However, the author also cautions to “beware carbon toe-prints.” He continues, “the most common abuse of the phrase carbon footprint is to miss out some or even most of the emissions caused.” Examples include measuring a personal carbon footprint by taking into account home energy and travel habits, but not the related goods and services that are purchased, or a magazine publisher that accounts for its office and cars, but not emissions caused by magazine production.
To provide perspective and scale, the author describes a ton of co2e as follows:
If you filled a couple of standard-sized 60-gallon garden water tanks to the brim with gasoline and set fire to them, about a ton of carbon would be directly released into the atmosphere. (The carbon footprint of burning that gas by driving is a bit more than that, for reasons explained later.) If you did the same with two cups of gas, that would release just over a kilogram (2 pounds) of carbon dioxide, and if you burned a blob about the size of a chickpea, that would release about a gram. There are a thousand grams in a kilogram and roughly a thousand kilograms in a ton.
According to the author, “The average North American currently has an annual carbon footprint of around 28 tons,” whereas the “global average is about 7 tons each.” The author proceeds to provide a sense of scale of a wide variety of items and activities beginning with a chapter entitled, “Under 10 grams,” which provides the carbon footprints of a text message, a cup of water (0.06 g co2e), a web search, walking through a door, an email, drying your hands, and a plastic carrier bag.
Subsequent chapters cover the following categories: “10 grams to 100 grams” (which includes bananas); “100 grams to 1 kilo (2.2 pounds)” (for example, a mug of tea or coffee, doing the dishes, or driving a mile); “1 kilo to 10 kilos (2.2 pounds to 22 pounds)” (for example a bottle of wine, a load of laundry, leaving the lights on); “10 kilos to 100 kilos (22 pounds to 220 pounds)” (which includes, a pair of shoes, a night in a hotel, and using a cellular phone); “100 kilos (220 pounds) to 1 ton” (for example New York City to Niagara Falls (405 miles) and back, insulating an attic, or a mortgage); “1 ton to 10 tons” (which includes, a heart bypass operation, photovoltaic panels, and flying from Los Angeles to Barcelona and return); “10 tons to 100 tons” (a car crash, a new car, a wind turbine, and a house); “100 tons to 1 million tons (having a child, a swimming pool, a hectare (2.5 acres) of deforestation, a space shuttle flight, a university); and “1 million tons and beyond” (a volcano, the World Cup, the world’s data centers, a forest fire, a country, a war, black carbon, the world (50 billion tons co2e per year), burning the world’s fossil reserves). Final chapters provide more about food and further information.
So how bad are bananas? According to the author, “[a]s it happens, they turn out to be a fine low-carbon food, though not totally free from sustainability issues to keep an eye on.”