| 1. |
- Feiz Aghaei, Roozbeh, et al.
(författare)
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The role of biogas solutions for enhanced nutrient recovery in biobased industries-three case studies from different industrial sectors
- 2021
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Ingår i: Resources, Conservation and Recycling. - : Elsevier. - 0921-3449 .- 1879-0658. ; 175
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Tidskriftsartikel (refereegranskat)abstract
- This study analysed to what extent biogas solutions can improve the nutrient recovery of biobased industrial clusters in different sectors. Three cases representing the agricultural, marine and forest sectors were analysed quantitatively using mass flow analysis. Adding a biogas plant facilitated production expansion and development of collaborative waste management, e.g. a wheat processing biorefinery with a mill and agricultural actors, or a pulp and paper mill with the aquaculture industry. In the marine- and forest-based cases, this decreased the total nitrogen (N) and phosphorous (P) input by 18% while increasing the recovery rate; e.g. for P from 32 to 96% for the marine-based and from 52 to 91%, for the forest-based. The impact in the agro-based case was minor as the actors were already operating with a high nutrient recovery. For the marine-based case, the impact was due to a huge increase in P recovery for the aquaculture actor while for the forest-based case, N from the aquacultural sector could be reused in the wastewater treatment. For the agro- and marine-based cases, adding a biogas plant also resulted in less transports and more local nutrient recycling; the total transport of organic waste, by-products and biofertilizers (in km x tonne) was reduced by 40% and 90%, respectively. The results demonstrate that biogas solutions can stimulate the development of biobased industrial symbiosis with integrated waste management, and contribute to more efficient recycling of key resources, which is essential for the transition to a circular society.
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| 2. |
- Feizaghaii, Roozbeh, 1975-, et al.
(författare)
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The biogas yield, climate impact, energy balance, nutrient recovery, and resource cost of biogas production from household food waste — A comparison of multiple cases from Sweden
- 2022
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Ingår i: Journal of Cleaner Production. - : Elsevier Science Ltd. - 0959-6526 .- 1879-1786. ; 378
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Tidskriftsartikel (refereegranskat)abstract
- The depletion of natural resources, climate change and energy security are some of today's societal challenges. One way to address these is through anaerobic digestion of food waste, which provides multiple benefits such as waste treatment, nutrient recycling and renewable energy, such as biogas. Biogas solutions tend to vary, so to gain a holistic understanding of their pros and cons there is a need to use a common analytical approach and simultaneously consider several issues. This study has analysed the climate impact, primary energy use, nutrient recycling potential, and resource cost of producing biogas from food waste in three Swedish biogas plants with different setups. In addition, several scenarios representing changes in the existing systems were analysed. The study aims to provide insights into factors that affect the performance of biogas production from food waste. The method applied is based on life cycle analysis and key performance indicators (KPIs), which were used to compare and analyse the performance of the biogas systems. The analysis synthesises a large amount of information about the performance of these systems and their sub-systems. Despite significant differences between the studied cases, all led to the production of biomethane with a low climate impact (62–80% less climate impact in grCO2eq/MJ compared with the fossil reference), low non-renewable primary energy use (16–31% MJ per MJ delivered biomethane), and significant nutrient recovery (e.g., 52–86% of phosphorus content of food waste was delivered as biofertilizer). In addition to the collection system, the efficiency of pretreatment, the choice of energy system (e.g., for heating the biogas plant), and a suitable digestate treatment were found to be among the main factors that influence the overall performance of these systems.
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| 3. |
- Graco-Roza, Caio, et al.
(författare)
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Distance decay 2.0 – A global synthesis of taxonomic and functional turnover in ecological communities
- 2022
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Ingår i: Global Ecology and Biogeography. - : Wiley. - 1466-822X .- 1466-8238. ; 31:7, s. 1399-1421
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Tidskriftsartikel (refereegranskat)abstract
- Aim: Understanding the variation in community composition and species abundances (i.e., beta-diversity) is at the heart of community ecology. A common approach to examine beta-diversity is to evaluate directional variation in community composition by measuring the decay in the similarity among pairs of communities along spatial or environmental distance. We provide the first global synthesis of taxonomic and functional distance decay along spatial and environmental distance by analysing 148 datasets comprising different types of organisms and environments.Location: Global.Time period: 1990 to present.Major taxa studied: From diatoms to mammals.Method: We measured the strength of the decay using ranked Mantel tests (Mantel r) and the rate of distance decay as the slope of an exponential fit using generalized linear models. We used null models to test whether functional similarity decays faster or slower than expected given the taxonomic decay along the spatial and environmental distance. We also unveiled the factors driving the rate of decay across the datasets, including latitude, spatial extent, realm and organismal features.Results: Taxonomic distance decay was stronger than functional distance decay along both spatial and environmental distance. Functional distance decay was random given the taxonomic distance decay. The rate of taxonomic and functional spatial distance decay was fastest in the datasets from mid-latitudes. Overall, datasets covering larger spatial extents showed a lower rate of decay along spatial distance but a higher rate of decay along environmental distance. Marine ecosystems had the slowest rate of decay along environmental distances.Main conclusions: In general, taxonomic distance decay is a useful tool for biogeographical research because it reflects dispersal-related factors in addition to species responses to climatic and environmental variables. Moreover, functional distance decay might be a cost-effective option for investigating community changes in heterogeneous environments.
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| 4. |
- Kazadi Mbamba, Christian, et al.
(författare)
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Modelling Industrial Symbiosis of Biogas Production and Industrial Wastewater Treatment Plants – Technical Report
- 2020
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The present-day treatment of pulp and paper mill effluents can be significantly improved by incorporating biogas production in the context of industrial symbiosis. In this work a new industrial symbiosis concept is presented, the focus being on modelling it in view of process optimization, design improvement and adoption by the pulp and paper industry. The concept consists of a first stage in which pulp and paper mill effluents are treated by high-rate anaerobic digestion in external circulation sludge bed (ECSB) reactors to produce biogas. In the second stage the removal of organic matter contained in the anaerobic effluent stream occurs through aerobic activated sludge treatment, aiming to achieve maximum sludge production with minimum aeration requirements. This sludge should in the case study then be co-digested with residues from fish farming industry to yield methane for energy production, nutrient-rich reject water that can be recycled to the activated sludge treatment for optimum microbial activities and production of a nutrient-rich soil amendment. The overall research aim was in this project to develop a mathematical model that describes the relevant process units and the dynamics of the different processes involving organic matter removal, biogas production and nutrient release. The plant-wide model used integrated activated sludge and anaerobic models with a physico-chemical modelling framework. Through systematic calibration good general agreement was obtained between the full-scale experimental and simulated results at steady state. Acceptable differences between measured and modelled biogas production (flow rate and methane concentration), nutrients release (N and P) and effluent quality (N, P and COD) of 2-3.2 %, 5.3-7.4 % and 1.4-1.9 %, respectively, were observed throughout the full-scale system. Model-based analysis shows that the model can predict and give insight on dynamic behaviours resulting from deliberate changes but also on disturbances in one of the systems and their subsequent impacts within the integrated plant. Additionally, the model allowed the prediction of nutrients release in anaerobic digestion and subsequent consumption upstream in the high-rate anaerobic system or activated sludge system. Simulations show that there is a need for imposing a basic control and operational strategy for efficient reject water recirculation to optimize the concentrations of N and P in the activated sludge system while also achieving nutrient levels required to meet the effluent discharge permits. Overall, the evaluated plant-wide model can jointly describe the relevant physico-chemical and biological processes and is therefore advocated as a tool for future extension of this type of industrial symbiosis concepts between biogas producers and industries producing large amounts of wastewater rich in organic material. The model can be used for design, multi-criteria performance assessment and optimization of different treatment plants.
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| 5. |
- Ometto, Francesco, 1985-, et al.
(författare)
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Anaerobic digestion: an engineered biological process
- 2019
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Ingår i: Substitute natural gas from waste: technical assessment and industrial applications of biochemical and thermochemical processes. - London : Elsevier. - 012815554X - 9780128155547 - 9780128156445 ; , s. 63-74
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Bokkapitel (refereegranskat)abstract
- Anaerobic digestion (AD) is a biological process where a variety of microorganisms are the key factors for transforming complex organic structure into biogas, a mixture of methane, carbon dioxide, and other trace gases. Linked to the production of biogas is also the unique possibility to utilize and recycle nutrients released during the digestion. This gives the AD-process a key role in the development of many biorefinery concepts supporting industrial symbiosis and circular economy. The overall process efficiency is linked to the microbial steps which are affected by regulating factors including the characteristic of the substrate and the engineered process layout, together with the targeted outputs (raw biogas, compressed/liquid biogas, fertilizer, and/or other refined products). Between the digestion steps, the hydrolysis, the first microbial step, is often the rate-limiting step in degradation of polymeric substrates. As such, securing efficient and cost-effective hydrolysis represents today the key to process complex biomasses not yet fully utilized within the AD despite its high methane potential.
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| 6. |
- Ometto, Francesco, et al.
(författare)
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Seasonal variation of elements composition and biomethane in brown macroalgae
- 2018
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Ingår i: Biomass and Bioenergy. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0961-9534 .- 1873-2909. ; 109, s. 31-38
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Tidskriftsartikel (refereegranskat)abstract
- To investigate the effect of seasonal variation on macroalgae biomass characteristics and its related energy content, four different algae species, two from the Fucales order (Fucus vesiculosus and Ascophyllum nodosum), and two from the Laminariales order (Saccharina latissima and Alaria esculenta), were harvested during spring, summer, autumn and winter over one year. The biomethane potential and the elemental composition were determined for all samples. Both Fucales species showed low biodegradability (< 30%) with methane yields consistently below 20 Nm(3) per wet tonne. Laminariales species, however, allowed up to 80% biodegradation efficiency, with methane yields varying between 20 and 70 Nm(3) per wet tonne depending on the harvesting season. For each of the four algae the biomass concentrations of potassium, phosphorus, calcium, magnesium, sodium, sulphur, aluminium and iron was higher during spring/summer compared to autumn/winter. For heavy metals, variation was seen mainly for arsenic with higher values during autumn/winter. The highest values were observed for Laminariales (30-120 mg/kg total solids). Modelling the co-digestion of each algae with municipal wastewater sludge showed Laminariales species having the greatest potential as a profitable substrate for additional biomethane production generating up to 0.38 million Euro. However, seasonal variation could affect this expected income over 60% due to fluctuation in biomethane yields and biodegradability efficiency. Furthermore, the additional loading of cadmium and arsenic into the AD process suggested possible limitation for digestate utilisation in arable lands.
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| 7. |
- Safaric, Luka, 1988-, et al.
(författare)
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A Comparative Study of Biogas Reactor Fluid Rheology : Implications for Mixing Profile and Power Demand
- 2019
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Ingår i: Processes. - Basel, Switzerland : MDPI. - 2227-9717. ; 7:10
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Tidskriftsartikel (refereegranskat)abstract
- Anaerobic digestion (AD) is an established process for integrating waste management with renewable energy and nutrient recovery. Much of the research in this field focuses on the utilisation of new substrates, yet their effects on operational aspects such as fluid behaviour and power requirement for mixing are commonly overlooked, despite their importance for process optimisation. This study analysed rheological characteristics of samples from 21 laboratory-scale continuous stirred-tank biogas reactors (CSTBRs) digesting a range of substrates, in order to evaluate substrate effect on mixing efficiency and power demand through computational fluid dynamics (CFD). The results show that substrate and process parameters, such as solids content and organic loading, all have a significant effect on CSTBR fluid rheology. The correlation levels between rheological and process parameters were different across substrates, while no specific fluid behaviour patterns could be associated with substrate choice. Substrate should thus be considered an equally important rheology effector as process parameters. Additional substrate-related parameters should be identified to explain the differences in correlations between rheological and process parameters across substrate groups. The CFD modelling revealed that the rheology differences among the AD processes have significant implications for mixing efficiency and power demand of the CSTBRs, highlighting the importance of considering the substrate-induced effects on CSTBR rheology before including a new substrate.
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| 8. |
- Whitton, Rachel, et al.
(författare)
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Influence of light regime on the performance of an immobilised microalgae reactor for wastewater nutrient removal
- 2019
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Ingår i: Algal Research. - : ELSEVIER. - 2211-9264. ; 44
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Tidskriftsartikel (refereegranskat)abstract
- Microalgae immobilised within a resin shaped into beads have demonstrated the ability to remediate nutrients from wastewater effluents within hydraulic retention times as low as 3 h. Methods to further optimise performance consider parameters relating to the bead with the impact of external conditions seldom investigated. Light is an essential parameter for microalgal growth with its effect on suspended cultures well documented. This work explores the influence of light on nutrient remediation by immobilised microalgae in order to recommend an optimal lighting solution for an immobilised microalgae technology based on Scenedesmus obliquus encapsulated within calcium-alginate beads. White light (400-700 nm) at a photon flux density (PFD) of 200 mu mol.m(-2).s(-1) was determined optimal when illuminating a packed bed configuration. When considering phosphate, these conditions supported a remediation rate of 10.7 ( +/- 0.01) mgP.h (-1).10(6) beads(-1) in comparison to 10.2 ( +/- 0.01) and 10.1 ( +/- 0.01) mgP.h(-1) .10(6) beads(-1) for the blue (465 nm) and red (660 nm) spectra respectively. Although similar performance was demonstrated, light transmission trials determined white light to penetrate to greater bed depths resulting in a larger photoactive zone. A PFD of 200 mu mol.m(-2).s(-1) was regarded as optimal when considering performance, attenuation depth and effective use of total supplied light. In addition, photoperiods trials determined lighting periods amp;lt; 12 h extended the overall treatment time.
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| 9. |
- Whitton, Rachel, et al.
(författare)
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Tertiary nutrient removal from wastewater by immobilised microalgae : impact of wastewater nutrient characteristics and hydraulic retention time (HRT)
- 2018
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Ingår i: H2Open Journal. - : IWA Publishing. - 2616-6518. ; 1:1, s. 12-25
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Tidskriftsartikel (refereegranskat)abstract
- Immobilising microalgal cells has been proposed as a process solution to overcome the barriers associated with the implementation of microalgae for wastewater remediation. This work evaluated the performance and remediation mechanisms of immobilised microalgae for continuous wastewater treatment under varying hydraulic retention times (HRT). Three domestic secondary wastewaters with differing concentrations of orthophosphate (PO4-P), ammonium (NH4-N) and nitrate (NO3-N) were treated by Scenedesmus obliquus immobilised within 2% calcium alginate. Trials were run in continuous operation at HRTs of 3, 6, 12 and 20 h. Removal rates for PO4-P improved with increasing HRT, with minimum residual concentrations of 0.3-3.1 mg center dot L-1 observed at 3 h and 0.01-0.2 mg center dot L-1 at 20 h. Ammonium remediation was not linked to HRT or NH4+ concentration with minimum residual concentrations of <0.001 mg center dot L-1. Reduction in NO3-N improved with increasing HRT, with minimum residual concentrations of <= 19.3 at 3 h and <= 0.4 mg center dot L-1 at 20 h. Remediation was achieved through a combination of mechanisms including biological uptake and precipitation as a by-product of photosynthesis and nutrient metabolism. As such, immobilised microalgae have been proven to be an effective alternative solution for PO43- and NH4+ remediation of wastewater effluents at HRTs of 6-12 h.
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