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- Hagelqvist, Alina
(författare)
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Sludge from pulp and paper mills for biogas production : Strategies to improve energy performance in wastewater treatment and sludge management
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The production of pulp and paper is associated with the generation of large quantities of wastewater that has to be purified to avoid severe pollution of the environment. Wastewater purification in pulp and paper mills combines sedimentation, biological treatment, chemical precipitation, flotation and anaerobic treatment, and the specific combination of techniques is determined by the local conditions. Wastewater treatment generates large volumes of sludge that after dewatering can be incinerated and thus used for bio-energy production. Sludge is currently viewed as biofuel of poor quality due to its high water content, and some mills treat it solely as a disposal problem.Two strategies have been identified as feasible options to improve the energy efficiency of sludge management. One is drying using multi-effect evaporation followed by incineration. The other is anaerobic digestion of the wet sludge to produce methane.This thesis explores the energy balances of sludge management strategies in pulp and paper mills with special focus on anaerobic digestion. The first part consists of a system analysis, used to evaluate some wastewater treatment processes and sludge management, and the second part of empirical studies of anaerobic digestion of pulp and paper mill sludge. It was shown that the use of energy for aeration in aerobic biological treatment should be kept to the minimum required for acceptable quality of the processed water. Additional aeration for reduction of the generated sludge will only result in reduced energy generation in a subsequent methane generation stage. In the second part of the thesis, it is shown that anaerobic digestion is a feasible option for sludge management as it leads to production of high value biogas. Co-digestion with grass silage, cow/pig manure or municipal sewage sludge should then be used to counteract the low nitrogen content of pulp and paper mill sludge.
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| 2. |
- Hedelin, Beatrice, 1974-
(författare)
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Planning for Sustainable Use of Water
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The basic problem that this work wishes to address concerns the unsustainable use of water resources in many places of the world. In some places, the problem leads to human suffering and death while also obstructing social and economic development. In other places, where the consequences are less severe, natural environments are seriously damaged. A significant part of the solution to this problem lies in the planning and decision-making domain. The overall aim of this thesis is therefore to contribute to the available knowledge on planning and management for the sustainable use of water resources. Planning as a process is in focus, both in itself and in the organisational and legal contexts that affect how planning processes are performed. The main methodological approach used, and the theoretical contribution made here, is the deriving and discussion of a set of deductive criteria for the development and assessment of planning processes for the sustainable use of water resources (Papers III and IV). The criteria were derived using a multi-disciplinary approach, where the relevant literature on how to transform the concepts of ‘integration’ and ‘participation’ – both key principles for sustainable development in relation to planning – into an analytical framework of twelve criteria, was reviewed and synthesised. The derived criteria concern issues such as, how to integrate knowledge and values into the planning process and how to generate commitment, legitimacy or acceptance for the resulting plan, by democratic means. The criteria are then used to assess the EU Water Framework Directive (WFD) – an extensive legal framework which will steer water planning in the EU Member States for several decades to come – and to assess the planning processes that follows on from WFD implementation in Sweden. The analysis contained in (Paper V) showed that the WFD erects few formal barriers to good planning practices. The analysis also showed however, that the planning processes that follow on from its implementation will need to be adapted to compensate for the weak legal support in a number of important areas, namely, the use of knowledge from beyond the natural sciences, the use of methodologies for the explicit handling of values and the use of procedures for democratic participation. Several recommendations are also made in respect of how the WFD could be supplemented in order for it to become a stronger support in planning processes for the sustainable use of water. The analysis of the ongoing water planning processes in Sweden (Paper VI) showed that knowledge of how to work with values and how to create forms and methods of participation and collaboration remain clearly underdeveloped. In consequence, the main objectives behind participation – the provision of knowledge and perspectives for the process and the creation of legitimacy, acceptance or engagement – are actually at risk. Recommendations include complementing the existing knowledge base with insights from the social sciences and the humanities, to create well informed learning systems within the new water administration and to make use of alternative methods for the handling of values. In addition to this, two papers from the thesis (Papers I and II) concern the situation pertaining before WFD implementation in Sweden. By comparing the system for municipal land and water planning (the former main system for long-term water planning in Sweden) with WFD prescriptions, and with the organisation of the new water administration bodies, some potential implications of WFD implementation were identified. From here it followed, that the development of forms of co-operation between the concerned administrative organisations, and in respect of the democratic involvement of the public and other concerned actors, were crucial in creating an integrative, effective and democratic system for water planning in Sweden. The thesis also illustrates the use of a tentative model for the operationalisation of ‘sustainable development’. The tentative model is described in the thesis, and it constitutes the methodological baseline for the thesis, since five of the papers contained herein use various approaches related to this model.
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| 3. |
- Ståhl, Magnus, 1973-
(författare)
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Improving Wood Fuel Pellets for Household Use : Perspectives on Quality, Efficiency and Environment
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Bioenergy is one of many contributors to reducing the use of fossil fuels in order to mitigate climate change by decreasing CO2-emissions, and the potential for biofuels are large. The wood fuel pellets are a refined biofuel made of sawdust, which is dried and compressed to achieve improved fuel and transportation properties. In 2007 the amount of wood fuel pellets used for heating purposes in Sweden was 1715000 tons. The aims of this work was: to examine the moisture content and emission of monoterpenes during the drying and pelletising steps of the pellets production (Paper I); to investigate how the recirculation of drying gases affects the energy efficiency of rotary dryers and how the energy efficiency is related to the capacity of the dryer. (Paper II); to analyse the causes of the problems encountered by household end-users of pellets and investigate whether an improved pellet quality standard could reduce these problems (Paper III); to investigate how the energy consumption of the pelletising machine and chosen pellet quality parameters were affected using an increased amount of rapeseed cake in wood fuel pellets (Paper IV); and to identify gaps of knowledge about wood fuel pellet technology and needs for further research on quality, environmental and health aspects throughout the wood fuel pellet chain, from sawdust to heat. (Paper V).
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