The catchphrase “reducing your carbon footprint” is spoken so often that many people don’t pay attention to it anymore. They understand that greenhouse gases are harmful but don’t understand how new trenchless construction or rehabilitation of subterranean systems can affect the atmosphere above.
Understanding what causes the greenhouse effect and trenchless construction’s role in reducing the “footprint” can help everyone.
Understanding Greenhouse Gases
The greenhouse effect is a necessary part of making the Earth inhabitable by humans as solar radiation passes through the atmosphere, the earth’s surface heats. The surface then re-emits the energy produced through this heating into the atmosphere.
Carbon Dioxide (CO2) and water vapor naturally found in the atmosphere absorb the infrared energy, helping to retain the heat produced. Without this process, which is known as the Greenhouse Effect, the average surface temperature would be approximately 28°C (82.4°F) colder than it usually is.
Without the appropriate concentration of CO2 in the atmosphere, the earth would be too cold for humans to inhabit. The climate would shift into an Ice Age, causing catastrophic conditions in which many would suffer and die.
While there is a natural greenhouse effect with the earth’s atmosphere, emissions from construction, transportation, and industrialization can exacerbate the impact. Additional CO2 can cause a rise in the average earth temperature.
A rise of just 2°C (35.6°F) can cause a drier world, making it harder to grow much-needed crops to feed the population. The warmer temperature can cause ice in artic areas to melt, forcing a rise in seawater which may wipe out low-lying areas.
Greenhouse Gas Emissions and Trenchless Construction
Some greenhouse gases are naturally occurring. Carbon Dioxide is an example of these naturally occurring gases and is regulated by plants using photosynthesis. While there are naturally occurring gases in the atmosphere, sampling data shows that in the last 150 years, since the industrialization of major cities, there is a significant increase in greenhouse gas levels.
With a 25 percent increase in gas levels, seeing a rise in average earth temperature is a real threat.
What does the rise in greenhouse gas emissions have to do with trenchless construction? While the rehabilitation and installation of new pipelines are not the sole cause of the increase, it is a contributing factor. In the past two decades, 75 percent of all CO2 emissions come from the burning of fossil fuels.
With installation and rehabilitation of pipes, these emissions come from two sources, construction, and transportation. (Learn more in Trenchless Rehabilitation Evaluation: How to Properly Inspect and Locate Damaged Pipelines.)
Underground construction can happen one of two ways: traditional open trench or the trenchless method. Trenchless construction does offer reduced CO2 emissions when compared to the conventional open trench method. However, there are still aspects of development that can give off CO2.
The number of emissions depends on the type of equipment used, the loading factor, hours of construction, and the emission factors of the machine. The emission factor is based on EPA standards. The calculations for HC, NOx and CO emissions vary based on the steady state at zero hours, transient, and deteriorate factors. Transient and deteriorate factors are a function of the age of the engine coupled with the type of equipment used.
According to research from Environmental Solutions, transportation emissions are the second factor when calculating the total emissions of a construction project. This factor stems from the use of diesel fuel to move equipment to and from the work site. To calculate the greenhouse gas impact from transportation, use the following equation:
Emissions = EFA x n x (Do + DR)
EFu= emissions faction from pollutant
n= number of trips required to transport equipment and materials
Do = Distance one-way to the site
DR= Distance one-way return trip from the site
Impacts of Trenchless Construction Emissions
Trenchless construction offers lower overall greenhouse gas emissions when compared to the open trench construction option. With an open trench option, the machinery must remove all material above the construction area. Once workers complete the removal, they may have to line the base area before rebuilding the ground over the pipe and reinstate the surface. This work requires large machines which use massive quantities of diesel.
With a trenchless rehabilitation and construction protocols, the tools reduce the amount of work necessary and amount of disturbed ground. For example, using a horizontal directional drill to install a new line may require a hole with a diameter of 300 mm. The total soil removed is 0.07 square meters per 100 meters of installed pipe.
With a traditional excavation, the trench would need to be at a minimum, 1.5 meters wide, with a depth of 2.5 meters or a total 3.75 square meters per 100 meters of installed pipe.
A lower amount of soil removed, means for less work, and uses less energy. The reduced amount of burning fossil fuels to complete repairs reduces the overall amount of additional CO2 and other greenhouse gas emissions into the atmosphere. Trenchless repair and rehabilitation do still emit these harmful mixtures into the air. However, the amount is substantially less than open trenching.
Ways to Mitigate Emission Impact
Along with using trenchless construction and rehabilitation techniques to install subterranean pipelines, there are other ways construction companies can decrease their overall greenhouse gas emissions. For starters, they can choose materials with lower embodied carbon. While this is a more difficult task than say using lower carbon emitting vehicles, builders can check the Inventory of Carbon and Energy database for details on how much energy suppliers consume during the manufacturing of their product.
Contractors can also recycle materials and create sustainable development with longer life spans. Long life reduces the embodied carbon found during demolition and rebuilding.
There is a much that goes into determining the amount of greenhouse gas emissions produced by trenchless technology. It is essential to consider all aspects of construction to successfully reduce the overall emissions of toxic gases which may warm our atmosphere.