No self-respecting environmentalist would be caught sipping from a plastic water bottle or toting around plastic bags filled with groceries. Some have even extended this idea to diapers and sanitary pads. But when one takes into account all of the electricity that goes into making reusable items and the water that goes into washing these items, is it really more sustainable?
The answer should be determined on a case-by-case basis. The scientific analysis of this question is called a life-cycle assessment, “a technique to assess environmental impacts associated with all the stages of a product's life from raw material extraction through materials processing, manufacture, distribution, use, repair and maintenance, and disposal or recycling”. Life-cycle assessments of sustainability projects can be surprising and controversial, such as the many assessments of green roof projects. You may have even seen a green roof on the University of Maryland campus. Since 2008, Cumberland Hall has had an 8,000 square foot green roof. Green roofs’ benefits include waste diversion, stormwater management, moderation of the urban heat island effect, improved air quality, energy efficiency, and improved aesthetics. However, it’s not that simple.
Findings from multiple studies have shown that green roofs’ benefits may be overexaggerated and limited only to commercial and multifamily buildings. Other studies have calculated that some green roofs only begin to provide net-positive up to 30 years after their completion. A 2008 study found “that the cost of green roofs installed in a watershed near Atlanta are approximately 10% higher than the environmental benefits of stormwater management, energy reductions, and improvements to air quality over a 40-year period”. These findings vary as dramatically as the designs of green roofs do, but they offer an important reality check for environmentalists. The most appealing solution isn’t always the best solution.
Other surprising realizations from life cycle assessments include that brewing coffee has more of an environmental impact than coffee’s packaging due to the high amount of energy needed to heat water. University of Oregon chemistry professor David Tyler has found that the carbon footprint of a plastic bag is less than a reusable cotton bag due to water and chemicals needed to produce cotton. The same principle can also be applied to ceramic mugs versus disposable cups. High energy usage associated with recycling can also lead to question the sustainability of items like bioplastic utensils, recycled paper, and LED lights. The answer depends on everything from whether the manufacturing facilities are modern to whether your local recycling facilities can handle certain types of materials.
These life-cycle assessment discoveries can be overwhelming and make consumers unsure of who to trust or what to do. The best solution for buying small items is to research the companies you are buying from and get to know where your recycling goes. According to the Office of Sustainability, at University of Maryland: “We recycle ALL plastics on campus including yogurt and detergent containers, frozen food containers, etc. PLEASE rinse out the food first! Bottle caps are okay! Rigid plastic is acceptable including plastic trays and even lawn furniture… Plastic bags and film plastic cannot be recycled through our single stream recycling.” For large projects, always ask if a life-cycle assessment has been done or will be done. In the long-term, most green infrastructure projects reduce carbon, but it’s valuable to know how many years the payoff will take.
|Chicago City Hall green roof. Source: National Geographic (2009).|
This post is brought to you by the BSOS Sustainability Task Force
Author: Jane Lyons
Editor: Megan Croly
For more info on the BSOS Sustainability Task Force, see blog.umd.edu/stf.