The Expanded Shale, Clay and Slate Industry is committed to the efficient production and long-term performance of expanded shale, clay and slate (ESCS) lightweight aggregate. The industry and its related association, the Expanded Shale, Clay and Slate Institute (ESCSI), are also committed to the sustainable development of the entire building industry. And ESCSI proves this commitment by being on the forefront of the environmental movement since the late 1990s, when it commissioned its first life-cycle inventory (LCI) of the lightweight aggregate manufacturing process. Since then, the industry has worked to benchmark its environmental performance and continue to reduce its environmental impact through additional research and development of a set of product category rules (PCR) for expanded shale, clay and slate lightweight aggregate.
Anticipating that its members will soon need to produce environmental product declarations (EPDs), ESCSI partnered with ASTM (as the program operator) to draft a PCR for lightweight aggregate. With representatives of (ESCSI) member companies, the PCR was developed over 9 months according to the ISO 14025 and ISO 21930 standards and released in April 2015.
In 2000, ESCSI published its first LCI “The Life-Cycle Inventory of the Lightweight Aggregate Manufacturing Process,” by Nisbet and VanGeem. Eleven plants, representing an estimated 2.5 million tons of production, responded to the survey of ESCSI members in 1999. Plants provided data on energy and materials consumed, and emissions to air, land, and water. Nisbet and VanGeem conducted the study according to the SETAC guidelines, and reported results per average ton (2000 lb) of lightweight aggregate produced.
Average energy consumption was calculated to be 2.36 MBtu per ton of lightweight aggregate produced. This energy includes process energy, energy used in mobile equipment, and fuel consumed in the transportation of coal and flue-gas scrubbing agents. ESCSI updated the study in 2006 with a larger data base of 13 plants and 3.8 million tons, which resulted in an average energy consumption of 2.16 MBtu per ton.
For additional information, read ESCSI Info Sheet #9153, Embodied Energy to Manufacture Expanded Shale, Clay and Slate Lightweight Aggregate (Jan. 2015).
In 2012, Walter P. Moore completed a study that compared the embodied energy in the structural system of a steel-framed building with lightweight concrete (LWC) floor slabs on composite steel deck to the same system using normalweight concrete (NWC). Four structural systems were compared, and all the systems had the same floor acceleration; fire rating; and live, wind and seismic loads.
This study only included the embodied energy of the buildings’ structural materials. It excluded any transportation energy impacts as well as the embodied energy in the building envelope (or other systems).
After performing the structural design for each of the building scenarios, a material inventory was created. For the concrete mixture proportions, Walter P. Moore used aggregated data from historical concrete mixture proportions used in its practice across the U.S. Energy intensities of the structural materials were taken from the 2011 Inventory of Carbon & Energy, version 2, by Hammond and Jones, which reports embodied energy of materials from a cradle-to-gate basis.
The results showed that one of the LWC scenarios had the lowest total embodied energy at 10,520 MMBTU, while the NWC scenario had a total embodied energy of 10,660 MMBTU. The study found that the energy required to produce LWA was offset by the following:
The sustainability movement has created a shift in attitudes and lifestyle awareness that has caused the building industry to evaluate itself from a green perspective. When the ESCSI looked at the uses and manufacturing of ESCS lightweight aggregate from a green perspective, we were pleasantly surprised.
Lightweight aggregate is an environmentally friendly product with unique features that has been successfully used for well over two millennia, with rotary kiln produced ESCS in widespread use for the past ninety years. It has been used in a multitude of applications that contributed to the sustainability of the site and structure long before the current green movement came to the forefront.