Carbon footprint of alternative processes for pea waste management

Sub-standard peas, a by-product from the pea industry, could be valorized for the production of whole flours suitable for human consumption. Such valorization route would require a drying stage, which could be carried out using consolidated techniques such as air drying and freeze-drying or a novel approch based on the use of supercritical carbon dioxide. In this work, a comparative Life Cycle Assessment (LCA) was performed to determine the carbon footprint of the valorization of sub-standard peas using the three alternative drying processes at both laboratory and prospective industrial scales. The study adopts a gate-to-ate perspective, considering as functional unit 1 kg of fresh peas to be processed. Primary data related to the drying process at the lab scale and proper upscaling techniques were used to perform mass and energy balance and compile the life cycle inventory. Results show that, at the laboratory scale, the most significant contributors to environmental impact are storage and drying, with freeze drying emerging as the most energy-intensive alternative due to its prolonged processing time. Supercritical CO₂ drying also has a high impact, primarily due to solvent consumption, while air drying presents a lower carbon footprint. When scaling up to the industrial level, the carbon footprint significantly decreases for all technologies, particularly for freezing and storage. Supercritical CO₂ drying remains heavily influenced by solvent use: a sensitivity analysis demonstrated a 60% reduction in emissions when optimizing ethanol recovery and process kinetics. This work contributes to the discussion on the sustainability of alternative pea waste valorisation techniques, offering pathways for industrial implementation while identifying open questions for future research.