Wood Poles: The Green Choice
Using wood poles is a positive step towards reducing the carbon footprint. First instinct tells us that using wood poles is bad for the environment because we are cutting down trees and depleting our national forests—but we rarely hear about what happens next.
By Deepa Akula
Electric utilities are working hard to reduce their carbon footprint to comply with local, regional and national goals to reduce greenhouse gas emissions and to be environmentally responsible. Per the EPA, some 30 percent of carbon dioxide released into the atmosphere is produced by burning fossil fuels to generate electricity. Moving away from coal and gas burning power plants is the logical next step for utilities. Building new infrastructure to support wind and solar power plants, however, takes much planning and capital investments, and the results are not immediate. Renewable power generation will help utilities significantly reduce their carbon footprint, but choosing the right material for distribution and transmission infrastructure can make a bigger impact on reducing greenhouse gases.
Using wood poles is a positive step towards reducing the carbon footprint. First instinct tells us that using wood poles is bad for the environment because we are cutting down trees and depleting our national forests—but we rarely hear about what happens next. On average, three seedlings are planted for every harvested tree. According to the Mississippi Forestry Commission, growth to harvest ratio of pine trees is 3:1. We have more trees in our national forests now than 100 years ago. Per the Food and Agriculture Organization (FAO), “Forest growth nationally has exceeded harvest since the 1940s. By 1997, forest growth exceeded harvest by 42 percent and the volume of forest growth was 380 percent greater that it had been in 1920.” The increase in number of trees can be attributed to responsible harvesting, replanting, conservation and preservation of our national forests by forest protection agencies.
Trees absorb carbon dioxide from the atmosphere, and with the help of radiant energy from the sun, they split carbon dioxide into carbon and oxygen. They store carbon and release oxygen—acting as natural carbon sinks. This reduces the amount of free carbon in our atmosphere, and, even after the tree is cut down, carbon is securely stored in the wood fiber.
Cutting trees to manufacture wood poles and planting young trees and seedlings accelerates the carbon sequestration and increases oxygen content in the atmosphere, because young trees produce more net oxygen than mature trees. Large trees produce more oxygen because of their size, but they consume all of it or more during respiration—which results in a net negative oxygen production.
Large trees absorb a large amount of carbon dioxide, but, because they are not actively growing, they use the absorbed carbon dioxide to produce sugar or to grow leaves. Sugar is used to generate energy and the carbon is released back into the atmosphere. Similarly, when the leaves fall off, the carbon stored in them gets released into the atmosphere. In contrast, young trees are absorbing carbon and using it as building blocks to generate wood fiber. When trees are harvested to make wood poles, new young trees are planted and they sequester more carbon and release more net oxygen because they grow vigorously.
Usually only 5 percent to 10 percent of the trees meet the specifications to be used as wood poles. After the selected tree is harvested, it is debarked, dried and treated with a suitable preservative. Manufacturing of wood poles requires less energy and releases the least amount of greenhouse gases and toxic gases into the atmosphere compared to alternative materials such as steel and concrete. Milling steel and manufacturing concrete requires more energy and is not environmentally friendly because it generates large amounts of greenhouse gases. Utilities can reduce their carbon footprint, increase oxygen level in the atmosphere, and encourage sustainable foresting techniques by using wood poles.
Trees are typically harvested in the northwest and southern states. Wood poles manufactured from Coastal Douglas Fir are usually used west of the Rocky Mountains and Southern Yellow Pine poles are used east of the Rockies. Round wood poles of either species can be used as distribution structures, and, if the required capacity of the structure exceeds round wood pole capacity, glued laminated wood poles can be used. Round wood poles are available from 30 feet to 125 feet, up to class H6, but laminated wood poles can be fabricated to any class and height. Laminated wood poles are fabricated with lamination grade lumber and are rectangular in cross-section. They are generally used for unguyed, angle and deadend applications. They are aesthetically pleasing and blend into their surroundings better than steel, concrete or fiber reinforced poles. Usually only two of the four sides of the pole are tapered, which provides an opportunity for mounting switches and crossarms on the flat surfaces. Laminated wood poles are torsonally sturdy and don’t twist in service, making them ideal for switch installations and operation. In addition, lead times for laminated wood poles are consistent because of the readily available material—around 6 weeks to 8 weeks for manufacturing and treatment.
By using wood poles, utilities can not only complete expansion and replacement projects on time and under budget, but also reduce greenhouse gases and increase oxygen levels in the atmosphere—making a bigger impact on the environment in a positive way.
About the author: Deepa Akula, PE, is the engineering manager at McFarland Cascade. She has nine years of experience designing overhead utility and telecommunication structures. She holds a Master of Science degree in Engineering from the University of Missouri and is a registered civil/structural professional engineer in eight states.