Stone: Life-cycle Assessment and Best Practices
As in every economic sector, the construction industry's purchases of materials and services creates a whole chain of processes from raw material selecting in situ, removal from the earth, usually proceeding to cutting, finishing, or processing/manufacturing, then transport, and retailing. All of these activities have significant upstream (off-site) environmental impacts, whether in terms of energy and raw resource use or emissions to air, land, or water impacting living organisms or the Earth's surface (non-organic). Life cycle assessment is a method for estimating and comparing a range of environmental performance measures (e.g. global warming, acidification potential, toxicity, ozone depletion potentials) over the full life cycle of a product, a building assembly, or a whole building. As such, it provides a comprehensive means for evaluating and comparing products rather than prescriptive measures of individual product characteristics.
The ASTM has some relevant standards, particularly a guide on environmental life cycle assessment of building materials/products (E1991) that shows how to minimize the subjectivity that commonly mars and confuses environmental decision making. In particular, this guide describes the inventory analysis phase that requires data that is suitable for its intended purpose, thus covering data quality (such as completeness, reliability, accuracy, and credibility) as well as the allocation of the data (for multiple inputs and outputs), among other things. Results have to be on a common basis to allow a statistically significant comparison of alternative building product differences in the interpretation.
The Natural Stone Council (NSC) has commissioned some life-cycle inventory data for use in life cycle assessments. Almost 90% of the effort in doing a life cycle assessment involves getting reliable data. For example, the NSC has data that the Global Warming Potential for granite quarrying is 100 kg of carbon dioxide equivalents and for granite processing is 500 (same units); and the Global Warming Potential for limestone quarrying is 20 kg carbon dioxide equivalents while for limestone processing it is 80 (same units). The data on energy and water use include everything back to removal of overburden in the dimension stone quarry and upstream production of energy and fuels, and forward to packaging of finished dimension stone product or slabs for shipment and transport, or to moving scrap stone to storage or reclamation and to capturing and treatment of dust and waste water. The data is then placed in an impact category (i.e. changes to air, changes to water), characterized as to the contribution of the item to the impact compared to other items, and then the impact categories are assigned weights among themselves to show their relative importance.
The Natural Stone Council has also commissioned four Best Practices. One is on water consumption, treatment, and reuse while extracting and processing dimension stone, including dust mitigation, sludge management, and maximizing water recycling. Another is on site maintenance and quarry closure, including minimizing dust, noise, vibration and keeping the operation clean and tidy, both of which help in restoring the surface upon quarry closure. A third one is on solid waste management, including overburden, damaged stone unsaleable as product, sludge deposited from waste water, spent or spilled petroleum products, or metal scrap. The fourth one is on efficiently transporting stone to be finished as products, then transporting the products to consumers by centralizing freight management, consolidating small loads, choosing appropriate trucks, balancing and securing the load, and packaging with sustainable materials.
Read more about this topic: Dimension Stone
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