Joshuah K. Stolaroff

Encapsulated liquid sorbents for carbon dioxide capture

Drawbacks of current carbon dioxide capture methods include corrosivity, evaporative losses and fouling. Separating the capture solvent from infrastructure and effluent gases via microencapsulation provides possible solutions to these issues. Here we report carbon capture materials that may enable low-cost and energy-efficient capture of carbon dioxide from flue gas. Polymer microcapsules composed of liquid carbonate cores and highly permeable silicone shells are produced by microfluidic assembly. This motif couples the capacity and selectivity of liquid sorbents with high surface area to facilitate rapid and controlled carbon dioxide uptake and release over repeated cycles. While mass transport across the capsule shell is slightly lower relative to neat liquid sorbents, the surface area enhancement gained via encapsulation provides an order-of-magnitude increase in carbon dioxide absorption rates for a given sorbent mass. The microcapsules are stable under typical industrial operating conditions and may be used in supported packing and fluidized beds for large-scale carbon capture.

Printable enzyme-embedded materials for methane to methanol conversion

An industrial process for the selective activation of methane under mild conditions would be highly valuable for controlling emissions to the environment and for utilizing vast new sources of natural gas. The only selective catalysts for methane activation and conversion to methanol under mild conditions are methane monooxygenases (MMOs) found in methanotrophic bacteria; however, these enzymes are not amenable to standard enzyme immobilization approaches. Using particulate methane monooxygenase (pMMO), we create a biocatalytic polymer material that converts methane to methanol. We demonstrate embedding the material within a silicone lattice to create mechanically robust, gas-permeable membranes, and direct printing of micron-scale structures with controlled geometry. Remarkably, the enzymes retain up to 100% activity in the polymer construct. The printed enzyme-embedded polymer motif is highly flexible for future development and should be useful in a wide range of applications, especially those involving gas–liquid reactions.

Microencapsulation of advanced solvents for carbon capture

Purpose-designed, water-lean solvents have been developed to improve the energy efficiency of CO2 capture from power plants, including CO2-binding organic liquids (CO2BOLs) and ionic liquids (ILs). Many of these solvents are highly viscous or change phases, posing challenges for conventional process equipment. Such problems can be overcome by encapsulation. Micro-Encapsulated CO2 Sorbents (MECS) consist of a CO2-absorbing solvent or slurry encased in spherical, CO2-permeable polymer shells. The resulting capsules have diameters in the range of 100-600 μm, greatly increasing the surface area and CO2 absorption rate of the encapsulated solvent. Encapsulating these new solvents requires careful selection of shell materials and fabrication techniques. We find several common classes of polymers are not compatible with MECS production, but we develop two custom formulations, a silicone and an acrylate, that show promise for encapsulating water-lean solvents. We make the first demonstration of an encapsulated IL for CO2 capture. The rate of CO2 absorption is enhanced by a factor of 3.5 compared to a liquid film, a value that can be improved by further development of shell materials and fabrication techniques.

Energy use and life cycle greenhouse gas emissions of drones for commercial package delivery

The use of automated, unmanned aerial vehicles (drones) to deliver commercial packages is poised to become a new industry, significantly shifting energy use in the freight sector. Here we find the current practical range of multi-copters to be about 4u2009km with current battery technology, requiring a new network of urban warehouses or waystations as support. We show that, although drones consume less energy per package-km than delivery trucks, the additional warehouse energy required and the longer distances traveled by drones per package greatly increase the life-cycle impacts. Still, in most cases examined, the impacts of package delivery by small drone are lower than ground-based delivery. Results suggest that, if carefully deployed, drone-based delivery could reduce greenhouse gas emissions and energy use in the freight sector. To realize the environmental benefits of drone delivery, regulators and firms should focus on minimizing extra warehousing and limiting the size of drones.The use of drones to deliver commercial packages is poised to become a new industry. Here the authors show that replacing truck delivery by drones can reduce greenhouse gas emissions and energy use when the drone size and additional warehousing requirements are limited.

Author Correction: Energy use and life cycle greenhouse gas emissions of drones for commercial package delivery

In the original version of this Article, the first sentence of the sixth paragraph of the “Comparing emissions” section, the Results originally incorrectly read as ‘In the base case, delivery of a small (0.5 kg) package with the small quadrotor drone has lower impacts than delivery by diesel truck, ranging from a 59% reduction in GHGs in California, to a 17% reduction in Missouri’. The correct version states ‘54%’ instead of ‘59%’ and ‘23%’ instead of ‘17%’.The fourth sentence of the same paragraph originally incorrectly read as ‘In the base case, delivery of a medium-sized (8 kg) package has 17% lower GHGs than delivery by truck in California, is about equivalent to delivery trucks for the U.S. average electricity mix, but has 77% higher GHGs than truck delivery in Missouri, which has a carbon-intensive electricity grid’. The correct version states ‘In the base case, delivery of a medium-sized (8 kg) package has 9% lower GHGs than delivery by truck in California, is about 24% higher than delivery trucks for the U.S. average electricity mix, and has 50% higher GHGs than truck delivery in Missouri, which has a carbon-intensive electricity grid.The last sentence of the seventh paragraph of the same section originally incorrectly read as ‘Because of the importance of electricity used to power the octocopter, charging with low-carbon electricity of 200u2009g GHG/kWh can reduce delivered package GHGs by 34% compared to diesel trucks’. The correct version states ‘37%’ instead of ‘34%’.These errors have been corrected in both the PDF and HTML versions of the Article.