| 1. |
- Ahmed, Mobyen Uddin, Dr, 1976-, et al.
(författare)
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Dilemmas in designing e-learning experiences for professionals
- 2021
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Ingår i: Proceedings of the European Conference on e-Learning, ECEL. ; , s. 10-17
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Konferensbidrag (refereegranskat)abstract
- The aims of this research are to enhance industry-university collaboration and to design learning experiences connecting the research front to practitioners. We present an empirical study with a qualitative approach involving teachers who gathered data from newly developed advanced level courses in artificial intelligence, energy, environmental, and systems engineering. The study is part of FutureE, an academic development project over 3 years involving 12 courses. The project, as well as this study, is part of a cross-disciplinary collaboration effort. Empirical data comes from course evaluations, course analysis, teacher workshops, and semi-structured interviews with selected students, who are also professionals. This paper will discuss course design and course implementation by presenting dilemmas and paradoxes. Flexibility is key for the completion of studies while working. Academia needs to develop new ways to offer flexible education for students from a professional context, but still fulfil high quality standards and regulations as an academic institution. Student-to-student interactions are often suggested as necessary for qualified learning, and students support this idea but will often not commit to it during courses. Other dilemmas are micro-sized learning versus vast knowledge, flexibility versus deadlines as motivating factors, and feedback hunger versus hesitation to share work. Furthermore, we present the challenges of providing equivalent online experience to practical in-person labs. On a structural level, dilemmas appear in the communication between university management and teachers. These dilemmas are often the result of a culture designed for traditional campus education. We suggest a user-oriented approach to solve these dilemmas, which involves changes in teacher roles, culture, and processes. The findings will be relevant for teachers designing and running courses aiming to attract professionals. They will also be relevant for university management, building a strategy for lifelong e-learning based on co-creation with industry.
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| 2. |
- Anbalagan, Anbarasan, 1988-
(författare)
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A passage to wastewater nutrient recovery units : Microalgal-Bacterial bioreactors
- 2018
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Konstnärligt arbete (övrigt vetenskapligt/konstnärligt)abstract
- In recent years, the microalgal–bacterial process has been considered to be a very attractive engineering solution for wastewater treatment. However, it has not been widely studied in the context of conventional wastewater treatment design under Swedish conditions. The technology holds several advantages: as a CO2 sink, ability to withstand cold conditions, ability to grow under low light, fast settling without chemical precipitation, and reducing the loss of valuable nutrients (CO2, N2, N2O, PO4). The process also provides the option to be operated either as mainstream (treatment of municipal wastewater) or side stream (treatment of centrate from anaerobic digesters) to reduce the nutrient load of the wastewater. Furthermore, the application is not only limited to wastewater treatment; the biomass can be used to synthesise platform chemicals or biofuels and can be followed by recovery of ammonium and phosphate for use in agriculture.In the present study, the feasibility of applying the process in Swedish temperature and light conditions was investigated by implementing microalgae within the activated sludge process. In this context, the supporting operational and performance indicators (hydraulic retention time (HRT), sludge retention time (SRT) and nutrients removal) were evaluated to support naturally occurring consortia in photo-sequencing and continuous bioreactor configuration. Furthermore, CO2 uptake and light spectrum-mediated nutrient removal were investigated to reduce the impact on climate and the technical challenges associated with this type of system.The results identified effective retention times of 6 and 4 days (HRT = SRT) under limited lighting to reduce the electrical consumption. From the perspective of nitrogen removal, the process demands effective CO2 input either in the mainstream or side stream treatment. The incorporation of a vertical absorption column demonstrated effective CO2 mass transfer to support efficient nitrogen and phosphorus removal as a side stream treatment. However, the investigation of a continuous single-stage process as the mainstream showed a requirement for a lower SRT in comparison to semi-continuous operation due to faster settlability, regardless of inorganic carbon. Furthermore, the process showed an effective reduction of influent phosphorus and organic compounds (i.e. COD/TOC) load in the wastewater as a result of photosynthetic aeration. Most importantly, the operation was stable at the temperature equivalent of wastewater (12 and 13 ˚C), under different lighting (white, and red-blue wavelengths) and retention times (6 and 1.5 d HRT) with complete nitrification. Additionally, the biomass production was stable with faster settling properties without any physiochemical separation.The outcomes of this thesis on microalgal–bacterial nutrient removal demonstrates that (1) photosynthesis-based aeration at existing wastewater conditions under photo-sequential and continuous photobioreactor setup, (2) flocs with rapid settling characteristics at all studied retention times, (3) the possibility of increasing carbon supplementation to achieve higher carbon to nitrogen balance in the photobioreactor, and (4) most importantly, nitrification-based microalgal biomass uptake occurred at all spectral distributions, lower photosynthetic active radiation and existing wastewater conditions.
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| 3. |
- Anbalagan, Anbarasan, et al.
(författare)
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Continuous microalgae-activated sludge flocs for remediation of municipal wastewater under low temperature
- 2017
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Konferensbidrag (refereegranskat)abstract
- The operational performance of indigenous microalgae-activated sludge was evaluated regarding the nutrient removal efficiency using raw wastewater collected from Västerås wastewater treatment plant, Sweden at limited artificial surface lighting (290 μmol m-1 sec-1) and Nordic wastewater conditions (13°C). Additionally, the oxygen production and consumption, biomass concentration and its settling was evaluated during the symbiotic algal-bacterial interaction. The results confirmed oxygenic organic compound removal (COD removal of 65-94%) at higher (31-45 d) and lower (13-18 d) sludge retention time (SRT). Also, a complete removal of ammonium throughout the process and partial nitrite-nitrate removal at all SRTs (total nitrogen removal of 41- 62%) were observed. Likewise, a partial phosphorus (P)removal was observed in the effluent which provides an opportunity to capture free P fromthe effluent for recovery as fertiliser. Further, the microalgal growth was slower due to lightor inorganic carbon limitation or ammonium repression caused by higher internal recirculationas observed from ammonium and nitrite-nitrate levels in the PBR. Most importantly, effectivePBR biomass concentration based nutrient removal and relative sludge recirculation have tobe considered in the PBR design to avoid light limitation and activate symbiosis.
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| 4. |
- Anbalagan, Anbarasan, 1988-
(författare)
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Indigenous microalgae-activated sludge cultivation system for wastewater treatment
- 2016
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The municipal wastewater is mainly composed of water containing anthropogenic wastes that are rich in nutrients such as carbon, nitrogen and phosphorous. The cost for biological treatment of wastewater is increasing globally due to the population growth in urban cities. In general, the activated sludge (AS) process is a biological nutrient removal process used in wastewater treatment plants (WWTPs). The AS is composed of different microorganisms in which bacteria play a crucial role in wastewater treatment (WWT). During the process, air is bubbled to supply oxygen and methanol is added to improve nitrogen removal, which is released as a gas. Phosphorous is removed in the expense of precipitation chemicals. Altogether, the current process requires electrical energy, precipitation chemicals, handling of excess sludge and it emits carbon dioxide (CO2) as a by-product. This process is still in practise in the WWTPs since 1914 although numerous modifications are implemented to meet the stringent regulations in the European Union and globally.Microalgae are microorganisms that perform photosynthesis like plants. They are green and reproduce fast using available nutrients (nitrogen and phosphorous) and CO2 from their environment in the presence of light. As a result of photosynthesis, oxygen is released as waste gas. The synthesised oxygen during this process can be implemented to support the AS bacteria that leads to the microalgae activated sludge (MAAS) process. The main advantage is combined removal of nutrients.The vision of the research is to implement the indigenous microalgae cultivation in activated sludge process to consume CO2 and recover the nutrients from wastewater. This study is performed to improve the understanding of the process such as: light utilisation, nutrient removal and recovery of the biomass from wastewater in closed photo-bioreactors. Photo-bioreactors are vessels where the cultivation is carried out in the presence of light. At first, the influence of the light spectrum on micro-algal cultivation is investigated for photosynthetic growth. This is followed by operational challenges of the microalgae cultivation during the AS process. The process is experimentally performed in the photo-bioreactors with different treatment time of the raw wastewater. The results showed that 2 - 6 days of treatment time can be used for reducing nutrients in wastewater if the process is optimised further. Also, nutrient ratio is analysed for the availability of the micro-algal growth. Furthermore, the biogas potential of MAAS showed a biogas yield of about 60-80% within 5 to 9 days.At last, the experimental verification of chemically precipitated wastewater showed limitation of phosphorous for micro-algal growth. Additionally, the optimal oxygen supply through light response is verified for photo-bioreactors. The outcome of this study shows that knowing the right conditions can lower the treatment time. By doing so, a stable nutrient removal and reduction of precipitation chemicals can be established as well as a better recovery of valuable nutrients as phosphorous and nitrogen.
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| 5. |
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| 6. |
- Anbalagan, Anbarasan, et al.
(författare)
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Influence of hydraulic retention time on indigenous microalgae and activated sludge process
- 2016
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Ingår i: Water Research. - : Elsevier BV. - 0043-1354 .- 1879-2448. ; 91, s. 277-284
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Tidskriftsartikel (refereegranskat)abstract
- Integration of the microalgae and activated sludge (MAAS) process in municipal wastewater treatment and biogas production from recovered MAAS was investigated by studying the hydraulic retention time (HRT) of semi-continuous photo-bioreactors. An average total nitrogen (TN) removal efficiency (RE) of maximum 81.5 ± 5.1 and 64.6 ± 16.2% was achieved at 6 and 4 days HRT. RE of total phosphorous (TP) increased slightly at 6 days (80 ± 12%) HRT and stabilized at 4 days (56 ± 5%) and 2 days (55.5 ± 5.5%) HRT due to the fluctuations in COD and N/P mass ratio of the periodic wastewater. COD and organic carbon were removed efficiently and a rapidly settleable MAAS with a sludge volume index (SVI_10) of less than 117 mL g-1 was observed at all HRTs. The anaerobic digestion of the untreated MAAS showed a higher biogas yield of 349 ± 10 mL g VS-1 with 2 days HRT due to a low solids retention time (SRT). Thermal pretreatment of the MAAS (120 °C, 120 min) did not show any improvement with biogas production at 6 days (269 ± 3 (untreated) and 266 ± 16 (treated) mL gVS-1), 4 days (258 ± 11(untreated) and 263 ± 10 (treated) mL gVS-1) and 2 days (308 ± 19 mL (treated) gVS-1) HRT. Hence, the biogas potential tests showed that the untreated MAAS was a feasible substrate for biogas production. Results from this proof of concept support the application of MAAS in wastewater treatment for Swedish conditions to reduce aeration, precipitation chemicals and CO2 emissions.
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| 7. |
- Anbalagan, Anbarasan, et al.
(författare)
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Influence of iron precipitated condition and light intensity on microalgae activated sludge based wastewater remediation
- 2017
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Ingår i: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; , s. 1523-1530
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Tidskriftsartikel (refereegranskat)abstract
- The indigenous microalgae-activated sludge (MAAS) process during remediation of municipal wastewater was investigated by studying the influence of iron flocculation step and light intensity. In addition, availability of total phosphorous (P) and photosynthetic activity was examined in fed-batch and batch mode under northern climatic conditions and limited lighting. This was followed by a semi-continuous operation with 4 d of hydraulic retention time and mean cell residence time of 6.75 d in a photo-bioreactor (PBR) with varying P availability. The fed-batch condition showed that P concentrations of 3–4 mg L−1 were effective for photosynthetic chl. a development in iron flocculated conditions. In the PBR, the oxygen evolution rate increased with increase in the concentration of MAAS (from 258 to 573 mg TSS L−1) at higher surface photosynthetic active radiation (250 and 500 μmol m−2 s−1). Additionally, the rate approached a saturation phase at low MAAS (110 mg L−1) with higher light intensities. Semi-continuous operation with luxury P uptake and effective P condition showed stable average total nitrogen removal of 88 and 92% respectively, with residual concentrations of 3.77 and 2.21 mg L−1. The corresponding average P removal was 68 and 59% with residual concentrations of 2.32 and 1.75 mg L−1. The semi-continuous operation produced a rapidly settleable MAAS under iron flocculated condition with a settling velocity of 92–106 m h−1 and sludge volume index of 31–43 ml g−1 in the studied cases.
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| 8. |
- Anbalagan, Anbarasan, et al.
(författare)
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Influence of light emitting diodes on indigenous microalgae cultivation in municipal wastewater
- 2015
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Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; 75, s. 786-792
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the effect of light emitting diodes (LEDs) on microalgae cultivation in municipal wastewater was examined in comparison to the fluorescent light. Two kinds of wastewater were evaluated: first one with low concentration of total phosphorous (TP) and second one with high TP concentration. The nutrient removal and biomass production using LEDs is efficient at photo-synthetically active radiation (PAR) intensity of 107-112 mu mol m(-2) s(-1) which is slightly higher than fluorescent light. Furthermore, this study demonstrates the applicability and distribution of light in wastewater where the environment is not defined. More importantly, winter and rainy periods contribute to dark condition and dilution of wastewater, intense LED light offers a feasible option for the functioning of closed micro algae based activated sludge (MAAS) process for recovery and reuse of nutrients.
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| 9. |
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| 10. |
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| 11. |
- Beckinghausen, A., et al.
(författare)
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From removal to recovery : An evaluation of nitrogen recovery techniques from wastewater
- 2020
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Ingår i: Applied Energy. - : Elsevier Ltd. - 0306-2619 .- 1872-9118. ; 263
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Tidskriftsartikel (refereegranskat)abstract
- Nitrogen recovery is the next step in the improvement of the wastewater treatment process, utilizing this important nutrient for fertilizers to decrease use of energy, petrochemicals, and impact on the environment. The majority of wastewater treatment plants currently employ methods to remove nitrogen which are energy intensive and have no additional benefits besides complying with effluent concentration limits. Instead, recovering nitrogen allows simultaneous treatment of wastewater while collecting a concentrated ammonia product, creating a circular economy solution. This review acts to compile current research regarding nitrogen recovery and compare different techniques' recovery efficiencies and energy requirements. One outcome of this review is that more than one third of the techniques reviewed had little comments around the energy question, and thus more research needs to take place as these recovery systems continue to evolve towards full scale implementation. Additionally, a basic economic analysis was completed to demonstrate potential investment opportunities to implement these technologies. From this investigation, gas permeable membrane technology has the potential to recover ammonia from wastewater using little energy and may provide a small income with the sale of the product. Other techniques such as vacuum membrane distillation with acid absorption need further validation to determine the energy costs, as the amount of heat recycling has a great impact on the overall energy and economic balances. Finally, a discussion of the misalignment of products from recovery techniques and fertilizers in use today highlights the lack of communication and information sharing between the research community and the end users.
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| 12. |
- Beckinghausen, Aubrey, 1991-
(författare)
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Investigation of nitrogen recovery from concentrated wastewater
- 2021
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Nitrogen recovery from wastewater treatment for fertilizers is a research topic that exists at the intersection of multiple topics important to the future of sustainable society. First, nitrogen recovery from wastewater implies a departure from the current methods of nitrogen mitigation, which involve nitrogen removal by conversion of various aqueous species to inert nitrogen gas. Secondly, by recovering nitrogen from wastewater specifically, there is the opportunity to begin a circular economy where value added products can be obtained from material that has historically been seen as a “waste”. Current wastewater treatment involves nitrogen removal through the biological transformation of aqueous nitrogen species to inert nitrogen gas. This process is energy intensive and risks the production of air pollutants such as N2O as intermediates in the biological transformation. If this nitrogen can be captured in a form that can be reused, a valuable product can be achieved with the potential reduction of both the energy required at the wastewater treatment plant as well as the carbon footprint. Finally, by recovering nitrogen in a form that can be used in agriculture as a fertilizer, additional environmental benefits can be realized by reducing reliance on Haber-Bosch based ammonia production, which is also energy intensive and contributes harmful emissions to the atmosphere.The work described in the following licentiate aims to consider the current status of nitrogen recovery from wastewater for fertilizers as a research topic. Literature was analytically examined to compare different techniques in terms of energy requirements, cost for fertilizer production, market for final fertilizer product, and technological readiness. The most interesting findings from this review were that there seems to be a disconnect between the fertilizer product produced by nitrogen recovery techniques and the market, which will become a challenge if these techniques are implemented at a large scale. The attitude of the farmers with regards to fertilizers from waste was overall positive, with their concerns mainly focused on the performance ability and cost of the product. Additionally, many techniques such as microbial fuel cells and microbial electrolysis cells have been unable to move past the laboratory phase despite being researched for many years. This indicates there are cost and technological barriers that are preventing the further scale up and implementation of these techniques. Energy and cost analyses will be crucial to motivate investment into these processes, and these are missing for many of the techniques found around this topic.To contribute to this field, experimental work was also included to assess the potential for ammonium adsorption from concentrated wastewater for fertilizer production. The experimental work focused on the utilization of the solid product of pyrolysis of sewage sludge (biochar) for adsorption and explored the potential enhancement of the char with various chemical treatments. The char with the best ammonium adsorption performance was found to be using a treatment of HNO3 followed by and NaOH, with an adsorption capacity of 4 mg NH4/g biochar. This char was compared with commercially activated carbon and clinoptilolite for full scale applications. It was found that even with this increased adsorption capacity, the use of chemically enhanced sewage sludge biochar for full scale applications is not realistic. The amount of raw material required for the complete recovery of ammonium from reject water at the municipal wastewater treatment plants exceeds the total amount of sewage sludge generated. Therefore it is recommended that the goal of incorporating sewage sludge biochar with wastewater treatment is to produce a solid fertilizer product loaded with ammonium (which would provide ammonium-N and phosphorus for plant growth, as well as carbon and other minerals for soil amendment) rather than having the goal be complete ammonium recovery from the wastewater stream.
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| 13. |
- Beckinghausen, Aubrey, et al.
(författare)
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Post-pyrolysis treatments of biochars from sewage sludge and A. mearnsii for ammonia (NH4-n) recovery
- 2020
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Ingår i: Applied Energy. - : ELSEVIER SCI LTD. - 0306-2619 .- 1872-9118. ; 271
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Tidskriftsartikel (refereegranskat)abstract
- NH4-N-loaded biochars are suitable candidates for soil amendment and fertilization. Sewage sludge-based biochar and biochar from the invasive species black wattle were used as sorbents for the adsorption of ammonia from a concentrated solution to mimic the wastewater treatment plant reject water stream. To increase ammonium recovery efficiency, two post-pyrolysis activation techniques were compared: steam activation and hydrogen peroxide treatment. It was found that the success of the treatment options was material dependent; therefore, post-pyrolysis treatments will require optimization for different applications based on feedstock. A simplified version of an adsorption process simulated in Aspen Tech predicts that NH4-N may be recovered at an energy cost lower than that of the Haber-Bosch process for black wattle biochar yields of below 19.5%. The biooil and syngas produced during pyrolysis can be used to lessen the energy requirements of the process, so that the solid portion may be utilized as an adsorbent and soil fertilizer. The energy-based sustainability of this technology warrants a more in-depth investigation for evaluation of the techno-economic feasibility for this class of loaded sorbents, and whether this method of nitrogen capture from wastewater is a suitable replacement of the costly Haber-Bosch process.
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| 14. |
- Hakalehto, E., et al.
(författare)
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Some remarks on processing of slaughterhouse wastes from ecological chicken abattoir and farm
- 2016
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Ingår i: Microbiological Industrial Hygiene. - : Nova Science Publishers, Inc.. - 9781634852937 - 9781634852685 ; , s. 271-293
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- In the meat industries, it is always of high importance to follow up the zoonotic and other hazardous micro-organisms, and to prevent their risky distribution, emission and dissemination. Besides proper hygiene control, as well as organized exploitation of the side streams and slaughterhouse wastes helps in the hygienization of the biomasses, processes, and the entire industry. During this experimentation it turned out that it was possible to produce gases and chemical goods, not only from the carboxylates, but also from the more tedious protein and lipid containing wastes. Moreover, these promising results were obtained from a substrate mix with manure and wood chips. These results implied to the high versatility and flexibility of the bioprocess during Pilot A tests within the European Union Baltic Sea region project ABOWE. In Sweden these tests were carried out using the combined wastes from the ecological chicken farm and abattoir as the raw materials. This is a report of the practical set up during intensive experimentation conducted jointly by the Swedish and Finnish personnel. The report of the runs in Sweden is presented also in the public report of the European Union funded project (www.abowe.eu).
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| 15. |
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| 16. |
- Klintenberg, Patrik, et al.
(författare)
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Is small-scale biogas production a viable source of electricity in rural Sub-Saharan Africa?
- 2024
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Ingår i: Energy Proceedings. - : Scanditale AB.
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Konferensbidrag (refereegranskat)abstract
- This study investigates the benefits and limitations of small-scale biogas technology at the household level in rural Sub-Saharan Africa. A literature study and a case study were done to explore if small-scale biogas production is a viable source of electricity in rural Sub-Saharan Africa. The results show that using cattle manure as feedstock requires a daily substrate flow of 750 L of the diluted substrate, i.e. 250 kg of manure and 500 L of water for a 24-hour electricity supply, using a 2-kW generator. This requires a minimum herd size of 25 cattle. Most households don’t have so many cattle. However, a herd of 10 cattle provides enough biogas to power several electrical appliances, significantly improving the household's energy situation. The study concludes that the uptake of biogas technology in Sub-Saharan Africa is slow. Common barriers include inadequate substrate supply, lack of water and variable temperatures, high initial costs, poor technical quality, intense labour operations and maintenance, and insufficient policy support. Improved uptake of biogas technology in Sub-Saharan Africa requires establishing national institutional frameworks and supporting policies, collaboration with the intended users of the technology and local support organisations, ensuring long-term local availability of spare parts and supplies, and, when household-level access to feedstock is limited, centralise biogas systems on the village level to combine feedstock into one production system. © 2024, Scanditale AB. All rights reserved.
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| 17. |
- Leithaeuser, Anna, et al.
(författare)
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Comparison of pyrochar, hydrochar and lignite as additive in anaerobic digestion and NH4+ adsorbent
- 2022
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Ingår i: Bioresource Technology. - : Elsevier. - 0960-8524 .- 1873-2976. ; 361
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Tidskriftsartikel (refereegranskat)abstract
- The impact of pyrochar, hydrochar and lignite addition on anaerobic digestion of food waste was investigated with and without ammonia inhibition under batch conditions. Furthermore, ammonium adsorption capacities of the chars were investigated. To determine anaerobic degradation of char, reference samples containing inoculum and char were analyzed, indicating a significant degradation of hydrochar. Depending on the evaluation method, the increase in methane yield due to hydrochar addition varied between no statistically significant difference and +14 %. No significant impact due to the addition of 5 g/l pyrochar and lignite on AD was found. NH4+ adsorption capacities showed a significantly higher net adsorption capacity of lignite (1.58 mgNH4+/gL), compared to pyrochar (0.63 mgNH4+/gPC). A negative NH4+ adsorption capacity (−0.51 mgNH4+/gHC) was found for hydrochar. A high H/C-ratio, O/C-ratio and cation exchange capacity of hydrochar and lignite indicate many functional groups and low chemical stability, enabling an increased interaction between NH4+ and char.
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| 18. |
- Li, Hailong, 1976-, et al.
(författare)
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Performance of flue gas quench and its influence on biomass fueled CHP
- 2019
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Ingår i: Energy. - : Elsevier. - 0360-5442 .- 1873-6785. ; 180, s. 934-945
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Tidskriftsartikel (refereegranskat)abstract
- For biomass/waste fueled power plants, stricter regulations require a further reduction of the negative impacts on the environment caused by the release of pollutants and withdrawal of fresh water externally. Flue gas quench (FGQ) is playing an important role in biomass or waste fueled combined heat and power (CHP) plants, as it can link the flue gas (FG) cleaning, energy recovery and wastewater treatment. Enhancing water evaporation can benefit the concentrating of pollutant in the quench water; however, when FG condenser (FGC) is not in use, it results in a large consumption of fresh water. In order to deeply understand the operation of FGQ a mathematic model was developed and validated against the measurements. Based on simulation results key parameters affecting FGQ have been identified, such as the flow rate and temperature of recycling water and the moisture content of FG. A guideline about how to reduce the discharge of wastewater to the external and the withdrawal of external water can be proposed. The mathematic model was also implemented into an ASPEN Plus model about a CHP plant to assess the impacts of FGQ on CHP. Results show that when the FGC was running, increasing the flow rate and decreasing the temperature of recycling water can result in a lower total energy efficiency.
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| 19. |
- Li, Xueqiang, et al.
(författare)
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Toxicity of ionic liquid on anaerobic digestion
- 2017
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Ingår i: Energy Procedia. - : Elsevier Ltd. - 1876-6102. ; 142, s. 938-942
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Tidskriftsartikel (refereegranskat)abstract
- Anaerobic digestion is a straightforward process to produce energy from biomass. However, the lignin composed of phenylpropanoid units induces a strong resistance for the hydrolysis step. Ionic liquids (ILs) have been applied in biomass pretreatment to dissolve the biomass components and enhance the anaerobic digestion. However, there are still some challenges such as the toxicity. ILs could inhibit the digestion process and reduce the CH4 production. In this work, a toxicity test for [BMIM]Cl (1-chlorobutane and N-methylimidazole) was conducted. Results show that IL has a strong inhibition and lowered CH4 production when its concentration was higher. At 0.2305±0.0116 g L-1 and 0.4367±0.0219 g L-1, the anaerobic digestion process was inhibited by 10 and 50%, respectively. Accordingly, a higher recovery ratio or a lower pretreatment ratio are necessary to avoid the negative impact of inhibition on BMP.
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| 20. |
- Lu, H., et al.
(författare)
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Accurately measurement and efficiently recovery of ionic liquid in energy utilization of microalgae
- 2019
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Ingår i: Energy Procedia. - : Elsevier Ltd. - 1876-6102. ; , s. 1337-1341
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Konferensbidrag (refereegranskat)abstract
- Chlorella vulgais, a kind of micro-alagae, is an attracting feedstock for bioenergy production, such as biodiesel and biogas. But its tough cell wall structure is the main obstacle to efficiently extracting lipids and other biomass. Ionic liquid (IL) can be used to hydrolyze its cell-wall. However, due to its high cost and toxicity, it is important to recover IL as much as possible. Therefore, a method that can accurately measure the content of ILs, is urgently needed. In this work, two common methods that are used to measure the content of ILs: equimolar titration method and ultraviolet absorbance spectra were compared. The results show that equimolar titration method is not available for trace quantity analysis of ionic liquids as the endpoint of titration is hard to be identified at low IL content (<10 mg/L); while UV absorbance spectra method can be used at low IL contents, whereas, it may result in big deviations. To further improve the accuracy of UV absorbance spectra method, concentrating the sample could be a potential solution.
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| 21. |
- Lu, H., et al.
(författare)
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Lipids extraction from wet Chlorella pyrenoidosa sludge using recycled [BMIM]Cl
- 2019
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Ingår i: Bioresource Technology. - : Elsevier Ltd. - 0960-8524 .- 1873-2976. ; 291
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Tidskriftsartikel (refereegranskat)abstract
- In this study, experiments on pretreating one species of microalgae (Chlorella pyrenoidosa) using one kind of ionic liquid (IL) of [BMIM]Cl were conducted. The aim of this work is to evaluate the recycling efficacy of expensive IL solvent for effective cell disruption. It was indicated that the molecular structure of IL was stable during the recycling test. Five times antisolvent precipitation of microalgae debris after lipid extraction using methanol recovered 99.8% IL with the energy consumption of 4.46 MJ per kg dry Chlorella pyrenoidosa. The chromatography was used to separate IL and hydrolysates, resulting in the IL loss below 1.97 g per kg dry Chlorella pyrenoidosa. © 2019 Elsevier Ltd
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| 22. |
- Mabecua, Fastudo Jorge, et al.
(författare)
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Agro-waste, a solution for rural electrification? : Assessing biomethane potential of agro-waste in inhambane province, southern mozambique
- 2021
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Ingår i: Water. - : MDPI AG. - 2073-4441. ; 13:7
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we investigated the biomethane potential of cassava peels from the four most common varieties of cassava grown in Inhambane Province in Mozambique, Chinhembue, Cussi, Cizangara and Nhassumbi. Agro-wastes from coconut wood and jambolan wood processing were also analyzed to give a complete analysis of the most significant sources of agro-waste in the province. The macromolecular composition (carbohydrates, lipids and proteins) was determined and used to calculate the theoretical maximum biochemical methane potential (BMP). The results show that cassava fiber and cassava peel, which are considered to be waste, are viable resources for biomethane production. Further, the results show that cassava fiber and cassava peel have a higher biomethane potential compared with sawdust, and are therefore more suitable for biomethane production. A study to investigate the effect of toxic cyanogenic glycosides and lignin on cassava peels, using pre-treatment techniques to enhance biogas yield, should be carried out. An estimate of how much electricity can be generated based on the availability of agro-waste (cassava residues) and the amount of biomethane produced in our laboratory experiment was carried out. The amount of electricity that can be produced is enough to provide a valuable contribution to the production process in small and medium sized enterprises (SMEs) and in the cassava industry, or some other use in the rural setting.
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| 23. |
- Malovanyy, Andriy, et al.
(författare)
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Återvinning av näringsämnen från avlopp : En litteraturstudie
- 2022
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Rapporten beskriver etablerade och nya tekniker för kväveåtervinning ur avloppsvatten, och jämföråtervinningsmetoderna med andra sätt att tillverka kvävegödsel när det gäller klimatpåverkan ochkostnader. Rapporten innehåller också en kort genomgång av möjligheter för återvinning av kalium ochsvavel och en statusuppdatering av metoder för återvinning av fosfor.
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| 24. |
- Malovanyy, Andriy, et al.
(författare)
-
Återvinning av näringsämnen från avlopp : En litteraturstudie
- 2022
-
Rapport (refereegranskat)abstract
- Rapporten beskriver etablerade och nya tekniker för kväveåtervinning ur avloppsvatten, och jämför återvinningsmetoderna med andra sätt att tillverka kvävegödsel när det gäller klimatpåverkan och kostnader. Rapporten innehåller också en kort genomgång av möjligheter för återvinning av kalium och svavel och en statusuppdatering av metoder för återvinning av fosfor.Återvinning av näringsämnen från avlopp i Sverige sker i dag nästan uteslutande genom spridning av avloppsslam på åkermark, men bara cirka en tredjedel av allt slam används på det viset. Avvattnat rötslam innehåller bara cirka 15 procent av det kväve som finns i inkommande avloppsvatten. Det gör att endast några få procent av kvävet återvinns i dag. Ökad återvinning av kväve har därför stor potential. Det finns risk att även den lilla mängden kväve som återförs med slam idag uteblir ifall slamanvändning på åkermark ska förbjudas samtidigt som det blir krav på återvinning av fosfor. De mest intressanta metoderna återvinner fosfor från aska efter slamförbränning, och det innebär att kväveinnehållet går förlorat.Dagens kväverening sker i huvudsak med biologiska metoder i reningsverkets huvudström. Ett alternativ är att avskilja det kväve som finns i rejektvatten, det vill säga det högkoncentrerade vatten som blir över vid avvattning av rötat slam. Kvävemängden i rejektvattnet är ungefär lika stor som kvävemängden i själva slammet. Kvävet i rejektvatten kan återvinnas till gödselprodukter med olika kemisk-fysikaliska metoder. Om kväve återvinns behöver mindre kväve renas biologiskt. Det sparar energi och minskar utsläppen av växthusgaser, framför allt lustgas. Men kväveåtervinningsprocesser är energi- och kemikalieintensiva, vilket ger indirekta utsläpp av växthusgaser och relativt hög kostnad.En litteraturstudie visade att ammoniakstrippning (avdrivning av ammoniak i gasfas) och kontaktmembran är de tekniker för kväveåtervinning från rejektvatten som finns i fullskala och som har liknande och relativt hög förbrukning av kemikalier och energi. För spillvattenströmmar som liknar rejektvatten har det testats andra metoder, bland annat termisk strippning av ammoniak med vidare kemisk reaktion med gips eller destillering till ammoniakvatten. Även indunstning och destillation är utvecklade tekniker som har potential för kväveåtervinning.Konventionell produktion av kvävegödsel är beroende av naturgas för att få energi. Flera tekniker utvecklas nu där förnybar energi kan användas för produktion av ammoniak. Projektet utvärderade klimatpåverkan och kostnader för olika kväveåtervinningsmetoder jämfört med produktion av kvävegödsel från fossila och förnybara energikällor. Återvinningsmetoderna visade stor variation, men några slutsatser kan dras. Driftkostnaden för kväveåtervinning med de etablerade teknikerna (ammoniakstrippning och kontaktmembran) är lite högre än kostnaden för produktion av kvävegödsel från fossila och förnybara energikällor, även när kostnaden för utebliven rening av rejektvatten med de mest kostnadseffektiva biologiska metoder dras av. Däremot är klimatpåverkan från kväveåtervinning lägre än klimatpåverkan från kvävegödselproduktion och biologisk kväverening. Flera nya återvinningstekniker, som till exempel termisk strippning av ammoniak och struvitfällning kombinerad med syrabehandlinging, har potential att ge både lägre kostnad och lägre klimatpåverkan.Ett alternativ för att återvinna så mycket kväve som möjligt är att införa källsorterande system och separat behandling av klosettvatten eller urin. Även återvinning från den lågkoncentrerade huvudströmmen av avloppsvatten med en jonbytesprocess följt av återvinning med strippning eller kontaktmembran har potential.
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| 25. |
- Olsson, Jesper, 1975-, et al.
(författare)
-
Anaerobic co-digestion of sludge and microalgae grown inmunicipal wastewater : A feasibility study
- 2018
-
Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 77:3, s. 682-694
-
Tidskriftsartikel (refereegranskat)abstract
- In this study a natural mix of microalgae grown in wastewater of municipal character was co-digested with sewage sludge in mesophilic conditions, in both batch and semi-continuous modes. The semicontinuous experiment was divided into two periods with OLR 1 (Organic Loading Rate) of 2.4 kg VS m3 d-1 and HRT1 (Hydraulic Retention Time) of 15 days, and OLR2 of 3.5 kg VS m3 d-1 and HRT2 of 10 days respectively. Results showed stable conditions during both periods. The methane yield was reduced when adding microalgae (from 200 ± 25 NmL CH4 g VSin-1 , to 168±22 NmL CH4 g VSin-1). VS reduction was also decreased by 51%. This low digestability was confirmed in the anaerobic batch test. However, adding microalgae improved the dewaterability of the digested sludge. The high heavy metals content in the microalgae resulted in a high heavy metals content in the digestate, making it more difficult to reuse the digestate as fertilizer on arable land. The heavy metals are thought to originate from the flue gas used as a CO2 source during the microalgae cultivation. Therefore the implementation of CO2 mitigation via algal cultivation requires careful consideration regarding thesource of the CO2-rich gas.
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| 26. |
- Olsson, Jesper, 1975-
(författare)
-
Co-digestion of microalgae and sewage sludge - A feasibility study for municipal wastewater treatment plants
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The increased emissions of anthropogenic greenhouse gases over the last 100 years is the reason for the acceleration in the greenhouse effect, which has led to an increase of the globally averaged combined land and ocean surface temperature of 0.85 °C between 1880 and 2012. A small fraction of the increased anthropogenic greenhouse gases originates from municipal wastewater treatment plants (WWTPs).This doctoral thesis was part of a larger investigation of using an alternative biological treatment based on the symbiosis of microalgae and bacteria (MAAS-process (microalgae and activated sludge)). This solution could be more energy efficient and potentially consume carbon dioxide from fossil combustion processes and also directly capture carbon dioxide from the atmosphere and thereby reduce the addition of anthropogenic greenhouse gases to the air. The objective of the thesis was to explore the effects when the microalgae-derived biomass from the biological treatment were co-digested with sewage sludge. The results from these experimental studies were then used to evaluate the effects on a system level when implementing microalgae in municipal WWTP. Microalgae grown from a synthetic medium improved the methane yield with up to 23% in mesophilic conditions when part of the sewage sludge was replaced by the microalgae. The microalgae grown from municipal wastewater showed no synergetic effect. In the semi-continuous experiments the methane yield was slightly reduced when implementing the microalgae. Furthermore the digestibility of the co-digestion between sewage sludge and microalgae were lower compared to the digestion of sewage sludge. The digestates containing microalgal substrate had higher heavy metals content than digestates containing only sewage sludge. This could have a negative effect on the potential to use this digestate on arable land in future, due to strict limits from the authorities. Filterability measurements indicated that the addition of microalgae enhanced the dewaterability of the digested sludge and lowered the demand for polyelectrolyte significantly. When a hypothetical MAAS-process replaced a conventional ASP-process the amount of feedstock of biomass increased significantly due to the increased production from the autotrophic microalgae. This increased the biogas production by 66-210% and reduced the heavy metal concentration in the digestate due to a dilution effect from the increased biomass production. The thesis demonstrates that microalgae in combination with bacteria from a MAAS-process can be a realistic alternative feedstock to WAS in the anaerobic digestion at a municipal WWTP. A few drawbacks need to be considered when choosing a MAAS-process as biological treatment.
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| 27. |
- Olsson, Jesper, 1975-, et al.
(författare)
-
Co-digestion of microalgae, grown on municipal wastewater, and primary sewage sludge– : Pilot study in thermophilic and mesophilic conditions
- 2017
-
Konferensbidrag (refereegranskat)abstract
- The most common biological treatment in a municipal waste water today is the activated sludge process (ASP). A possible substitution of the ASP could be the utilization of microalgae for the reduction and/or transformation of nutrients. The produced algal biomass can be converted to biofuel by anaerobic digestion. In the present study, co-digestion of primary sludge and microalgae are studied in semi-continuous tests at mesophilic and thermophilic conditions. Two reactors fed by waste activated sludge and primary sludge are used as reference. The results show that thermophilic digestion of microalgae and primary sludge is less attractive since the methane yield is approximately the same as the mesophilic digestion. In mesophilic conditions the results are approximately the same in the two pilot reactors and also comparable with the mesophilic full-scale digesters in Västerås, Sweden.
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| 28. |
- Olsson, Jesper, 1975-, et al.
(författare)
-
COMPARATIVE STUDY – PHARMACEUTICAL RESIDUES IN WASTEWATER AND SLUDGE FROM A MICORALGAE PLANT AND AN ACTIVATED SLUDGE PROCESS
- 2016
-
Konferensbidrag (refereegranskat)abstract
- This study explores the possibility of using a microalgae based activated sludge – process (MAAS-process) to increase the reduction of pharmaceutical residues in outgoing wastewater, compared to a conventional wastewater treatment plant with activated sludge process. In an on-site study, residual sludge from four pilot scale digesters fed with primary sludge and waste activated sludge or microalgae were sampled and analysed for pharmaceutical residues. The aim of the study was to compare the reduction efficiencies of a microalgae based process with a conventional biological treatment and also to explore the reduction of the residues in the different process steps including the sewage sludge thickening before the anaerobic digestion, the digestion and the secondary treatment with the sludge dewatering process. The results show that the total reduction of pharmaceutical residues in the water phase appears to be significantly higher in the MAAS-process. The substance diclofenac was not degraded in any of the biological processes in the study. The reduction of pharmaceutical residues in digested sludge seems to be higher in mesophilic conditions compared with thermophilic conditions.
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| 29. |
- Olsson, Jesper, et al.
(författare)
-
CONTINUOUS CO-DIGESTION OF MICROALGAE AND REPRESENTATIVE MIX OF SEWAGE SLUDGE : -
- 2014
-
Konferensbidrag (refereegranskat)abstract
- A natural mix of microalgae grown on wastewater was co-digested with a representative mix of sewage sludge in a semicontinuous pilot digester system. The share of microalgae in the mix were 37 % calculated as VS-content. The organic loading rate was 2.4 kg VS (volatile solids) m-3d-1 and the hydraulic retention time was 15 d in a reference reactor, with just a representative mix of sewage sludge, and a digester where microalgae were added. The results from the three retention times showed that the addition of the microalgae enhanced the methane yield with 39 % for every gram reduced VS in the reactors. The specific methane yield for every gram added VS to the reactors were 9 % lower in the digester where microalgae had been added. Less sludge was degraded when microalgae were added, but more methane was produced for every gram VS reduced. CST-measurements indicated that the addition of microalgae enhance the dewaterability of the digested sludge.
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| 30. |
|
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| 31. |
- Olsson, Jesper, 1975-, et al.
(författare)
-
Microalgae as biological treatment for municipal wastewater - Effects on the sludge handling in a treatment plant
- 2018
-
Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 78:3, s. 644-654
-
Tidskriftsartikel (refereegranskat)abstract
- A mix of microalgae and bacteria was cultivated on pre-sedimented municipal wastewater in a continuous operated microalgae-activated sludge process. The excess material from the process was co-digested with primary sludge in mesophilic and thermophilic conditions in semi-continuous mode (5 L digesters). Two reference digesters (5 L digesters) fed with waste-activated sludge (WAS) and primary sludge were operated in parallel. The methane yield was slightly reduced (≈10%) when the microalgal-bacterial substrate was used in place of the WAS in thermophilic conditions, but remained approximately similar in mesophilic conditions. The uptake of heavy metals was higher with the microalgal-bacterial substrate in comparison to the WAS, which resulted in higher levels of heavy metals in the digestates. The addition of microalgal-bacterial substrate enhanced the dewaterability in thermophilic conditions. Finally, excess heat can be recovered in both mesophilic and thermophilic conditions.
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| 32. |
- Salman, Chaudhary Awais, et al.
(författare)
-
Enhancing biomethane production by integrating pyrolysis and anaerobic digestion processes
- 2017
-
Ingår i: Applied Energy. - : Elsevier Ltd. - 0306-2619 .- 1872-9118. ; 204, s. 1074-1083
-
Tidskriftsartikel (refereegranskat)abstract
- The anaerobic digestion of source-separated organic waste is a mature and increasingly used process for biomethane production. However, the efficient use of different fractions of waste is a big concern in anaerobic digestion plants. This study proposes the use of a new process configuration that couples the anaerobic digestion of biodegradable waste with the pyrolysis of lignocellulosic or green waste. The biochar obtained from pyrolysis was added to a digester as an adsorbent to increase the biomethane content and to support the development of a stable microbial community. In addition, the bio-oil and syngas produced by the pyrolysis process were reformed into syngas and then converted to biomethane via methanation. Modelling and simulations were performed for the proposed novel process. The results showed an approximately 1.2-fold increase in the biomethane volume produced. An overall efficiency of 67% was achieved, whereas the stand-alone anaerobic digestion system had an efficiency of only 52%. The results also indicated a high annual revenue for the integrated process compared to that for an alternative treatment (incineration) of green waste.
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| 33. |
- Salman, Chaudhary Awais, 1986-, et al.
(författare)
-
Identification of thermochemical pathways for the energy and nutrient recovery from digested sludge in wastewater treatment plants
- 2019
-
Ingår i: Energy Procedia. - : Elsevier Ltd. - 1876-6102. ; , s. 1317-1322, s. 1317-1322
-
Konferensbidrag (refereegranskat)abstract
- There are several restrictions and limitations on the emissions and disposal of materials and pollutants related to wastewater treatment plants (WWTPs) emphasizing improvement of current processes and development of new methods. Process integration is one way to use all fractions of waste for improved efficiency. WWTPs produces sludge which is usually anaerobically digested to produce biogas and a byproduct called digestate. Digestate is an organic material that contains macro and micronutrients such as nitrogen, phosphorous, and potassium and also contains heavy metals. Digestate is mainly used for agricultural applications because of the presence of nutrients. However, digestate also contains energy in the form of carbon and hydrogen which can be harnessed through various processes and integrated with nitrogen recovery process. This study aims to recover the energy and nutrients from digestate through thermochemical treatment processes. Combustion, pyrolysis, and gasification are assessed and compared in this work. An ammonia stripping method is assumed to recover nitrogen from digestate. The thermochemical processes are heat integrated with ammonia stripping through modeling and simulation. Results show that almost half of the energy present in digested sludge is required for its drying. Moreover, nitrogen recovery also requires much energy. The combustion and gasification of digested sludge give better results than pyrolysis. The heat integration becomes feasible when the auxiliary biogas is also burned along with products from the thermochemical treatment of sludge.
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| 34. |
- Salman, Chaudhary Awais, et al.
(författare)
-
Predictive Modelling and Simulation of Integrated Pyrolysis and Anaerobic Digestion Process
- 2017
-
Ingår i: 8th International Conference on Applied Energy, ICAE 2016; Beijing; China; 8 October 2016 through 11 October 2016. - : Elsevier. ; 105, s. 850-857
-
Konferensbidrag (refereegranskat)abstract
- Anaerobic co-digestion plant with biodegradable organic feedstock separated from municipal solid waste (MSW) have become a mature technology in past decade. The biogas produced can be upgraded to bio-methane or used in heat and power applications. However, not all the municipal waste fractions such as ligno-cellulose and green waste, are suitable for biodegradation. In this work, the non-biodegradable organic waste named as green waste is investigated as a potential substrate for a bio refinery concept based on combination of pyrolysis and anaerobic digestion. The main aim of the study was to evaluate whether or not the anaerobic digestion and pyrolysis process coupling could be beneficial from an energy and exergy point of view. The simulation results shows that the integration of pyrolysis process gives approximately 59% overall efficiency as compared to the 52% for anaerobic digestion stand-alone process. The results also revealed that the pyrolysis of green waste is more beneficial than green waste incineration for heat and power production.
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| 35. |
- Salman, Chaudhary Awais, et al.
(författare)
-
Process simulation and comparison of biological conversion of syngas and hydrogen in biogas plants
- 2017
-
Ingår i: International Conference on Advances In Energy Systems And Environmental Engineering (ASEE17). - : EDP Sciences.
-
Konferensbidrag (refereegranskat)abstract
- Organic waste is a good source of clean energy. However, different fractions of waste have to be utilized efficiently. One way is to find pathways to convert waste into useful products via various available processes (gasification, pyrolysis anaerobic digestion, etc.) and integrate them to increase the combined efficiency of the process. The syngas and hydrogen produced from the thermal conversion of biomass can be upgraded to biomethane via biological methanation. The current study presents the simulation model to predict the amount of biomethane produced by injecting the hydrogen and syngas. Hydrogen injection is modelled both in-situ and ex-situ while for syngas solely the ex-situ case has been studied. The results showed that 85% of the hydrogen conversion was achieved for the ex-situ reactor while 81% conversion rate was achieved for the in-situ reactor. The syngas could be converted completely in the bio-reactor. However, the addition of syngas resulted in an increase of carbon dioxide. Simulation of biomethanation of gas addition showed a biomethane concentration of 87% while for hydrogen addition an increase of 74% and 80% for in-situ and ex-situ addition respectively.
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| 36. |
- Salman, Chaudhary Awais, 1986-, et al.
(författare)
-
Synergistic combination of pyrolysis, anaerobic digestion, and CHP plants
- 2019
-
Ingår i: Energy Procedia. - : Elsevier. - 1876-6102. ; , s. 1323-1329, s. 1323-1329
-
Konferensbidrag (refereegranskat)abstract
- The anaerobic digestion of biodegradable fraction of municipal solid waste (MSW) is a widely used process for biogas production. However, the biodegradable fraction of MSW also contains lignocellulosic waste which hinders the biogas production if added to the digester in higher quantity. So it needs to be separated from biodegradable waste and sent for alternate treatment, e.g., incineration, landfilling or compositing. Pyrolysis of lignocellulosic waste to produce biochar, syngas, and bio oil is an alternate treatment to consider. Furthermore, there is a reported correlation between the addition of biochar in the digester and higher biogas production. Previously, we coupled the pyrolysis of lignocellulosic waste with anaerobic digestion plant. Pyrolysis produces the biochar and vapors. Biochar was added in the digester to enhance the biomethane production. The vapors produced in the pyrolysis process were converted to biomethane through the catalytic methanation process. The combination gives the overall efficiency of 67%. In this work, we modified the process concept to increase the integration level of these processes. The main issue with the pyrolysis process is its heat required to operate, while some of its downstream processes also generate excess heat. In this study, the pyrolysis of lignocellulosic waste is integrated with an operating combined heat and power (CHP) plant, by using its existing infrastructure for heat transport among different pyrolysis operations. The combustor of the CHP plant provides the heat for drying and pyrolysis while the excess heat is transferred back to the combustor. The biochar produced from pyrolysis is transported back to the digester as an adsorbent. The process simulation results show that the combined efficiency of pyrolysis with CHP plant reached 80%. If the biochar is sent back to the anaerobic digester, the synergetic efficiency of all three processes, i.e., pyrolysis-CHP and anaerobic digestion was obtained at 79.7% as compared with the 67% efficiency when the pyrolysis was only integrated with the anaerobic digestion process.
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| 37. |
- Schwede, Sebastian, et al.
(författare)
-
Biological syngas methanation via immobilized methanogenic archaea on biochar
- 2017
-
Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; 105, s. 823-829
-
Tidskriftsartikel (refereegranskat)abstract
- Syngas containing H2, CO, CO2 and CH4 produced by thermalprocesses such as gasification or pyrolysis is typically converted to methane via thermochemical methanation. This process is characterized by a high heat demand utilizing a sensitive chemical catalyst at increased pressure conditions. Alternatively, methanogenic archaea could be exploited as a naturalcatalyst in a biological methanation process with a lower energy demand. However, the mass transfer between the gas phase and the microbial cell is a major challenge for efficient conversion of the syngas components. Therefore, in this work methanogenic archaeafrom anaerobic digestion residueswere successfully immobilized on biochar particles obtained from green waste pyrolysis with two distinct particle sizes (0.25-1 mm and 1-2 mm). After incubation of the inoculated particles with an artificial syngas mixture CH4 was formed within the first 24 hours, while H2, CO2 and CO simultaneously declined. However, the particle size had no influence on the CH4 yield, content and conversion efficiency. According to the maximum theoretical conversion rate of H2 with CO2 and CO to CH4 only about 50% of the syngas components were converted to methane. These results suggest that CO was rather utilized by the methanogens involved for acetate/formate formation than for methanogenesis due to slight inhibition of the latter processby CO present in the syngas. The impact of CO inhibition during biological syngas methanation needs to be further evaluated for a continuous application of the process. However, a proof of concept for this process using inoculated biochar particles could be shown within the study presented here.
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| 38. |
- Schwede, Sebastian, et al.
(författare)
-
Effect of municipal solid green waste derived biochar on anaerobic digestion
- 2017
-
Konferensbidrag (refereegranskat)abstract
- Biochar as a soil amendment has the potential to sequester carbon dioxide from the atmosphere and improve crop yields by reducing nutrient leaching and increasing soil aeration and water holding capacity. Additional nutrients can be introduced into the soil by activation of the biochar with nutrient rich materials such as manure or digestion residues. Likewise, the anaerobic digestion performance might be affected by the biochar addition during the activation.This study investigates the effect of municipal solid green waste derived biochar on mesophilic anaerobic digestion in terms of particle size and amount of added biochar to the digestion of microcrystalline cellulose. Both, particle size and biochar concentration, affected the methane yield and degradation kinetics. While small particles (0.125-0.25 mm) had a slight negative effect, both middle- (0.5-1 mm) and high-sized (2-4 mm) particles had a positive effect on the initial and final methane yield increasing with the concentration (1, 2.5 and 5 g L-1). The improvement of the initial methane yield could be attributed to the available colonialization area for microorganisms on the biochar, whereas the increased final methane yield was influenced by the own gas potential of the biochar. The results suggest that municipal solid green waste is a suitable feedstock for biochar production and the subsequent integration within the anaerobic digestion process chain.
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| 39. |
- Schwede, Sebastian, et al.
(författare)
-
Evaluation of the microalgae-based activated sludge (MAAS) process for municipal wastewater treatment on pilot scale
- 2016
-
Konferensbidrag (refereegranskat)abstract
- The microalgae-based activated sludge (MAAS) process was evaluated regarding the removal efficiency of organic matter and nitrogen from physiochemically pretreated municipal wastewater at different hydraulic retention time (HRT) on pilot scale. Additionally, the interplay between the algal and bacterial consortium was evaluated regarding the ability of the algal consortium to provide oxygen for bacterial oxidation processes. The results showed in general high organic matter (COD removal 75-90%) and total nitrogen (40-50%) removal at all HRTs (6, 4 and 2 days). The dissolved oxygen (DO) concentration was maintained stable at 6 days (6.04±0.47 mg L-1) and 4 days (4.24±0.62 mg L-1) HRT. However, the DO significantly declined at 2 days HRT due to loss of biomass at the high influent flow in the sedimentation unit. Nevertheless, the MAAS process functioned as a symbiotic algal-bacterial system with bacterial organic matter oxidation and nitrification and algal nutrient removal.
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| 40. |
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| 41. |
- Schwede, Sebastian
(författare)
-
Microbial Community, Its Maintenance and Raw Material Composition in Biogas Production Units
- 2016
-
Ingår i: Microbiological Industrial Hygiene. - : Nova Science Publishers, Inc.. - 9781634852685
-
Bokkapitel (refereegranskat)abstract
- Anaerobic digestion is a widely applied process to recover energy and nutrients duringthe stabilization of organic waste or to produce a renewable energy carrier in form of biogasfrom various organic materials. The process application ranges from simple householdscale to complex industrial scale systems to produce a methane-rich biogas that can beutilized for heating and cooking, electricity and heat provision or a replacement of naturalgas.The anaerobic digestion process is a natural process conducted by various microbialgroups in oxygen-free environments. The consecutive process phases during thedecomposition of organic matter to biogas are characterized by so-called syntrophicrelationships, where all involved microbial groups depend on successful collaborationalong the various process phases. However, not all microbial groups share the samerequirements to their environments imposing compromises on some groups to maintainphysiological activity of the total system. Additionally, some microbial groups are moresensitive to inhibitory compounds that might be introduced into the process with theorganic material or formed during the degradation. The maintenance of suitable conditionsfor all involved microbial groups is the major challenge especially during anaerobicdigestion at industrial scale, where consistent treatment or production efficiency isrequired. The following chapter provides the basis to understand the microbialinterrelationships and process conditions to exploit anaerobic digestion as an economicallyand ecologically beneficial technology.
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| 42. |
- Schwede, Sebastian, et al.
(författare)
-
Using slaughterhouse waste in a biochemical-based biorefinery – results from pilot scale tests
- 2017
-
Ingår i: Environmental technology. - : Informa UK Limited. - 0959-3330 .- 1479-487X. ; , s. 1275-1284
-
Tidskriftsartikel (refereegranskat)abstract
- A novel biorefinery concept was piloted using protein-rich slaughterhouse waste, chicken manureand straw as feedstocks. The basic idea was to provide a proof of concept for the production ofplatform chemicals and biofuels from organic waste materials at non-septic conditions. Thedesired biochemical routes were 2,3-butanediol and acetone–butanol fermentation. The resultsshowed that hydrolysis resulted only in low amounts of easily degradable carbohydrates.However, amino acids released from the protein-rich slaughterhouse waste were utilized andfermented by the bacteria in the process. Product formation was directed towards acidogeniccompounds rather than solventogenic products due to increasing pH-value affected by ammoniarelease during amino acid fermentation. Hence, the process was not effective for 2,3-butanediolproduction, whereas butyrate, propionate,γ-aminobutyrate and valerate were predominantlyproduced. This offered fast means for converting tedious protein-rich waste mixtures intoutilizable chemical goods. Furthermore, the residual liquid from the bioreactor showedsignificantly higher biogas production potential than the corresponding substrates. Thecombination of the biorefinery approach to produce chemicals and biofuels with anaerobicdigestion of the residues to recover energy in form of methane and nutrients that can beutilized for animal feed production could be a feasible concept for organic waste utilization.
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| 43. |
- Shenk, Aubrey, et al.
(författare)
-
Analysis of Influencing Characteristics of Biochars for Ammonium Adsorption
- 2022
-
Ingår i: Applied Sciences. - : MDPI. - 2076-3417. ; 12:19
-
Tidskriftsartikel (refereegranskat)abstract
- This article summarizes and performs a systematic analysis using experimental results from recent research on ammonium recovery from aqueous sources using biochar. Numerous studies have focused on using different materials to produce biochar adsorbents, and many have attempted to draw conclusions about the physical or chemical characteristics that dominate the adsorption to infer the mechanism. However, to date, there has not been statistical analysis performed on a large set of adsorption data and physical/chemical characteristics of chars to be able to draw conclusions about ammonium adsorption mechanisms. From this analysis, it was found that consistency in experimental methods and characteristic measurement reporting is lacking, and therefore it is difficult to perform metadata analysis and draw conclusions about ammonium adsorption on biochar. Among the important factors influencing ammonia recovery proposed in literature, the meta-analysis only strongly supports the effect of BET surface area and NH4+ concentration, with weaker support for the importance of cation exchange capacity and pyrolysis temperature. This suggests that standard procedures for biochar production, experiments and analysis of physical and chemical characteristics are needed to usefully compare results across different studies. Examples of the present difficulty in identifying trends across studies are shown by comparing clusters in the data identified by the analysis. The ability to make such comparisons would provide clearer direction in how best to further improve the adsorption capacity of biochars.
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| 44. |
- Shinde, Amar Mohan, et al.
(författare)
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Life cycle assessment of bio-methane and biogas-based electricity production from organic waste for utilization as a vehicle fuel
- 2021
-
Ingår i: Clean Technologies and Environmental Policy. - : SPRINGER. - 1618-954X .- 1618-9558. ; 23:6, s. 1715-1725
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Tidskriftsartikel (refereegranskat)abstract
- The concerns about climate change, energy security and price fluctuation of fossil fuels are driving the growing interest in the development and utilization of renewable energy as a transportation fuel. In this aspect, the utilization of organic household waste for the production of biogas avoids the environmental impact of landfills. The further upgrading and utilization of biogas as a vehicle fuel avoids the environmental impact of fossil fuels. This paper presents the life cycle assessment of two utilization pathways of biogas produced from co-digestion of organic household waste, grease trap removal sludge and ley crops grown by local farmers. Specifically, this study assessed and compared the environmental impact of the production and utilization of bio-methane and biogas-based electricity as a vehicle fuel for public transport buses in Vasteras, Sweden. The system boundary for biogas production covered seven main steps: cultivation, harvesting and transport of ley crops, collection and transport of waste, pre-treatment and co-digestion of the substrate. The system boundary for bio-methane was further extended to account for the upgrading process and tailpipe emissions from combustion of bio-methane in the buses. In the case of biogas-based electricity, the system boundary was further extended to account for the combustion of biogas in the CHP unit and further utilization of electricity in the electric bus. The evaluation of the production routes showed that the methane losses and high energy consumption for both biogas production and upgrading process dominated the environmental impact of bio-methane production. However, the emissions from the CHP unit were solely responsible for the environmental impact of biogas-based electricity production. The functional unit identified for this study is 1 vehicle km travelled (VKT) of the bio-methane fuelled bus and electric bus. The global warming potential of the electric buses was 0.11 kg CO2-eq/VKT compared to 0.26 kg CO2-eq/VKT for the bio-methane buses. The electric buses could also reduce about half of the acidification and eutrophication impacts associated with the bio-methane fuelled buses. The lower fuel efficiency and high tailpipe emissions decreased the environmental advantages of the bio-methane buses. Eventually, this study ensures the biogas utilization which is environmentally sound and compares favourably with the alternative options. [GRAPHICS] .
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| 45. |
- Thorin, Eva, 1967-, et al.
(författare)
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Biogas from Co-digestion of Sewage Sludge and Microalgae
- 2017
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Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; , s. 1037-1042
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Konferensbidrag (refereegranskat)abstract
- Microalgae cultivated in waste water could contribute to increased biomass production at municipal waste watertreatment plants. The biomass could be utilized for biogas production when co-digested with sewage sludge. In thispaper previous published results on co-digestion of sewage sludge and microalgae are summarized and remainingknowledge gaps are identified. The available batch tests in literature mostly concern digestion at mesophilicconditions. Some of those tests indicate a synergetic effect for the co-digestion. Investigations at thermophilicconditions and of semi-continuous processes are scarce. The available results show good possibilities for co-digestionof sewage sludge and microalgae. Further investigations are needed to find optimal conditions for biogas production.
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| 46. |
- Thorin, Eva, 1967-, et al.
(författare)
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Co-digestion of sewage sludge and microalgae : Biogas production investigations
- 2018
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Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 227, s. 64-72
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Tidskriftsartikel (refereegranskat)abstract
- In municipal wastewater treatment plants (WWTPs), algae could be utilised for cleaning the water and, at thesame time, produce a biomass that can be used for energy. Through anaerobic digestion, microalgae can contributeto biogas production when co-digested with sewage sludge. In this paper, previous published results onthe co-digestion of sewage sludge and microalgae are summarised and reviewed, and any remaining knowledgegaps are identified. The batch tests currently documented in literature mostly concern digestion under mesophilicconditions, and studies investigating thermophilic conditions are less common. The average biochemicalmethane potential (BMP) for 29 different mixtures co-digested under mesophilic conditions is 317 ± 101 N cm3CH4 gVS−1 while the result for 12 different mixtures investigated under thermophilic conditions is a BMP of318 ± 60 N cm3 CH4 gVS−1. An evaluation of the heat required for increasing the temperature from mesophilicto thermophilic conditions shows that increased methane production under thermophilic conditions can beenough to create a positive energy balance. For a full-scale WWTP, using thermophilic digestion on sludge, or acombination of sludge and microalgae could therefore be of interest. This is dependent on the demands onsanitation of the sludge and the possibilities for heat recovery.Most of the mesophilic investigations indicate a synergetic effect for co-digestion, with enhancements of up toalmost 70%. However, the results are uncertain since the standard deviations for some of the BMP tests are in thesame order of magnitude as the identified enhancement. Neither of the presented publications provide an understandingof the basic mechanisms that led to higher or lower BMP when microalgae were mixed with wastewatersludge. We, therefore, call for care to be taken when assuming any effects related to the specification ofsubstrates. Microalgae and wastewater sludge have several similarities, and the specific results of BMP in themixtures relate more to the specifics of the respective materials than the materials themselves.Investigations into semi-continuous processes of co-digestion of microalgae and sludge are scarce. The yieldsfor three co-digestion studies show high variation, with an average of 293 ± 112 N cm3 gVSin−1. The availableresults show strong potential for co-digestion of sewage sludge and microalgae. Further investigations are requiredto identify optimal conditions for biogas production, and analysis of microalgae implementation onwastewater treatment at a system level is also needed to identify the total mass balance of substrate and nutrientrecovery.
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| 47. |
- Thorin, Eva, 1967-, et al.
(författare)
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DRY DIGESTION PILOT TESTS USING RESIDUAL MUNICIPAL WASTE AS SUBSTRATE
- 2015
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Ingår i: Sardinia 2015. - Padova : CISA publisher. - 9788862650212
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Konferensbidrag (refereegranskat)abstract
- A pilot plug-flow dry digestion process was tested for production of biogas from the fine fraction of the residual municipal solid waste after source sorting of the organic fraction of the waste. The residual waste is complex, containing a mix of hard and soft plastic, paper, metal, glass, and a varying amount of organic material. The utilization as a substrate for biogas production is therefore challenging. The purpose of the pilot tests was to determine if it is technically feasible to produce biogas from this waste. The plant was operated under thermophilic conditions for almost three months. In parallel also a garage fermentation batch pilot plant was tested with the same substrate. The results from the tests are promising concerning the biogas production even if there are indications that the process in the plug-flow reactor was operated in so called inhibited steady state at the higher loading rates.
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| 48. |
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| 49. |
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| 50. |
- Törnwall, Elin, et al.
(författare)
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Post-treatment of biogas digestate – An evaluation of ammonium recovery, energy use and sanitation
- 2017
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Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; 142, s. 957-963
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Tidskriftsartikel (refereegranskat)abstract
- The utilization of digestate from anaerobic digestion (AD) processes offers the possibility to recycle nutrient from organic wastematerials back to the food chain. However, digestates are characterized by a high water content resulting in high storagecapacities and transportation costs. Various organic wastes such as organic municipal solid waste (oMSW) require sanitation withat least one hour hydraulic retention time (HRT) at 70°C to inactivate pathogens for the safe release of the material.Consequently, the sanitation process is one of the largest energy consumers in the whole AD process chain. In this study, a posttreatmentof the biogas digestate was evaluated regarding the potential for energy savings and nutrient recovery via nitrogenstripping in comparison to the conventional pre-sanitation of the organic waste. With increasing HRT (one to three hours) andaeration flow (0.0-5.3 L air per L digestate and minute) more condensate and ammonia was removed from the digestate. The totalammonia removal from the digestate after one and three hours with the highest aeration flow rate reached 42% and 80%,respectively. However, energy requirement for aeration exceeded energy savings from the lower volume for sanitation after thedigestion substantially. On a system level, a positive energy balance could still be achieved by taking energy savings from thereplacement of mineral fertilizer (36 GJ per ton NH4) into account. Moreover, the digestate as fertilizer could be applied in amore demand-oriented way by adding ammonium sulphate obtained by the ammonia stripping during the post-treatment.
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