available spices on the organoleptic and storage periods of Heterotis niloticus

Investigation were carried out on the effect of some locally available species in the enhancement of the organoleptic quality and the storage periods of smoked Heterotis niloticus using Pprosopis africana as common smoke sources. Samples of fresh H. niloticus were bought, cut into chunks while extract juice from pepper, ginger rhizomes, garlic, onion bulb were used as sources of spices. Samples of fish were divided randomly into five (5) batches dipped into spice extract juices for 10 minutes drained and smoked with common firewood. Treatment without spice extract juice served as control. Each batch of fish was smoked for 7 hours on a drum-made smoking kiln products were individually packaged in polythene bag stored at room temperature and used for sensory evaluation and microbial analysis. Results of the sensory evaluation indicated that there was significant difference (P<0.005) for taste, appearance, colour and overall acceptance for the treatments. Ginger juice extract had the best overall acceptance. Similarly there was significant difference (P>0.05) in the microbial analysis. The garlic juice extract had the longest storage period with minimum total plate and mould count after 8 weeks

Investment opportunity in improved fish smoker (IFS) as food security for artisanal women fish processors (AWOFPS) in Nigeria: a case study of Kainji Lake area

The Improved Fish Smoker (IFS) was designed and constructed by NIFFR in collaboration with GTZ in 1997. After the on-station trials, five fishing villages with pronounced fishing activities were selected for the demonstration. The IFS and the traditional Smoking Kiln were compared in one of the fishing villages using Gross Margin analysis (GM) and productivity index to determine the profitability and productivity of the two kilns. It was found that the average income of IFS users at fully capacity was N5, 555.50 per day in a year N1.3 million would be realized. Conversely, the average income of the users of Traditional Smoking Kiln (TSK) was N649.00 per day and about N152, 150.50 would be realized in a year. From this estimate, it is evident that the IFS are more profitable than the TSK. Productivity index of the two kilns also revealed that the productivity of IFS is higher than the TSK. Thus, using the IFS would enhance the income of artisanal women Fish Processors (AWOFPS) and ensure food security for the household

Avaliação das fendas marginais em restaurações de resina composta com variação de alguns determinanates clínicos

O objetivo deste estudo foi comparar, por meio de mensuração das fendas na interface dentina - restauração de resina composta com utilização de algumas variáveis: fotoativação com lâmpada halógena e com LED; utilização de resina microhíbrida com partículas nanométricas Filtek Z350 ou sem estas partículas Filtek Z250; variação do sistema adesivo (Adper Single Bond 2 ou Adper Scotchbond Multi Purpose); variação da temperatura da resina composta; uso de dessensibilizante dentinário ou não; remoção do colágeno da dentina ou não e variação da intensidade de luz na fotoativação. Foram utilizados 70 molares humanos recém-extraídos, com cavidades circulares na dentina superficial de cada face proximal, foram divididos em 10 amostras para cada variável citada acima. Os dentes foram devidamente restaurados, seguindo as instruções dos fabricantes, para todos os grupos e mantidos em estufa bacteriológica por um período de 7 dias, após este período, foram polidos e as réplicas de resina epoxídica foram confeccionadas a partir de uma moldagem com silicone por adição, as mesmas foram levadas ao MEV, para a análise. As fendas foram mensuradas com o auxílio do software UTHSCSA Image tool e os dados foram submetidos à análise estatística pelo teste t de Student para a obtenção dos resultados. Com base nos resultados obtidos pode-se concluir que: os menores valores de fendas marginais foram obtidos quando da utilização de luz halógena (t=3,246 e p= 0,02) e com variação da intensidade desta luz (t= - 8,808 e p= 0,00). Os menores valores relativos de fendas, mas sem diferença estatística significante, foram encontrados, também, quando a resina Filtek Z350 foi comparada com a resina Filtek Z250 (t=-0,426 e p= 0,672) e quando o adesivo Adper Scotchbond Multi Purpose foi comparado com o Sistema Adper Single Bond 2 (t= 0,883 e p= 0,382). Os maiores valores de fendas marginais foram obtidos com a resina Filtek Z350 préaquecida a 60oC (t= -3,961 e p=0,000); com o uso de dessensibilizante dentinário (t=-3,062 e p=0,004) e com a remoção do colágeno pelo hipoclorito de sódio (t= -8,808 e p= 0,000).

Comparative evaluation of the proximate composition of smoked and salted-dried Oreochromis niloticus

This study was carried out to evaluate and compare the shelf life of smoked and salted-dried Oreochromis niloticus over a relative time period. Improved traditional smoking kiln and salting were employed respectively. The smoking kiln was constructed with iron metal with a dimension of 120cm x 70cm and consisting of three smoking racks with dimension of 30 x 30cm each. Table salt was used for preservation of some of the specimens. A total of 30 samples weighing 7.1kg were used. Fifteen (15) samples each were used respectively for smoking and salting. Satisfactory smoking was achieved in two days while salting to dryness was accomplished in four days. The initial percentage proximate compositions of the smoked products were 7.94%, 66. 97%, 8.`84% and 2.96% for moisture, protein, lipid and ash respectively, while that of the salted products were 8.37%, 63.93%, 12.91% and 3.95% for moisture, protein, lipid and ash. Preliminary results of the proximate compositions of the two products at the end of the fifth week of storage were as follows; 8.23%, 65.70%, 10.63% and 2.23% for moisture, protein, lipid and ash respectively of the smoked products, while 6.33%, 64.25%, 11.28% and 2.38% represent the values of moisture, protein, lipid and ash of the salted-dried products. By the individual product proximate characterization, it was discovered that both products were still relatively in good and acceptable condition. However, the protein and moisture values of the smoked products were relatively greater than those of the salted-dried products, while on the other hand, lipid and ash were relatively greater in salted-dried products. The prevailed relative higher moisture in the smoked products constitutes a predisposing condition for microbial activity and spoilage of the products, while the relative higher percentage lipid in the salted-dried products predisposes the products to lipid oxidation and rancidity.

Aquaculture technology transfer to smallholder farmers in Malawi, Southern Africa

Details are given of activities conducted in Zomba, Malawi, in order to demonstrate new aquaculture technologies and encourage their use by smallholder fish farmers. The following technologies were introduced: napier grass as a pond output; use of a reed fence for harvesting fish; developing a high-quality compost as a pond input; vegetable-pond integration; chicken-pond integration; smoking kiln; pond stirring; and rice-fish integration. The reactions of the farmers to these technologies and their testing by the farmers are outlined briefly.

Comparison of stabilised/solidified mixes of model drill cuttings based on the North Sea and Red Sea Areas

Following the global stringent legislations regulating the wastes generated from the drilling process of oil exploration and production activities, the management of hazardous drill cuttings has become one of the pressing needs confronting the petroleum industry. Most of the prevalent treatment techniques adopted by oil companies are extremely expensive and/or the treated product has to be landfilled without any potential end-use; thereby rendering these solutions unsustainable. The technique of stabilisation/solidification is being investigated in this research to treat drill cuttings prior to landfilling or for potential re-use in construction products. Two case studies were explored namely North Sea and Red Sea. Given the known difficulties with stabilising/solidifying oils and chlorides, this research made use of model drill cutting mixes based on typical drill cutting from the two case studies, which contained 4.2% and 10.95% average concentrations of hydrocarbons; and 2.03% and 2.13% of chlorides, by weight respectively. A number of different binders, including a range of conventional viz. Portland cement (PC) as well as less-conventional viz. zeolite, or waste binders viz. cement kiln dust (CKD), fly ash and compost were tested to assess their ability to treat the North Sea and Red Sea model drill cuttings. The dry binder content by weight was 10%, 20% and 30%. In addition, raw drill cuttings from one of the North Sea offshore rigs were stabilised/solidified using 30% PC. The characteristics of the final stabilised/solidified product were finally compared to those of thermally treated cuttings. The effectiveness of the treatment using the different binder systems was compared in the light of the aforementioned two contaminants only. A set of physical tests (unconfined compressive strength (UCS)), chemical tests (NRA leachability) and micro-structural examinations (using scanning electron microscopy (SEM), and X-ray diffraction (XRD)) were used to evaluate the relative performance of the different binder mixes in treating the drill cuttings. The results showed that the observed UCS covered a wide range of values indicating various feasible end-use scenarios for the treated cuttings within the construction industry. The teachability results showed the reduction of the model drill cuttings to a stable non-reactive hazardous waste, compliant with the UK acceptance criteria for non-hazardous landfills: (a) by most of the 30% and 20% binders for chloride concentrations, and (b) by the 20% and 30% of compost-PC and CKD-PC binders for the Red Sea cuttings. The 20% and 30% compost-PC and CKD-PC binders successfully reduced the leached oil concentration of the North Sea cuttings to inert levels. Copyright 2007, Society of Petroleum Engineers.

Sustainable binders for soil stabilisation

Portland cement is the most commonly and widely used binder in ground improvement soil stabilisation applications. However, many changes are now affecting the selection and application of stabilisation additives. These include the significant environmental impacts of Portland cement, increased use of industrial by-products and their variability, increased range of application of binders and the development of alternative cements and novel additives with enhanced environmental and technical performance. This paper presents results from a number of research projects on the application of a number of Portland cement-blended binders, which offer sustainability advantages over Portland cement alone, in soil stabilisation. The blend materials included ground granulated blastfurnace slag, pulverised fuel ash, cement kiln dust, zeolite and reactive magnesia and stabilised soils, ranging from sand and gravel to clay, and were assessed based on their mechanical performance and durability. The results are presented in terms of strength and durability enhancements offered by those blended binders.

回转窑热解处理废锌锰电池试验研究

我国电池生产量已经达到209亿节（2003年），多年来一直占据世界第一大电池生产国的地位，其中锌锰电池占大多数。废锌锰电池丢弃后，其中的重金属物质会逐渐渗透到地下，污染土壤和水体。重金属在生物体内富集，会使生物体致畸或致变。但同时，废锌锰电池中也含有大量有用的资源如锌、二氧化锰等。应对其进行回收利用，变废为宝。本文介绍了废锌锰电池回收处理的主要技术及研究进展，不同的处理技术回收废锌锰电池时的目标产物各不相同，但一般可分为以下几种：以单质形式回收锌、锰和汞；以合金的形式回收锌和锰；回收锌和二氧化锰；回收各金属元素制备复合微量元素肥料；回收锌、锰元素制备锰锌铁氧体；回收锌、锰元素制备硫酸锌和碳酸锰等。本文对一些废锌锰电池回收处理技术的优缺点从无害化程度、资源化程度、产品等级、工艺要求以及二次污染五个方面进行了分析和比较。在对国内外废锌锰电池回收处理技术进行分析比较的基础上提出了一种成本较低、可操作性较强的处理技术：先以干法除去废锌锰电池中的汞，然后以湿法除去其它的有害重金属并进一步加工制备有机螯合微量元素肥料。 本文以回转窑中物料停留时间的经验公式和传热学的知识设计和计算了回转窑的长度和内径尺寸、电热丝的功率以及外围的保温材料厚度等参数。用保温材料和润滑油相结合的方式对回转窑的连接部分实行密封。通过调整回转窑的转速和回转窑支架两端高度差的方式控制物料在回转窑中的停留时间，从而调节热解时间的长短。利用自动控制设备调节电热丝的功率从而调节试验中的热解温度。利用该回转窑在不同条件下对热解处理废锌锰电池进行了试验研究，热解过程中产生的尾气和颗粒物用一系列吸收液进行吸收和固定。 在热解试验中改变影响热解过程的三种因素：热解温度、热解时间和载气流速并按三因素四水平的正交方法安排试验。改变废锌锰电池热解过程中的热解温度、热解时间和载气流速三种因素进行正交试验并利用正交统计学的方法分析了这三种因素对热解除汞率的影响。利用ICP检测仪测定了各吸收液中汞的含量，并分析热解气体产物经过系列吸收液时汞被吸收的情况以及汞的形态分布。利用气相色谱仪对尾气成分进行了测定，并对热解过程中产气的过程和规律进行了分析。用X射线衍射测试的方法研究了热解前后锌锰电池的物质形态变化情况。对除汞率的正交统计分析表明，合适的热解条件为：热解温度690℃，热解时间100min，载气流速0.06m3/h，在这种试验条件下热解处理废锌锰电池的除汞率达到100%。同时还得到：热解时间对除汞效果影响最大，热解温度次之，载气流速的影响较小。ICP测试的结果表明：热解尾气在经过试验中设置的吸收瓶后，其中的汞被完全吸收，尾气中95%以上的汞以单质的形式存在。气相色谱分析的结果表明，热解开始后，废锌锰电池中的有机质迅速分解，其产物为C2H4、CH4和H2等。一段时间后，有机质的分解量大幅度减少，同时废电池中的石墨碳和高价金属氧化物发生氧化还原反应，生成CO气体。对废锌锰电池原料以及热解残渣的X射线衍射分析表明，当热解温度为350℃时，X射线衍射图谱上2θ值为35°附近的区域有新峰出现，但不明显，说明有结晶体形成但量不大。500℃时上述峰明显增强，这是由于ZnO和FeO形成了结晶体，同时在2θ值为41°附近有新峰出现，这是高价锰氧化物与石墨碳发生氧化还原反应生成了MnO并形成了结晶体。650℃时，2θ值在41°附近的峰显著增强，且热解过程中形成的峰稳定下来，基本上不再有新的结晶体生成。热解后，高价锰氧化物的相对含量从32.2%下降到4.6%，而MnO的相对含量则从6.4%上升到38.6%。热解后的残渣中晶体物质含量大，金属元素大多以低价态存在，适合于制备有机螯合微量元素肥料。

基于多重分形的水泥回转窑工况识别研究

鉴于多重分形理论在定量描述复杂系统非线性运行规律方面具有的独特优势,将多重分形理论引入到工况特征识别研究中来,确认了水泥回转窑窑电流信号的多重分形特性。在此基础上,研究了窑电流多重分形谱参数随工况变化的情况,发现多重分形谱参数的变化趋势与回转窑内工况状态的变化趋势之间具有较强的关联性,进而提出了基于多重分形谱参数进行水泥回转窑异常工况特征提取的新方法,为水泥生产过程中工况状态的在线监控和预报提供了有力支持。

Bauxite residue (Red mud) as a pulverised fuel ash substitute in the manufacture of lightweight aggregate

This study looked at the potential of bauxite residue or red mud to be used in the manufacture of lightweight aggregate in replacement of pulverised fuel ash (PFA), commonly used as a way of recycling problematic wastes. The percentage replacements of red mud with PFA were as follows: 25, 31, 38, 44 and 50%. These were blended in a mix with waste excavated clay and sewage sludge – all from the Chongqing municipality in China. Lightweight pellets were produced using a Trefoil rotary kiln and were sintered to 1200 °C. Results showed that 44 % bauxite residue replacement produced lightweight pellets with the highest compressive strength, highest density and largest water holding capacity. This would be expected in materials with a low level of silicates, which causes insufficient glass phase viscosity and therefore poor bloating during firing; producing an aggregate with a higher density but with open pores that allowed for larger water absorption. All ratios of red mud aggregates were significantly reduced in pH after firing to around pH 8, and this reduced the leachability of the aggregates to levels below those set by the European landfill directive (2003/33/EC).

Caracterización y determinación del proceso para la producción de cal comercial a partir de la piedra caliza

La cal es un material producido a partir de la calcinación de la roca caliza y tiene diversas utilidades en el mundo de la industria como la siderúrgica, papelera, alimentaria, en la construcción, entre otras. Es fundamental conocer todas las características de la caliza para poder determinar su grado de calcinación. Con el presente trabajo se pretende estudiar las propriedades de la caliza para su posterior calcinación y el dimensionamento de una planta de producción de cal desde que el mineral llega de la explotación hasta que sale al mercado.Para determinar los equipos se calularon sus dimensiones para una producción de 600 t/h de cal, sabiendo que la planta principal de machaquero solo trabajará 5 días de la semana en jornadas de 8 horas, mientras que a partir del horno de calcinación estará en funcionamento los 7 dias de la semana, 24 horas al día. A partir de esas consideraciones se obtienen las dimensiones de todos los equipos y se realiza un estudio para la elección de un horno, o un horno de eje vertical y un horno rotativo, así como el combustible empleado, ya que es una parte fundamental para determinar los costes para la producción de cal.Tmbién fue objeto de este trabajo, el estudio ambiental de la instalación de la planta, en función de la mezcla de combustible empleada y del impacto en el entorno de la lisma, así como un estudio de viabilidad de la planta, estimando unos costes de la misma y un precio de mercado "ex Works".

Assessment of Energy Conservation in Indian Cement Industry and Forecasting of Co2 Emissions

Cement industry ranks 2nd in energy consumption among the industries in India. It is one of the major emitter of CO2, due to combustion of fossil fuel and calcination process. As the huge amount of CO2 emissions cause severe environment problems, the efficient and effective utilization of energy is a major concern in Indian cement industry. The main objective of the research work is to assess the energy cosumption and energy conservation of the Indian cement industry and to predict future trends in cement production and reduction of CO2 emissions. In order to achieve this objective, a detailed energy and exergy analysis of a typical cement plant in Kerala was carried out. The data on fuel usage, electricity consumption, amount of clinker and cement production were also collected from a few selected cement industries in India for the period 2001 - 2010 and the CO2 emissions were estimated. A complete decomposition method was used for the analysis of change in CO2 emissions during the period 2001 - 2010 by categorising the cement industries according to the specific thermal energy consumption. A basic forecasting model for the cement production trend was developed by using the system dynamic approach and the model was validated with the data collected from the selected cement industries. The cement production and CO2 emissions from the industries were also predicted with the base year as 2010. The sensitivity analysis of the forecasting model was conducted and found satisfactory. The model was then modified for the total cement production in India to predict the cement production and CO2 emissions for the next 21 years under three different scenarios. The parmeters that influence CO2 emissions like population and GDP growth rate, demand of cement and its production, clinker consumption and energy utilization are incorporated in these scenarios. The existing growth rate of the population and cement production in the year 2010 were used in the baseline scenario. In the scenario-1 (S1) the growth rate of population was assumed to be gradually decreasing and finally reach zero by the year 2030, while in scenario-2 (S2) a faster decline in the growth rate was assumed such that zero growth rate is achieved in the year 2020. The mitigation strategiesfor the reduction of CO2 emissions from the cement production were identified and analyzed in the energy management scenarioThe energy and exergy analysis of the raw mill of the cement plant revealed that the exergy utilization was worse than energy utilization. The energy analysis of the kiln system showed that around 38% of heat energy is wasted through exhaust gases of the preheater and cooler of the kiln sysetm. This could be recovered by the waste heat recovery system. A secondary insulation shell was also recommended for the kiln in the plant in order to prevent heat loss and enhance the efficiency of the plant. The decomposition analysis of the change in CO2 emissions during 2001- 2010 showed that the activity effect was the main factor for CO2 emissions for the cement industries since it is directly dependent on economic growth of the country. The forecasting model showed that 15.22% and 29.44% of CO2 emissions reduction can be achieved by the year 2030 in scenario- (S1) and scenario-2 (S2) respectively. In analysing the energy management scenario, it was assumed that 25% of electrical energy supply to the cement plants is replaced by renewable energy. The analysis revealed that the recovery of waste heat and the use of renewable energy could lead to decline in CO2 emissions 7.1% for baseline scenario, 10.9 % in scenario-1 (S1) and 11.16% in scenario-2 (S2) in 2030. The combined scenario considering population stabilization by the year 2020, 25% of contribution from renewable energy sources of the cement industry and 38% thermal energy from the waste heat streams shows that CO2 emissions from Indian cement industry could be reduced by nearly 37% in the year 2030. This would reduce a substantial level of greenhouse gas load to the environment. The cement industry will remain one of the critical sectors for India to meet its CO2 emissions reduction target. India’s cement production will continue to grow in the near future due to its GDP growth. The control of population, improvement in plant efficiency and use of renewable energy are the important options for the mitigation of CO2 emissions from Indian cement industries

Zur Reaktionskinetik der Oxidation von Kohlenstoffmaterialien aus Biomasse

Zur Modellierung von Vergasungs- und Verbrennungsprozessen zur energetischen Nutzung von Biomasse ist die Kenntnis von reaktionskinetischen Daten für die Sauerstoff-Oxidation von Biomassepyrolysaten erforderlich. Eine ausführliche Literaturübersicht zeigt den Stand der Forschung bezüglich der experimentellen Ermittlung von reaktionskinetischen Parametern für die Oxidation von Pyrolysaten aus Lignin, Cellulose und pflanzlicher Biomasse sowie der Suche nach einem plausiblen Reaktionsmechanismus für die Reaktion von Sauerstoff mit festen Kohlenstoffmaterialien. Es wird eine Versuchsanlage mit einem quasistationär betriebenen Differentialreaktor konstruiert, die eine Messung der Reaktionskinetik und der reaktiven inneren Oberfläche (RSA) für die Reaktion eines Pyrolysats aus Maispflanzen mit Sauerstoff ermöglicht. Die getrockneten und zerkleinerten Maispflanzen werden 7 Minuten lang bei 1073 K in einem Drehrohrofen pyrolysiert. Das Pyrolysat zeichnet sich vor allem durch seine hohe Porosität von über 0,9 und seinen hohen Aschegehalt von 0,24 aus. Die RSA wird nach der Methode der Messung von Übergangskinetiken (TK) bestimmt. Die Bestimmung der RSA erfolgt für die Reaktionsprodukte CO und CO2 getrennt, für die entsprechend ermittelten Werte werden die Bezeichnungen CO-RSA und CO2-RSA eingeführt. Die Abhängigkeit dieser Größen von der Sauerstoffkonzentration läßt sich durch eine Langmuir-Isotherme beschreiben, ebenso das leichte Absinken der CO-RSA mit der Kohlendioxidkonzentration. Über dem Abbrand zeigen sich unterschiedliche Verläufe für die CO-RSA, CO2-RSA und die innere Oberfläche nach der BET-Methode. Zur Charakterisierung der Oberflächenzwischenprodukte werden temperaturprogrammierte Desorptionsversuche (TPD) durchgeführt. Die Ergebnisse zeigen, daß eine Unterscheidung in zwei Kohlenstoff-Sauerstoff-Oberflächenkomplexe ausreichend ist. Die experimentellen Untersuchungen zum Oxidationsverlauf werden im kinetisch bestimmten Bereich durchgeführt. Dabei werden die Parameter Temperatur, Sauerstoff-, CO- und CO2-Konzentration variiert. Anhand der Ergebnisse der reaktionskinetischen Untersuchungen wird ein Reaktionsmechanismus für die Kohlenstoff-Sauerstoff-Reaktion entwickelt. Dieser Reaktionsmechanismus umfaßt 7 Elementarreaktionen, für welche die reaktionskinetischen Parameter numerisch ermittelt werden. Darüber hinaus werden reaktionskinetische Parameter für einfachere massenbezogene Reaktionsgeschwindigkeitsansätze berechnet und summarische Reaktionsgeschwindigkeitsansätze für die Bildung von CO und CO2 aus dem Reaktionsmechanismus hergeleitet.

Zur Adsorption und Reaktion von Stickstoffmonoxid an Aktivkohle

Die Verwendung von Aktivkohlen und -koksen stellt eine Alternative zu herkömmlichen Prozessen zur Verminderung der NOx-Emissionen in Rauchgasen dar. An diesen Materialien wird Stickstoffmonoxid adsorbiert und katalytisch zu N2 reduziert. Eine einheitliche Erklärung über die ablaufenden Vorgänge und die Reaktionsmechanismen gibt es noch nicht. Die Ergebnisse der bisher veröffentlichten wissenschaftlichen Arbeiten sind sehr unterschiedlich, wenn nicht sogar widersprüchlich. In dieser Arbeit wird, anhand der Messung von NO-Durchbruchskurven und thermischen Desorptionsspektren, die Adsorption und Reaktion von Stickstoffmonoxid an Aktivkohlen und -koksen in Anwesenheit von Sauerstoff und Wasserdampf untersucht. Zur Durchführung der experimentellen Untersuchungen wird eine Versuchsanlage, bestehend aus einer Vorrichtung zur Gasgemischaufbereitung, einem Festbettreaktor und einer Gasanalytik, konzipiert und aufgebaut. Die Untersuchungen erfolgen bei Temperaturen zwischen 100 und 150 °C. Die NO-, O2- und H2O-Konzentrationen werden anhand der Rauchgaszusammensetzung kohlegefeuerter Kraftwerke gewählt. Die experimentellen Untersuchungen konzentrieren sich auf die Verwendung einer Aktivkohle aus Ölpalmschalen, die in einem Drehrohrreaktor am Institut für Thermische Energietechnik der Universität Kassel hergestellt wurde. Die experimentellen Ergebnisse zeigen, dass während des Prozesses NO-Adsorption, -Reduktion und -Oxidation, NO2-Bildung, -Adsorption und -reduktive Desorption, H2O-Adsorption sowie O2-Vergasung gleichzeitig stattfinden. Bei niedrigen Temperaturen werden die NO2-Bildung und die Adsorption bevorzugt. Die NO-Reduktion läuft über adsorbiertes NO mit CO2- und CO-Bildung. Durch O2-Vergasung werden aktive freie Cf-Plätzen für die NO-Reaktion und -Adsorption gebildet. Wasserdampf wird an der Aktivkohle adsorbiert und belegt aktive Plätze für diese Prozesse. Aus den experimentellen Ergebnissen werden kinetische und Gleichgewichtsparameter der NO-Sorption bestimmt. Ein vereinfachtes mathematisches Modell des Festbettreaktors, das zur Berechnung der NO-Durchbruchskurven bei unterschiedlichen Temperaturen dient, wird aufgestellt.

Agricultural practices and horizontal nutrient balances in urban gardens and the alternative use of urban agricultural land in Khartoum, Sudan

The surge in the urban population evident in most developing countries is a worldwide phenomenon, and often the result of drought, conflicts, poverty and the lack of education opportunities. In parallel with the growth of the cities is the growing need for food which leads to the burgeoning expansion of urban and peri-urban agriculture (UPA). In this context, urban agriculture (UA) contributes significantly to supplying local markets with both vegetable and animal produce. As an income generating activity, UA also contributes to the livelihoods of poor urban dwellers. In order to evaluate the nutrient status of urban soils in relation to garden management, this study assessed nutrient fluxes (inputs and outputs) in gardens on urban Gerif soils on the banks of the River Nile in Khartoum, the capital city of Sudan. To achieve this objective, a preliminary baseline survey was carried out to describe the structure of the existing garden systems. In cooperation with the author of another PhD thesis (Ms. Ishtiag Abdalla), alternative uses of cow dung in brick making kilns in urban Khartoum were assessed; and the socio-economic criteria of the brick kiln owners or agents, economical and plant nutritional value of animal dung and the gaseous emission related to brick making activities were assessed. A total of 40 household heads were interviewed using a semi-structured questionnaire to collect information on demographic, socio-economic and migratory characteristics of the household members, the gardening systems used and the problems encountered in urban gardening. Based on the results of this survey, gardens were divided into three groups: mixed vegetable-fodder gardens, mixed vegetable-subsistence livestock gardens and pure vegetable gardens. The results revealed that UA is the exclusive domain of men, 80% of them non-native to Khartoum. The harvested produce in all gardens was market oriented and represented the main source of income for 83% of the gardeners. Fast growing leafy vegetables such as Jew’s mallow (Corchorous olitorius L.), purslane (Portulaca oleracea L.) and rocket (Eruca sativa Mill.) were the dominant cultivated species. Most of the gardens (95%) were continuously cultivated throughout the year without any fallow period, unless they were flooded. Gardeners were not generally aware of the importance of crop diversity, which may help them overcome the strongly fluctuating market prices for their produce and thereby strengthen the contributions of UA to the overall productivity of the city. To measure nutrient fluxes, four gardens were selected and their nutrients inputs and outputs flows were monitored. In each garden, all plots were monitored for quantification of nutrient inputs and outputs. To determine soil chemical fertility parameters in each of the studied gardens, soil samples were taken from three selected plots at the beginning of the study in October 2007 (gardens L1, L2 and H1) and in April 2008 (garden H2) and at the end of the study period in March 2010. Additional soil sampling occurred in May 2009 to assess changes in the soil nutrient status after the River Nile flood of 2008 had receded. Samples of rain and irrigation water (river and well-water) were analyzed for nitrogen (N), phosphorus (P), potassium (K) and carbon (C) content to determine their nutrient inputs. Catchment traps were installed to quantify the sediment yield from the River Nile flood. To quantify the nutrient inputs of sediments, samples were analyzed for N, P, K and organic carbon (Corg) content, cation exchange capacity (CEC) and the particle size distribution. The total nutrient inputs were calculated by multiplying the sediment nutrient content by total sediment deposits on individual gardens. Nutrient output in the form of harvested yield was quantified at harvest of each crop. Plant samples from each field were dried, and analyzed for their N, P, K and Corg content. Cumulative leaching losses of mineral N and P were estimated in a single plot in garden L1 from December 1st 2008 to July 1st 2009 using 12 ion exchange resins cartridges. Nutrients were extracted and analyzed for nitrate (NO3--N), ammonium (NH4+-N) and phosphate PO4-3-P. Changes in soil nutrient balance were assessed as inputs minus outputs. The results showed that across gardens, soil N and P concentrations increased from 2007 to 2009, while particle size distribution remained unchanged. Sediment loads and their respective contents of N, P and Corg decreased significantly (P < 0.05) from the gardens of the downstream lowlands (L1 and L2) to the gardens of the upstream highlands (H1 and H2). No significant difference was found in K deposits. None of the gardens received organic fertilizers and the only mineral fertilizer applied was urea (46-0-0). This equaled 29, 30, 54, and 67% of total N inputs to gardens L1, L2, H1, and H2, respectively. Sediment deposits of the River Nile floods contributed on average 67, 94, 6 and 42% to the total N, P, K and C inputs in lowland gardens and 33, 86, 4 and 37% of total N, P, K and C inputs in highland gardens. Irrigation water and rainfall contributed substantially to K inputs representing 96, 92, 94 and 96% of total K influxes in garden L1, L2, H1 and H2, respectively. Following the same order, total annual DM yields in the gardens were 26, 18, 16 and 1.8 t ha-1. Annual leaching losses were estimated to be 0.02 kg NH4+-N ha-1 (SE = 0.004), 0.03 kg NO3--N ha-1 (SE = 0.002) and 0.005 kg PO4-3-P ha-1 (SE = 0.0007). Differences between nutrient inputs and outputs indicated negative nutrient balances for P and K and positive balances of N and C for all gardens. The negative balances in P and K call for adoptions of new agricultural techniques such as regular manure additions or mulching which may enhance the soil organic matter status. A quantification of fluxes not measured in our study such as N2-fixation, dry deposition and gaseous emissions of C and N would be necessary to comprehensively assess the sustainability of these intensive gardening systems. The second part of the survey dealt with the brick making kilns. A total of 50 brick kiln owners/or agents were interviewed from July to August 2009, using a semi-structured questionnaire. The data collected included general information such as age, family size, education, land ownership, number of kilns managed and/or owned, number of months that kilns were in operation, quantity of inputs (cow dung and fuel wood) used, prices of inputs and products across the production season. Information related to the share value of the land on which the kilns were built and annual income for urban farmers and annual returns from dung for the animal raisers was also collected. Using descriptive statistics, budget calculation and Gini coefficient, the results indicated that renting the land to brick making kilns yields a 5-fold higher return than the rent for agriculture. Gini coefficient showed that the kiln owners had a more equal income distribution compared to farmers. To estimate emission of greenhouse gases (GHGs) and losses of N, P, K, Corg and DM from cow dung when used in brick making, samples of cow dung (loose and compacted) were collected from different kilns and analyzed for their N, P, K and Corg content. The procedure modified by the Intergovernmental Panel on Climate Change (IPCC, 1994) was used to estimate the gaseous emissions of cow dung and fuel wood. The amount of deforested wood was estimated according to the default values for wood density given by Dixon et al. (1991) and the expansion ratio for branches and small trees given by Brown et al. (1989). The data showed the monetary value of added N and P from cow dung was lower than for mineral fertilizers. Annual consumption of compacted dung (381 t DM) as biomass fuel by far exceeded the consumption of fuel wood (36 t DM). Gaseous emissions from cow dung and fuel wood were dominated by CO2, CO and CH4. Considering that Gerif land in urban Khartoum supports a multifunctional land use system, efficient use of natural resources (forest, dung, land and water) will enhance the sustainability of the UA and brick making activities. Adoption of new kilns with higher energy efficiency will reduce the amount of biomass fuels (cow dung and wood) used the amount of GHGs emitted and the threat to the few remaining forests.