Food co-ops are a type of consumer cooperative  Consumer cooperatives offer the same products as other stores but usually more cheaply
It is ttherefore more economical to shop at a food co-op than at a supermarket
By that line of reasoning, we could conclude that a person who rides a bicycle causes more pollution per mile traveled than one who rides a public bus, since bicycling is a private means of transportation and private means of transportation tend to generate more pollution per mile traveled than do public means.