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Waste Not, Want Not


Can you explain changes to construction waste recovery?


Statistics reveal that a copious amount of waste material is generated during the construction, renovation or demolition of a building. There is a heightened awareness of the impact of this waste when viewed under the light of land usage and sustainability. Traditional practice was to send this waste to a landfill for disposal. As a result, certain state and model building codes now require that waste generated during construction, renovation and demolition be collected and diverted to a material recovery facility. Here the construction waste can be processed and reintroduced into the marketplace as a raw material for multiple industries. If a building is designed to achieve any level of a USGBC LEED® certification, then construction and demolition waste recovery must be taken into account. Common building products that are suitable for landfill diversion include gypsum panels and cold-formed steel framing.

    

The procurement and recycling of construction waste contributes to achieving two main goals: The first is landfill diversion, the second supports the reduction of greenhouse gas emissions. The latter is to help slow global warming. In this same effort is the concept of a material’s carbon content. Many designers are insisting that building product manufacturers provide data on the carbon content of the products they sell. Reducing carbon content of a material decreases the climatic impact of the entire structure. Therefore, the use of recycled materials produces a positive effect on the structure’s carbon content.

    

Collecting construction waste can help create what is called a circular economy, where the basic materials are captured and reprocessed into a new product. The process that supports the circular economy has become highly sophisticated with new technologies emerging to facilitate the five steps: source, collection, sorting, recovery and recycling. In construction demolition and waste, the source of the waste can be seen as the construction site. This is where the leftover building materials, or what is called the feedstock for recovery, is generated.

    

After the collection and shipment of the materials to be recycled is complete, it is readied for the sorting step. This is where the collected materials are separated by their composition. Sorting has evolved with the advances in technology to become a highly efficient and rapid process. Years ago, a continuously running conveyor belt carried the construction waste past a human worker who identified it as being wood, gypsum, ferrous and nonferrous metals, gypsum or concrete. At this point, each type was manually separated. Today, self-teaching robotics can be employed and specialized equipment can verify the material composition. The robotics are programmed to select specific content and even “learn” new substances as they are introduced.

    

Once the materials are collected, sorted and separated, they move to the recovery phase. This occurs at the material recovery facility, where it is further processed. Steel material can be re-introduced into either an electric arc furnace  or to a smaller extent, a basic oxygen furnace where new steel is produced. This is the recycle phase. Once the new coil of steel is produced, it can go into any industry that requires steel.

    

Like steel, the gypsum mineral (and the gypsum panel) are ideally suited for recovery. Once the mineral is isolated, for example the removal of facers from the gypsum panel and additional processing, it is potentially ready for reintroduction, or recycled for use in multiple industries. The two most common industries are construction as gypsum panel production and in agriculture. Gypsum has multiple beneficial attributes when used as a soil additive.

    

A new ASTM standard, ASTM C1881, Standard Guide for Closed-Loop Recycling of Scrap Gypsum Panel Products, has been published to provide guidance on the selection and procurement of gypsum for recycling. It provides guidance on obtaining gypsum scrap destined for reuse in gypsum panel products. An association specific to the recovery of construction materials is the Construction & Demolition Recycling Association. Its members represent entities that are involved in construction and recycling of construction materials, including contractors.

    

For the contractor, the growth of this industry is driven by state and local municipalities concerned with landfill diversion. It is further driven by designers concerned about sustainability. This growth will impact contractors. If contractors are not currently required to collect their construction and demolition waste, it may soon be part of their scope of work. To achieve any level of a LEED® certification, there is a prerequisite that a program be in place that monitors construction and demolition waste. Along with that is a requirement for extensive documentation that must be provided, which may fall on the contractor. The experienced contractor may have a competitive edge in this era of carbon content concern.

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Robert Grupe is AWCI’s director of technical services. Send your questions to grupe@awci.org, or call him directly at (703) 538.1611.

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