Eco-Friendly Products

The amount of energy consumed during the life cycle of a reusable bag varies according to the material it is made from. A good way to find out how much energy it takes to produce a reusable bag is to find a life cycle assessment of the material it contains. Comparing cotton and polyester, for example, reveals that cotton uses less energy during its life cycle than polyester, though cotton consumes more water and emits more CO2. According to Sustainability-Ed.org, 1 kg of cotton fabric requires 140.1 mega joules (MJ) of energy during a two-year life cycle (which includes 12 washes), while 1 kg of polyester uses 171.5 MJ. A medium-weight cotton or polyester tote weighs about 8-10 oz., or between 0.2 and 0.3 kg, so these figures represent the two-year life cycles of about four reusable bags.

Compared to any type of disposable bag, both cotton and polyester bags consume less energy if used regularly for two years in place of disposable bags. According to a life cycle analysis conducted by the American Chemistry Council, the life cycle of 1,500 polyethylene plastic bags consumes 763 MJ of energy. In a two year period, the average American uses about 660 plastic bags, consuming about 336 MJ. At 140.1 MJ for cotton and 171.5 MJ for polyester, four reusable bags consume about one half the energy of disposable polyethylene over the course of two years. If eight bags are used for two years, reusable polyester bags consume slightly more energy than disposable polyethylene, and cotton bags still consume considerably less. If reusable bags made from recycled or second-hand materials are used, a great deal of energy can be saved from the fiber production process. According to a life cycle assessment published in “Resources Conservation and Recycling” comparing reused and recycled textiles with those processed from virgin material, the energy involved in preparing used cotton garments for reuse is only 2.6% that involved in making new cotton garments, and for polyester the figure is 1.8%.
The difference in energy consumption between reusable and disposable bags is more extreme when comparing reusable bags with paper or compostable plastic. According to the American Chemistry Council, paper bags consume 2,622 MJ during the life cycle 1,000 bags, which have approximately the same carrying capacity as 1,500 plastic bags. If we use the same carrying capacity of paper in place of plastic, over the course of two years we consume about 1155 MJ— nearly seven times the energy of four reusable polyester bags and over eight times that of four cotton bags. If we use compostable bags, we consume about 912 MJ, over five times the energy of four reusable polyester bags and about 6.5 times the energy of four reusable cotton bags. If eight reusable shopping bags are used in place of either of these disposables for two years, we still use considerably less energy.