Browsing by Author "Wagland, Stuart T."
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Item Open Access Assessing metal extraction from metalliferous waste: A study using deep eutectic solvents and chelating agents vs. ethylenediaminetetraacetic acid(Elsevier, 2024-06-07) Huntington, Victoria E.; Coulon, Frederic; Wagland, Stuart T.Conventional methods of metal recovery involving solvents have raised environmental concerns. To address these concerns and promote sustainable resource recovery, we explored the use of deep eutectic solvents (DES) and chelating agents (CA) as more environmentally friendly alternatives. Goethite and blast oxide slag dust (BOS-D) from heap piles at their respective sites and characterised via ICP-MS. The greatest extraction of critical metals was from goethite, removing 38% of all metals compared to 21% from the blast oxide slag. Among the tested CA, nitrilotriacetic acid (NTA) was the most effective, while for DES, choline chloride ethylene glycol (ChCl-EG) demonstrated superior performance in extracting metals from both blast oxide slag dust and goethite. The study further highlighted the selectivity for transition metals and metalloids was influenced by the carboxyl groups of DES. Alkaline metals and rare earth lanthanides extractions were favoured with DES due to improved mass transfer and increased denticity, respectively. In comparison to ethylenediaminetetraacetic acid (EDTA), typically used for metal extraction, CA and DES showed comparable extraction efficiency for Fe, Cu, Pb, Li, Al, Mn, and Ni. Using these greener chelators and solvents for metal extraction show significant promise in enhancing the sustainability of solvometallurgy. Additional conditions e.g., temperature and agitation combined with a cascading leaching process could further enhance metal extraction potential.Item Open Access Characterisation of excavated plastics for thermochemical upcycling to platform chemicals and liquid fuels(2018-2-28) Canopoli, Luisa; Fidalgo Fernandez, Beatriz; Wagland, Stuart T.In Europe there are ~500,000 landfills; plastics represent a consistent and significant proportion of waste in landfill (typically 5-25% w/w). This fraction remains in the landfill, along with other non-biodegradable materials, long after the readily biodegradable organics have degraded. During storage in landfill the plastics physicochemical structure is likely to change because of the occurrence of chemical and biochemical reactions, which can lead to their degradation. For instance, H2S and organic acids produced during the acetogenesis phase of landfill are known to degrade plastics, therefore it can be hypothesised that plastics excavated from landfill are not suitable for conventional recycling. The fate of plastics in landfill has not been largely investigated and limited data exists addressing the changes in chemical and physical properties. The aim of this work is to investigate the degradation of plastics in landfill by characterising chemical and physical properties of samples excavated from different landfill depths. Waste samples were extracted from landfills across the UK at depths of 5-40 m. These were sorted in order to determine the total plastic content and the percentage of each type of plastic present (i.e. PET, HDPE etc). The types of plastics were identified using near infrared [NIR] spectroscopy. The surface properties of the excavated plastics were characterised using SEM/EDS to analyse and evaluate their degradation and contamination levels. Chemical characterisation of each plastic fraction has been carried out by proximate and ultimate analyses. Finally, the surface contamination (metal content) of the plastics was determined by ICP. Fresh, non-landfilled, plastic samples matching the plastic types of those found in landfill were characterised for comparison. The data highlighted plastic type variation across the samples, largely dependent on the age of the excavated material. The extent of degradation, was found to depend on the type of plastic and depth of the sample. This work contributes to address the potential utilisation of excavated plastics, such as for upcycling to platform chemicals and/or liquid fuels through thermochemical conversion.Item Open Access Degradation of excavated polyethylene and polypropylene waste from landfill(Elsevier, 2019-08-26) Canopoli, Luisa; Coulon, Frederic; Wagland, Stuart T.In 2016, it was estimated that 7.4 million tonnes of plastic waste have been disposed in landfill in Europe. This waste represents an important opportunity for resource recovery through enhanced landfill mining consistent with recent Circular Economy initiatives. However, a recent review found a lack of data describing the degradation of excavated plastic waste and the potential impact on recycling products such as pyrolysis oil. In this study, the physicochemical characteristics of the main plastic types found in landfills and their implications for recovery and recycling were investigated using a combination of scanning electron microscopy energy dispersive spectroscopy (SEM-EDS), attenuated total reflectance Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). Loss of gloss was visually detected for the buried plastic waste samples (polyethylene (PE) and polypropylene (PP)) compared to fresh plastic samples. The SEM-EDS analysis further showed that oxygen was the main element related to the plastic surface alteration. The carbonyl index (CI) of plastic samples buried for >10 years was between 1.5 and 2 times higher than <10 years and fresh materials. Similarly, the degree crystallinity of the old samples (>10 years) was 2 times higher than the fresh and < 10 years samples. Based on these findings, tertiary recycling, such as pyrolysis, seems to be a convenient route for upcycling of recovered plastics from municipal solid waste landfills.Item Open Access Design, process simulation and construction of a 100 kW pilot-scale CO2 membrane rig: Improving in situ CO2 capture using selective exhaust gas recirculation (S-EGR)(Elsevier, 2017-12-01) Darabkhani, Hamidreza Gohari; Jurado Pontes, Nelia; Prpich, George; Oakey, John E.; Wagland, Stuart T.; Anthony, Edward J.Carbon capture and storage (CCS) from natural gas-fired systems is an emerging field and many of the concepts and underlying scientific principles are still being developed. Preliminary studies suggest this approach can boost the CO2 content in the feed gas up to 3 times compared to the ‘no recycle’ case (CO2 concentration increased to 18% vs. 6%), with a consequent reduction in flow to the post-combustion capture unit by a factor of three compared to conventional, non-S-EGR. For this project, Cranfield University developed a pilot-scale 100 kW CO2 membrane rig facility in order to investigate simultaneously EGR and S-EGR technologies, the latter being achieved by using a CO2 sweep air polymeric membrane. A bench-scale membrane rig has also been developed to investigate the permeability and selectivity of different polymeric membranes to CO2. Currently a small-scale polydimethylsiloxane (PDMS) membrane module is also being investigated to study its selectivity/permeability. The tests include exploring the performance improvement of the PDMS membrane using different operating conditions with a view to developing scale-up procedures for the membrane unit for the actual 100 kW pilot-scale rig. Process simulations were performed using Aspen Plus software to predict the behaviour of the pilot-scale rig using a model developed based on empirical parameters (i.e., mass transfer coefficient of CO2 through the membrane and permeance), measured in the bench-scale membrane test unit. The results show that CO2 concentrations of up to 14.9% (comparable to CO2 level in coal combustion) can be achieved with 60% EGR, with a 90% CO2 removal efficiency of the membrane units. However, the results generated with the membrane model in which specific permeance values to PDMS were applied, predicted concentrations of CO2 in flue gases up to 9.8% (v/v) for a selective recycle of 60%. The study shows that the S-EGR technique is an effective method that can provide similar conditions to that of a coal-fired power plant for the post-combustion capture system operating on natural gas-fired units, but also highlights the fact that more research is required to find more suitable materials for membranes that optimise the CO2 removal efficiencies from the flue gas.Item Open Access Developing the case for enhanced landfill mining in the UK(CISA Publisher, 2019-02-07) Wagland, Stuart T.; Coulon, Frederic; Canopoli, LuisaAcross the UK there are around 22,000 landfills sites, suggesting a significant opportunity for recovering value from previously discarded materials. Enhanced landfill mining (ELFM) has been identified as a concept to recover value from landfills through optimized valorization of the resources extracted. This approach, including waste-to-energy (WtE), waste-to-material (WtM) and waste-to-land (WtL) options can also assist in addressing critical and secondary raw material demands and scarcity. However, to date, there is still limited evidence on this potential. In this paper, the results of 9 UK landfill sites characterization and feasibility studies for ELFM are presented. Waste characterisation from 9 landfill sites located in the UK was carried out. Overall 36 core drills and 118 unique waste samples were analysed. High volumes of fines (soil-like) organic material were observed across all samples and significant levels of valuable metals were observed in this fraction. Previous work had determined significant aluminium and copper are contained in the soil-like fines fraction, which does not include the separate metals fraction (i.e. aluminium cans, copper wires etc). At one site the combustible fraction was assessed as a potential refuse-derived fuel [RDF]. Typically, 10-40% by weight of the samples at this site were ‘combustible’, with an average gross calorific value of 12.9 MJ/kg. Plastics extracted from the sites are contaminated and degraded, therefore further work is required to understand the extent of degradation and to assess available options upcycle these materials.Item Open Access Development and prototype testing of a novel small-scale pyrolysis system for the treatment of sanitary sludge(Elsevier, 2022-12-31) Beik, Farhad; Williams, Leon; Brown, Tim; Wagland, Stuart T.An innovative twin auger pyrolysis reactor for the intermediate conversion of partially wet sanitary faecal sludge generated on train toilets (mobile applications) is designed and successfully commissioned. The effects of operating temperature, feedstock feeding rates and moisture content and their interaction on the distribution and properties of product biofuels with the use of no carrier gas were assessed. Approximate yields of 50 %, 40 % and 10 % were observed for the biooil, syngas and biochar respectively at 500 °C. Meanwhile, the highest calorific value (HHV) of the syngas did not exceed 10 MJ/Nm3. Acidic compounds (10 % RPA) and nitrogen-containing hydrocarbons (18 % RPA) substituted the abundant species in biooil fraction at 500 °C with the lowest feed volumes of feedstock. Biochar presented the highest fixed carbon (58 %) and ash content (37 %) upon higher operating temperatures for the minimum and maximum volumes of feedstock. Interestingly, the retention of inorganics within the structure of char were observed. Meanwhile, the calorific value of the biochar reduced due to intensive reduction reactions at higher temperatures ranging to a minimum of 19 MJ/kg. Effects of reactor design and configuration on the pyrolytic products are discussed accordingly and further implications are provided. Overall, extensive further research for the end-use of pyrolytic products and the investigation of emissions, upon energy recovery or land-application of by-products are suggested.Item Open Access Extracting metal ions from basic oxygen steelmaking dust by using bio-hydrometallurgy(Elsevier, 2024-06-07) Tezyapar Kara, Ipek; Huntington, Victoria E.; Simmons, Nuannat; Wagland, Stuart T.; Coulon, FredericThis study aimed to optimise metal extraction from secondary hazardous sources, such as basic oxygen steelmaking dust (BOS-D). Initially, three batch systems approaches, including bioleaching using Acidithiobacillus ferrooxidans, chemical leaching using choline chloride-ethylene glycol (ChCl-EG) and a combined approach were compared. Then, scaling up was evaluated through a semi-continuous bioleaching column system with varied leachate recirculation over 21 days, focusing on Y, Ce, Nd, Li, Co, Cu, Zn, Mn, and Al. Bioleaching outperformed the control experiments within 3 days in the batch, demonstrating the key role of A. ferrooxidans. Chemical leaching conducted with a solid concentration of 12.5 % (w/v) successfully dissolved over 50 % of all metals within 2 h. For rare earth elements (REE), both bioleaching and hybrid leaching outperformed chemical leaching. However, considering factors such as process duration, overall efficiency, and ease of extraction, chemical leaching was the most effective method. Leachate recirculation reached a plateau after 11 days, resulting in extraction efficiency of 39 % when semi-continuous column set-up was used. Interestingly, variations in recirculation rates did not influence the extraction efficiency. Overall, this study emphasizes the considerable potential of bioleaching for metal recovery, but also highlights the need for further studies for enhancing permeability for percolation methods and optimisation, particularly in parameters such as aeration rate, when transitioning to larger scale systems.Item Open Access Increasing recovery opportunities of metal(loid)s from municipal solid waste via landfill leachate recirculation(Elsevier, 2023-01-17) Lee, Hyeyeon; Coulon, Frederic; Beriro, D. J.; Wagland, Stuart T.The recovery of 12 critical raw materials (CRM) from municipal solid wastes (MSW) via leachate recirculation was evaluated using a 4 L semi-pilot scale column percolation. The results showed that the recovery of the metal(loid)s was mainly influenced by order of importance: pH > organic content > type of metal(loid)s > age of the waste > redox potential. Among the CRM, Cd and Ni were the most mobile elements, while As and Cr were the least mobile. A comparison of leachate from the leachate recirculated columns before and after the initiation of recirculation indicates an increase in the concentrations of certain CRM and metalloids. The first recirculation cycle supported achieving 100 % recovery. CRM and metalloids in leachate can be recovered; however, the concentrations of CRM and metalloids are usually below 1 mg/L. In this regard, leachate recirculation may enhance the increasing concentration of CRM in landfill leachate. For example, after first recirculation cycle, Ni concentration increased from 0.05 mg/L to 0.11 mg/L. The results obtained from this study can develop further methodologies for the potential recovery of CRM and help foster further research into overcoming limitations for recovering CRM in landfill leachate.Item Open Access Innovative resource recovery from industrial sites: a critical review(MDPI, 2022-12-28) Huntington, Victoria E.; Coulon, Frederic; Wagland, Stuart T.Global net-zero pledges are instigating a societal shift from a fossil-fuel-based economy to renewables. This change facilitates the use of batteries, solar photovoltaic (PV), wind turbines, etc., all of which are underpinned by critical metals. Raw metal extraction is not renewable and environmental pledges made by the government will not be met if this continues. Historic industrial sites contain vast waste stocks. These sites already have an established infrastructure for resource extraction. Applying green solvents and deep eutectic solvents (DES) to such sites for resource recovery alleviates pressure on existing raw extraction processes whilst generating more immediate stores of critical metal along with relatively insignificant environmental impacts. Existing remediation/recovery options have varying metal recovery efficiencies usually combined with high operating costs. Using novel green solvents, such as DES, on historic sites provides an opportunity to recover metals from waste that ordinarily would be looked over. Increased extraction of critical metals from waste material within the UK will reduce reliance on imported metals and improve critical metals security of supply to UK markets and the wider economy The use of these solvents provides an environmentally friendly alternative but also regenerates the legacy of waste from historic industrial sites and consequently implements a circular economy. Adopting the use of green solvents will meet EU environmental pledges, and boost the economy, by recovering metals from legacy sites to meet exponentially growing metal demand.Item Open Access Interactions and interferences of Cu, Cr and As during contaminated waste wood gasification: A thermodynamic equilibrium study(2018-05-24) Al-Badri, Shurooq; Jiang, Ying; Wagland, Stuart T.Waste wood (WW) is one of the major sources of renewable energy. However, it often contaminated with metal(loid) elements at concentrations leading to toxicity emissions and damages to facilities during thermal conversion. Thence, procedures for preventing and/or reducing the negative impacts of these elements require further understanding, specifically their phase transformations during thermal conversion processes. Although it is well known that phase transformation depends on different factors such as vaporization characteristics of elements, operational conditions and process configuration, influences of atmosphere composition of the reaction are rarely investigated. Based on thermodynamic equilibrium principles, this study investigates the behaviors of most regulated elements (Cu, Cr and As) in contaminated WW in relation to the presence/absence of Ca, Na, S, Cl, Fe and Ni during gasification. Thermodynamic calculations were performed across gasification temperature range of 0-1800°C, under the atmospheric pressure. Refinement of possible interactions and interferences reveals that Ni-As interactions generate dominant species As 2 Ni 5 and As 8 Ni 11 , which increase the solid-gaseous transformation temperature of As. Furthermore, interactions between Ca and Cr predominantly forms C 3 Cr 7 ; whereas absence of Ca leads to form CnNa 2 O 4 which causes instability in Cr phase formation. The findings of this study indicate that the evaluation of speciation due to interactions and interferences can provide quantitative and qualitative assessments of the metal(loid) behavior in gasification.Item Open Access Investigation of municipal solid waste (MSW) and industrial landfills as a potential source of secondary raw materials(2018-03-31) Särkkä, Heikki; Kaartinen, Tommi; Hannus, Esa; Hirvonen, Sami; Valjus, Tuire; Lerssi, Jouni; Dino, Giovanna A.; Rossetti, Piergiorgio; Griffiths, Zoe; Wagland, Stuart T.; Coulon, FredericMany of the secondary raw materials (SRM) in landfills constitute valuable and scarce natural resources. It has already been recognised that the recovery of these elements is critical for the sustainability of a number of industries and SRM recov¬ery from anthropogenic waste deposits represents a significant opportunity. In this study, the characterisation of the different waste fractions and the amount of SRM that can potentially be recovered from two landfill sites in Finland is presented. The first site was a municipal solid waste (MSW) landfill site and it was specifically in¬vestigated for its metals, SRM, plastics, wood, paper, and cardboard content as well as its fine fraction (<20 mm). The second site was an industrial landfill site contain¬ing residual wastes from industrial processes including 1) aluminium salt slag from refining process of aluminium scrap and 2) shredding residues from automobiles, household appliances and other metals containing waste. This site was investigated for its metals and SRM recovery potential as well as its fine fraction. Results suggest that the fine fraction offers opportunities for metal (Cr, Cu, Ni, Pb, and Zn) and SRM extraction and recovery from both landfill site types while the chemical composition of the industrial waste landfill offered greater opporutinity as it was comparable to typical aluminium salt slags. Nevertheless, the concentrations of rare earth metals (REE) and other valuable elements were low even in comparison with the concentra¬tions found in the Earth’s crust. Therefore mining landfill sites only for their metals or SRM content is not expected to be financially viable. However, other opportunities, such as waste-derived fuels from excavated materials especially at MSW landfill sites, still exists and fosters the application and feasibility of landfill mining.Item Open Access Managing full-scale dry anaerobic digestion: semi-continuous and batch operation(Elsevier, 2022-07-09) Rocamora, Ildefonso; Wagland, Stuart T.; Rivas Casado, Monica; Hassard, Francis; Villa, Raffaella; Peces, Miriam; Simpson, Edmon W.; Fernández, Oliver; Bajón Fernández, YadiraDry anaerobic digestion usually results in inhibitors accumulation, which can be solved by adapting operation. Multiple strategies targeting increased stability are implemented in full-scale, but impacts are poorly documented. Two full-scale dry AD plants treating organic fraction of municipal solid waste (OFMSW) were investigated: a semi-continuous plant with compost addition and a batch plant testing different percolate recirculation strategies and inoculum to substrate ratios. Regression tree analysis was used to evaluate the effect of these strategies on methane yields and inhibitors accumulation. Compost addition in the semi-continuous plant reduced volatile fatty acids content but dropped methane flow up to 10 % when compost constituted over 10.1 % in weight of the incoming feedstock. This reduction was linked to the limited availability of easily degradable material in the compost. In batch dry AD, methane yields increased as percolate recirculated raised up to a range of 182–197 m3 (0.342–0.363 m3/t of biomass mix). Recirculation of higher percolate volumes reduced methane production, probably linked to pile compaction and inhibitors accumulation. The ratio of OFMSW, digestate and woodchip (bulking agent) fed was determinant, and methane production was higher when digestate was over 43.1 %, waste between 45 % and 47.5 % and woodchip over 8.2 % in weight in as received basis. Woodchip influenced percolation through the pile and supported reduced total ammonia levels of 3.2 g/l when kept over 8.2 %, which raised to 5.2 g/l for lower values.Item Open Access Managing non-sewered human waste using thermochemical waste treatment technologies: a review(MDPI, 2021-11-17) Beik, Farhad; Williams, Leon; Brown, Tim; Wagland, Stuart T.The utilisation of micro-scale thermal treatment technologies for non-sewered applications has been emerging as a prominent route for the safe treatment and disposal of high water content hazardous feedstock. This study provides a comprehensive review of the technological concepts practiced up to date in commercial/pilot and small scales for various types of solid fuels. The respective challenges are critically described and discussed to aid in the selection of promising technology for on-site sanitary applications. Furthermore, the challenges observed with the nominated (pyrolysis) technology are discussed in detail and addressed. This study suggests rapid energy recovery from by-products primarily made up of the highest yield of syngas with a desirable calorific value. The optimum operating ranges are discussed to ensure a reliable thermal conversion of sludge materials considering the application constraints and technology drawbacks. However, further studies are needed to investigate the uncertainties regarding emissions, energy consumption and overall associated costs.Item Open Access Physico-chemical properties of excavated plastic from landfill mining and current recycling routes(Elsevier, 2018-04-02) Canopoli, Luisa; Fidalgo, Beatriz; Coulon, Frederic; Wagland, Stuart T.In Europe over 5.25 billion tonnes of waste has been landfilled between 1995 and 2015. Among this large amount of waste, plastic represents typically 5–25 wt% which is significant and has the potential to be recycled and reintroduced into the circular economy. To date there is still however little information available of the opportunities and challenges in recovering plastics from landfill sites. In this review, the impacts of landfill chemistry on the degradation and/or contamination of excavated plastic waste are analysed. The feasibility of using excavated plastic waste as feedstock for upcycling to valuable chemicals or liquid fuels through thermochemical conversion is also critically discussed. The limited degradation that is experienced by many plastics in landfills (>20 years) which guarantee that large amount is still available is largely due to thermooxidative degradation and the anaerobic conditions. However, excavated plastic waste cannot be conventionally recycled due to high level of ash, impurities and heavy metals. Recent studies demonstrated that pyrolysis offers a cost effective alternative option to conventional recycling. The produced pyrolysis oil is expected to have similar characteristics to petroleum diesel oil. The production of valuable product from excavated plastic waste will also increase the feasibility of enhanced landfill mining projects. However, further studies are needed to investigate the uncertainties about the contamination level and degradation of excavated plastic waste and address their viability for being processed through pyrolysis.Item Open Access Prediction of combined sorbent and catalyst materials (CSCM) for SE-SMR, using QSPR and multi-task learning(American Chemical Society, 2022-06-23) Nkulikiyinka, Paula; Wagland, Stuart T.; Manovic, Vasilije; Clough, Peter T.The process of sorption enhanced steam methane reforming (SE-SMR) is an emerging technology for the production of low carbon hydrogen. The development of a suitable catalytic material, as well as a CO2 adsorbent with high capture capacity, has slowed the upscaling of this process to date. In this study, to aid the development of a combined sorbent catalyst material (CSCM) for SE-SMR, a novel approach involving quantitative structure–property relationship analysis (QSPR) has been proposed. Through data-mining, two databases have been developed for the prediction of the last cycle capacity (gCO2/gsorbent) and methane conversion (%). Multitask learning (MTL) was applied for the prediction of CSCM properties. Patterns in the data of this study have also yielded further insights; colored scatter plots were able to show certain patterns in the input data, as well as suggestions on how to develop an optimal material. With the results from the actual vs predicted plots collated, raw materials and synthesis conditions were proposed that could lead to the development of a CSCM that has good performance with respect to both the last cycle capacity and the methane conversion.Item Open Access Retrieving back plastic wastes for conversion to value added petrochemicals: opportunities, challenges and outlooks(Elsevier, 2023-06-01) Kumar, Manish; Bolan, Shiv; Padhye, Lokesh P.; Konarova, Muxina; Foong, Shin Ying; Lam, Su Shiung; Wagland, Stuart T.; Cao, Runzi; Li, Yang; Batalha, Nuno; Ahmed, Mohamed; Pandey, Ashok; Siddique, Kadambot H.M.; Wang, Hailong; Rinklebe, Jörg; Bolan, NanthiPlastic production and its unplanned management and disposal, has been shown to pollute terrestrial, aquatic, and atmospheric environments. Petroleum-derived plastics do not decompose and tend to persist in the surrounding environment for longer time. Plastics can be ingested and accumulate into the tissues of both terrestrial and aquatic animals, which can impede their growth and development. Petrochemicals are the primary feedstocks for the manufacture of plastics. The plastic wastes can be retrieved back for conversion to value added petrochemicals including aromatic char, hydrogen, synthesis gas, and bio-crude oil using various technologies including thermochemical, catalytic conversion and chemolysis. This review focusses on technologies, opportunities, challenges and outlooks of retrieving back plastic wastes for conversion to value added petrochemicals. The review also explores both the technical and management approaches for conversion of plastic wastes to petrochemicals in regard to commercial feasibility, and economic and environmental sustainability. Further, this review work provides a detailed discussion on opportunities and challenges associated with recent thermochemical and catalytic conversion technologies adopted for retrieving plastic waste to fuels and chemicals. The review also recommends prospects for future research to improve the processes and cost-efficiency of promising technologies for conversion of plastic wastes to petrochemicals. It is envisioned that this review would overcomes the knowledge gaps on conversion technologies and further contribute in emerging sustainable approaches for exploiting plastic wastes for value-added products.Item Open Access Techno-economic assessment of bioleaching for metallurgical by-products(Elsevier, 2024-04-20) Tezyapar Kara, Ipek; Wagland, Stuart T.; Coulon, FredericThis study focused on the economic feasibility of two potential industrial-scale bioleaching technologies for metal recovery from specific metallurgical by-products, mainly basic oxygen steelmaking dust (BOS-D) and goethite. The investigation compared two bioleaching scaling technology configurations, including an aerated bioreactor and an aerated and stirred bioreactor across different scenarios. Results indicated that bioleaching using Acidithiobacillus ferrooxidans proved financially viable for copper extraction from goethite, particularly when 5% and 10% pulp densities were used in the aerated bioreactor, and when 10% pulp density was used in the aerated and stirred bioreactor. Notably, a net present value (NPV) of $1,275,499k and an internal rate of return (IRR) of 65% for Cu recovery from goethite were achieved over 20-years after project started using the aerated and stirred bioreactor plant with a capital expenditure (CAPEX) of $119,816,550 and an operational expenditure (OPEX) of $5,896,580/year. It is expected that plant will start to make profit after one year of operation. Aerated and stirred bioreactor plant appeared more reliable alternative compared to the aerated bioreactor plant as the plant consists of 12 reactors which can allow better management and operation in small volume with multiple reactors. Despite the limitations, this techno-economic assessment emphasized the significance of selective metal recovery and plant design, and underscored the major expenses associated with the process.Item Open Access Unlocking the hidden value of industrial by-products: Optimisation of bioleaching to extract metals from basic oxygen steelmaking dust and goethite(Elsevier, 2023-09-28) Tezyapar Kara, Ipek; Simmons, Nuannat; Wagland, Stuart T.; Coulon, FredericIn this study, the potential of bioleaching to extract valuable metals from industrial by-products, specifically basic oxygen steelmaking dust (BOS-D) and goethite was investigated. These materials are typically discarded due to their high zinc content and lack of efficient regeneration processes. By using Acidithiobacillus ferrooxidans, successful bioleaching of various metals, including heavy metals, critical metals, and rare earth elements was achieved. The Taguchi orthogonal array design was used to optimise the bioleaching process, considering four variables at three different levels. After 14 days, the highest metal extraction for the BOS-D (11.2 mg Zn/g, 3.2 mg Mn/g, 1.6 mg Al/g, 0.0013 mg Y/g, and 0.0026 mg Ce/g) was achieved at 1% solid concentration, 1% energy source concentration, 1% inoculum concentration, and pH 1.5. For goethite, the optimal conditions were 1% solid concentration, 4% energy source concentration, 10% inoculum concentration, and pH 2 resulting in a extraction of 26.6 mg Zn/g, 2.1 mg/g Mn, 1.8 mg Al/g, 0.01 mg Co/g, 0.0022 mg Y/g. These findings are significant, as they demonstrate the potential to extract valuable metals from previously discarded industrial by-products. The extraction of such metals can have substantial economic and environmental implications, while simultaneously reducing waste in the metallurgical industry. Furthermore, the preservation of initial concentration of iron in both BOS-D and goethite residues represents a significant step towards implementing more sustainable industrial practices.Item Open Access Use of inoculum, water and percolate as strategy to avoid inhibition on dry-batch anaerobic digestion of organic fraction of municipal solid waste(Springer, 2021-06-22) Rocamora, Ildefonso; Wagland, Stuart T.; Villa, Raffaella; Simpson, Edmon W.; Fernández, Oliver; Bajón Fernández, YadiraThe impact of inoculum to substrate ratio (I:S) and the addition of water and percolate on stopping inhibition in dry batch anaerobic digestion of organic fraction municipal solid waste (OFMSW) was investigated. In particular, ratios of I:S from 1:2 to 1:16 and total solid contents from 40 to 25% with water and percolate addition were analysed. Tested I:S did not avoid acidification of the anaerobic digesters (ADs), and the highest biogas and methane production (16.2 and 1.7 L/kg VSadded, respectively) was achieved with the 1:4 ratio. Water addition was also insufficient to avoid acidification, and while biogas increased as TS decreased, 40.9 L/kg VSadded for 25% TS, methane yield remained low at 1.2 L/kg VSadded due to the inhibition of methanogenic archaea. Percolate addition proved a suitable strategy to increase pH buffering, with an increased methane production of 199.4 L/kg VSadded at similar TS ranges (27%). Impact on kinetics of methane formation was assessed by kinetic modelling with logistic model identified as the better fit for most of the ADs. Shorter lag phases were observed as TS were reduced, regardless of the acidification, as mass transfer limitations were reduced at the beginning of the batch, but an increase was observed when percolate was used instead of water. Increases of the maximum methane rate (Rmax) was also achieved with TS reduction, but only when acidification was avoided. This study has highlighted the need to profile percolate composition during batch digestion in order to balance recirculation of nutrients, microbial communities and toxic compounds.