Consumers will soon be able to quantify the carbon footprint of products they consume, and that could begin to change consumer behavior. The common banana you buy, say organic or not, is probably labeled by the country or origin. Increasingly, you might see a second sticker adorning your beloved yellow fruit – it will be a tally of the banana’s total carbon emissions as it moved from farm to table. That single number is not a simple one. If the bananas you bought this week were transported from Indonesia by boat––they have a different carbon footprint than the bunch you consumed last month grown, say in Mexico, and moved by rail. Behind this labeling system are a complex supply chain, logistics, and transportation considerations. And behind the measurement of this network is the research of Edgar Blanco and his colleagues at MIT. He begins with a consumer perspective.  Beginning in 2006, in reaction to climate change, consumers, many large companies and the media wanted to assess the full environmental impact of finished products, be they bananas, potato chips, or cars. Blanco compares the measurement of the carbon trail for consumer goods to, “developing a really large map of what happens behind the product”. He challenges, “ If you have a number (of how much emissions a product creates), what should you do about it?... Partially, the exercise gives consumer information, but it is also vital so that you have information about emissions, so you can do something about redesigning the supply chain.” The measurement of the carbon trail is vastly complex, and goes well beyond knowing the CO2 emissions produced by the transport sector. In one exercise, the research team compared the carbon footprint of bottled water manufactured and shipped in the U.S. versus bottled water originating in Fiji but sold in the U.S. The product imported from Fiji turned out to have a lower carbon footprint. Despite the 4,800 miles of ocean transport, the thermal/solar/wind ener...