Sustainable Recovery and Reuse of Respiration-Derived CO2 from Controlled-Atmosphere Fruit Storage for Greenhouse Enrichment

Ultra-low oxygen (ULO) fruit-storage systems generate respiration-derived CO2 that is removed by cyclic adsorption-regeneration systems but is commonly discharged as regeneration exhaust without reuse. This study evaluated a decentralized recovery and redistribution architecture for converting this transient exhaust from commercial apple storage into a secondary CO2 source for controlled-environment agriculture. Operational monitoring was performed using a STOREX ST500 adsorber installed in commercial ULO infrastructure. Estimated CO2 concentration in regeneration exhaust ranged from 0.33 to 7.09%, and the theoretical CO2 load reached 0.69–3.99 kg per cycle in ULO chambers. During the monitored storage season, the ULO installation generated approximately 4.5 t CO2; assuming 50–70% recovery, approximately 2.3–3.2 t CO2 could be recovered and reused as greenhouse-enrichment gas. Stored apples alone could theoretically generate approximately 1.1–4.4 Mt CO2 per 180 d storage season globally, if about two-thirds of global apple production is assumed to be held in refrigerated controlled-atmosphere storage. The proposed architecture integrates gas buffering, conditioning, compression, storage, and controlled redistribution. These results indicate that commercial apple controlled-atmosphere CA/ULO storage may represent a measurable decentralized CO2 source that could reduce uncontrolled venting while providing a locally recovered biogenic CO2 stream for potential greenhouse enrichment.