Ángel Galán-Martín

The construction sector is a major contributor to resource consumption, waste generation, and global impacts, underscoring the need for circular strategies while reducing environmental burdens. In this study, biochar-based geopolymers incorporating construction and demolition waste are investigated as a pathway that closes material loops while enabling carbon mitigation. An experimental design was first applied to evaluate the influence of biochar incorporation (0–7.50 wt %) on material performance. A compromise formulation containing 5.00 wt % biochar was identified, providing a favorable balance between strength and matrix integrity, with a compressive strength of 24.9 ± 0.9 MPa after 28 curing days, alongside reduced porosity and water absorption relative to the control. The selected formulation was subsequently assessed using prospective life cycle assessment to quantify environmental impacts under current (2020) and future net-zero (2050NZ) energy scenarios. Under present-day conditions, the geopolymer exhibits a carbon footprint of ∼116 kg CO2-eq t–1, corresponding to a ∼86% reduction compared with Portland cement, driven by clinker avoidance and permanent carbon sequestration associated with biochar (∼146 kg CO2-eq t–1). Under the 2050NZ scenario, the geopolymer becomes net-negative (–107 kg CO2-eq t–1), whereas cement remains carbon-positive due to residual process emissions. The multi-indicator assessment reveals trade-offs in water consumption and land occupation associated with biomass sourcing and alkaline activators, although most energy- and emission-related impacts improve under future decarbonized systems. Overall, the integrated experimental-prospective framework demonstrates that biochar-based geopolymers represent a promising class of circular, low-carbon, and potentially carbon-negative construction materials required for deep decarbonization of the built environment.

Meeting climate goals will most likely require large-scale carbon dioxide removal, yet its sustainability implications remain poorly understood. Here, we conduct a prospective life cycle assessment of multiple negative emissions technologies and practices, integrating mineral resource, health, and absolute sustainability indicators to quantify impacts between 2030 and 2050. Our comprehensive analysis reveals previously overlooked bottlenecks: biochar and bioenergy with carbon capture and storage could sharply raise nutrient demand, further compromising food security, while direct air carbon capture and storage and ocean liming could critically exacerbate the mining levels of key mineral resources, despite their lower collateral damage. These findings will help guide the sustainable and safe expansion of the carbon dioxide removal industry by balancing multiple risks, thereby minimizing unintended environmental and resource-related consequences.

Have you ever wondered what happens to the leftovers from plants and fruits, like the pulp left after making juice or oil? These leftovers are called biomass, and instead of throwing them away as waste, we can reuse them. Scientists are discovering smart ways to turn biomass into useful things—a process called valorization. This article looks at olive waste biomass, which is the material left after making olive oil. With special tools and processes, olive biomass can be changed into energy to heat homes, fuel for cars and trucks, or ingredients for cosmetics and medicines. By learning the chemistry behind olive biomass you will discover how to reuse it, which protects the environment, and supports local communities. This idea is part of what is called a circular economy, where nothing is wasted and everything gets reused—helping to build a cleaner and better future for everyone.

Ceramic manufacturing is a hard-to-abate industry given its intrinsic reliance on high-temperature operations and fossil-based thermal energy. Capitalizing on detailed industrial data, this study presents a prospective life cycle assessment of decarbonization pathways for ceramic brick production grounded in forward-looking energy system projections. Six technology adoption scenarios are evaluated for 2020 and 2050 under both current policy and net-zero trajectories. Results show that integrating heat pumps today for low-temperature drying can reduce the global warming potential (GWP) by up to 24% compared to continued natural gas use. Fuel-switching to hydrogen or biogas enables substantial reductions in the GWP of around 85% under net-zero conditions. Notably, coupling biogas combustion with carbon capture and storage (CCS) already achieves net-negative emissions, reaching -29.95 kg CO₂-eq per tonne in 2020 and up to -73.05 kg by 2050, positioning it as a viable carbon dioxide removal strategy. However, several scenarios exhibit important trade-offs, including increased water consumption and land occupation, particularly in hydrogen and biobased pathways. Our findings underscore the need for integrated policies and multicriteria decision-making considering impacts beyond climate change to align energy transition and technology adoption, ensuring decarbonization strategies in the ceramic sector are both practical and sustainable.

European Union (EU) policies and regulations aim to transform the light-duty road passenger transport (LRPT) sector by setting development targets and incentivizing technologies such as battery electric vehicles. However, it remains uncertain whether these transformation pathways align with the Earth's ecological limits. This study applies a planetary boundary-based life cycle assessment (LCA) to the entire EU LRPT sector, examining seven powertrain options across climate and policy scenarios under a prospective approach that explicitly accounts for how future economic trends will affect the sector’s performance. Results show that the transport sector will likely fail to remain within the Earth’s carrying capacity, even with projected technology and supply chain advances. In five of the sixteen impact categories, namely climate change, land use, particulate matter formation, freshwater ecotoxicity, and material resource use (minerals and metals), the LRPT sector already exceeds the EU safe operating space share. Climate change transgression decreases from 2.4 to 1.3 under a < 2°C pathway, but material resource use rises from 1.4 to 2.8, with other transgressed categories also worsening. Regional and time-explicit LCA reveals that local electricity mixes and temporal dynamics play a major role, pointing towards the need for localized measures implemented at the right location and time. Looking ahead, systemic reduction strategies will be essential to operate within the Earth’s carrying capacity, including expanded recycling, circular business models, alternative materials, higher vehicle occupancy, and modal shifts toward public and active transport. While not evaluated in detail in this study, these measures, together with policy dialogues on sufficiency and cross-sectoral trade-offs, could form the basis for embedding absolute sustainability principles into long-term EU transport planning, supported by life cycle optimization approaches with high technological, spatial, and temporal granularity levels.