Built to demolish, demolish to build
will happen so far into the future, says Horvath. Instead of predicting the costs of emissions associated with fuused in demolishing a building All things must come to the end ture demolition of buildings, the and transporting the waste prodof their lives, and buildings are no authors credit the use of recycled ucts), the environmental costs of exception. When buildings die, materials to the new building bemanaging the toxic waste in the they end up in heaps of rubble that ing designed. The method doesn’t debris, and the benefits of reusmake their way into landfills. Only directly calculate the end-of-life ing the waste for new buildings are some parts—the metals and some costs of the new building, but it never considered in the LCAs that of the concrete—get recycled. Conhelps reduce the environmenare currently conducted. sequently, dead and demolished tal impacts from demolition buildings can contribute up to by encouraging the reuse of 40% of a country’s waste mamaterials. terials. A study in ES&T (pp Using concrete as an exam4663–4669) takes a life-cycle ple, the researchers show that approach to show that taking ramping up concrete recycling into account the end-of-life imfrom the current 27% to even pacts of buildings can increase 50% would reduce 2.7–5.6 milthe recycling of materials from lion tons of CO2 annually, which demolished ones and thereby significantly lower a buildequals taking 612,000 cars off ing’s environmental footprint, U.S. roads. including its greenhouse gas “When building or designing emissions. a building, one never conceives When buildings’ energy and of [the demolition phase], mostwater requirements are added ly because it is 40 or 100 years in, it becomes clear that their away,” says Robert Boughton, environmental impact is huge. senior engineer at the CaliforBuildings swallow up to 30–40% nia Department of Toxic Subof the world’s energy and 16% of stances Control, a state agency the planet’s water requirement, that regulates toxic wastes. according to the coauthors of the Horvath agrees. “Few people study, Arpad Horvath and Pedro look so many decades ahead Vieira, both environmental engiand try to figure out what is goneers at the University of Califoring to happen to that building. nia Berkeley. They’re happy to have a shiny An increasing awareness new building and . . . happy The U.S. generates 136 million tons of construction- and demolition-related wastes every day. of buildings’ contributions to occupants.” Demolition debris alone can contribute up to global warming has led engiThe study will provide great 40% of the country’s waste. neers and construction comvalue to designers by making panies to perform life-cycle them aware of “overall life cycles” Horvath and Vieira developed assessments (LCAs), which analyze of buildings, says Boughton. “It’s the a hybrid LCA method that calcua product’s environmental impact first paper . . . I have seen that really lates the benefits from the reuse of through its life span. The results got into this end-of-life [assessment] building materials. The method, of the LCA allow engineers to find and tried to give a tool and some which combines process-based ways to cut energy costs, associatmethodology for doing it.” analysis with economic input–outed greenhouse gas emissions, and It is very “timely” and a good put data, is not new. What is new toxic waste products. There are no “first stab at the end-of-life issues of is how the authors used it to solve policies that mandate LCAs, but buildings,” adds Aurora Sharrard, some of the long-existing problems the green building movement, inresearch manager with the Green associated with assessing future cluding the rush to obtain LeaderBuilding Alliance, a group of procosts of tearing down buildings ship in Energy and Environmental fessional designers and builders. (the main problem is the uncerDesign (LEED) certification—the But she cautions that many chaltainty of future impacts and their nationally accepted benchmark for lenges remain, including taking costs). Finding data on emissions green building design, construcinto account building materials that associated with building waste and tion, and operation—has encourcannot be readily recycled, such as deciding “a priori what’s going to aged designers and builders to pay gypsum. “There is certainly a lot be important and what is not” is heed to such issues. But the endfurther to go from here,” she adds. very difficult because the events of-life impacts (such as the energy —RHITU CHATTERJEE RHITU CHAT TERJEE
Interview
4622 ■ Environmental Science & Technology / July 1, 2008
