<
strong>
Motivation:<
/strong>
A major bottleneck for growing microalgae as a sustainable alternative to fossil carbon in economically producing fuels and chemical products is the cost of delivering CO<
sub>
2<
/sub>
in sufficient concentrations for it not to limit growth. This project sought to develop and integrate two innovative technologies for capturing and concentrating CO<
sub>
2<
/sub>
from air and delivering it to microalgae with high efficiency into an Atmospheric CO<
sub>
2<
/sub>
Enrichment and Delivery (ACED) system. The CO<
sub>
2<
/sub>
capture technology is based on moisture swing sorption (MSS), where specialized resin materials selectively capture CO<
sub>
2<
/sub>
when dry and release it when wet into a confined space where the concentration can be increased up to 500-fold. The CO<
sub>
2<
/sub>
-delivery technology is based on membrane carbonation (MC), which uses hollow fiber membranes that allow CO<
sub>
2<
/sub>
to diffuse into the algae-containing liquid without forming bubbles, achieving nearly 100% delivery efficiency. <
strong>
Work completed:<
/strong>
1. Subsystem design, construction, and characterization [Months 1-6]. ACED integration requirements were defined
prototype MSS and MC sub-systems were constructed to conform to these requirements and characterized independently. 2. Subsystem optimization and evaluation [Months 7-12]. An iterative process of operating and upgrading each subsystem at lab scale, leading to compatibility at full integration. 3. System Integration with open raceway, testing, and modeling [Months 13-24]. Operation and testing of the integrated ACED system in an open raceway pond and modeling. <
strong>
Broader impacts:<
/strong>
The ACED research program added to our understanding of 1) MC technology?s (i.e., hollow fiber membranes) utility for transferring pure CO<
sub>
2<
/sub>
and CO<
sub>
2<
/sub>
gas mixtures into microlagal cultures in laboratory and outdoor environments, 2) the first-of-a-kind MSS technology to capture CO<
sub>
2<
/sub>
from ambient outdoor air, and 3) methods for storing captured CO<
sub>
2<
/sub>
in carbonate/bicarbonate brines from which the CO<
sub>
2<
/sub>
can be retrieved at high concentration (>
90%). Near-term commercial opportunities were outlined for the MC technology for small scale algae cultivation with high CO<
sub>
2<
/sub>
costs (>
$100/ton) and larger scale operators with continued development. This will help reduce costs for producing sustainable fuels and products and reduce cost for microalgal research for developing new applications. Research areas were identified for MSS technology to achieve cost competitive CO<
sub>
2<
/sub>
produced from ambient air ($100/ton) as a means for closing the carbon cycle to make products from atmospheric CO<
sub>
2<
/sub>
instead of fossil fuels and remove CO<
sub>
2<
/sub>
from air to mitigate climate change.