Come January, Marin Sun Farms will no longer process meat at its Petaluma slaughterhouse—the last remaining slaughterhouse in the Bay Area—from producers who do not sell to its two labels. The move leaves some West Marin ranchers scrambling for far-away alternatives or closing up shop altogether; the closest beef processing facility is in Modesto.
Co-owners David Evans, a fourth-generation rancher on Point Reyes, and Claire Herminjard, the founder of Mindful Meats, said customer conduct has…