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In the continuing evolvement of today’s green society, which has caused sweeping changes into the use of ecologically-benign building products and practices, the mere fact that a product may be considered green in its final application is no longer sufficient. Products and practices used in the building industry now must also provide environmental, social and economic benefits while protecting the public’s health and welfare from the extraction of raw materials to their final disposition. These new requirements are collectively referred to as sustainability and only products that are considered green and sustainable are being fully credited by the accountability point systems, such as the Leadership in Energy and Environmental Design, BRE Environmental Assessment Method and Green Globes.
For all practical purposes, common usage of the term “sustainability” began with the 1987 publication of the World Commission on Environment and Development report Our Common Future. Also known as the Brundtland Report, this document defined sustainable development as “development that meets the needs of the present without compromising the ability of future generations to meet their own needs.” However, it may have been Albert Einstein who first embraced a movement of sustainability when he said, “The significant problems we face cannot be solved at the same level of thinking we were at when we created them.”
In today’s market-driven society, some companies may choose to “green-wash” a product by only promoting a portion of the product’s total environmental impact in touting that the product is, say, “phosphate free” and therefore doesn’t contain a dangerous surface-water pollutant. However, the product may not be ecologically friendly if its life cycle includes steps that are harmful, such as the destruction of habitats in material extraction; use and release of toxic materials in manufacturing; and, persistent chemical byproducts that remain hazardous in storage, treatment and disposal. In other words, a product may be green in its ultimate application but only sustainable in the way it’s made.
Many people have a laptop computer that is green in its application. For instance when a person downloads a book off the Internet from Amazon.com onto a laptop, it reduces pollution because a download eliminates printing, binding, packaging and shipping, then the laptop is green in its application. Yet, if the laptop itself is made in a toxic manufacturing facility in Japan, and draws power from coal-produced electricity here in the U.S., its manufacture and operation contaminates the air that we breathe and prevents it from being sustainable.
In restorative construction, a chemical-resistant urethane used to provide a non-porous surface finish to protect and enhance an existing warehouse floor as well as contribute to less maintenance and less repair, allows the urethane to have green characteristics. However, if it’s made with hazardous chemicals and the manufacturing process is poisonous or it emits toxic fumes during its application posing health risks to the installers, it’s not sustainable.
SUSTAINABLE DESIGN & GREEN ENGINEERING
In a continuing effort to reduce overall energy consumption throughout the country, most industries now embrace the concept of sustainable development. Architects and building designers are implementing “whole building” design strategies to create high-performance buildings from an ecological standpoint. Because operating a building over time is far more energy intensive than developing it, demand for durability and energy performance has become paramount in project planning.
Recognizing that U.S. buildings use nearly 10 percent of the world’s energy, and also use three times more energy than comparable buildings in similar climates in Europe, the U.S. government is adopting green building programs and an increasing number of states are offering tax benefits for green public buildings. The U.S. government defines green buildings as those that demonstrate the efficient use of energy, water and essential materials; limit impact on the outdoor environment; and, provide a healthier indoor environment.
Projects are required to reduce waste, adapt to the site, use renewable energy and materials from local sources, creatively seek synergies from all building and site components, and, above all, avoid toxic materials, protect ecosystems and restore damaged surroundings. As a result, all of this has created vast new markets for green building materials, and green building practices (i.e., sustainability).
The LEED Green Building Rating System was conceived and implemented by the United States Green Building Council to define and measure the sustainability of “green buildings.” Since the introduction of Version 2.0 in March 2000, the LEED rating system has radically transformed building design and construction by awarding points for its evaluation in five separate categories that reduce the negative impact of buildings. Those categories are: Sustainable Site Planning; Water Efficiency & Conservation; Renewable Energy & Efficiency; Materials & Resources Conservation; and Indoor Environmental Quality. The greater the point total, the more sustainable the project. Importantly, LEED does not certify products. Only projects can be LEED certified with a maximum of 69, and a minimum of 26 points required for certification.
CEMENT PRODUCTS: GREEN AND SUSTAINABLE
The cement industry utilizes industrial byproducts like fly ash, and consumes less energy than its competitors. Fly ash is a byproduct of coal-fired power plants that is difficult to use because of inconsistent grind and weight, and because it contains some radioactivity; massive amounts of fly ash are unused and go to landfills for disposal. However, a ton of fly ash used in concrete can save almost a ton of carbon-dioxide (CO2) emissions from entering the atmosphere and contributing to global warming. In 2005, more than 20.5 million metric tons of fly ash was used in concrete, and 3 million metric tons of recycled slag, a byproduct of steel production, was used saving millions of tons of CO2 from entering the air we breathe.
CO2 results from the combustion of carbon-based fuels, i.e., the burning of oil, natural gas or coal, and raw material changes occurring from intense heat, which is the conversion of carbonates in the raw materials into the various compounds that gives cement its unique properties. However, most cement manufacturers are now closing wet process kilns that require large amounts of water and energy to grind raw materials, and installing energy efficient dry process plants which use energy-rich alternative fuels that are consumer wastes or byproducts from other industries. This type of energy recovery conserves valuable fossil fuels for future generations while safely destroying wastes that would otherwise be deposited in landfills.
Although the U.S. is the world’s third largest manufacturer of cement, U.S. Department of Energy statistics show that U.S. cement production accounts for just 0.33 percent (about one-third of 1 percent) of energy consumption in the U.S.-lower than petroleum refining at 6.5 percent, steel production at 1.8 percent, and wood production at 0.5 percent. The greatest consumption of energy comes from the homes and buildings we live and work in at 38.8 percent of total U.S. consumption, and the cars and trucks we drive at 27.6 percent.
Since 1975, the cement industry has improved energy efficiency by 33 percent. Today, the cement industry accounts for less than 2 percent of all U.S. carbon dioxide emissions, well below other national sources such as electric power plants at 33 percent, transportation at 27 percent, and industrial operations at 19 percent.
Specifically designed and delivered for each project, concrete typically produces very little waste. The major ingredients in concrete, cement, sand and coarse aggregates, are typically obtained and manufactured locally, reducing shipping impacts and benefiting the local economy. When a concrete structure has served its purpose, it can be crushed for use as aggregate in new concrete or as base materials for roads, sidewalks and concrete slabs. Even the reinforcing steel in concrete (which is often made from recycled materials) can be recycled and reused. In 2006, the Construction Materials Recycling Association estimated that approximately 125 to 140 tons of concrete are recycled each year.
Further still, the cement industry uses about 65 million scrap tires, or over 20 percent of the total amount of scrap tires each year, as an alternative fuel source during cement production. Pound for pound, tires contain one-third more energy than coal. Recycling tires in this way effectively removes them from landfills or other disposal methods.
Finally, structures built with concrete have optimal energy performance. Homes and buildings constructed with insulated concrete walls are not subject to large daily temperature fluctuations. This means home or building owners can lower heating and cooling bills up to 25 percent. Also, heating, ventilating and air-conditioning systems can be designed with smaller capacity equipment. High performance insulated concrete wall systems provide high R-value and thermal mass with low air infiltration to provide superior thermal efficiency.
The manufacture of cement and its ultimate use in concrete is an outstanding example of sustainable design and green engineering for environmentally sound construction as it reduces waste, reduces carbon emissions, and increasingly uses new sources of renewable energy. W&C
Research Sources:
Concrete Home Building Council
NAHB Green Building Program
U.S. Green Building Council
LEED Reference Guide
Portland Cement Association
Environmental Protection Agency
Sustainable Buildings Industry Council
Research and Markets.com
The Science of Sustainability & Green Engineering
Internet Search Engines
QSI Quality Control Research
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