Trade-offs between Sustainable Development Goals in carbon capture and utilisation.

Carbon capture and utilisation (CCU) provides an appealing framework to turn carbon emissions into valuable fuels and chemicals. However, given the vast energy required to activate the CO2 molecule, CCU may have implications on sustainable development that are still poorly understood due to the narrow scope of current carbon footprint-oriented assessments lacking absolute sustainability thresholds. To bridge this gap, we developed a power-chemicals nexus model to look into the future and understand how we could produce 22 net-zero bulk chemicals of crucial importance in a sustainable manner by integrating fossil, CCU routes and power technologies, often assessed separately. We evaluated the environmental performance of these technologies in terms of their contribution to 5 Sustainable Development Goals (SDGs), using 16 life cycle assessment metrics and 9 planetary boundaries (PB) to quantify and interpret the impact values. We found that fossil chemicals could hamper the attainment of SDG 3 on good health and well-being and SDG 13 on climate change. CCU could help meet SDG 13 but would damage other SDGs due to burden-shifting to human health, water scarcity, and minerals and metals depletion impacts. The collateral damage could be mitigated by judiciously combining fossil and CCU routes with carbon-negative power sources guided by optimisation models incorporating SDGs-based performance criteria explicitly. Our work highlights the importance of embracing the SDGs in technology development to sensibly support the low-carbon energy and chemicals transition.

Deep eutectic solvents for improved biomass pretreatment: Current status and future prospective towards sustainable processes.

Pretreatment processes - recognized as critical steps for efficient biomass refining - have received much attention over the last two decades. In this context, deep eutectic solvents (DES) have emerged as a novel alternative to conventional solvents representing a step forward in achieving more sustainable processes with both environmental and economic benefits. This paper presents an updated review of the state-of-the-art of DES-based applications in biorefinery schemes. Besides describing the fundamentals of DES composition, synthesis, and recycling, this study presents a comprehensive review of existing techno-economic and life cycle assessment studies. Challenges, barriers, and perspectives for the scale-up of DES-based processes are also discussed.

Human and planetary health implications of negative emissions technologies.

Meeting the 1.5 °C target may require removing up to 1,000 Gtonne CO2 by 2100 with Negative Emissions Technologies (NETs). We evaluate the impacts of Direct Air Capture and Bioenergy with Carbon Capture and Storage (DACCS and BECCS), finding that removing 5.9 Gtonne/year CO2 can prevent <9·102 disability-adjusted life years per million people annually, relative to a baseline without NETs. Avoiding this health burden-similar to that of Parkinson's-can save substantial externalities (≤148 US$/tonne CO2), comparable to the NETs levelized costs. The health co-benefits of BECCS, dependent on the biomass source, can exceed those of DACCS. Although both NETs can help to operate within the climate change and ocean acidification planetary boundaries, they may lead to trade-offs between Earth-system processes. Only DACCS can avert damage to the biosphere integrity without challenging other biophysical limits (impacts ≤2% of the safe operating space). The quantified NETs co-benefits can incentivize their adoption.

Social life cycle assessment of green methanol and benchmarking against conventional fossil methanol.

Green methanol could play a major role in decarbonising both the chemical and energy sectors. While techno-economic and environmental studies on green methanol following a life-cycle perspective are available, its social implications from a supply-chain standpoint remain largely unexplored. In order to fill this gap, this work presents the first social life cycle assessment of green methanol produced with CO2 directly captured from the air and hydrogen from wind power electrolysis. When compared to conventional methanol from natural gas, the results suggest an unfavourable performance of green methanol under negative social indicators (forced labour, women in the sectoral labour force, health expenditure, social responsibility promotion, and fair salary) due to the increased supply-chain complexity of the green system. In contrast, green methanol would outperform its conventional counterpart in terms of sectoral contribution to economic development, a positive social indicator which would benefit from the increase in working hours. Besides future consideration of a higher number of positive indicators and potential improvements in country- and sector-specific risk levels towards high-quality social and working conditions, an enhanced social life-cycle performance of green methanol requires technical improvements to reduce the high demand for energy inputs and equipment across its supply chain. Acknowledging decarbonisation as the actual driver of green methanol deployment, future social studies are suggested to focus on the comparison of renewable alternatives for its production and the effect of social regulations.

Delaying carbon dioxide removal in the European Union puts climate targets at risk.

Carbon dioxide removal (CDR) will be essential to meet the climate targets, so enabling its deployment at the right time will be decisive. Here, we investigate the still poorly understood implications of delaying CDR actions, focusing on integrating direct air capture and bioenergy with carbon capture and storage (DACCS and BECCS) into the European Union power mix. Under an indicative target of -50 Gt of net CO2 by 2100, delayed CDR would cost an extra of 0.12-0.19 trillion EUR per year of inaction. Moreover, postponing CDR beyond mid-century would substantially reduce the removal potential to almost half (-35.60 Gt CO2) due to the underused biomass and land resources and the maximum technology diffusion speed. The effective design of BECCS and DACCS systems calls for long-term planning starting from now and aligned with the evolving power systems. Our quantitative analysis of the consequences of inaction on CDR-with climate targets at risk and fair CDR contributions at stake-should help to break the current impasse and incentivize early actions worldwide.

The role of hydrogen in heavy transport to operate within planetary boundaries.

Green hydrogen, i.e., produced from renewable resources, is attracting attention as an alternative fuel for the future of heavy road transport and long-distance driving. However, the benefits linked to zero pollution at the usage stage can be overturned when considering the upstream processes linked to the raw materials and energy requirements. To better understand the global environmental implications of fuelling heavy transport with hydrogen, we quantified the environmental impacts over the full life cycle of hydrogen use in the context of the Planetary Boundaries (PBs). The scenarios assessed cover hydrogen from biomass gasification (with and without carbon capture and storage [CCS]) and electrolysis powered by wind, solar, bioenergy with CCS, nuclear, and grid electricity. Our results show that the current diesel-based-heavy transport sector is unsustainable due to the transgression of the climate change-related PBs (exceeding standalone by two times the global climate-change budget). Hydrogen-fuelled heavy transport would reduce the global pressure on the climate change-related PBs helping the transport sector to stay within the safe operating space (i.e., below one-third of the global ecological budget in all the scenarios analysed). However, the best scenarios in terms of climate change, which are biomass-based, would shift burdens to the biosphere integrity and nitrogen flow PBs. In contrast, burden shifting in the electrolytic scenarios would be negligible, with hydrogen from wind electricity emerging as an appealing technology despite attaining higher carbon emissions than the biomass routes.

Process modelling and life cycle assessment coupled with experimental work to shape the future sustainable production of chemicals and fuels.

Meeting the sustainable development goals and carbon neutrality targets requires transitioning to cleaner products, which poses significant challenges to the future chemical industry. Identifying alternative pathways to cover the growing demand for chemicals and fuels in a more sustainable manner calls for close collaborative programs between experimental and computational groups as well as new tools to support these joint endeavours. In this broad context, we here review the role of process systems engineering tools in assessing and optimising alternative chemical production patterns based on renewable resources, including renewable carbon and energy. The focus is on the use of process modelling and optimisation combined with life cycle assessment methodologies and network analysis to underpin experiments and generate insight into how the chemical industry could optimally deliver chemicals and fuels with a lower environmental footprint. We identify the main gaps in the literature and provide directions for future work, highlighting the role of PSE concepts and tools in guiding the future transition and complementing experimental studies more effectively.

Global environmental and nutritional assessment of national food supply patterns: Insights from a data envelopment analysis approach.

The global food system inextricably connects human health and environmental integrity. It holds the transformative capability to significantly reduce levels of environmental degradation, caused by current food production practices, and alleviate the 'triple burden' of malnutrition, existing due to food consumption patterns. System-wide transitions are therefore paramount to tackling environmental and nutritional challenges that are exacerbated by a rapidly growing population. This work presents a novel application of Data Envelopment Analysis (DEA) to study the sustainability of food supply patterns around the world and appraise the potential to lower environmental pressure without compromising the supply of calories and nutritional quality. By relating environmental impacts to caloric availability and nutritional adequacy, DEA computes a relative performance score for 139 countries and identifies only 18 countries with per capita food supplies that are 'efficient' in transforming five environmental inputs (land use, greenhouse gas emissions, acidification potential, eutrophication potential and freshwater withdrawals) into calories and nutrition. The widespread extent of 'inefficiency' stresses that the significant opportunity and need to reduce environmental impacts from food is truly global and extensive. Results of this analysis also provide quantitative information on the varying degrees of potential to improve the ways in which each nation's population is fed and therefore offers country-specific insight for decision-makers into the integration of environmental and nutritional outcomes for sustainable development.

Powering sustainable development within planetary boundaries.

The concept of planetary boundaries identifies a safe space for humanity. Current energy systems are primarily designed with a focus on total cost minimization and bounds on greenhouse gas emissions. Omitting planetary boundaries in energy systems design can lead to energy mixes unable to power our sustainable development. To overcome this conceptual limitation, we here incorporate planetary boundaries into energy systems models, explicitly linking energy generation with the Earth's ecological limits. Taking the United States as a testbed, we found that the least cost energy mix that would meet the Paris Agreement 2 degrees Celsius target still transgresses five out of eight planetary boundaries. It is possible to meet seven out of eight planetary boundaries concurrently by incurring a doubling of the cost compared to the least cost energy mix solution (1.3% of the United States gross domestic product in 2017). Due to the stringent downscaled planetary boundary on biogeochemical nitrogen flow, there is no energy mix in the United States capable of satisfying all planetary boundaries concurrently. Our work highlights the importance of considering planetary boundaries in energy systems design and paves the way for further research on how to effectively accomplish such integration in energy related studies.