Composite Small Cell Towers and Sustainability

By Dr. Mary Comstock

Abstract

With an exponential need for data worldwide, and the predicted demand in associated 5G and IoT infrastructure, the telecom industry finds itself with an interesting problem on its hands. With all the talk of high tech, there still must be an actual physical system to support the equipment. Even as they seek to build out this tower-intensive infrastructure, communities, carriers and installers are simultaneously seeking ways to lower carbon footprint, prolong usability and increase sustainability, as well as to decrease chemical, noise and traffic impacts. The traditional methods of metal and wood as tower materials prove problematic on several environmental fronts. The quest is for another type of small cell infrastructure solution, one which fits the world’s rapidly growing need for ultra high speed communications, yet with diminished impact on increasingly populated urban spaces.

Unprecedented urban demand

Home to more than half of the world’s population, cities account for more than 70 percent of global energy-related CO2 emissions and an estimated 50 percent of global waste. By 2050, it's projected that 68 percent of the world's population will live in urban areas (an increase from 54 percent in 2016). With this increase, cities are laboring to become more ecologically responsible and enact policies around sustainability. However, they are now met with another challenge that may further impact the environment: the rollout of 5G connectivity. Because of its shorter wavelength, 5G demands installations at approximately every 800 to 1000 feet to provide uninterrupted connectivity for both User Equipment (UE) and Internet of Things (IoT) devices. While many of the new installations will use existing towers and other infrastructure, urban densification calls for an enormous buildout of new towers, which will create corresponding environmental degradation if traditional methods continue to be used. There is a need for another way. 

Traditional approach

Most existing small cell towers are made of steel, aluminum or wood. These are installed using a team of at least four, and often up to six workers. These teams use gas-powered, heavy duty equipment to transport, hoist and then lower the towers into place. Concrete foundations, which take several hours to cure, typically secure the tower. All aspects of the traditional approach take their toll on our environment and most of them contribute to climate change.

Ill effects from metal tower manufacturing

Iron used in steel manufacturing is obtained by open pit mining, also known as open cast mining. So is aluminum. This method, even when properly regulated, poses a series of threats to the environment:

Air pollution and dust production from heavy equipment, drilling and shoveling

Sound pollution from blasting 

Ground vibration

Water pollution

Deforestation 

Acidification of soil

The refining of metal releases dangerous emissions including CO, SOx, NOx, PM2, as well as wastewater contaminants, hazardous wastes, and solid wastes. Additional air pollution comes from diesel generators, trucks and other mining equipment. Steel production is a major contributor to global warming, adding more than 3.3 million tons annually to global emissions. On average, 1.83 tons of CO2 are emitted for every ton of steel produced. Aluminum has an even more destructive carbon footprint. Each ton of aluminum emits 11.7 tons of carbon, nearly six times that of steel. A life-cycle assessment of the aluminum industry shows additional harmful emissions of methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride. The average lifespan for steel and aluminum towers is 15-30 years, depending on variables such as local weather and how well the tower is constructed and finished. In any case, replacement of corroded or weather-damaged towers is an ongoing problem. It is certainly possible to recycle corroded steel, but it is not always feasible, especially when other components such as plastic laminates or paint are present. To recycle steel, the material is shredded and then melted to create new sheets of metal. This process takes time and energy, and is not a simple matter. For example, if the rust on steel towers is simply melted, it will re-form once the metal cools, demanding even more complex and time-consuming recycling processes.   

Consequences of wood pole production and use

Alternately, the use of wooden towers (most commonly made from western red cedar, Douglas fir and southern pine), presents further impacts on the environment. These trees, with their deep taproots and soil-sustaining root systems, are vital to forest ecosystems. The continuous harvesting of this resource decreases carbon storage, alters hydrology, increases erosion, and seriously affects wildlife habitats. Once trees are harvested for use as towers, new dangers are introduced. Wooden utility towers are often treated with pentachlorophenol (PCP) to protect them against fungi and termites. Copper, chromium, arsenic and creosote are also used. Exposure to PCP and other preservative chemicals can cause reproductive and developmental problems, damage to the immune system, and even cancer. Since towers will be installed not only in downtown areas, but in residential neighborhoods, the potential risks to children and developing fetuses are critical to consider. The EPA has calculated that children face 220 times the usual risk of cancer from exposure to soil contaminated with PCP. The chemical is also highly toxic to birds, mammals, and aquatic organisms as well as plant life.

Shipping emissions make a significant difference

Another consideration in building out infrastructure must be shipping, handling and storing the small cell towers. This journey from manufacturing site to warehouse or job site to final installation site is a significant part of the environmental footprint. The heavy weight of metal and even wood towers contributes to measurable emissions at every step along the transportation pathway.

Installation further increases the impact

Even after production and transportation are accounted for, the next step in the journey of a typical small cell tower is installation. In the case of traditional metal towers, this process usually takes at least two days, and sometimes longer. During this time, traffic is either waiting and idling or being re-routed around the site, increasing CO2 production. Emissions and noise pollution from the heavy equipment required is also an issue during installation, especially in areas of neighborhoods, schools and hospitals. In addition, the heavy weight of steel towers demands substantial foundation work such as new or deeper concrete caissons. These require concrete and pump trucks which add additional emission burdens to the carbon footprint.  Steel, aluminum, and wood towers are secured using concrete foundations. The cement industry is a leading producer of carbon dioxide, creating up to eight percent of worldwide man-made emissions, both from the chemical process and from burning fuel used in its manufacture. Ranked alongside CO2 emissions from individual countries, the cement industry is the third-highest emitter after China and the United States. Use of cement exacerbates urban runoff, in which storm water tends to pick up gasoline, motor oil, heavy metals, trash and other pollutants, contributing to water pollution.

Seeking a cleaner, better way forward

The engineering team at EasyStreet Systems™ has worked determinedly to find a more sustainable solution. That solution includes the use of glass fiber for a new kind of small cell tower. Glass fiber’s primary component, sand, is readily available and constantly renewing itself via natural processes of wave action and erosion. Because glass fiber is extremely lightweight, a cement base is unnecessary. Instead, the composite tower is anchored using sustainable, quick-drying, polyurethane foam.  

Advantages of glass fiber as a material

Glass fiber’s distinguishing characteristics include mechanical strength, permeability, and stability. It can withstand an impressive range of temperature, from 40 degrees below zero Fahrenheit to hotter than 350 degrees Fahrenheit. It is not susceptible to corrosion, degradation, rust or fatigue; therefore, theoretically, a tower only has to be produced, shipped and installed once, where a steel tower must go through this sequence every time it degrades.    Glass fiber offers the same strength and stiffness as metal, and is actually more impact resistant. It holds steady in winds up to 200 miles per hour. It requires no maintenance and is not prone to degradation by moisture nor impacted by UV. EasyStreet applies a polyurea coating to the tower which provides further UV and corrosion resistance. Polyurea is free from solvents and contains neither plasticizers nor volatile organic compounds. Hardening within seconds, the components chain together permanently. Glass fiber is also easy to transport. Because it weighs 80-90 percent less than steel, it requires significantly less fuel for transportation and hence creates fewer emissions. Lightweight construction also means that a small crew of two or three workers can install a steel-equivalent 30-foot-tall 150-pound composite tower in about two hours. Installation uses primarily hand tools, minimizing air and noise pollution, and takes hours rather than days, which facilitates traffic flow and cuts down on emissions from idling vehicles.   Glass fiber is recycled using a pyrolyzation process, in which it decomposes into three recoverable substances: pyro-gas, pyro-oil, and a solid byproduct. All three can be recycled. The pyro-gas has the same energy content as natural gas and can even be used as an alternative to natural gas. Compared to the mining and processing of other construction materials like concrete and metals, glass fiber is the least energy-intensive, consumes fewer fossil fuels, and ultimately creates the least amount of harmful greenhouse emissions.

A lower impact form of manufacturing

In the manufacture of its towers, EasyStreet Systems uses a low emission process called pultrusion. Pultrusion is widely employed in the composites industry due to its continuous, automated, and highly productive nature. Towers can be manufactured in any length reducing the need for retooling. The process requires far less heat than manufacturing aluminum and steel. Lower heat significantly reduces the amount of water needed for cooling.   Minimizing foundation work also has dramatic emissions savings over traditional methods. Unlike steel and wood towers which are stabilized using cement, fast-drying polyurethane foam, with a negligible environmental impact, can be used to securely set these lightweight towers in place.

Summary: Composite towers and the future

At a glance, the two major objectives for telecom’s next big push into 5G, IoT and Smart Cities would seem to be at direct odds: Build out a dense infrastructure as quickly and nimbly as possible, while minimizing critical impacts to air, soil, water, abating noise and ultimately lessening the overall environmental impacts of this installation to booming city populations and the planet. But our research shows that composite towers, sustainably created with a primary ingredient of glass fiber, and shipped and installed within significantly lower particulate and noise thresholds, can certainly accomplish both objectives equally well. As metal and wood materials of the past become increasingly difficult to source, and onerous to install and maintain, composite glass fiber towers would very much appear to be the way of the future.   

Supporting materials

By 2050, more than two-thirds of the world will live in urban areas https://ourworldindata.org/urbanization

Composites and sustainability – when green becomes golden  https://www.materialstoday.com/composite-industry/features/composites-and-sustainability-when-green-becomes/  

Composites vs. other materials in industrial applications https://discovercomposites.com/industrial/composites-vs-other-materials-in-industrial-applications/  

Pultrusion of advanced fibre-reinforced polymer (FRP) composites https://www.sciencedirect.com/science/article/pii/B9780857094186500090  

Do fiber-reinforced polymer composites provide environmentally benign alternatives? A life-cycle-assessment-based study www.cambridge.org/core/journals/mrs-bulletin/article/do-fiberreinforced-polymer-composites-provide-environmentally-benign-alternatives-a-lifecycleassessmentbased-study/6B4BA944EF6BB811E727BC38BF5CFABA 

Cement and concrete: The environmental impact https://psci.princeton.edu/tips/2020/11/3/cement-and-concrete-the-environmental-impact 

Environmental carbon footprints sciencedirect.com/science/article/pii/B9780128128497000088

Environmental concerns expected to help spur strong demand for polyurea coatings www.adhesivesmag.com/articles/97101-environmental-concerns-expected-to-help-spur-strong-demand-for-polyurea-coatings  

Fiberglass green and sustainability https://fgiaonline.org/pages/fiberglass-green-and-sustainability  

Is fiberglass recyclable? https://www.conserve-energy-future.com/is-fiberglass-recyclable.php 

You really shouldn’t touch those wooden utility poles: Millions of these poles continue to be coated with PCP, a carcinogenic chemical https://www.earthisland.org/journal/index.php/articles/entry/you_really_shouldnt_touch_wooden_utility_poles/ 

Mitigating the environmental effects of opencast mining https://www.miningweekly.com/article/mitigating-the-environmental-effects-of-opencast-mining-2014-05-09 

Environmental impact of steel production https://www.theworldcounts.com/challenges/planet-earth/mining/environmental-impact-of-steel-production/story 

Concrete: the most destructive material on Earth https://www.theguardian.com/cities/2019/feb/25/concrete-the-most-destructive-material-on-earth

Distribution pole installation https://www.youtube.com/watch?v=rpXaUEBrTTg  

MRWA standard light pole installation https://www.youtube.com/watch?v=jKuI8r4VY5M