Hydrogen as a zero-carbon energy carrier has the potential to transform fundamentally the global energy landscape—but the production must benefit the environment, according to experts at Rice University’s Baker Institute for Public Policy.

Rachel Meidl, the fellow in energy and environment at the institute’s Center for Energy Studies, and Emily Yedinak, a doctoral candidate in materials science and nanoengineering at Rice, published a new brief, “Measuring the True Cost of Sustainability: A Case Study in a Green Energy Approach.”

We are transitioning to a new age of human development, one where the environmental and societal consequences must now be balanced with economic ambitions. If the fossil fuel industry wishes to remain relevant, it must adapt and explore paths towards zero-carbon or low-carbon energy and carbon utilization strategies.

—Yedinak & Meidl

According to the brief, the US Energy Information Administration (EIA) projects a 28% increase in average world energy consumption between 2015-2040, with fossil fuels continuing to take up 50-80% of that consumption.

Yedinak and Meidl argue that hydrogen, used as a zero-carbon energy carrier, has the potential to transform the global energy landscape.

Unlike solar and wind energy, hydrogen is a more natural substitute for fossil fuels in sectors that are particularly difficult to decarbonize (i.e. transportation and industrial) and where the ability to quickly respond to sudden increases in energy demand or to maintain consistent energy supply is critical. Hydrogen can be produced from several diverse and geographically dispersed resources, and its utility cuts across multiple sectors including metals refining, fuels upgrading, and ammonia production. Furthermore, hydrogen fuel cells are two to three times more efficient than internal combustion engines, thereby offering additional energy efficiency gains.

However, to be competitive with gasoline, the cost of hydrogen production must be lower than $2/kilogram (kg) (< $4/kg delivered and dispensed), and this begs the question of how hydrogen production will be scaled to meet future energy demand.

—Yedinak & Meidl

The brief presents a case study that considers the technological merits of methane pyrolysis—the direct conversion of methane in natural gas to hydrogen and value-added carbon materials— while also addressing real-world implications including health and safety risks and commercial risks for introducing new carbon supply chains.

At the hydrogen production scales that would be required for a global energy market (~300 MT of hydrogen to meet 10% of 2019 global energy demand), significant carbon production (~1 GT carbon) will be realized. The value proposition of methane pyrolysis relies on the availability of equally large markets that can absorb carbon from a new supply chain.

The largest markets for non-combusted carbon are carbon black (~10s MT), graphite (~0.1 MT), and carbon fiber (~0.1 MT), all of which are only a fraction of the carbon produced that could be expected if hydrogen production was scaled to meet a significant portion of global energy demand. Potential applications for a burgeoning carbon supply chain would need to move beyond the traditional markets. The recent discoveries and research in advanced carbon nanomaterials pose interesting value propositions for carbon supply chains.

—Yedinak & Meidl

The value-added carbon materials that are produced through pyrolysis, alongside hydrogen, could theoretically be a substitute for hard-to-decarbonize industrial processes and materials such as steel, copper and aluminum. This is due to the light weight, strength and conductivity of carbon nanotubes.

However, several challenges remain in assessing nanosafety risks, the authors observe. Risks include unintended chemical exposure throughout the supply chain that would need oversight.

Even beyond the technical hurdles of making the process efficient and scalable, the authors explain, expanding on or creating new carbon supply chains from large-scale methane pyrolysis will also require companies to overcome regulatory hurdles. “Legislation has not kept pace with the rapid rate of innovation,” the authors wrote.

As new supply chains for carbon and carbon dioxide are introduced, companies will need to weigh the economic benefits with the social costs—determining how the supply chain will affect the environment. The authors argue that companies as well as governments must guide investment decisions toward solutions that benefit society as well as the bottom line.

Resources

• Emily Yedinak and Rachel Meidl (2020) Baker Institute Issue Brief “Measuring the True Cost of Sustainability: A Case Study in a Green Energy Approach”