An Overview of Recent Advances in Using Direct Air Capture for Greenhouse Enrichment

Rising anthropogenic CO2 emissions contribute to the adverse effects of climate change as the current atmospheric CO2 concentration exceeds 400 ppm. Fortunately, carbon capture, utilization, and storage (CCUS) methods are under development to reduce atmospheric CO2 concentrations. Direct air capture (DAC) methods are of particular interest, as they enable CO2 to be captured from any point in the atmosphere. A practical application of DAC is greenhouse enrichment, whereby captured CO2 is used to raise CO2 concentrations in greenhouses. This work reviews and discusses the integration of DAC in greenhouses, which serves the dual purpose of mitigating climate change and improving agricultural yields. DAC allows greenhouses to quickly achieve CO2 concentrations as high as 1200 ppm, which is consistent with an enrichment factor of 3 (1200 ppm/400 ppm). This enrichment factor and optimal photosynthesis conditions allow various crops, including fruits and vegetables, to increase yields ranging from 21 to 61%, even when grown out-of-season. Furthermore, we compare different adsorbents to understand which are most practical for greenhouse enrichment. Results reported in the literature show that greenhouse enrichment requirements can be achieved using adsorbents that occupy 0.05% to 1.5% of the greenhouse volume. Moreover, a brief techno-economic analysis is presented to compare the benefits of different greenhouse adsorbents to other methods of providing CO2 enrichment. The cost of DAC adsorbents ranges from about 34.68 to 120 USD/tonne of CO2. Lastly, this paper reports on the limited research in greenhouse DAC regarding techno-economic assessments and life cycle analysis, as well as the optimization of numerous DAC systems and adsorbent properties.