Global concerns about climate change were once again expressed at the COP27 in Sharm El-Sheikh. Seaweed is frequently presented as a solution for climate mitigation. For a proper appraisal of its contribution to mitigating climate change, it is necessary to distinguish between, and critically scrutinize, the various pathways seaweed-based climate mitigations can take. This article identifies four different climate mitigation pathways and critically reflects on each. First, carbon sequestration, occurring when grown seaweed is left in the seas or, second, purposefully sunk. Third, carbon emission reduction, resulting when seaweed-based products replace products with a higher carbon footprint, either fossil based products or other organic material. Fourth, carbon emission avoidance, taking place when seaweed products are used to avoid greenhouse gas emissions in other production processes. Each of these pathways requires specific methods to quantify their magnitude and comes with critical questions to ask. The sequestration pathway requires monitoring of net carbon production and the amount of carbon that is eventually exported to the deep sea. Pathways 3 and 4 require Life Cycle Assessment and/or Carbon Footprint with system boundaries set to include the production system itself and installation thereof. We propose an unequivocal categorization in a belief that confusion on the benefits of seaweed will eventually impede development of seaweed-based solutions.

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海藻作为气候缓解解决方案：对四种气候缓解途径的分类和反思

在沙姆沙伊赫举行的 COP27 会议上，全球再次表达了对气候变化的担忧。海藻经常被视为缓解气候变化的解决方案。为了正确评估其对缓解气候变化的贡献，有必要区分并严格审查基于海藻的气候缓解措施可以采取的各种途径。本文确定了四种不同的气候缓解途径，并对每一种途径进行了批判性反思。首先，当生长的海藻被留在海洋中或故意沉没时，就会发生碳固存。第三，减少碳排放，当海藻产品取代碳足迹较高的产品（化石产品或其他有机材料）时就会产生碳排放。第四，避免碳排放，即在使用海藻产品时避免其他生产过程中的温室气体排放。每一条途径都需要特定的方法来量化其规模，并提出一些关键问题。封存途径需要监测净碳产量和最终出口到深海的碳量。途径 3 和 4 需要生命周期评估和/或碳足迹，系统边界设置为包括生产系统本身及其安装。我们提出明确的分类，因为我们相信，对海藻益处的混淆最终将阻碍基于海藻的解决方案的开发。