Person:

Hua, Charles

The transportation sector is the second-largest source of CO2 emissions, after electricity and heat generation, accounting for about 25 percent of global emissions.1 However, it is also one of the most challenging to decarbonize due to its distributed nature and the advantages of fossil fuels in terms of high energy densities, ease of transportation, and storage. Moreover, the degree of difficulty in decarbonizing varies significantly across the sector, making the challenge even more daunting.

So far, emissions reduction strategies have focused on improving vehicle and system-wide efficiencies, mode switching, and electrification. The latter is proving relatively easy for smaller vehicles that travel shorter distances and carry lighter loads. However, sector-wide decarbonization pathways will require a transition to low-carbon fuels and the deployment of enabling infrastructure to support innovation at scale.

Renewable hydrogen holds promise in sustainable mobility applications, whether by powering fuel-cell electric vehicles (FCEVs) like cars, trucks, and trains or as a feedstock for synthetic fuels for ships and airplanes. Fuel cells convert hydrogen-rich fuels into electricity through a chemical reaction. FCEVs use a fuel cell, rather than a battery, to power electric motors, and operate near-silently and produce no tailpipe emissions.

Hydrogen-powered vehicles offer key advantages, including shorter refueling times, longer ranges, and a lower material footprint compared to lithium battery-powered alternatives. However, high costs of ownership and a lack of enabling infrastructure are key challenges that must be addressed through policy support, technological innovation, and financial investment.

Hydrogen can complement existing efforts to electrify road and rail transportation and provide a scalable option for decarbonizing shipping and aviation. Figure 1 summarizes the mobility segments for which battery electric vehicles (BEVs), FCEVs, and vehicles running on bio- or hydrogen-based synthetic fuels are most applicable.

To accelerate the global transition to a low-carbon economy, all energy systems must be actively decarbonized. While hydrogen has been a staple in the energy and chemical industries for decades, clean hydrogen – defined as hydrogen produced from water electrolysis with zero-carbon electricity – has captured increasing political and business momentum as a versatile and sustainable energy carrier in the future carbon-free energy puzzle. But taking full advantage of this potential will require a coordinated effort between the public and private sectors focused on scaling technologies, reducing costs, deploying enabling infrastructure, and defining appropriate policies and market structures. Only in this way can we avoid replicating the system-wide inefficiencies of the past that have characterized regional approaches to deploying new energy infrastructure.

A rainbow of colors currently dominates almost every conversation on the transition to a low-carbon economy: green, grey, blue, turquoise, pink, yellow[1] - an ever-increasing palette to describe the same colorless, odorless, and highly combustible molecule, hydrogen. The only difference is the chemical process used to produce it.

The colors of hydrogen are crucial for the energy transition because each production pathway generates different amounts of greenhouse gas emissions. For example, while grey hydrogen, produced from fossil fuels, yields up to 20 tons of carbon dioxide per ton of hydrogen, green hydrogen, produced from renewable energy sources like solar and wind, yields no emissions. Furthermore, although these colors all refer to the same molecule, production costs differ: green hydrogen remains substantially more costly today.

With aggressive development and deployment of electrolyzers and other hydrogen technologies at scale, green hydrogen could become cost-competitive with blue hydrogen, produced from natural gas with carbon capture, by 2030 in many countries.[2] Overall, the rate at which green hydrogen costs decrease will also depend on government policies and incentives, such as carbon pricing and tax credits.

Therein lies a critical challenge for the successful transition to a low-carbon economy. As energy systems increasingly evolve from centralized to decentralized, from “grey” to “green,” stakeholders will need to efficiently account for and track emissions and green molecules in a transparent, secure, and standardized way, and must be able to do so along value chains from production to consumption.