Synergies and gaps between circularity assessment and Life Cycle Assessment (LCA)

Life cycle assessment and industrial synergy for carbon reduction: A circular economy approach

In the face of the climate change crisis, circular economy (CE) is put forward as a promising key to the sustainable development goals (SDGs) riddle. In this context that affects developed and developing countries alike, circular initiatives arise, such is the case for Morocco where an industrial synergy based on the CE concept of 'waste is food' can be envisioned between the local phosphate and cement industries. In order to support and guide this initiative, a life cycle assessment (LCA) was conducted to compare the environmental performance of the production of ordinary Portland cement (OPC), limestone calcined clay cement (LC3) and a phosphate waste-based cement known as calcined marl cement (CMC). In addition to a mass-based functional unit (FU), a performance-based FU was adopted to account for the 'longer service lives' concept of CE, which necessitated the estimation of cements' service lives and CO2 uptake potentials. Results show that CMC and LC3 production respectively reduce impacts on global warming by 23 % and 60 %, while the country aims for a 18.3 % reduction by 2030; mineral resource scarcity is reduced by 30 % and 48 %; and other impacts by 10 % and 40 % compared with OPC. This is chiefly due to CMC and LC3's better durability performance and lower clinker content. Using LCA results, carbon tax was pre-estimated to drop by 9 and 18$/ton of cement for CMC and LC3. A life cycle costing and a social LCA must be conducted to comprehensively guide stakeholders in their decision-making process regarding a phosphate-cement synergy.

Life cycle assessment on the role of H2S-based hydrogen via H2S-methane reforming for the production of sustainable fuels

Meeting current decarbonization targets requires a shift to a hydrogen energy nexus, yet, water is a valuable resource for hydrogen production, shifting the perspective to the use of H2S instead within the context of circular economy. A comprehensive understanding of the environmental impacts, using a cradle-to-gate life cycle assessment (LCA), was developed focusing on the operation of hydrogen sulfide-methane reforming (H2SMR) for H2 production benchmarked to conventional technologies, steam methane reforming (SMR) and SMR + carbon capture (CC), as feedstock to produce sustainable fuels (i.e., methanol and ammonia). The environmental impact of the different application routes was evaluated in terms of normalized impact categories and monetized indicators by calculating the environmental damage cost. The results indicated that the environmental impact increased when moving from H2SMR < SMR + CC < SMR, and ammonia compared to methanol production. Across all the processing schemes, the impact on human health is the largest based on the normalized values, representing 63.0-85.0 % of endpoint level impacts. Within the scope of climate change, the use of H2SMR is indeed more supportive of climate mitigation efforts, reducing environmental costs related to GWP by 58.0 % from SMR and 12.0 % from SMR + CC. Addressing these concerns demands a comprehensive overhaul of existing practices within the oil and gas sector concerning raw material extraction, coupled with the implementation of effective waste management strategies to significantly minimize adverse environmental effects.

Chemical catalytic upgrading of polyethylene terephthalate plastic waste into value-added materials, fuels and chemicals

The substantial production of polyethylene terephthalate (PET) products, coupled with high abandonment rates, results in significant environmental pollution and resource wastage. This has prompted global attention to the development of rational strategies for PET waste treatment. In the context of renewability and sustainability, catalytic chemical technology provides an effective means to recycle and upcycle PET waste into valuable resources. In this review, we initially provide an overview of strategies employed in the thermocatalytic process to recycle PET waste into valuable carbon materials, fuels and typical refined chemicals. The effect of catalysts on the quality and quantity of specific products is highlighted. Next, we introduce the development of renewable-energy-driven electrocatalytic and photocatalytic systems for sustainable PET waste upcycling, focusing on rational catalysts, innovative catalytic system design, and corresponding underlying catalytic mechanisms. Moreover, we discuss advantages and disadvantages of three chemical catalytic strategies. Finally, existing limitations and outlook toward controllable selectivity and yield enhancement of value-added products and PET upvaluing technology for scale-up applications are proposed. This review aims to inspire the exploration of waste-to-treasure technologies for renewable-energy-driven waste management toward a circular economy.