Phenyl Disulfide Additive for Solution‐Mediated Carbon Dioxide Utilization in Li–CO2 Batteries

Phenyl disulfide (PDS) is employed as an electrolyte additive in lithium–carbon dioxide (Li–CO₂) batteries to allow for a solution‐mediated carbon dioxide reduction pathway. Thiophenolate anions, generated via electrochemical reduction of PDS, act as CO₂ capture agents by forming the adduct S‐phenyl carbonothioate (SPC^?) in solution. A mechanism of SPC^?‐mediated CO₂ capture and utilization is proposed and supported via carbon‐13 nuclear magnetic resonance spectroscopy and Fourier‐transform infrared spectroscopy. Reversible formation and decomposition of lithium carbonate and amorphous carbon during cycling, facilitated by the solution‐mediated pathway, are demonstrated with an array of characterization techniques. Li–CO₂ batteries employing the PDS additive show vastly improved capacity, energy efficiency, and cycle life. The enhanced Li–CO₂ battery performance offered by the proposed solution‐mediated reaction pathway offers a compelling step forward in the pursuit of reversible CO₂ utilization.     

Comparative life cycle assessment of autotrophic cultivation of Scenedesmus dimorphus in raceway pond coupled to biodiesel and biogas production

Life cycle assessment (LCA) of indigenous freshwater microalgae, Scenedesmus dimorphus, cultivation in open raceway pond and its conversion to biodiesel and biogas were carried out. The LCA inventory inputs for the biogas scenario was entirely based on primary data obtained from algal cultivation (in pilot scale raceway pond), harvesting, and biogas production; while only the downstream processing involved in biodiesel production namely drying, reaction and purification were based on secondary data. Overall, eight scenarios were modeled for the integrated process involving: algae-based CO₂ capture and downstream processing scenarios for biodiesel and biogas along with impact assessment of nutrient addition and extent of recycling in a life cycle perspective. The LCA results indicated a huge energy deficit and net CO₂ negative in terms of CO₂ capture for both the biodiesel and biogas scenarios, majorly due to lower algal biomass productivity and higher energy requirements for culture mixing. The sensitivity analysis indicated that variability in the biomass productivity has predominant effect on the primary energy demand and global warming potential (GWP, kg CO₂ eq.) followed by specific energy consumption for mixing algal culture. Furthermore, the LCA results indicated that biogas conversion route from microalgae was more energy efficient and sustainable than the biodiesel route. The overall findings of the study suggested that microalgae-mediated CO₂ capture and conversion to biodiesel and biogas production can be energy efficient at higher biomass productivity (> 10 g m⁻² day⁻¹) and via employing energy-efficient systems for culture mixing (< 2 W m⁻³).

     

Atmospheric impact of bioenergy based on perennial crop (reed canary grass,Phalaris arundinaceae,L.) cultivation on a drained boreal organic soil

Marginal organic soils, abundant in the boreal region, are being increasingly used for bioenergy crop cultivation. Using long‐term field experimental data on greenhouse gas (GHG) balance from a perennial bioenergy crop [reed canary grass (RCG), Phalaris arundinaceae L.] cultivated on a drained organic soil as an example, we show here for the first time that, with a proper cultivation and land‐use practice, environmentally sound bioenergy production is possible on these problematic soil types. We performed a life cycle assessment (LCA) for RCG on this organic soil. We found that, on an average, this system produces 40% less CO₂‐equivalents per MWh of energy in comparison with a conventional energy source such as coal. Climatic conditions regulating the RCG carbon exchange processes have a high impact on the benefits from this bioenergy production system. Under appropriate hydrological conditions, this system can even be carbon‐negative. An LCA sensitivity analysis revealed that net ecosystem CO₂ exchange and crop yield are the major LCA components, while non‐CO₂ GHG emissions and costs associated with crop production are the minor ones. Net bioenergy GHG emissions resulting from restricted net CO₂ uptake and low crop yields, due to climatic and moisture stress during dry years, were comparable with coal emissions. However, net bioenergy emissions during wet years with high net uptake and crop yield were only a third of the coal emissions. As long‐term experimental data on GHG balance of bioenergy production are scarce, scientific data stemming from field experiments are needed in shaping renewable energy source policies.     

Life Cycle Based CO2 Emission Credits: Options for Improving the Efficiency and Effectiveness of Current Tailpipe Emissions Regulation in the Automotive Industry

The current focus on the use phase in automotive carbon dioxide (CO₂) legislation bares a risk of unintended consequences as often reductions in the use phase come along with increasing CO₂ emissions in other life cycle (LC) phases. This study presents voluntary policy options in form of LC‐based CO₂ emission credits. They were developed by desk research considering existing applications of LCA in practice (e.g., environmental reports) and feedback obtained in a structured stakeholder dialogue. A variety of credit options were identified, including rather simple ones based on life cycle thinking (LCT) and more advanced options which rely on quantitative LCA: LCT options that reward innovations leading to CO₂ reductions, for example, in the production phase. LCA‐based options reward CO₂ reductions along the LC (credits for an International Organization for Standardization [ISO] 14044 conforming externally reviewed LCA showing a continuous improvement) or reductions of other environmental impacts. It was shown that the credit options can be implemented throughout a simplified and robust methodology, for example, with defined rules for conducting the LCA based on international standards and established industry practice, and for calculating the credits (e.g., a credit of 1 gram [g] of CO₂/km [kilometer] for savings of 10 g of CO₂/km). Voluntary credit options as a complementary modality to the current automotive tailpipe‐based CO₂ regulations would help to improve its efficiency and effectiveness and support and reward efforts on achieving real net CO₂ emission reductions. The credit options were developed with a first focus on CO₂ and automotive industry, but can generally be transferred to other environmental impacts and sectors as well.     

Effects of non-aqueous solvents on CO2 absorption in monoethanolamine: Ab initio calculations

Monoethanolamine (MEA) is the most typical alkanolamine and its aqueous solutions are widely used for CO₂ absorption with mature technology, but the regeneration process is energy consuming. To reduce the energy demand, non-aqueous solvents, such as methanol and ethanol are proposed to substitute water in amine solutions. To understand the influence of the aqueous and non-aqueous solvents on CO₂ capture process, the chemical reactions of MEA absorbing CO₂ were conducted via ab initio calculations. The non-aqueous solvents discussed in this paper are methanol, ethanol, 1-propanol and 2-propanol. The reaction patterns were investigated and energy barriers were observed. The results show that zwitterion formation and the followed intermolecular hydrogen transfer are proven to be the most possible reaction pattern in both aqueous and non-aqueous solvents. The energy analysis shows that the forward reaction energy barriers increase while the backward barriers decrease as the solvent changes from water to methanol, ethanol, 1-propanol and 2-propanol in turn. The decreases of the energy barriers for backward processes are much higher than the corresponding increases for forward processes. These results indicate that lower energies are required in non-aqueous solvents than in water during the desorption reactions and the non-aqueous solvents are very promising to reduce the regeneration energy consumption in MEA capturing CO₂ process. Moreover, the reaction energy gaps between different solvation effects were found to have linear relationship with the logarithm of the dielectric constant difference, which could provide an easy way to theoretically predict the reaction energies of monoethanolamine absorbing CO₂ in other solvation effect and can be used to screen appropriate CO₂ capture solvent.     

CO2 methanation activated by magnetic heating: life cycle assessment and perspectives for successful renewable energy storage

Purpose

Technologies with low environmental impacts and promoting renewable energy sources are required to meet the energetic demand while facing the increase of gas emissions associated to the greenhouse effect and the depletion of fossil fuels. CO₂ methanation activated by magnetic heating has recently been reported as a highly efficient and innovative power-to-gas technology in a perspective of successful renewable energy storage and carbon dioxide valorisation. In this work, the life cycle assessment (LCA) of this process is performed, in order to highlight the environmental potential of the technology, and its competitivity with in respect to conventional heating technologies.

Methods

The IMPACT 2002+ was used for this LCA. The process studied integrates methanation, water electrolysis and CO₂ capture and separation. This “cradle-to-gate” LCA study does not consider the use of methane, which is the reaction product. The functional unit used is the energy content of the produced CH₄. The LCA was carried out using the energy mix data for the years 2020 and 2050 as given by the French Agency for Environment and Energy management (ADEME). Consumption data were either collected from literature or obtained from the LPCNO measurements as discussed by Marbaix (2019). The environmental impact of the CO₂ methanation activated by magnetic heating was compared with the environmental impact of a power-to-gas plant using conventional heating (Helmeth) and considering the environmental impact of the natural gas extraction.

Results

It is shown that the total flow rate of reactants, the source of CO₂ and the energy mix play a major role on the environmental impact of sustainable CH₄ production, whereas the lifetime of the considered catalyst has no significant influence. As a result of the possible improvements on the above-mentioned parameters, the whole process is expected to reduce by 75% in its environmental impact toward 2050. This illustrates the high environmental potential of the methanation activated by magnetic heating when coupled with industrial exhausts and renewable electricity production.

Conclusions

The technology is expected to be environmentally competitive compared with existing similar processes using external heating sources with the additional interest of being extremely dynamic in response, in line with the intermittency of renewable energy production.

     

Growing season net ecosystem CO2 exchange of two desert ecosystems with alkaline soils in Kazakhstan

Central Asia is covered by vast desert ecosystems, and the majority of these ecosystems have alkaline soils. Their contribution to global net ecosystem CO₂ exchange (NEE) is of significance simply because of their immense spatial extent. Some of the latest research reported considerable abiotic CO₂ absorption by alkaline soil, but the rate of CO₂ absorption has been questioned by peer communities. To investigate the issue of carbon cycle in Central Asian desert ecosystems with alkaline soils, we have measured the NEE using eddy covariance (EC) method at two alkaline sites during growing season in Kazakhstan. The diurnal course of mean monthly NEE followed a clear sinusoidal pattern during growing season at both sites. Both sites showed significant net carbon uptake during daytime on sunny days with high photosynthetically active radiation (PAR) but net carbon loss at nighttime and on cloudy and rainy days. NEE has strong dependency on PAR and the response of NEE to precipitation resulted in an initial and significant carbon release to the atmosphere, similar to other ecosystems. These findings indicate that biotic processes dominated the carbon processes, and the contribution of abiotic carbon process to net ecosystem CO₂ exchange may be trivial in alkaline soil desert ecosystems over Central Asia.     

Preliminary assessment for global warming potential of leading contributory gases from a 40-in. LCD flat-screen television

Purpose  

As liquid crystal display (LCD) flat-screen televisions increase in popularity, their potential contribution to global warming has received wide attention. This study presents global warming impacts resulting from the life cycle assessment (LCA) of LCD flat-screen televisions for key global warming contributors from the “cradle-to-gate” and use stages of the product’s life cycle. The emissions from nitrogen trifluoride (NF₃), a greenhouse gas with a global warming potential (GWP) 17,000 times more potent than carbon dioxide (CO₂), are not monitored in the Kyoto Protocol. Emissions in the cradle-to-gate and use stages were modeled in this study according to their GWP (kg CO₂ equivalent), focusing and analyzing the most significant source of NF₃ emissions.     

Consideration of carbon dioxide release during shell production in LCA of bivalves

Purpose

Life cycle assessment (LCA) can be used to understand the environmental impacts of the shellfish aquaculture and wild harvest industries. To date, LCA of shellfish exclude carbon dioxide (CO₂) release from bivalve shell production when quantifying global warming potential per functional unit. In this study, we explain the rationale for including CO₂ released during shell production in LCA of bivalves, demonstrate a method for estimating this CO₂ release, and apply the method to previous studies to demonstrate the importance of including CO₂ from shell production in LCA.

Methods

A simple approach for calculating CO₂ from bivalve shell production was developed utilizing the seacarb package in R statistical software. The approach developed allows for inclusion of site-specific environmental parameters such as water temperature, salinity, pH, and pCO₂ when calculating CO₂ release from shell production. We applied the method to previously published LCA of bivalve production systems to assess the impact of including this CO₂ source in the LCA. The past studies include aquaculture and wild harvest production strategies and multiple bivalve species.

Results and discussion

When we recalculated the total kg CO₂ released in past studies including CO₂ release from shell production, the additional CO₂ release increased the total global warming impact category (CO₂ equivalents) in cradle-to-gate studies by approximately 250% of the original reported value. Discussion of our results focuses on the importance of different components of our calculations and site-specific environmental parameters. We make predictions on how the magnitude and importance of CO₂ released during shell production could change due to climate change and ocean acidification, and provide suggestions on how CO₂ release from shell production can be reduced through careful selection of aquaculture facility location and aquaculture practices.

Conclusions

We provide a method for including CO₂ from shell release in LCA of bivalves and recommend that future LCA of bivalves include this CO₂ as part of the global warming impact category.

     

Preliminary comparison of atmospheric CO2 enhancement to photosynthesis of Pyropia yezoensis (Bangiales,Rhodophyta) leafy thalli and filamentous thalli

Intertidal macroalgae are submerged in seawater at high tide and exposed to air at low tide. When they are exposed to the air, CO₂ is the main inorganic carbon source. In this study, the photosynthetic performances of PSI and PSII were measured in different generations of Pyropia yezoensis (leafy thalli and filamentous thalli) that had been exposed to air containing different CO₂ concentrations. Changes in photosynthesis during dehydration and salt treatment under the different CO₂ concentrations were also analyzed. The results showed that in leafy thalli, the effective photochemical quantum yield of PSII (YII) was enhanced as CO₂ increased, which suggested that CO₂ assimilation was enhanced and that they can utilize CO₂ in the air directly, even when they are subjected to moderate stress. These findings could explain why, in P. yezoensis aquaculture, moderate exposure to air does not lead to a decrease in crop yield. However, in filamentous thalli, there were no significant differences in YII at the CO₂ concentrations tested. The expression of genes involved in the Calvin cycle in leafy thalli was higher than that in filamentous thalli. CO₂ uptake and biomass of P. yezoensis leafy thalli is larger than filamentous thalli, which may be due to its different carbon utilization mechanism and the adaptation of intertidal environment in the evolutionary process.     

Environmental assessment of German electricity generation from coal-fired power plants with amine-based carbon capture

Background, aim, and scope  

One of the most important sources of global carbon dioxide emissions is the combustion of fossil fuels for power generation. Power plants contribute more than 40% of the worldwide anthropogenic CO₂ emissions. Therefore, the increased requirements for climate protection are a great challenge for the power producers. In this context a significant increase in power plant efficiency will contribute to reduce specific CO₂ emissions. Additionally, CO₂ capture and storage (CCS) is receiving considerable attention as a greenhouse gas (GHG) mitigation option. CCS allows continued use of fossil fuels with no or little CO₂ emissions given to the atmosphere. This could approve a moderate transition to a low-carbon energy generation over the next decades. Currently, R&D activities in the field of CCS are mainly concentrated on the development of capture techniques, the geological assessment of CO₂ storage reservoirs, and on economic aspects. Although first studies on material and energy flows caused by CCS are available, a broader environmental analysis is necessary to show the overall environmental impacts of CCS. The objectives in this paper are coal-based power plants with and without CO₂ capture via mono-ethanolamine (MEA) and the comparison of their environmental effects based on life cycle assessment methodology (LCA).     

CO2 emissions from biomass combustion for bioenergy: atmospheric decay and contribution to global warming

Carbon dioxide (CO₂) emissions from biomass combustion are traditionally assumed climate neutral if the bioenergy system is carbon (C) flux neutral, i.e. the CO₂ released from biofuel combustion approximately equals the amount of CO₂ sequestered in biomass. This convention, widely adopted in life cycle assessment (LCA) studies of bioenergy systems, underestimates the climate impact of bioenergy. Besides CO₂ emissions from permanent C losses, CO₂ emissions from C flux neutral systems (that is from temporary C losses) also contribute to climate change: before being captured by biomass regrowth, CO₂ molecules spend time in the atmosphere and contribute to global warming. In this paper, a method to estimate the climate impact of CO₂ emissions from biomass combustion is proposed. Our method uses CO₂ impulse response functions (IRF) from C cycle models in the elaboration of atmospheric decay functions for biomass‐derived CO₂ emissions. Their contributions to global warming are then quantified with a unit‐based index, the GWP_bio. Since this index is expressed as a function of the rotation period of the biomass, our results can be applied to CO₂ emissions from combustion of all the different biomass species, from annual row crops to slower growing boreal forest.     

Multi-Shell Copper Catalysts for Selective Electroreduction of CO2 to Multicarbon Chemicals

Electrocatalytic CO₂ reduction (CO₂R) coupled with renewable electricity has been considered as a promising route for the sustainability transition of energy and chemical industries. However, the unsatisfactory yield of desired products, particularly multicarbon (C₂₊) products, has hindered the implementation of this technology. This work describes a strategy to enhance the yield of C₂₊ product formation in CO₂R by utilizing spatial confinement effects. The finite element simulation results suggest that increasing the number of shells in the catalyst wil lead to a high local concentration of *CO and promotes the formation of C₂₊ products. Inspired by this, Cu nanoparticles are synthesized with desired hollow multi-shell structures. The CO₂ reduction results confirm that as the number of shells increase, the hollow multi-shell copper catalysts exhibit improved selectivity toward C₂₊ products. Specifically, the Cu catalyst with 4.4-shell achieved a high selectivity of over 80% toward C₂₊ at a current density of 900 mA cm⁻². Evidence from in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy unveils that the multi-shell Cu catalyst exhibits an enhanced *CO_atop coverage and the stronger interaction with *CO_atop compared to commercial Cu, confirming the simulation results. Overall, the work promises an effective approach for boosting CO₂R selectivity toward value-added chemicals.     

Life cycle energy consumption and CO2 emission of an office building in China

Purpose  

Building is one of the main factors of energy use and greenhouse gas emissions. Reducing energy consumption and carbon dioxide (CO₂) emission from building is urgent for environmental protection and sustainable development. The objective of this study is to develop a life cycle assessment (LCA) model for an office building in China to assess its energy consumption and CO₂ emission, determine the whole life cycle phases, and the significant environmental aspects that contribute most to the impact.     

Understanding the future of lithium: Part 2, temporally and spatially resolved life‐cycle assessment modeling

An array of emerging technologies, from electric vehicles to renewable energy systems, relies on large‐format lithium ion batteries (LIBs). LIBs are a critical enabler of clean energy technologies commonly associated with air pollution and greenhouse gas mitigation strategies. However, LIBs require lithium, and expanding the supply of lithium requires new lithium production capacity, which, in turn, changes the environmental impacts associated with lithium production since different resource types and ore qualities will be exploited. A question of interest is whether this will lead to significant changes in the environmental impacts of primary lithium over time. Part one of this two‐part article series describes the development of a novel resource production model that predicts future lithium demand and production characteristics (e.g., timing, location, and ore type). In this article, part two, the forecast is coupled with anticipatory life‐cycle assessment (LCA) modeling to estimate the environmental impacts of producing battery‐grade lithium carbonate equivalent (LCE) each year between 2018 and 2100. The result is a normalized life‐cycle impact intensity for LCE that reflects the changing resource type, quantity, and region of production. Sustained growth in lithium demands through 2100 necessitates extraction of lower grade resources and mineral deposits, especially after 2050. Despite the reliance on lower grade resources and differences in impact intensity for LCE production from each deposit, the LCA results show only small to modest increases in impact, for example, carbon intensity increases from 3.2 kg CO₂e/kg LCE in 2020 to 3.3 kg CO₂e/kg LCE in 2100.     

No overall stimulation of soil respiration under mature deciduous forest trees after 7 years of CO2 enrichment

The anthropogenic rise in atmospheric CO₂ is expected to impact carbon (C) fluxes not only at ecosystem level but also at the global scale by altering C cycle processes in soils. At the Swiss Canopy Crane (SCC), we examined how 7 years of free air CO₂ enrichment (FACE) affected soil CO₂ dynamics in a ca. 100‐year‐old mixed deciduous forest. The use of ¹³C‐depleted CO₂ for canopy enrichment allowed us to trace the flow of recently fixed C. In the 7th year of growth at ～550 ppm CO₂, soil respiratory CO₂ consisted of 39% labelled C. During the growing season, soil air CO₂ concentration was significantly enhanced under CO₂‐exposed trees. However, elevated CO₂ failed to stimulate cumulative soil respiration (R_s) over the growing season. We found periodic reductions as well as increases in instantaneous rates of R_s in response to elevated CO₂, depending on soil temperature and soil volumetric water content (VWC; significant three‐way interaction). During wet periods, soil water savings under CO₂‐enriched trees led to excessive VWC (>45%) that suppressed R_s. Elevated CO₂ stimulated R_s only when VWC was ≤40% and concurrent soil temperature was high (>15 °C). Seasonal Q₁₀ estimates of R_s were significantly lower under elevated (Q₁₀=3.30) compared with ambient CO₂ (Q₁₀=3.97). However, this effect disappeared when three consecutive sampling dates of extremely high VWC were disregarded. This suggests that elevated CO₂ affected Q₁₀ mainly indirectly through changes in VWC. Fine root respiration did not differ significantly between treatments but soil microbial biomass (C_mic) increased by 14% under elevated CO₂ (marginally significant). Our findings do not indicate enhanced soil C emissions in such stands under future atmospheric CO₂. It remains to be shown whether C losses via leaching of dissolved organic or inorganic C (DOC, DIC) help to balance the C budget in this forest.     

Inclusion of carbonation during the life cycle of built and recycled concrete: influence on their carbon footprint

Background, aim, and scope  

When the service life (or primary life) of built concrete infrastructure has elapsed, a common practice is that the demolished concrete is crushed and recycled, then incorporated into new construction. LCA studies of CO₂ emissions focus on the manufacturing and construction and occupancy/utilization phases, without consideration of the demolition and application of recycled concrete into a secondary construction application. Concrete has a documented ability to chemically react with airborne carbon dioxide (CO₂); however, carbon capture (or carbonation) by concrete during the primary and secondary life, is not considered in LCA models. This paper incorporates CO₂ capture during both primary and secondary life into an LCA model for built concrete.     

Life cycle of CO2-emissions from electric vehicles and gasoline vehicles utilizing a process-relational model

This article aims at estimating life cycle CO₂ emissions from electric vehicles (EV) and gasoline vehicles (GV), although the estimation in this study is not an LCA according to ISO14040s. For this purpose, a mathematical tool called the Process-relational model was developed. The Process-relational model is used for establishing life cycle inventories. The model has a structure which improved the principle of input-output analysis in econometrics that only one product is generated by one process. This model enabled us to overcome difficulties of LCA in retracing complicated repercussions among production systems. Then, life cycle CO₂, emissions from electric vehicles (EV) and gasoline vehicles (GV) were estimated with this model. Estimated results indicated that the manufacture and driving of EV resulted in less CO₂ emissions than chose of GV. However, the difference between EV and GV dramatically changed depending on traffic situations. Namely, the difference became larger as the average velocity of the vehicles became lower. We also compared CO₂, emission from manufacturing EV with that from driving EV. The share of manufacture was shown to increase in total CO₂, emissions as the average velocity of the EV became higher. In conclusion, we clarified the direction of research and development of EV and GV for reducing the life cycle CO₂.     

Minor Changes in Vegetation and Carbon Gas Balance in a Boreal Mire under a Raised CO<Subscript>2</Subscript> or NH<Subscript>4</Subscript>NO<Subscript>3</Subscript> Supply

Increasing concentrations of carbon dioxide (CO₂) in the atmosphere or continuous nitrogen (N) deposition might alter the carbon (C) cycle in boreal mires and thus have significant impacts on the development of climate change. The atmospheric impact of the C cycle in mires is twofold: C accumulation attenuates and CH₄ release strengthens the natural greenhouse effect. We studied the effects of an increased supply of CO₂ or NH₄NO₃ on the vegetation and annual CO₂ exchange in lawns of a boreal oligotrophic mire in eastern Finland over a 2-year period. Ten study plots were enclosed with mini-FACE (Free Air Carbon Dioxide Enrichment) rings. Five plots were vented with CO₂-enriched air (target 560 ppmv), while their controls were vented with ambient air; five plots were sprayed with NH₄NO₃, corresponding to a cumulative addition of 3 g N m⁻² a⁻¹, while their controls were sprayed with distilled water only. A raised NH₄NO₃ supply seemed to affect the composition of the moss layer. Raised CO₂ did not affect the vegetation, but gross photosynthesis increased significantly. The change in net CO₂ exchange depended on the annual weather conditions. Our results suggest that C accumulation may increase in wet years and compensate for the warming effect caused by the increase in CH₄ release from this mire. In contrast, a relatively dry and warm growing period favors decomposition and can even make the CO₂ balance negative. Along with the increased CH₄ release under raised CO₂, the decreased C accumulation then increases the radiative forcing of boreal mires. Received 22 October 2001; accepted 13 May 2002.