| 1. |
- Andersson, Eva Ingeborg Elisabeth, 1956, et al.
(författare)
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Pulp-mill integrated biorefineries: a framework for assessing net CO2 emission consequences
- 2004
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Ingår i: Proceedings, AIChE 2004 Fall Annual Meeting. Nov 7-12, 2004, Austin, Texas, USA. ; , s. p 203-208, s. 203-208
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- There is currently much interest in producing biofuel-based transportation fuels. However, since biofuel is a limited renewable resource, it is important to assess whether such fuels are both produced and used as efficiently as possible. Efficient production can be achieved in the future by integrated biorefinery operations at pulp mill sites, co-producing pulp and biofuel-based energy products. This paper compares production of transportation fuel with other biorefinery options for future pulp mills. The comparison is based on net CO2 emissions, i.e. accounting for off-site consequences associated with changes in the net flows of electricity, biofuel and biofuel-based transportation fuel entering or leaving the mill. The most important conclusion is that system variables (e.g. assumptions regarding the reference fuel and engine efficiency for future transportation systems) are of decisive importance for the net CO2 emissions associated with pulp mill biorefinery operations. This paper illustrates such aspects and underlines the importance of a system perspective in process engineering research.
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| 2. |
- Bylund, Jonas
(författare)
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What's The Problem With Non-conventional Technology? : The Stockholm Local Investment Programme and the Eco-cycling Districts
- 2003
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Ingår i: Time to turn down energy demand. - Stockholm : European Council for an Energy-Efficient Economy - ECEEE. - 9163140012 ; , s. 853-861
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Bokkapitel (refereegranskat)abstract
- This paper analyses barriers towards implementation of non-conventional energy and resource efficient technology in the context of urban development. It gives tentative conclusions based on an ongoing Ph.D. dissertation project. The case is the measures the city of Stockholm launched with the help of a Swedish Governmental subsidy program – the Local Investment Program (LIP). The LIP runs from 1998 to 2003 and is intended to help municipalities nationwide adapt to the demands of an ecologically sustainable society. Measures that uses new, or in the terminology of this paper, non-conventional technology are explicitly supported in the program. Stockholm was granted 67 million Euro to subsidize different projects, among them the eco-cycling districts of Hammarby Sjöstad, Östberga and Skärholmen. Experiences reported by the municipal LIP co-ordinators nationwide are that only half of all the programs are realized as intended in the applications. As the project is work in progress this paper will try to answer the following questions: Why are some projects successful and others not? Why are sustainability-measures in these projects not carried out completely? Which agents and mediators do help or hinder the subsidies to become a realized and working technology in the city? What is the problem with non-conventional technology really? What parts does politics, policy and administrative practices as well as ‘rational’ economical behaviours play? Some old obstacles, but are new solutions dependent on unorthodox practice or simply more money? Knowledge on these issues is (still) important for subsequent policies and programs on energy and resource efficiency.
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| 3. |
- Marques, Marcia, et al.
(författare)
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Water environments : Anthropogenic pressures and ecosystem changes in the Atlantic drainage basins of Brazil
- 2004
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Ingår i: Ambio. - : Royal Swedish Academy of Sciences. - 0044-7447 .- 1654-7209. ; 33:1-2, s. 68-77
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Tidskriftsartikel (refereegranskat)abstract
- Densely occupied drainage basins and coastal zones in developing countries that are facing economic growth are likely to suffer from moderate to severe environmental impacts regarding different issues. The catchment basins draining towards the Atlantic coast from northeastern to southern Brazil include a wide range of climatic zones and diverse ecosystems. Within its borders lies the Atlantic rain forest, significant extensions of semiarid thorn forests (caatinga), vast tree and scrub woodlands (cerrado) and most of the 6670 km of the Brazilian coast and its marine ecosystems. In recent decades, human activities have increasingly advanced over these natural resources. Littoralization has imposed a burden on coastal habitats and communities. Most of the native vegetation of the cerrado and caatinga was removed and only 7% of the original Atlantic rainforest still exists. Estuaries, bays and coastal lagoons have been irreversibly damaged. Land uses, damming and water diversion have become the major driving forces for habitat loss and aquatic ecosystem modification. Regardless of the contrast between the drought-affected northeastern Brazil and the much more prosperous and industrialized southeastern/southern Brazil, the impacts on habitat and communities were found equally severe in both cases. Attempts to halt environmental degradation have not been effective. Instead of focusing on natural resources separately, it is suggested that more integrated environmental policies that focus on aquatic ecosystems integrity are introduced.
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| 4. |
- Guieysse, Benoit
(författare)
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Innovative Bioreactors for the Degradation of Polycyclic Aromatic Hydrocarbons
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The development of biological reactors for the treatment of toxic and recalcitrant organic pollutants is a complex task. Firstly, microbial inoculation, acclimation and selection must be optimized to provide the best microflora possible. Secondly, innovative technologies must be developed to overcome the intrinsic low degradation rates of hardly-degradable pollutants in order to allow short treatment times. Finally, since the pollutants involved are often toxic, it is also important to use well-managed treatment system that limit potential process hazards. Efficient inoculum was provided by using a mixture of indigenous soil microflora, most likely containing contaminant-degrading species, and activated sludge sample to provide microbial diversity as a protection against metabolite accumulation and substrate inhibition effects. Both fed-batch and continuous cultivations were suitable for microbial selection. Since the selection of degrading species depends on the origin of the inoculum and the procedure and system used, inoculation, acclimation and selection should be performed each time the treatment of a new effluent or the performance of a new process is studied. Both Suspended-Carrier and Packed-Bed reactors allowed the fast treatment of diluted contaminated effluent. The packed-bed reactor was preferred since it favored the development of very diverse microflora and was based on the use of a cheaper carrier. Special care should be taken in controlling pollutant adsorption to the carriers. Biphasic reactors were found to be suitable for the treatment of concentrated mixtures of contaminants such as soil extracts. Besides reducing the aqueous toxicity of the contaminants, the use of an organic phase in biphasic reactor advantageously permitted to avoid pollutant volatilization and adsorption. However, their large-scale application remains dependent on several improvements. The potential of algae photosynthesis to produce oxygen in-situ in the reactor, which limits the risk for pollutant volatilization, was clearly demonstrated. Emphasis should be given on optimizing photosynthesis efficiency, which depends on the light intensity and the algal population size, rather that the degradation of the pollutants. Since recording pollutant disappearance does not inform about the mechanism of removal and the pollutants involved are toxic, it is very important to monitor microbial activity during the entire process. The rate of disappearance of the electron acceptor used by the microflora could often be well correlated with the microbial activity and the pollutant biodegradation rate. This could lead to the development of biosensors and monitoring strategies suitable for the biological treatment of toxic and recalcitrant pollutants. Finally, although it was often difficult to avoid abiotic removal mechanisms and to monitor microbial degradation, it was still possible to evaluate and control these phenomena in most of the systems described in this thesis work. This clearly demonstrates a very important advantage of ex-situ remediation processes compared to in-situ processes.
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| 5. |
- Öhman, Marcus, et al.
(författare)
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Reasons for slagging during stemwood pellet combustion and some measures for prevention
- 2004
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Ingår i: Biomass and Bioenergy. - Oxford : Pergamon Press. - 0961-9534 .- 1873-2909. ; 27:6, s. 597-605
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Tidskriftsartikel (refereegranskat)abstract
- Ash related problems have more than occasionally been observed in pellet burners during the last years. These problems lead to reduced accessibility of the appliances and also bad publicity for the pellet market. The objectives of the present work were therefore to: (i) determine the critical levels of the problematic ash components in stemwood pellets regarding slagging, (ii) document the variations of these problematic elements in the outgoing pellets from two pellet-mills during one operational season, (iii) determine how frequently these elements exceed the critical levels, (iv) determine how different sub-processes in the pelletising process (especially the dryer) effect the slagging properties of the pellet, and if possible (v) suggest some measures for prevention. A significant number of wood pellets reported to be problematic and problem-free, regarding slagging in ordinary residential pellet burners, were collected from the Swedish market. The ash compositions of these fuels were analysed and the results compiled in a database. Partial Least-Squares Discriminant Analysis (PLS-DA) and F-tests were used to statistically identify both the critical ash components and the critical levels of these components that separated the two reported classes. In addition, chemical equilibrium model calculations were used to interpret the findings. The variations of these elements in the in-going raw material and in the produced pellets were determined during one season in two pellet mills equipped with exhaust gas dryers. The results showed that the problematic wood-pellets had a significantly higher amount of Si, but also Al and Fe, in the fuel ash. The critical level of Si (given as SiO2) was about 20-25 wt% of the fuel ash, i.e. pellets with levels in or over this range resulted in slagging problems in residential burners. This critical Si content was exceeded once and twice for the analysed samples in the two studied pellet mills. In one of the studied mills, this was because of contamination by sand of the raw material during storage and handling, and in the other mill the reason was found to be contamination of the raw material by elutriated particles from the dryer fuel. The major conclusion of the work is that both raw materials and drying fuels/processes should be carefully treated to avoid mineral contamination, and an additional cyclone separator could potentially also be used to improve the pellet quality.
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| 6. |
- Leckner, Bo G, 1936, et al.
(författare)
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Emissions from co-combustion of coal, wood and sludge in CFB
- 2003
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Ingår i: Fluidization 2003, Proceedings of the 8th China-Japan Symposium on Fluidization, Gifu Japan, December 3-5, 2003. ; 8, s. 28-35
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Konferensbidrag (refereegranskat)abstract
- This paper reports on gaseous emission from co-combustion of sewage sludge with coal or wood in circulating fluidised bed (CFB). Dried, or in some cases "wet" (mechanically dewatered), municipal sewage sludge was investigated. The fuels coal and wood were used in contrast to each other. The emissions of CO, NO, N2O, SO2 and HCl were measured from various sludge fractions and air supply methods in two CFB combustion units: the 12 MWth boiler at Chalmers University of Technology and the laboratory scale unit at the Technical University Hamburg-Harburg. The two units were scaled according to approximate scaling rules and give comparable emissions. It was shown that the emissions were moderate despite the considerable quantities of fuel nitrogen and sulphur in the sludge. For commercially interesting sludge fractions (
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| 7. |
- Sandström, K. J. Mattias, et al.
(författare)
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A gas-phase biosensor for environmental monitoring of formic acid: laboratory and field validation
- 2003
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Ingår i: Journal of Environmental Monitoring. - : Royal Society of Chemistry. - 1464-0325 .- 1464-0333. ; 5:3, s. 477-482
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Tidskriftsartikel (refereegranskat)abstract
- In order to encourage more exposure measurements to be performed, a formic acid gas-phase biosensor has been developed for this purpose. In the present paper, an enzyme based biosensor has been validated with respect to analyte selectivity and on-site use. To ensure that the sampler developed measures the compound of interest the biosensor was exposed to three near structural homologues to formic acid, i.e. acetic acid, methanol and formaldehyde. These vapours were generated with and without formic acid and the only compound that was found to have an effect on the performance of the biosensor, albeit a small one, was acetic acid. The field test was performed in a factory using formic acid-containing glue for glulam products. In parallel to the measurements with the biosensor a well defined reference method was used for sampling and analysing formic acid. It was found that the biosensor worked satisfactorily in this environment when used in a stationary position. It was also shown that the biosensor could determine formic acid vapour concentrations down to 0.03 mg m(-3).
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| 8. |
- Sandström, K. J. Mattias, et al.
(författare)
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Amperometric biosensor for formic acid in air
- 2000
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 70:1–3, s. 182-187
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Tidskriftsartikel (refereegranskat)abstract
- The possibility of developing a simple, inexpensive and specific personal passive “real-time” air sampler incorporating a biosensor for formic acid was investigated. The sensor is based on the enzymatic reaction between formic acid and formate dehydrogenase (FDH) with nicotinamide adenine dinucleotide (NAD+) as a co-factor and Meldola's blue as mediator. An effective way to immobilise the enzyme, co-factor and Meldola's blue on screen-printed, disposable, electrodes was found to be in a mixture of glycerol and phosphate buffer covered with a gas-permeable membrane. Steady-state current was reached after 4–15 min and the limit of detection was calculated to be below 1 mg/m3. However, the response decreased by 50% after storage at −15°C for 1 day.
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| 9. |
- Routh, Joyanto, 1968-, et al.
(författare)
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Volatile organic acids and microbial processes in the Yegua formation, east-central Texas
- 2001
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Ingår i: Applied Geochemistry. - : Elsevier. - 0883-2927 .- 1872-9134. ; 16:2, s. 183-195
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Tidskriftsartikel (refereegranskat)abstract
- Geochemical and microbiological evidence indicates that viable microorganisms produce and consume volatile organic acids (VOA) in the Yegua formation. Acetic and propionic acid concentrations in mudstones range from 200 to 1270 and 20 to 38 nmol·gdw−1 respectively, whereas concentrations in sands are 50–200 and less than 20 nmol·gdw−1. VOA concentrations in sediments and in laboratory incubations suggest net production of VOAs by microorganisms in mudstones, and net consumption of VOAs by SO4 reducing bacteria (SRB) in sands. Notably, SRB activity is mostly confined to aquifer sands. Vertical diffusion and advection were modeled to estimate acetic acid transport from aquitard to aquifer. Assuming that SRB completely respire the acetic acid transported into the aquifer (3.2 μmol·l−1·m·a−1), the CO2 production rate in the aquifer sands is 5.3 μmol·l−1·a−1. This slow mineralization rate of in situ organic matter is within the range for deep aquifers, and probably accounts for the long-term survival of microorganisms in oligotrophic environments. Finally, the microbial communities in Yegua sediments appear to exhibit a loose commensalism, with microorganisms in aquitards providing VOAs for respiratory processes (i.e., SO4 reduction) in aquifers.
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| 10. |
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