Reducing Global Carbon Emissions

As global temperatures continue to rise, scientists are racing toward solutions that will reduce the emissions of greenhouse gases such as CO₂ to the atmosphere and avoid the worst effects of climate change.

A key aspect of this challenge is that 80% of the world’s energy supply relies on carbon-containing fuels, which are not easily replaced at the scale of today’s civilization.

Hertz Fellow David Dankworth, a program executive and distinguished scientific advisor at ExxonMobil, contemplates this idea often: “How can I take today’s energy system and transform it efficiently to achieve net-zero greenhouse gas emissions?”

While some of the needed transformation will come from deployment of renewable electricity and electrification of some vehicles, Dankworth believes there will be a continued need for fossil hydrocarbons to enable reliable energy supply and as feedstock for manufacturing. The key is to mitigate the emissions as rapidly, efficiently and affordably as possible—all of which require bringing multiple new technologies to commercial scale within the next decade or two.

Dankworth has long been passionate about developing chemical process technology that can be deployed at massive scale to meet global needs for clean, affordable products.

While a Hertz Fellow in chemical engineering at Princeton University 30 years ago, Dankworth uncovered the mathematical structure behind regime transitions in complex gas-liquid-solid flows. These are often a key feature of industrial chemical reactors, and their complexity makes scale-up difficult without large, expensive experiments. Dankworth joined a group at Exxon that was developing the first computational fluid dynamics codes for multiphase flows. Such are now routinely used to accelerate the design process through computer simulation of the reacting flow system. 

The energy challenge in the 90s was removing the sulfur from gasoline and diesel to reduce smog. Regulations were coming into effect on a tight schedule, and the technology of the day was not ready. In a series of roles at ExxonMobil, Dankworth took part in the research and the commercial deployment of new desulfurization technology to dozens of refineries around the world.

It’s an effort that Dankworth continues with the new challenge of developing and deploying technology for the energy transition.

At ExxonMobil, Dankworth is focused on the decarbonization of natural gas, an effort that could help meet the targets of the Paris Climate Agreement.

“Decarbonization is a big word for something pretty simple: ‘blue’ hydrogen,” said Dankworth, “It means harvesting the hydrogen while moving the carbon into another form that can be either stored underground or used in durable materials.”

One way to do this is through steam reforming, which is used to produce hydrogen today. In the future, the reforming technology must be integrated with CO₂ capture technology, without greatly increasing the cost or impacting the efficiency of the process. 

Another pathway to hydrogen runs through methane pyrolysis. When natural gas is heated under pressure to about 1000 degrees Celsius, the carbon and hydrogen will split apart. Hydrogen is recovered for use as fuel, and the carbon can be used or stored. 

This path does not require infrastructure for storing CO₂, and renewable electricity can be used to provide the needed heat. Adding a metal catalyst to the process can yield nanotubes that are turned into carbon fiber, a product stronger than steel that can be used for building infrastructure, with much lower GHG emissions.

Arriving at lower-emissions energy solutions across all sectors of the economy will require expedient and massive innovation in the years ahead.

In addition to gas decarbonization, Dankworth explained that ExxonMobil R&D is working on better solutions for direct air capture and lower emission fuels, which offer cheaper and faster paths to a net-zero economy. To accelerate solutions, he collaborates with a number of university centers that have formed partnerships with ExxonMobil and other companies, from across the U.S. to Singapore.