Understanding How Kelp Farming Can Help Capture Carbon and Reduce Erosion

Greg Howard
3rd August, 2024

Understanding How Kelp Farming Can Help Capture Carbon and Reduce Erosion

Image Source: Natural Science News, 2024

Key Findings

  • The study in Porthallow Bay, Cornwall, UK, measured the growth, erosion, and dislodgement rates of farmed Saccharina latissima (sugar kelp) over a typical cultivation season
  • Kelp blade growth rates increased from 1.3 cm/day in March to 2.3 cm/day in April, then decreased to 1.4 cm/day by May
  • The farm captures 0.14 tons of carbon per hectare per year, but up to 70% is released back into the environment as particulate organic carbon
Climate change mitigation requires innovative approaches, among which carbon dioxide removal (CDR) is critical. The ocean, with its vast surface area and depth, plays a central role in potential CDR strategies. One promising method involves the cultivation of seaweed, particularly kelp, which is believed to enhance local carbon sequestration rates. However, direct field-based measurements of carbon assimilation and release have been scarce. A recent study by Newcastle University[1] addresses this gap by quantifying the growth, erosion, and dislodgement rates of farmed Saccharina latissima in Porthallow Bay, Cornwall, UK, throughout a typical cultivation season. The study observed that blade elongation rates of Saccharina latissima increased from approximately 1.3 cm per day to 2.3 cm per day between March and April, before declining to 1.4 cm per day by May. Erosion rates remained low, ranging from about 0.5 to 0.8 cm per day, while dislodgement rates decreased from 20% of plants in January-February to 5% in April-May. These measurements provided insights into the carbon sequestration potential of small-scale kelp farms. The researchers estimated that the farm captures 0.14 tons of carbon per hectare per year, with up to 70% released into the environment as particulate organic carbon. Based on previous estimates of carbon burial and storage rates, the farm may sequester 0.05 tons of CO2 equivalent per hectare per year. These findings suggest that scaling up European kelp farming should be motivated by other co-benefits, such as low-carbon product alternatives, job creation, and potential biodiversity gains, rather than solely by a perceived significant increase in carbon sequestration. This study ties into earlier findings on the role of seaweed in CDR. Previous research has highlighted the potential of marine macroalgae to contribute to carbon offset schemes[2]. To verify the effectiveness of seaweed in carbon trading, it is essential to quantify the air-sea CO2 equilibrium and link this process to seaweed carbon storage pools. This process involves understanding how CO2 is drawn down from the atmosphere into seawater and subsequently fixed into organic carbon by seaweed photosynthesis[2]. Furthermore, the complexity of verifying carbon sequestration in marine environments compared to terrestrial systems has been acknowledged[3]. Factors such as the rapid turnover of seaweed biomass, the fate of carbon via particulate and dissolved organic carbon pathways, and the key role of atmosphere-ocean CO2 exchange must be considered. A forensic carbon accounting approach has been proposed to thoroughly analyze carbon flows between the atmosphere and ocean and into and out of seaweeds[3]. The Newcastle University study builds on these earlier findings by providing direct field-based measurements of carbon dynamics in a kelp farm. By quantifying growth, erosion, and dislodgement rates, the study offers valuable data on the carbon sequestration potential of seaweed farming. However, the results indicate that the contribution of small-scale kelp farms to meaningful carbon sequestration may be limited. This underscores the importance of obtaining further information from various cultivation sites to develop a comprehensive understanding of carbon dynamics associated with kelp farms. In conclusion, while seaweed cultivation holds promise for CDR, this recent study suggests that its primary benefits may lie in other areas, such as providing low-carbon product alternatives, creating jobs, and enhancing biodiversity. Further research is needed to fully understand the carbon sequestration potential of seaweed farming and to develop effective strategies for mitigating climate change.

EnvironmentSustainabilityMarine Biology

References

Main Study

1) Quantifying growth, erosion and dislodgement rates of farmed kelp (Saccharina latissima) to examine the carbon sequestration potential of temperate seaweed farming

Published 31st July, 2024

https://doi.org/10.1007/s10811-024-03323-w

Related Studies

2) Air-sea carbon dioxide equilibrium: Will it be possible to use seaweeds for carbon removal offsets?

https://doi.org/10.1111/jpy.13405

3) Forensic carbon accounting: Assessing the role of seaweeds for carbon sequestration.

https://doi.org/10.1111/jpy.13249


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