Greener groceries All illustrations by @businessfrog The average supermarket has about 30,000 items on its shelves, so discerning shoppers are awash in a sea of choices—organic vegetables, artisanal cheeses, grass-fed meats, fair-trade coffee. But what if shoppers want to purchase foods that minimize their impact on the environment? Information on a product’s carbon footprint typically can’t be found on its label. Enter Marble, a startup co-founded by a Harvard graduate student that enables shoppers to scan a food product’s barcode with their smartphone and see an estimate of that item’s carbon footprint (in kilograms of CO2).