Revitalizing plastic wastes employing bio-circular-green economy principles for carbon neutrality

The use of plastics has become deeply ingrained in our society, and there are no indications that its prevalence will decrease in the foreseeable future. This article provides a comprehensive overview of the global plastic waste disposal landscape, examining it through regional perspectives, various management technologies (dumping or landfilling, incineration, and reuse and recycling), and across different sectors including agriculture and food, textile, tourism, and healthcare. Notably, this study compiles the findings on life-cycle carbon footprints associated with various plastic waste management practices as documented in the literature. Employing the bio-circular-green economy model, we advocate for the adoption of streamlined and sustainable approaches to plastic management. Unique management measures are also discussed including the utilization of bioplastics combined with smart and efficient collection processes that facilitate recycling, industrial composting, or anaerobic digestion. Moreover, the integration of advanced recycling methods for conventional plastics with renewable energy, the establishment of plastic tax and credits, and the establishment of extended producer responsibility are reviewed. The success of these initiatives relies on collaboration and support from peers, industries, and consumers, ultimately contributing to informed decision-making and fostering sustainable practices in plastic waste management.

Sustainability in the IVF laboratory: recommendations of an expert panel

The healthcare industry is a major contributor to greenhouse gas emissions. Assisted reproductive technology is part of the larger healthcare sector, with its own heavy carbon footprint. The social, economic and environmental costs of this collective carbon footprint are becoming clearer, as is the impact on human reproductive health. Alpha Scientists in Reproductive Medicine and the International IVF Initiative collaborated to seek and formulate practical recommendations for sustainability in IVF laboratories. An international panel of experts, enthusiasts and professionals in reproductive medicine, environmental science, architecture, biorepository and law convened to discuss the topics of importance to sustainability. Recommendations were issued on how to build a culture of sustainability in the workplace, implement green design and building, use life cycle analysis to determine the environmental impact, manage cryostorage more sustainably, and understand and manage laboratory waste with prevention as a primary goal. The panel explored whether the industry supporting IVF is sustainable. An example is provided to illustrate the application of green principles to an IVF laboratory through a certification programme. The UK legislative landscape surrounding sustainability is also discussed and a few recommendations on 'Green Conferencing' are offered.

Life-cycle assessment of a microalgae-based fungicide under a biorefinery approach

The aim of this work was to perform a life-cycle analysis of the production process of a fungicide based on amphidinols. Two scenarios were evaluated: (1) biorefinery process -biofungicide, fatty acids and carotenoids were considered as co-products-, and (2) biofungicide as only product. Inventory data were taken and scaled-up from previous work on pilot-scale reactors, as well as lab-scale downstream equipment. A yearly production of 22,000 L of fungicide, was selected as the production objective. Despite, photosynthetic biomass is a sink of anthropogenic CO2, harvesting and downstream processing have large carbon footprints that exceed the biomass fixed carbon. Producing the biofungicide resulted in 34.61 and 271.33 ton of CO2e (15 years) for the Scenarios 1 and 2, respectively. Different commercial agricultural fungicides were compared with the microalgal fungicide. A lower impact of the microalgal product for most of the indicators, including carbon footprint, was shown.

Vehicle-cycle and life-cycle analysis of medium-duty and heavy-duty trucks in the United States

Medium- and heavy-duty vehicles account for a substantial portion (25 %) of transport-related greenhouse gas (GHG) emissions in the United States. Efforts to reduce these emissions focus primarily on diesel hybrids, hydrogen fuel cells, and battery electric vehicles. However, these efforts ignore the high energy intensity of producing lithium (Li)-ion batteries and the carbon fiber used in fuel-cell vehicles. Here, we conduct a life-cycle analysis to compare the impacts of the vehicle manufacturing cycle for Class 6 (pickup-and-delivery, PnD) and Class 8 (day- and sleeper-cab) trucks with diesel, electric, fuel-cell, and hybrid powertrains. We assume that all trucks were manufactured in the US in 2020 and operated over 2021-2035, and we developed a comprehensive materials inventory for all trucks. Our analysis reveals that common systems (trailer/van/box, truck body, chassis, and lift-gates) dominate the vehicle-cycle GHG emissions (64-83 % share) of diesel, hybrid, and fuel-cell powertrains. Conversely, propulsion systems (lithium-ion batteries and fuel-cell systems) contribute substantially to these emissions for electric (43-77 %) and fuel-cell powertrains (16-27 %). These vehicle-cycle contributions arise from the extensive use of steel and aluminum, the high energy/GHG intensity of producing lithium-ion batteries and carbon fiber, and the assumed battery replacement schedule for Class 8 electric trucks. A switch from the conventional diesel powertrain to alternative electric and fuel-cell powertrains causes an increase in vehicle-cycle GHG emissions (by 60-287 % and 13-29 %, respectively) but leads to substantial GHG reductions when considering the combined vehicle- and fuel-cycles (Class 6: 33-61 %, Class 8: 2-32 %), highlighting the benefits of this shift in powertrains and energy supply chain. Finally, payload variation significantly influences the relative life-cycle performance of different powertrains, while LIB cathode chemistry has a negligible effect on BET life-cycle GHGs.

Lignin valorization: Status, challenges and opportunities

As an abundant aromatic biopolymer, lignin has the potential to produce various chemicals, biofuels of interest through biorefinery activities and is expected to benefit the future circular economy. However, lignin valorization is hindered by a series of constraints such as heterogeneous polymeric nature, intrinsic recalcitrance, strong smell, dark colour, challenges in lignocelluloses fractionation and the presence of high bond dissociation enthalpies in its functional groups etc. Nowadays, industrial lignin is mostly combusted for electricity production and the recycling of inorganic compounds involved in the pulping process. Given the research and development on lignin valorization in recent years, important applications such as lignin-based hydrogels, surfactants, three-dimensional printing materials, electrodes and production of fine chemicals have been systematically reviewed. Finally, this review highlights the main constraints affecting industrial lignin valorization, possible solutions and future perspectives, in the light of its abundance and its potential applications reported in the scientific literature.

Environmental and energetic analysis of coupling a biogas combined cycle power plant with carbon capture, organic Rankine cycles and CO2 utilization processes

Greenhouse gas emissions from power plants that use fossil fuels cause a serious impact to the environment, for this reason the use of renewable energy technologies is an important alternative as a way of combatting climate change. The production of power via biomass is considered as a carbon neutral energy resource, but it is well known that the non-fossil CO₂ emitted from this type of processes can also be captured. In order to do so, in this work it is proposed a match between a Biogas combined cycle power plant and postcombustion carbon capture process, to capture the CO₂ produced by the biogas combustion, and also it considered a match with an organic Rankine cycle that uses the wasted energy of the combustion gases. Additionally, it is considered that the captured carbon is used to produce some value-added chemicals and fuels. Environmental and energetic evaluations were carried out for the coupling of those technologies. The implementation of the carbon capture plant, results on a diminution of the 87% of the emission of the combined cycle power plant. The life cycle analysis results show that the study case of Syngas production via dry reforming of methane, presents the lower global warming potential (0.088 CO₂-eq kg/kg) and it was also found that the global warming potential has a reduction with the help of the mass integration between the different alternatives of CO₂ utilization. Finally, it was found an annual reduction of 0.055 CO₂-eq t for the system with mass integration compared with the cases without mass integration.

Life-cycle assessment of hydrogen production via catalytic gasification of wheat straw in the presence of straw derived biochar catalyst

The environmental footprints of H₂productionviacatalytic gasification of wheat straw using straw-derived biochar catalysts were examined. The functional unit of 1 kg of H₂was adopted in the system boundaries, which includes 5 processes namely biomass collection and pre-treatment units (P1), biochar catalyst preparation using fast pyrolysis unit (P2), two-stage pyrolysis-gasification unit (P3), products separation unit (P4), and H₂distribution to downstream plants (P5). Based on the life-cycle assessment, the hot spots in this process were identified, the sequence was as follows: P4 > P2 > P1 > P3 > P5. The end-point impacts score for the process was found to be 93.4017 mPt. From benchmarking analysis, the proposed straw-derived biochar catalyst was capable of offering almost similar catalytic performance with other metal-based catalysts with a lower environmental impact.

Dataset concerning the hourly conversion factors for the cumulative energy demand and its non-renewable part, and hourly GHG emission factors of the Swiss mix during a one-year period (2016 and 2017)

The provided data are the hourly CO2-eq emission factors, and the hourly conversion factors for the cumulative energy demand and its non-renewable part for the Swiss electricity mix over one year (2016 and 2017). These data have been assessed on the base of an inventory of the technology used for electricity generation and an attributional life-cycle approach according to the methodology presented in Vuarnoz and Jusselme (2018). Compared with Vuarnoz and Jusselme [2], electricity imports from Italy to Switzerland are not neglected anymore, and lead to more accurate output data. The utility of the proposed data lies in the multiple possible applications. The presented data are necessary for conducting a life cycle assessment of all processes and products using electricity in Switzerland. Moreover, the presented data could serve as a sustainable benchmark of electricity when implementing renewable energy systems and energy storage [7]. Because of their temporal accuracy, the hourly conversion factors enable the development of energy management strategies taking into account the time-dependent life cycle impacts. Finally, they can be used for the quantitative follow-up of the decarbonization process of the grid electricity at the national level over a given lapse of time.

Impact of various microalgal-bacterial populations on municipal wastewater bioremediation and its energy feasibility for lipid-based biofuel production

The microalgal-bacterial co-cultivation was adopted as an alternative in making microbial-based biofuel production to be more feasible in considering the economic and environmental prospects. Accordingly, the microalgal-bacterial symbiotic relationship was exploited to enhance the microbial biomass yield, while bioremediating the nitrogen-rich municipal wastewater. An optimized inoculation ratio of microalgae and activated sludge (AS:MA) was predetermined and further optimization was performed in terms of different increment ratios to enhance the bioremediation process. The nitrogen removal was found accelerating with the increase of the increment ratios of inoculated AS:MA, though all the increment ratios had recorded a near complete total nitrogen removal (94-95%). In light of treatment efficiency and lipid production, the increment ratio of 0.5 was hailed as the best microbial population size in accounting the total nitrogen removal efficiency of 94.45%, while not compromising the lipid production of 0.241 g/L. Moreover, the cultures in municipal wastewater had attained higher biomass and lipid productions of 1.42 g/L and 0.242 g/L, respectively, as compared with the synthetic wastewater which were only 1.12 g/L (biomass yield) and 0.175 g/L (lipid yield). This was possibly due to the presence of trace elements which had contributed to the increase of biomass yield; thus, higher lipid attainability from the microalgal-bacterial culture. This synergistic microalgal-bacterial approach had been proven to be effective in treating wastewater, while also producing useful biomass for eventual lipid production with comparable net energy ratio (NER) value of 0.27, obtained from the life-cycle analysis (LCA) studies. Thereby, contributing towards long-term sustainability and possible commercialization of microbial-based biofuel production.

Life cycle environmental impacts of biogas production and utilisation substituting for grid electricity, natural gas grid and transport fuels

In this study, life cycle analysis (LCA) has been applied to evaluate the environmental impacts of biogas production and utilisation substituting for grid electricity, natural gas grid and transport fuels, with a focus on Greenhouse Gas (GHG) emissions. The results demonstrate significant reductions in greenhouse gas emissions for the biogas as a fuel scenario due to the displacement of fossil petrol and diesel fuels (scenario 3), with savings of between 524 and 477 kg of CO₂ equivalent (per MWh of energy provided by the fuels). The utilisation of biogas for electricity generation saves around 300 kg of CO₂ equivalent per MWh of electricity injected into the grid (scenario 1), while Scenario 2, the upgrading of biogas to biomethane and its injection into the gas grid for heating saves 191 kg of CO₂ equivalent (per MWh of energy generated by the biomethane). The results emphasise the benefits of using life cycle analysis to provide an evidence based for bioenergy policy. The limitations of the research are identified and recommendations made for future research priorities to further the use of LCA in the evaluation of bioenergy systems.

Cradle-to-grave life-cycle assessment within the built environment: Comparison between the refurbishment and the complete reconstruction of an office building in Belgium

In the current context of the necessary sustainability transition of the built environment, it is widely recognized that buildings are a major contributor to the energy consumption of fossil fuels and the emission of CO₂. Most of the debates, policies and research are however dedicated to the sole construction of new very efficient (up to zero-energy) building, neglecting the potential of actions on the existing building stock. In this context, we argue that LCA tools are of a huge interest to objectivise the need to refurbish old buildings, in order to increase their energy efficiency and extend their life span, and to compare this strategy to the demolition/reconstruction of buildings. To achieve this aim, this paper aims at updating an existing tool that enables to carry out the life cycle assessment of buildings, by taking into account demolition and construction phases. Then, the tool is applied to one case study of the low-energy refurbishment of a public office building in Brussels, to compare the impacts of the complete demolition followed by a complete reconstruction (rebuild project) to the retrofitting of the existing building (retrofit project). Our main findings confirm the huge impact of the use phase, highlight the impact (energy and CO₂ emissions) of the construction and demolition phases and show that the in-depth renovation of this building leads to lower environmental indicators compared to its full reconstruction. The tool and results provided in this paper support the development of policies in favour of the retrofitting of the existing building stock and highlight the importance of including the whole life cycle of the building in the analysis.

Science foresight using life-cycle analysis, text mining and clustering: A case study on natural ventilation

Science foresight comprises a range of methods to analyze past, present and expected research trends, and uses this information to predict the future status of different fields of science and technology. With the ability to identify high-potential development directions, science foresight can be a useful tool to support the management and planning of future research activities. Science foresight analysts can choose from a rather large variety of approaches. There is, however, relatively little information about how the various approaches can be applied in an effective way. This paper describes a three-step methodological framework for science foresight on the basis of published research papers, consisting of (i) life-cycle analysis, (ii) text mining and (iii) knowledge gap identification by means of automated clustering. The three steps are connected using the research methodology of the research papers, as identified by text mining. The potential of combining these three steps in one framework is illustrated by analyzing scientific literature on wind catchers; a natural ventilation concept which has received considerable attention from academia, but with quite low application in practice. The knowledge gaps that are identified show that the automated foresight analysis is indeed able to find uncharted research areas. Results from a sensitivity analysis further show the importance of using full-texts for text mining instead of only title, keywords and abstract. The paper concludes with a reflection on the methodological framework, and gives directions for its intended use in future studies.

Well-to-wake analysis of ethanol-to-jet and sugar-to-jet pathways

BACKGROUND

To reduce the environmental impacts of the aviation sector as air traffic grows steadily, the aviation industry has paid increasing attention to bio-based alternative jet fuels (AJFs), which may provide lower life-cycle petroleum consumption and greenhouse gas (GHG) emissions than petroleum jet fuel. This study presents well-to-wake (WTWa) results for four emerging AJFs: ethanol-to-jet (ETJ) from corn and corn stover, and sugar-to-jet (STJ) from corn stover via both biological and catalytic conversion. For the ETJ pathways, two plant designs were examined: integrated (processing corn or corn stover as feedstock) and distributed (processing ethanol as feedstock). Also, three H₂ options for STJ via catalytic conversion are investigated: external H₂ from natural gas (NG) steam methane reforming (SMR), in situ H₂, and H₂ from biomass gasification.

RESULTS

Results demonstrate that the feedstock is a key factor in the WTWa GHG emissions of ETJ: corn- and corn stover-based ETJ are estimated to produce WTWa GHG emissions that are 16 and 73%, respectively, less than those of petroleum jet. As for the STJ pathways, this study shows that STJ via biological conversion could generate WTWa GHG emissions 59% below those of petroleum jet. STJ via catalytic conversion could reduce the WTWa GHG emissions by 28% with H₂ from NG SMR or 71% with H₂ from biomass gasification than those of petroleum jet. This study also examines the impacts of co-product handling methods, and shows that the WTWa GHG emissions of corn stover-based ETJ, when estimated with a displacement method, are lower by 11 g CO₂e/MJ than those estimated with an energy allocation method.

CONCLUSION

Corn- and corn stover-based ETJ as well as corn stover-based STJ show potentials to reduce WTWa GHG emissions compared to petroleum jet. Particularly, WTWa GHG emissions of STJ via catalytic conversion depend highly on the hydrogen source. On the other hand, ETJ offers unique opportunities to exploit extensive existing corn ethanol plants and infrastructure, and to provide a boost to staggering ethanol demand, which is largely being used as gasoline blendstock.

Life-cycle analysis of bio-based aviation fuels

Well-to-wake (WTWa) analysis of bio-based aviation fuels, including hydroprocessed renewable jet (HRJ) from various oil seeds, Fischer-Tropsch jet (FTJ) from corn-stover and co-feeding of coal and corn-stover, and pyrolysis jet from corn stover, is conducted and compared with petroleum jet. WTWa GHG emission reductions relative to petroleum jet can be 41-63% for HRJ, 68-76% for pyrolysis jet and 89% for FTJ from corn stover. The HRJ production stage dominates WTWa GHG emissions from HRJ pathways. The differences in GHG emissions from HRJ production stage among considered feedstocks are much smaller than those from fertilizer use and N2O emissions related to feedstock collection stage. Sensitivity analyses on FTJ production from coal and corn-stover are also conducted, showing the importance of biomass share in the feedstock, carbon capture and sequestration options, and overall efficiency. For both HRJ and FTJ, co-product handling methods have significant impacts on WTWa results.