Geoengineering, marine microalgae, and climate stabilization in the 21st century

Abstract

Society has set ambitious targets for stabilizing mean global temperature. To attain these targets, it will have to reduce CO 2 emissions to near zero by mid-century and subsequently remove CO 2 from the atmosphere during the latter half of the century. There is a recognized need to develop technologies for CO 2 removal; however, attempts to develop direct air-capture systems have faced both energetic and financial constraints. Recently, BioEnergy with Carbon Capture and Storage (BECCS) has emerged as a leading candidate for removing CO 2 from the atmosphere. However, BECCS can have negative consequences on land, nutrient, and water use as well as biodiversity and food production. Here, we describe an alternative approach based on the large-scale industrial production of marine microalgae. When cultivated with proper attention to power, carbon, and nutrient sources, microalgae can be processed to produce a variety of biopetroleum products, including carbon-neutral biofuels for the transportation sector and long-lived, potentially carbon-negative construction materials for the built environment. In addition to these direct roles in mitigating and potentially reversing the effects of fossil CO 2 emissions, microalgae can also play an important indirect role. As microalgae exhibit much higher primary production rates than terrestrial plants, they require much less land area to produce an equivalent amount of bioenergy and/or food. On a global scale, the avoided emissions resulting from displacement of conventional agriculture may exceed the benefits of microalgae biofuels in achieving the climate stabilization goals.

Cross-study analysis of factors affecting algae cultivation in recycled medium for biofuel production

“…Given that seawater is one of the more sustainable water sources for cultivation [135], and that only 23% of the total 518 treatments in this meta-analysis grew marine algae, more marine algae stains should also be tested in recycled medium. Here, marine algae were associated with lower mean ES C and ES µ than freshwater algae, though the results are not significant( Figure S13).…”

Marine Microalgae Contribution to Sustainable Development

“…In order to have positive effects on CO 2 bio-mitigation, it is necessary to improve the power requirement in the cultivation stage [2]. In this sense, the cultivation of marine microalgae in outdoor systems involves a greater reduction of the energy requirements and would allow the upscaling of the cultivation of microalgae biofuels [9,14].…”

“…The existing literature and life cycle assessments (LCAs) have shown contradictory results, which complicate the understanding of the feasibility of the process [2,12,13]. However, there is a consensus to deeply explore the real possibilities, especially for marine microalgae in coastal areas [14].…”

“…Most studies pay attention to freshwater microalgae [15,16]. Marine microalgae have also been described as potential biomass producers [14], and have been targeted as biofuels under different conditions [17][18][19]. Independent studies have highlighted the importance of considering local coastal resources for biofuel production [7] while exploiting other products that can be used with cultivated biomass [20].…”

Integrating Algae with Bioenergy Carbon Capture and Storage (ABECCS) Increases Sustainability

“…In fact, the IPCC suggested that in addition to many low/zero emissions technologies (e.g., solar, wind, and nuclear power, fossil energy with carbon capture and storage [CCS], carbon neutral crops, etc.) net‐negative‐emissions technologies are needed to limit temperatures to less than 2°C above preindustrial conditions (Fuss et al, ; Greene et al, , ; IPCC, ; Walsh et al, ). Net‐negative‐emissions technologies include bioenergy with CCS (BECCS), afforestation, direct capture of carbon dioxide (DAC) from the air, and other carbon dioxide removal technologies.…”