Environmental and experimental evaluation of producing chemicals from CO2 using bioelectrochemical systems

Ph. D. ThesisMicrobial electrosynthesis (MES) which uses microbes and electricity to generate high grade chemicals could contribute to the reduction of greenhouse emissions as it uses CO2 in the process. The implementation of this technology on an industrial scale could be on the horizon. Currently, little is known about the environmental loads associated with the successful scale up of the technology with regards to global warming potential and other environmental burdens. Such knowledge is needed in order for relatively new bioprocesses like MES to be sustainably scaled up and industrially applied. This research conducted an empirical and environmental investigation of MES for the synthesis of chemicals from CO2. Experimentally, MES for bio production of chemicals from CO2 was investigated using mixed culture as biocatalyst. CO2 introduced into H-shaped bioelectrochemical systems produced methane, formic, acetic and propionic acids more readily however under some conditions isobutyric acid and ethanol were synthesized. Different polarizations (-0.8V, -1.0V, -1.2V and -1.4V vs Ag/AgCl) and temperatures (27oC and 40oC) were used revealing that bioproduction was affected by changes to these parameters. Biofilm growth and gradual acclimation to CO2 achieved a maximum production rate of 3677μM/day at -1.4V vs Ag/AgCl and 40oC. However an average decline of 18 percent in the coulombic efficiency was observed when the potential was reduced by 0.2V.This showed that there may be energy and environmental risks associated with products synthesized at lower potentials needing confirmation by an environmental analysis. The environmental impacts of products synthesized through MES were examined by modelling a simulated industrial plant (1000 tonnes/year). Environmental analyses were used to reveal the main products to target for MES. Different MES plants generating a range of biochemicals were modelled considering two sources of energy (natural gas and UK national grid), one at a time. This gave specific and detailed scenarios that allowed comparison of the environmental impacts. Results shows that the synthesis of acetic acid, propionic acid, ethanol and methanol released more carbon dioxide than it used for both natural gas and the UK national grid. However, formic acid (-3,421 tonnes CO2 eqv) was found to be the only product having a negative global warming potential using natural gas and comparatively low environmental impacts in other environmental categories. It was concluded that formic acid synthesis through MES is a more suitable product than the other biochemicals analysed in terms of energy efficiency, global warming potential and other potentially harmful environmental impact categories.Petroleum Technology Development Fund, Nigeri

A comprehensive review on life cycle assessment of commercial and emerging thin-film solar cell systems

Thin film solar cells offer several benefits over conventional first-generation technologies including lighter weight, flexibility, and a wider range of optoelectronic tunability. Their environmental impact however needs to be investigated comprehensively to provide a clear comparison point with the first generation photovoltaics currently dominating the market. The main objective of this review is to evaluate current Life Cycle Assessment (LCA) studies conducted on thin film solar cells, highlighting the key parameters considered including life cycle stages, impact categories, and geographical locations. This included both commercially available thin film solar cells (a-Si, CIGS, CIS, CdTe, GaAs and GaAs tandem) as well as emerging (PSC, PSC tandem, DSSC, OPV, CZTS, QD) ones. A critical assessment of the results of 58 LCA studies was conducted and compared with traditional silicon based solar cells. Results indicate that emerging thin film solar cells hold great promise, as they tend to perform better than commercially available ones in the specified indicators, especially for CZTS and OPV. The assessment demonstrated that overall thin film solar cells had less energy requirement and better environmental performance than conventional crystalline silicon solar cell systems. However, due to their lower efficiencies their energy payback time was higher. This review provides a benchmark for the environmental LCA of different thin film solar cell technologies in order to highlight the relevance of these devices for sustainable energy generation and to give manufacturers and LCA experts information and a basis for future evaluation of solar cells

Life cycle assessment of different chalcogenide thin-film solar cells

Thin-film photovoltaics (PV) cells offer several benefits over conventional first-generation PV technologies, including lighter weight, flexibility, and lower power generation cost. Among the competing thin-film technologies, chalcogenide solar cells offer promising performance on efficiency and technological maturity level. However, in order to appraise the performance of the technology thoroughly, issues such as raw materials scarcity, toxicity, and environmental impacts need to be investigated in detail. This paper therefore, for the first time, presents a cradle to gate life cycle assessment for four different emerging chalcogenide PV cells, and compares their results with copper zinc tin sulfide (CZTS) and the commercially available CIGS to examine their effectiveness in reducing the environmental impacts associated with PV technologies. To allow for a full range of indicators, life cycle assessment methods CML 2001, IMPACT 2002+, and ILCD 2011 were used to analyse the results. The results identify environmental hotspots associated with different materials and components and demonstrate that using current efficiencies, the environmental impact of copper indium gallium selenide (CIGS) for generating 1kWh electricity was lower than that of the other studied cells. However, at comparable efficiencies the antimony-based cells offered the lowest environmental impacts in all impact categories. The effect of materials used was also found to be lower than the impact of electricity consumed throughout the manufacturing process, with the absorber layer contributing the most to the majority of the impact categories examined. In terms of chemicals consumed, cadmium acetate contributed significantly to the majority of the environmental impacts. Stainless steel in the substrate/insulating layer and molybdenum in the back contact both contributed considerably to the toxicity and ozone depletion impact categories. This paper demonstrates considerable environmental benefits associated with non-toxic chalcogenide PV cells suggesting that the current environmental concerns can be addressed effectively using alternative materials and manufacturing techniques if current efficiencies are improved.Peer ReviewedPostprint (published version

Environmental performance of Kesterite monograin module production in comparison to thin-film technology

Kesterite-based structures are being extensively studied for solar module productions due to their earth abundant and nontoxic nature, high absorption coefficient, and a wide variety of scalable deposition methods. Kesterites are mostly manufactured using thin-film technology. However, in the last decade, the monograin approach has gained further attention, providing a third alternative to mono-crystalline wafer and thin film methods. This is due to its high throughput, low-cost deposition techniques, flexibility, and light weight. Despite the technical advancements in the monograin technology, their environmental impacts have not been studied in the literature. This paper, for the first time, presents a cradle to gate environmental life cycle assessment of CZTS monograin module production. The analysis is designed to identify the environmental hotspots associated with materials, energy usage, and manufacturing processes. The results were compared to CZTS thin-film and the commercially available CIGS technologies. The analyses suggested that the front contact accounted for the majority of impact in all categories due to the use of silver. The normalisation results showed that the marine aquatic ecotoxicity impact category dominated the overall impact results. A comparison of CZTS monograin and thin film production demonstrated that monograin outperformed the thin film technology when silver was substituted with alternative materials and was proximate to CIGS even considering their higher achieved efficiency. The analysis presents considerable environmental benefits associated with the monograin technology. Further savings in emissions could be achieved with improved conversion efficiency and usage of renewable energy sources in the manufacturing stages

The Economic Costs of Unsupplied Electricity in Nigeria's Industrial Sector: The Roles of Captive Power Generation and Firm Characteristics

Power failure is the most influential business constraint in Nigeria. In this study we pursue answers to two questions concerning policies to mitigate the problem. In the first, we model firms' perception of power failure constraint and found that small and medium enterprises are most constrained. In the second, we examined firms' willingness to pay to avoid power outages and found that on average and ceteris paribus, firms are willing to commit extra 15% of their annual sales to ensure uninterrupted power supply. Furthermore, captive power generating firms are even willing to pay more for uninterrupted power supply. The analysis was based on a sample of 2,676 firms compiled from 2014 World Bank's Enterprise Survey (WBES) for Nigeria. The empirical estimations were based on ordered probit and censored Tobit models respectively.  Keywords: Power outages; industrial sector; captive power generation; firm JEL Classifications: L6; D21; C5 DOI: https://doi.org/10.32479/ijeep.768

Oil Exploration and Exploitation in Nigeria and the Challenge of Sustainable Development: An Assessment of the Niger Delta

The study seeks to evaluate the environmental problems associated with oil exploration and exploitation in the Niger Delta area of Nigeria on one part with a focus on empirical examination of one of the variables highlighted in the literature - emission of CO2 on people's health. With data 1980-2015 drawn from CBN bulletin, we employed OLS and 3SLS regression model to analyze. Life expectancy at birth is the dependent variable, while carbon emission, gross domestic product per capital, female education, and public health expenditure are explanatory variables. Findings show that Carbon emission (CO2EM) has a negative coefficient which is in line with the theoretical expectation.  It is observable that an increase in carbon emission by one unit will reduce life expectancy by 0.04 per cent. This result supports the unsustainability of the business and gas emissions and oil spill in the Delta region as harmful to the wellbeing of the masses. Keywords: Carbon emission, Oil exploration, environmental degradation, resource curse,  JEL Classifications: O13, Q33, Q34 DOI: https://doi.org/10.32479/ijeep.781

The use of carbon dioxide in microbial electrosynthesis ::advancements, sustainability and economic feasibility

This study examines the latest advancements in the field of Microbial ElectroSynthesis (MES) and reports a unique sustainability and economic assessment for the production of five alternative compounds (formic, acetic, propionic acids; methanol and ethanol). Different chemical production conditions were compared by modelling a 1000 t per year production plant. Three sustainability indicators; net energy consumption (NEC), energy gain (EG) and global warming ratio (GWR), were used; along with three economic indicators: production cost, pay-back period and discounted cash flow rate of return. NEC analysis revealed substantial energy requirements in the MES reactor and rectification unit. The former due to the energy required to synthesise CO2to longer chains and the later due to increased water molecules formed during synthesis. EG values suggested that producingformic acid and methanol using MES were lower than conventional processes. MES was shown to use more carbon dioxide for methanol, ethanol and formic acid synthesis than those produced. The economic analysis showed that formic acid and ethanol had a long pay-back period of 15 years. However, production costs were found to be competitive with the market only for formic acid (0.30 £/kg) and ethanol (0.88 £/kg). Moreover, high returns were evaluated for formic acid (21%) and ethanol (14%) compared to the minimum requirements of the industry (11.60%) making these products economically attractive. Our findings reveal insights about the use and scale up of MES for a sustainable and economically viable chemical production process

Comparative life cycle assessment of different vacuum insulation panel core materials using a cradle to gate approach

The global market trend for Vacuum Insulation Panels (VIPs) is projecting a significant increase in their uptake in the construction sector. This is mainly due to the uniquely high-performance properties of the ultra-thin insulation materials. This uptake, however, can potentially be hindered by the VIPs’ higher cost and environmental impacts when compared with conventional insulation materials. This paper, for the first time, presents a detailed evaluation of the environmental impact of the most common type of VIPs currently used in different applications with a focus on alternating the core material as the main contributing component to their footprint. Pyrogenic silica, glass fibre, expanded polystyrene, aerogel and a silica/sawdust hybrid core were analysed from cradle to gate. The study, on a comparative basis, demonstrates the sensitivity of the various environmental impact categories to the internal vacuum pressure and the subsequent thermal conductivity values. The results show a lower environmental impact for glass fibre and low density expanded polystyrene compared to the other alternatives. Pyrogenic silica, the most common core material, had the highest environmental impact out of the core materials considered. The higher environmental impacts of pyrogenic silica suggest that measures such as the recycling of the core material alongside the deployment of eco-friendlier manufacturing techniques should be considered if the material is to compete environmentally with the other alternative materials

Environmental performance of Kesterite monograin module production in comparison to thin-film technology

<p>Kesterite-based structures are being extensively studied for solar <a href="https://www.sciencedirect.com/topics/engineering/module-production">module productions</a> due to their earth abundant and nontoxic nature, high absorption coefficient, and a wide variety of scalable <a href="https://www.sciencedirect.com/topics/engineering/deposition-method">deposition methods</a>. Kesterites are mostly manufactured using thin-film technology. However, in the last decade, the monograin approach has gained further attention, providing a third alternative to mono-crystalline wafer and <a href="https://www.sciencedirect.com/topics/materials-science/thin-films">thin film</a> methods. This is due to its high throughput, low-cost <a href="https://www.sciencedirect.com/topics/chemistry/deposition-technique">deposition techniques</a>, flexibility, and light weight. Despite the technical advancements in the monograin technology, their environmental impacts have not been studied in the literature. This paper, for the first time, presents a cradle to gate <a href="https://www.sciencedirect.com/topics/engineering/life-cycle-assessment">environmental life cycle assessment</a> of CZTS monograin module production. The analysis is designed to identify the environmental hotspots associated with materials, energy usage, and <a href="https://www.sciencedirect.com/topics/engineering/production-process">manufacturing processes</a>. The results were compared to CZTS thin-film and the commercially available <a href="https://www.sciencedirect.com/topics/engineering/indium">CIGS</a> technologies. The analyses suggested that the front contact accounted for the majority of impact in all categories due to the use of <a href="https://www.sciencedirect.com/topics/chemistry/silver">silver</a>. The normalisation results showed that the marine aquatic ecotoxicity impact category dominated the overall impact results. A comparison of CZTS monograin and thin film production demonstrated that monograin outperformed the thin film technology when silver was substituted with alternative materials and was proximate to CIGS even considering their higher achieved efficiency. The analysis presents considerable environmental benefits associated with the monograin technology. Further savings in emissions could be achieved with improved conversion efficiency and usage of <a href="https://www.sciencedirect.com/topics/engineering/renewable-energy-source">renewable energy sources</a> in the manufacturing stages.</p&gt