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Kelp Versus Trees: The Comparison We Cannot Yet Make

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Fast fact: there is no defensible universal statistic showing kelp farms sequester more carbon dioxide than trees. NOAA reports kelp productivity comparable to tropical rainforests, but productivity is not the same as durable carbon storage. In its regional Greater Farallones assessment, NOAA estimates about 660 megagrams of carbon per year from kelp export. That is a regional total, not a per-hectare farm rate. Separate measurements of kelp detritus show uptake of about zero point seven six to zero point nine eight milligrams of carbon per gram per hour, but that is an uptake measurement, not an annual sequestration comparison.