Carbon sequestration assessment and analysis in the whole life cycle of seaweed

Methods for carbon sequestration are warranted to tackle climate change caused by greenhouse gases released from anthropogenic activities. Seaweed is a type of marine plant that utilizes carbon dioxide for photosynthesis and has a substantial capacity to sequestrate carbon. Despite the huge potential, the long-lasting carbon sequestration (LLCS) of seaweed has never been calculated throughout its whole life cycle (nursery, temporary rearing, maturation, harvesting, and processing). In this paper, we use a life cycle assessment (LCA) approach to calculate the LLCS of seaweed, which can be understood as the difference between carbon fixation and released carbon throughout the life cycle of seaweed. Using kelp (Laminaria japonica) as an example of seaweed, the present study validates the procedure of calculating the LLCS of seaweed throughout its whole life cycle in Ailian Bay from nursery to processing into biochar (fertilizer) as the final product. The results showed that the carbon sequestration (full life cycle) of kelp in Ailian Bay was 97.73 g C m(-2) year. Biomass carbon accounts for approximately 86% of the total value (982.53 g C m(-2) year) of carbon absorption source of kelp in Ailian Bay, with the remaining 14% consisting of recalcitrant dissolved organic carbon and sedimentary carbon. Moreover, we calculated the amount of biomass carbon that was sequestrated by seaweed production in China from 2010 to 2020. Thus, the present study demonstrates that the mass production of seaweed can be utilized as an efficient method to sequestrate carbon and a feasible method for evaluating the effect of kelp farms on climate change.