Chemical Approaches to Carbon Capture and Release – Inspiration from Natural Solutions to Gas Exchange
The Big Picture:
We are learning how natural systems have achieved such elegant and efficient gas exchange systems for both the molecular and the micron scale. We then seek to apply this understanding to solve current social and economic exchange problems On the top of our list is capture and release of carbon dioxide, but fundamental understanding could also be used to improve exchange of ions in Li-ion batteries, the exchange of oxygen for purification, and the separation of hydrocarbons.
Mankind emits a tremendous amount of CO2; however, it pails in comparison to the amount that is naturally respirated by biological species.
What tricks has nature developed in the 1 billion years it has been performing gas exchange? How does it minimize the energy required to breathe? Why can’t we build a lung-like system with these same principles? These questions motivate us to look at biological systems. We think that birds, nature’s master respirators, can teach us a lot about carbon capture and release.
The Nitty Gritty:
Designing Exchangers Based on the Avian Physiology
In this project, we are interested in studying and extracting the basic design principles found in natural systems greatest exchanger: the avian lung. Natural systems have spent over a billion years optimizing gas exchange, trying and rejecting hundreds of contactor designs to find those that enhance surface area to volume to facilitate mass transfer.
As a point of comparison, currently, the best manmade exchangers operate with surface area to volume ratios of approximately 10,000 meters2 per meters3. In contrast, the hummingbird, which has the highest specific surface area, has an exchange membrane of 500,000 meters2 per meters3.
Birds, due to their metabolic demands and the low gas concentrations in flight, evolved unique lung structures for rapid exchange of oxygen and CO2. In fact, bird lungs are so efficient that species of birds migrate over the Himalayas with only 2% O2. In examining the design of birds lungs, we found many similarities in biological exchangers, tiers of hierarchical organization, mathematical packing of compact circles, and specific distances between exchange elements.
We have developed a suite of technologies and techniques that enable us to replicate and design different exchangers built around the principles of the bird’s lung, using the best-in-class synthetic membranes for CO2 purification and separation.
Morphogenesis for Mass Energy Exchange
Natural systems achieved these sophisticated mass exchange structures by a technique known as morphogenesis: the combination of material synthesis and reaction-diffusion chemistry programmed at a genetic level. We recapitulated the essential elements of a morphogenetic system in synthetic materials creating materials that adapt to and transform into their application niche.
We have developed a basic system that allows the coupling of polymerization, depolymerization, and reaction diffusion to enable preliminary versions of synthetic morphogenesis.
Cooperativity in Gas Binding
Beyond the micron level, natural systems created rapid acquisition and release of gases using cooperativity in gas binding.
Hemoglobin is a beautifully constructed molecule that enables the rapid accumulation and release of oxygen across a narrow isobar. Hemoglobin operates through allosteric cooperativity, the changing of protein conformational dynamics to enable different binding parameters at individual heme sites.
We use the principles of cooperativity to design systems that cooperatively bind and release carbon dioxide.
Alternative Sources for CO2 Release
An extension of our work in understanding microvascular exchange and thermal management is developing alternative energy sources for the release of carbon dioxide from capture solutions.
A potential avenue for lowering overall energy costs of carbon capture and release is finding energy sources not utilized in the process.
In particular, we have focused on developing systems that use waste heat on a large scale, enabling release of CO2 with microvascular systems, as well as exploring photo-thermal effects for the release of CO2 using solar energy.
Combining the fundamental with a large, applied problem like the capture and release of CO2 requires a long-term vision that motivates us to pursue both engineering approaches and fundamental understanding of biological systems. There is not magic bullet to big problems, but they can stimulate exciting new ideas and potential solutions by challenging our understanding.