| 1. |
- Amjad, Um-e-Salma, et al.
(författare)
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Catalytic cracking of polystyrene pyrolysis oil: Effect of Nb2O5 and NiO/Nb2O5 catalyst on the liquid product composition
- 2022
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Ingår i: Waste Management. - : Elsevier. - 0956-053X .- 1879-2456. ; 141, s. 240-250
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Tidskriftsartikel (refereegranskat)abstract
- The catalytic cracking of polystyrene pyrolysis oil was investigated over a Nb2O5 and a NiO/Nb2O5 catalyst in a fixed bed reactor. First, the pyrolysis of two different polystyrene feedstock (polystyrene foam and polystyrene pellet) was carried out in a semi-batch reactor, and the resulting polystyrene pellets pyrolysis oil was selected for catalytic cracking reaction because of its high liquid yield (85%). Catalytic cracking experiments were then performed at different temperatures (350–500 °C) using Nb2O5 or NiO/Nb2O5 catalyst. Gas chromatography–mass spectrometry analysis of liquid product obtained from the catalytic cracking process showed that the dimers in the pyrolysis oil were converted to monomers during the catalytic cracking process. The catalytic cracking results also showed that the NiO/Nb2O5 catalyst (having slightly higher acidic sites) had slightly higher activity for monomer conversion than the Nb2O5 catalyst (having less acidic sites). X-ray diffraction, transmission electron microscopy, pyridine Fourier transform infrared spectroscopy, NH3 Temperature Programmed Desorption and X-ray photoelectron spectroscopy were used to characterize the catalyst. The highest catalytic cracking activity was observed at 400 °C with the Nb2O5 catalyst with 4% toluene, 6% ethylbenzene, approximately 50% styrene, 13% α-methyl styrene, and only 6% of dimers in the liquid oil. The increase in temperature positively affected the yield of gases during catalytic cracking process.
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| 2. |
- Andreasi Bassi, Susanna, et al.
(författare)
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A life cycle assessment framework for large-scale changes in material circularity
- 2021
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Ingår i: Waste Management. - : Elsevier BV. - 0956-053X .- 1879-2456. ; 135, s. 360-371
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Tidskriftsartikel (refereegranskat)abstract
- Increasing material circularity is high on the agenda of the European Union in order to decouple environmental impacts and economic growth. While life cycle assessment (LCA) is useful for quantifying the associated environmental impacts, consistent LCA modeling of the large-scale changes arising from policy targets addressing material circularity (i.e., recycled content and recycling rate) is challenging. In response to this, we propose an assessment framework addressing key steps in LCA, namely, goal definition, functional unit, baseline versus alternative scenario definition, and modeling of system responses. Regulatory and economic aspects (e.g., trends in consumption patterns, market responses, market saturation, and legislative side-policies affecting waste management) are emphasized as critical for the identification of potential system responses and for supporting regulatory interventions required to reach the intended environmental benefits. The framework is recommended for LCA studies focusing on system-wide consequences where allocation between product life cycles is not relevant; however, the framework can be adapted to include allocation. The application of the framework was illustrated by an example of implementing a policy target for 2025 of 70% recycled content in PET trays in EU27+1. It was demonstrated that neglecting large-scale market responses and saturation lead to an overestimation of the environmental benefits from the policy target and that supplementary initiatives are required to achieve the full benefits at system level.
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| 3. |
- Asim Ibrahim, Muhammad, et al.
(författare)
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Early detection of deep-seated smouldering fires in wood waste storage using ERT
- 2024
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Ingår i: Waste Management. - 0956-053X .- 1879-2456. ; 182, s. 215-224
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Tidskriftsartikel (refereegranskat)abstract
- Incidents of waste and biofuel fires are common at all stages of the waste recycling chain and have grave implications for business, employees, firefighters, society, and environment. An early detection of waste and biofuel fires in the smouldering stage could save precious lives, resources, and our environment. Existing fire detection methodologies e.g. handheld temperature sensors, IR cameras, gas sensors, and video and satellite-based monitoring techniques have inherent limitations to efficiently detect smouldering fires. An attempt was made to explore the potential of electrical resistivity tomography (ERT) as an alternate tool to address the problem. In the experiments an externally powered resistive wire was employed to initiate the smouldering fire inside the test material (wood pellets, wood shavings, wood fines). Time series of ERT that followed the initiation and development of smouldering were recorded using an automated monitoring instrument setup. The actual geometry of the experimental sample container and electrode setup was integrated in the 3D finite element method (FEM) model grid to perform inverse numerical modelling (inversion) and to develop resistivity tomographic images. The study shows a sharp increase in ratio of resistivity (?/?? ≥ 50 %) in the test material in the region of smouldering hotspot and demonstrates the potential use of ERT technique for the detection of smouldering hotspots in silos and pile storage of organic material such as wood-based fuels, wood waste, coal, municipal solid waste (MSW), recyclables etc. More research is however required for enabling the use of this technique at the practical scale for different storage conditions.
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| 4. |
- Bagheri, Marzieh, et al.
(författare)
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Introducing hydrothermal carbonization to sewage sludge treatment systems—a way of improving energy recovery and economic performance?
- 2023
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Ingår i: Waste Management. - : Elsevier. - 0956-053X .- 1879-2456. ; 170, s. 131-143
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Tidskriftsartikel (refereegranskat)abstract
- Hydrothermal carbonization (HTC) can mitigate the disposal costs of sewage sludge in a wastewater treatment plant. This study analyzes the impact of integrating HTC with anaerobic digestion (AD) and combustion from a combined energy and economic performance perspective. Net energy balance and investment opportunity are investigated for a number of technical scenarios considering i) different combinations of the technologies: AD + HTC, AD + thermal dryer + combustion, and AD + HTC + combustion, ii) different options for HTC process water treatment: wet oxidation (WO) + AD, and direct return to AD, and iii) different products: heat-only, heat and electricity, hydrochar, and phosphorus.The results show trade-offs between investment cost, self-supplement of heat, and output electricity when WO is used. In AD + HTC, net heat output decreases compared to the reference plant, but avoided disposal costs and hydrochar revenue result in profitable investment when the process water is directly returned to the AD. Although HTC has a lower heat demand than the thermal dryer, replacing the thermal dryer with HTC is only possible when AD, HTC, and combustion are connected, or when WO covers HTC’s heat demand. HTC may impair the electricity production because of the necessity for a high-temperature heat source, whereas the thermal dryer can utilize a low-temperature heat source. In conclusion, energy advantages of HTC in AD + HTC + combustion are insufficient to provide a promising investment opportunity due to high investment costs of HTC. The investment opportunity improves by co-combustion of hydrochar and external sludge.
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| 5. |
- Barbato, Paula Martina, et al.
(författare)
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Quality degradation in glass recycling: substitutability model proposal
- 2024
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Ingår i: Waste Management. - 0956-053X .- 1879-2456. ; 182, s. 124-131
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Tidskriftsartikel (refereegranskat)abstract
- The sustainability assessment of waste management systems requires tools capable of evaluating material quality degradation during recycling. Existing research has predominantly focused on the development of substitutability models for plastics, leaving a gap in addressing other materials like glass. Glass is commonly regarded as endlessly recyclable, even though its actual recyclability depends on several crucial factors, such as colour and pollutant contamination. Many Life Cycle Assessment (LCA) studies in this field assume a one-to-one substitution coefficient, neglecting material deterioration and inaccurately representing real-world scenarios. This study proposes and assesses a substitutability model for glass, aiming to measure the replacement extent between virgin materials and recycled crushed glass (cullet). The methodology is based on two key factors: technical quality substitutability, considering impurities and colour contaminations in cullet, and market applicability, accounting for market demand. Once formulated, the model was applied to a European case study on glass waste treatment. Two scenarios were considered: one assuming complete substitution between cullet and raw materials, the other incorporating quality degradation. Findings indicate that, accounting for quality degradation, only 83% of cullet effectively replaces raw materials, resulting in a decrease of the benefit associated with recycling of 13–23% for the different examined impact categories, compared to complete replacement assumption. This underscores the importance of considering quality deterioration in glass recycling impact assessments.
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| 6. |
- Benavente, Veronica, et al.
(författare)
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Co-hydrothermal carbonization of microalgae and digested sewage sludge : Assessing the impact of mixing ratios on the composition of primary and secondary char
- 2024
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Ingår i: Waste Management. - : Elsevier. - 0956-053X .- 1879-2456. ; 174, s. 429-438
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Tidskriftsartikel (refereegranskat)abstract
- The role of microalgae cultivation in wastewater treatment and reclamation has been studied extensively, as has the potential utility of the resulting algal biomass. Most methods for processing such biomass generate solid residues that must be properly managed to comply with current sustainable resource utilization requirements. Hydrothermal carbonization (HTC) can be used to process both individual wet feedstocks and mixed feedstocks (i.e., co-HTC). Here, we investigate co-HTC using microalgae and digested sewage sludge as feedstocks. The objectives were to (i) study the material's partitioning into solid and liquid products, and (ii) characterize the products’ physicochemical properties. Co-HTC experiments were conducted at 180–250°C using mixed microalgae/sewage sludge feedstocks with the proportion of sewage sludge ranging from 0 to 100 %. Analyses of the hydrochar composition and the formation and composition of secondary char revealed that the content of carbonized material in the product decreased as the proportion of sewage sludge in the feedstock increased under fixed carbonization conditions. The properties of the hydrochars and the partitioning of material between the liquid phase and the hydrochar correlated linearly with the proportion of microalgae in mixed feedstocks, indicating that adding sewage sludge to microalgae had weak or non-existent synergistic effects on co-HTC outcomes. However, the proportion of sewage sludge in the feedstock did affect the secondary char. For example, adding sewage sludge reduced the abundance of carboxylic acids and ketones as well as the concentrations of higher molecular weight cholesterols. Such changes may alter the viable applications of the hydrochar.
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| 7. |
- Brancoli, Pedro, 1989-, et al.
(författare)
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Environmental impacts of waste management and valorisation pathways for surplus bread in Sweden
- 2020
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Ingår i: Waste Management. - : Elsevier BV. - 0956-053X .- 1879-2456. ; 117, s. 136-145
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Tidskriftsartikel (refereegranskat)abstract
- Bread waste represents a significant part of food waste in Sweden. At the same time, the return system established between bakeries and retailers enables a flow of bread waste that is not contaminated with other food waste products. This provides an opportunity for alternative valorisation and waste management options, in addition to the most common municipal waste treatment, namely anaerobic digestion and incineration. An attributional life cycle assessment of the management of 1 kg of surplus bread was conducted to assess the relative environmental impacts of alternative and existing waste management options. Eighteen impact categories were assessed using the ReCiPe methodology. The different management options that were investigated for the surplus bread are donation, use as animal feed, beer production, ethanol production, anaerobic digestion, and incineration. These results are also compared to reducing the production of bread by the amount of surplus bread (reduction at the source). The results support a waste hierarchy where reduction at the source has the highest environmental savings, followed by use of surplus bread as animal feed, donation, for beer production and for ethanol production. Anaerobic digestion and incineration offer the lowest environmental savings, particularly in a low-impact energy system. The results suggests that Sweden can make use of the established return system to implement environmentally preferred options for the management of surplus bread.
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| 8. |
- Carlos-Pinedo, Sandra, et al.
(författare)
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Assessment of a full-scale solid-state anaerobic co-digestion: A multi-component substrate analysis by using ORWARE
- 2022
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Ingår i: Waste Management. - : Elsevier. - 0956-053X .- 1879-2456. ; 146, s. 36-43
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Tidskriftsartikel (refereegranskat)abstract
- Long-term sustainable biogas production requires different raw material alternatives, especially when reducing the most desirable organic substrate, food waste, which has been set as a goal in the 2030 Agenda. In Sweden, horse manure (HM) is generated in large quantities, and due to its physical and chemical characteristics, it has the potential to be used as a raw material to produce biogas through anaerobic digestion (AD). In order to investigate the challenges that HM digestion can impose in terms of methane yield and/or digestate quality, the modified ORganic WAste REsearch (ORWARE) AD model was applied. The aim was to study the effects of different substrates and combinations of these on the AD process during a full-scale solid-state (SS)-AD. In this sense, the model allows for the analysis of the digestion process of multicomponent substrates at the element level. The simulation results suggested that the replacement of green waste (GW) by HM with wood chips as bedding material gave the best improvement in terms of energy turnover; the liquid fraction of the digestate of this mixture of substrates presented the highest concentration in all the nutrients analyzed, specifically in total carbon-biological and phosphorus. The nutrient concentrations in the digestate from the aforementioned scenario are in line with the SPCR120 certification.
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| 9. |
- Carlos-Pinedo, Sandra, et al.
(författare)
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Study of the digestion process at a full-scale solid-state biogas plant by using ORWARE : Model modification and implementation
- 2020
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Ingår i: Waste Management. - : Elsevier. - 0956-053X .- 1879-2456. ; 107, s. 133-142
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Tidskriftsartikel (refereegranskat)abstract
- The configuration of the reactor influences the digestion process and thus the product yields; other factors such as the rate of biogas production or biogas loss also affect the process specifically with high solid configuration. With these in mind, the ORganic WAste REsearch (ORWARE) anaerobic digestion sub-model was modified to be able to study solid-state anaerobic digestion (SS-AD) (using plug-flow reactor). The simulation results from the updated model agreed with the operational data with respect to methane yield, digestate yield and energy turnover. The model was found to be sensitive to changes in feedstock composition but to a lesser extent to changes in process temperature and retention time. By applying the model on several cases of liquid anaerobic digestion (L-AD), it was noticed that L-AD at mesophilic condition with 25 retention days seemed to be superior to other cases of L-AD with regard to energy turnover. However, even if similar methane production were observed for L-AD and SS-AD, the model suggested higher energy turnover for the case of SS-AD at thermophilic condition, being 10% more in average in comparison with cases of L-AD.
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| 10. |
- Caspersen, Siri, et al.
(författare)
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Nutrient challenges with solid-phase anaerobic digestate as a peat substitute-Storage decreased ammonium toxicity but increased phosphorus availability
- 2023
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Ingår i: Waste Management. - 0956-053X .- 1879-2456. ; 165, s. 128-139
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Tidskriftsartikel (refereegranskat)abstract
- The solid fraction (SD) obtained after liquid - solid separation of anaerobic digestate is interesting as a potential fertilizer as well as a peat substitute in horticultural growing substrates. We investigated the effect of incubation of the SD obtained by screw-press separation of digestate produced from food waste and plant residues on potentially plant available mineral nutrients and plant growth. The NH4-N concentration was initially > 1000 mg L-1 but rapidly decreased, probably due to NH3 emission promoted by a high initial pH. No nitrate was detected during the first four weeks of incubation. The concentrations of potentially available P and Mg were closely related and strongly increased during incubation. The effect of adding 20 or 30 vol% of SD to a peat-based growing substrate on the growth of basil and lettuce was investigated before and after the incubation period. With the unincubated SD, the initial substrate NH4-N of 200-300 mg L-1 was potentially phytotoxic. Plant growth response ranged from inhibition to stimulation, probably reflecting variation in substrate ammonium status. After 96 days of incubation, ammonium concentrations had decreased with > 50% and basil growth was generally positively affected by addition of incubated SD. However, available P concentrations of 140-210 mg L-1 in the incubated substrates posed a high risk of P leakage. In conclusion, storage greatly reduced NH4-N con-centrations and phytotoxicity when the SD was used as a partial substituent for peat in a horticultural growing substrate. Measures are needed, however, to limit available P concentrations in high-P solid digestate fractions.
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