A 2011 IBWA lifecycle inventory study found that the production, packaging, and transportation of bottled water within the United States consumes of energy annually, which represents about 0.07% of yearly energy consumption in the country. According to the same study, 6.8 million tons of CO2 eq are emitted by the bottled water industry a year in the United States, about 0.08% of annual emissions. An Aetna Group study in 2015 concluded that each litre of bottled water requires 240 kilojoules of energy to produce. The lifecycle carbon footprint for a half litre of small pack bottled water is 111 grams CO2 eq. By comparison, the same sized PET plastic-bottled soft drink produces 240 grams CO2 eq. Soft drink bottles require much thicker plastic due to carbonation, and therefore many more grams of CO2 eq.