A detailed life cycle assessment study commissioned by the Steel Market Development Institute, a business unit of the American Iron and Steel Institute, finds that when comparing overall environmental performance, galvanized steel utility poles outperform wood poles in key environmental measures.
The peer-reviewed study, conducted in compliance with international assessment standards (ISO-14040-series), is the most comprehensive environmental assessment of its kind to date, bringing a new level of transparency to the comparative performance of these two material choices.
“Every material choice has environmental consequences at some point during its manufacture, use and disposal,” said Lawrence W. Kavanagh, president of SMDI. “Manufacturers have a responsibility to know what these consequences are in order to identify improvement opportunities, while simultaneously helping customers make the best informed decisions. We are pleased to be able to share the results of this study with our customers, demonstrating that steel poles have superior environmental performance for a wide range of indicators.”
The study compared the use of galvanized steel and wood utility poles in the southeastern U.S. over a 40-year time horizon. It stands apart from previous studies in that it applied advanced assessment methods to ensure a more comprehensive assessment and reporting of the full range of potential environmental impacts associated with both galvanized steel and wood, including local and regional ecological impacts.
Among its findings, the study showed that replacing wood utility poles with galvanized steel will likely result in lower levels of greenhouse gas and aerosol emissions associated with global climate change, a lower burden on critical energy resources, reduced impacts on the habitats of many threatened and endangered species, and reduced impacts associated with hazardous emissions and wastes. The primary drivers for these findings are the longer lifespan of steel poles, high steel recycling rates, and the overall ecological and land use impacts of growing, harvesting and replanting the forests used to produce wood poles.
“The fact that the steel pole option has relatively lower greenhouse gas emissions and impacts on energy resources reflects the greater durability of steel poles as compared to their wood pole counterparts,” said Kavanagh. “Steel’s high recycling rate also means that it gets used over and over in all of its applications and that steel poles offer a clear advantage in terms of life-cycle cost efficiency.”
The study considered 45-foot-tall, Class 2/Grade B distribution poles and included the production, installation, maintenance and disposal of the poles. It assessed wood poles made from southern yellow pine grown in the southeastern region of the U.S. and treated with chromated copper arsenic (CCA), a typical practice. The steel poles in the study were produced using North American hot-rolled steel coil and were hot-dip galvanized.
Two different scenarios were compared — one in which wood poles were taken out of service as a result of pole failure and continued to be replaced by Class 2 wood poles, and the other in which wood poles taken out of service due to pole failure were replaced by galvanized steel utility poles.
In both scenarios, the total number of utility poles in operation was held constant at one million poles. Based on prevailing industry data, the wood poles were assumed to be replaced at a rate of 2.5 percent per year (40-year lifespan), while steel poles were assumed to be replaced at a rate of 1.25 percent per year (80-year lifespan).
The study found that replacing wood poles with steel poles resulted in several environmental benefits, including:
· Lower greenhouse gas and aerosol emissions associated with global climate change. When considered over the entire 40-year time span, the accumulated greenhouse gas and aerosol emissions associated with global climate change are lower for the steel pole scenario. This result challenges the common assumption that treated wood products have a lower carbon footprint than steel products. It reflects the emissions of greenhouse gases and aerosols associated with the CCA-treatment and installation of the wood poles, as well as the production of wood from southern yellow pine using short-rotation, even-aged forest management practices, which result in losses of forest carbon storage of between 20 to 30 percent, equivalent to 20 to 40 tons of carbon dioxide per acre. Emissions related to steel poles occur during hot-rolled coil steel production, galvanization, zinc smelting and installation.
· Lower energy resource depletion values. The steel pole scenario results in the use of about half the non-renewable energy resources, requiring 300,000 fewer barrels of oil (equivalent) vs. the wood pole scenario over a 40-year timeframe.
· Lower impacts on the habitats of threatened and endangered animal species. In the steel pole scenario, the habitats of three key terrestrial species are impacted, compared to seven key terrestrial species in the wood pole scenario. In terms of key wetland species, the steel pole system does not have any significant impacts, while 81 species experienced disturbance to freshwater and/or wetland habitats in the wood pole scenario.
· Lower impacts to terrestrial biomes. When averaged over the 40-year time horizon, the results for terrestrial biome disturbance are equivalent to the full disturbance of about 12,000 acres for the wood pole scenario, compared to only about 15 acres in the steel pole scenario.
· Reduced hazardous emissions and wastes. The CCA formulation used for wood pole treatment is made from arsenic ore that is mined primarily in China. Arsenic is known to be chronically toxic and carcinogenic at elevated levels. In the U.S., old wood poles are exempted from management as a hazardous waste under the Resource Conservation and Recovery Act, though CCA-treated lumber in residential applications is considered a hazardous waste. In the wood pole scenario, their disposal results in more than 590,000 tons of waste over a 40-year timeframe.
· The study was conducted by SCS Global Services, a global leader in third-party environmental and sustainability certification, auditing, testing and standards development for nearly 30 years. SCS programs span a wide cross-section of sectors, recognizing exemplary performance in natural resource management, green building, product manufacturing, food and agriculture, retailing and more. SCS is a Certified B Corporation, reflecting its commitment to socially and environmentally responsible business practice.