Two Studies Examine Benefits, Hurdles of ‘Decarbonization’ Strategies

Efforts to “decarbonize” America’s transportation system to reduce greenhouse gas or GHG emissions could produce widespread health benefits, according to one report, but simultaneously face major cost and technological hurdles, a separate study noted.

[Photo courtesy of the New York State Department of Transportation.]

First, a report by the Transportation, Equity, Climate and Health or TRECH project headed by Harvard University analyzed the potential benefits of GHG reduction efforts being considered by the Transportation Climate Initiative – a regional coalition of 12 Northeastern and Mid-Atlantic states, along with the District of Columbia, that is expected to finalize a memorandum of understanding this fall.

According to a statement, the TRECH project report said the estimated health benefits from changes in active mobility and on-road emissions under the TCI policy scenarios include up to about 1,000 deaths avoided and nearly 5,000 childhood asthma cases avoided annually, if full implementation of those policies occurs in 2032. Furthermore, the “monetized value” of the subset of total health benefits included in the report are “larger than the estimated annual TCI program proceeds in 2032” under all of the TCI policy scenarios.

The TRECH Project added that its analysis “does not include climate-related health benefits and other potential health benefits from improving transportation systems” such as those from reduced traffic congestion and noise pollution as well as improved traffic safety and access to jobs, healthcare, and education.

However, a separate study conducted by the Brookings Institution cautioned that there are major “decarbonization challenges” when it comes to transitioning medium- and heavy-duty vehicles away from petroleum-based fuels and propulsion systems, which generate large amounts of carbon emissions.

“The degree of difficulty in decarbonizing transport varies across the sector. Electrification is relatively easy for smaller vehicles that travel shorter distances carrying lighter loads,” the organization noted in a statement. “For these vehicles, the added weight of a battery is less of a hindrance and the inherently simpler and more efficient electric motor and drivetrain make up for some of the weight penalty. However, the heavier forms of transportation are among the fastest growing, meaning that we must consider solutions for these more difficult vehicles as well.”

The Brookings Institution noted in its report that while “technology exists to decarbonize the heavy transport sector,” many of those advanced technologies “are expensive and not proven at scale.”

The report added that the challenge for policymakers will be keeping technology advances and policy in alignment as the technology advances. “The COVID-19 pandemic adds a degree of difficulty since it is unclear how it may shift demand and consumer preferences in transport,” the group noted. “For example, consumers may remain reluctant to use urban public transport, and shorter supply chains may be attractive to businesses seeking to become more resilient in the face of a global disruption.”

FHWA Unveils New CMAQ Emissions Calculator

The Congestion Mitigation and Air Quality Improvement or CMAQ program offered via the Federal Highway Administration provides funding to state and local governments for transportation projects and programs that reduce emissions and help improve air quality and congestion. And to help those agencies track the emissions benefits of their projects, the FHWA developed and is now rolling out a new CMAQ Emissions Calculator Toolkit.

“CMAQ project justification as well as annual reporting require the development of reliable air quality benefit estimates,” the agency explained. “Realizing that every potential project sponsor may not have the capacity for developing independent air quality benefit estimates, the FHWA has undertaken the initiative of developing a series of spreadsheet based tools to facilitate the calculation of representative air quality benefit data.”

There are 10 tools currently available which cover a wide range of CMAQ-eligible project types, including: bicycle-pedestrian improvements; transit service and fleet expansion; alternative fuels and vehicles; diesel retrofit/repower; and traffic flow improvements.

More information about the new CMAQ tools can be found by clicking here.

Can Highway Construction Achieve “Net Zero” Carbon Emissions?

What does it mean to be “net zero” in the transportation world today?  When talking about carbon emissions, it refers to achieving an overall balance between emissions produced and emissions taken out of the atmosphere.

For example, the building industry has been working toward “net zero” infrastructure for years.  According to the World Green Building Council, buildings are currently responsible for 39 percent of global energy-related carbon emissions: with 28 percent coming from operational emissions – from the energy needed to heat, cool, and power the structures – and the remaining 11 percent from materials and construction. 

Though highway roads and structures do not have the same level of operating emissions as a building, “embodied” carbon from the construction process significantly adds to transportation’s carbon footprint. Embodied carbon is the carbon footprint of a material. It considers how many greenhouse gases (GHGs) are released throughout the supply chain. This includes the extraction of materials from the ground, transport, refining, processing, assembly, in-use and finally its end of life recycling of disposal.  

The building industry now believes that embodied carbon in projects can be reduced 10 percent to 20 percent without increasing capital costs. One new study out of Sweden believes net-zero carbon emissions in construction supply chains can be reached by 2045.

Photo courtesy Hawaii DOT

But what exactly does this mean for highway and bridge construction? Many believe that policy is the starting point for significant reductions in carbon in highway projects. Globally, many countries are already requiring “net zero” infrastructure design. In Sweden, for instance, large transport infrastructure projects (roads, rail, tunnels) are required to calculate and report embodied carbon and monetary incentives awarded if embodied carbon is below a specified target. 

Some state departments of transportation are already working toward similar goals. For example, the Hawaii Department of Transportation started a testing project in 2019 using a concrete mix injected with waste carbon dioxide (CO2). The CO2 is mixed into the concrete using CarbonCure technology. The resulting product traps carbon dioxide in mineral form within the concrete and improves the comprehensive strength of the material. 

The test project involves a pour of 150 cubic yards of carbon-injected concrete next to an equivalent pour of standard concrete mix on an access road for the Kapolei Interchange. This test will allow the Hawaii DOT to do a side-by-side comparison of the carbon reducing mix versus a standard mix to determine specifications for the use of carbon-injected concrete for road projects in the future.

“We’ve seen the benefits to CO2 mineralized concrete and will be using it when appropriate in Hawaii’s road and bridge projects,” explained Ed Sniffen, Hawaii DOT’s deputy director for highways. “The availability of environmentally friendly materials such as carbon injected concrete is necessary for us to move forward in reducing the carbon footprint of our construction projects.” 

In an interview with Smart Cities Dive, Sniffen added that the carbon-injected material has turned out to be stronger and more workable, with no increase in cost over traditional concrete. “The overall carbon savings is significant,” he said. “We reduce it overall about 1,500 pounds into the environment. Now, that doesn’t sound like a lot, but really, that equals up to one car driving 1,600 miles continuously. So, it builds up quite a bit.”

How can such “embodied” carbon in highway construction be reduced? In general, highway designers can use Life Cycle Analysis based tools to determine the environmental footprint of a whole project and search for ways to reduce life cycle GHG emissions and other impacts through strategies such as:

  • Ensuring efficient use of materials (i.e. “right-sizing”)
  • Selecting materials with more efficient manufacturing processes
  • Minimizing transportation impacts through use of local materials
  • Using robust materials that require less maintenance, repair, and refurbishment
  • Choosing materials that can be reused or recycled instead of landfilled

Although there may be a learning curve and increased costs initially to incorporate embodied carbon reduction into construction decisions, it appears that the incremental costs of incorporating this analysis is comparatively small for the potential benefit it could provide. Complicated decisions and life cycle analysis must be done from the planning phase of the project through design and construction to significantly reduce embodied carbon and hit the “net zero” goal. In the future, these efforts will be driven by government policy and environmental stewardship of firms and contractors. It is inevitable that the wave of “net zero” goals in the building industry will continue to transition into the highway industry as well.