Researchers Examine Circular Carbon Economy to Protect the Earth

Several efficient ways have been devised by Earth for preserving the atmospheric concentrations of carbon dioxide (CO₂)—from sequestration by oceans and forests to the formation of fossil fuels and limestone by organisms that have been dead for a long time.

However, the emission of CO₂ gas through manmade and natural activities is contributing to more atmospheric CO₂ than can be handled by the Earth’s natural processes.

Hence, in an effort to mitigate that stressor, a research team at the U.S. Department of Energy’s (DOE) Argonne National Laboratory is exploring the idea of a circular carbon economy.

The circular carbon economy, in its most basic form, is all about changing mindsets—be it individual or corporate—from a stance of “make it, break it, throw it away” to one of “reuse and recycle.”

It’s an alternative economy that takes into consideration the reuse, recovery and recycling of carbon-containing materials to keep carbon out of the atmosphere, creating a loop that incorporates the same carbon over and over into different products.

Cristina Negri, Director, Environmental Sciences Division, Argonne National Laboratory

While Japan, Europe, and other countries, have adopted this concept, it is still a relatively new one in the U.S. Nevertheless, the concept is beginning to gain attention among corporations that are aware of its positive environmental and economic impact, observed Meltem Urgun-Demirtas, a team leader of process development research in the Applied Materials division of Argonne National Laboratory.

Together, Urgun-Demirtas and Negri help companies in devising ways that will account for waste and byproducts and recycle them for use as energy or new products. However, such an undertaking is not an easy feat and needs the wherewithal for tracking, recovering, and processing those dissipated materials.

We have found that many companies don’t have the resources that Argonne has to achieve some of these goals. So our aim is to help a company examine its processes and suggest a specific circular economy approach.

Meltem Urgun-Demirtas, Group Leader, Applied Materials Division, Argonne National Laboratory

Urgun-Demirtas is also Argonne National Laboratory’s laboratory relationship manager for DOE’s Bioenergy Technologies Office (BETO), which is located within the Office of Energy Efficiency and Renewable Energy.

For instance, the duo is working with Koppers, Inc.—the global chemistry and materials company—to come up with such a technique and design studies that can establish whether the company’s choices will have an impact on reducing carbon.

From its side, Koppers has been allowing some type of a circular carbon economy before this word was coined. Koppers is the largest railroad tie manufacturer in North America, and for a number of years, it was focusing on finding innovative applications for coal tar, which is a carbon-rich byproduct of the coking processes used in the steel industry.

Creosote is one of those products, which is still being used by Koppers as a kind of preservative for the rail ties. Additional wood preservation chemicals are also being made by another division, with most of these chemicals predominantly composed of recycled copper.

As a matter of fact, most of the raw materials used by Koppers are either scrap materials or waste products, and these are subsequently changed into productive materials, observed Joe Dowd, vice president for Koppers’ Global Safety, Health, Environmental and Process Excellence. To some extent, one can say the same for the wood used by the company in the production of utility poles and railroad.

The logic is that while chopping down trees to produce a rail tie can eliminate resources that are involved in carbon sequestration, the carbon is permanently immobilized in the creosote-preserved product that could last as long as five decades.

Afforestation—that is, growing trees where none had grown before—is also being explored by Koppers as an additional strategy to offset carbon. In association with Argonne National Laboratory and local partners, Koppers is correcting one of its locations to promote the growth of hardwood trees to substitute some of the foliage that they harvest for production purposes.

In order to complete the circle, Koppers is recovering the rail ties and using them for producing energy. For instance, when these rail ties are treated and used as fuel for a paper mill boiler, they reduce the cost and requirement to burn fossil fuels, and also cut down the need for disposing the rail ties toward their end of their useful life.

Encouraging a wider use of wood may appear to be contrary to what one might think of in terms of sustainability, but for Negri, it is “expanding the box.”

From the perspective of the U.S. Forest Service and other agencies, making the same structures in concrete would create more CO₂ because concrete requires more resources, and more energy to make it, transport it, pour it, etc. There is no totally perfect solution, but the end of the story is that only an accurate lifecycle balance may tell you if wood products are gentler on the environment in terms of CO₂ emissions.

Cristina Negri, Director, Environmental Sciences Division, Argonne National Laboratory

Michael Wang is a systems assessment manager in Energy Systems division of Argonne National Laboratory. He works on lifecycle analyses related to a circular carbon economy but now, he is currently working on a National Petroleum Council study that investigates opportunities for reuse of the CO₂ gas, deducing whether the capture and recycling of CO₂ is environmentally feasible or not.

Most of the CO₂ sources are fossil fuel plants, specifically coal-fired power plants, in which the concentrations of CO₂ in the flue gases average 20%–25%. Furthermore, Wang’s team is looking at the energy and cost needed for capturing, purifying, and transporting pure CO₂ gas to a utilization site. In order to check the long-term mitigation impacts of CO₂, the researchers also need to know its fate.

If we produce a fuel, the embedded CO₂ will eventually get burned and return to the atmosphere. But the CO₂ in the fuel can come from fossil or biogenic sources. So we want to know under what circumstances we will get permanent mitigation and when will it be temporary.

Michael Wang, Systems Assessment Manager, Energy Systems Division, Argonne National Laboratory

Throughout the world, numerous projects are there that are studying different methods of using waste stream CO₂—from generating liquid fuels through renewable energy to producing artificial concrete.

Perpetually, ensuring that the energy fed into any system is below the energy that comes out of it is important to bring any kind of circular carbon economy strategy to a successful conclusion.

The ability to achieve that goal is what makes Argonne a key factor for companies looking to develop this approach. We have a highly diverse workforce with the resources to help them assess economic feasibility, model their processes and identify whether those processes are resilient.

Meltem Urgun-Demirtas, Group Leader, Applied Materials Division, Argonne National Laboratory