High quality compost made from sargassum

Sargassum, a type of floating brown seaweed, can be composted into a product with no detrimental salt levels, according to a recent study done at Texas State University. Sargassum drifts that wash up on beaches are considered an invasive eyesore with ill effects on tourism in Texas’ beach communities.

Sargassum, which is common in coastal regions within the Gulf of Mexico, is traditionally disposed of by being integrated into dunes along the shoreline or into landfills. However, it contains potentially useful nutrients that could benefit plant growth on land. Diverting this resource into compost could help beautify beaches as well as promote a greater stewardship directed toward minimizing the strain placed on overflowing landfill spaces.

Among the concerns realized by attempting to use sea matter applied to garden growth is the detrimental effect salt content can have on land-based plants. However, this study found that sargassum could be incorporated into compost piles with no detrimental effects because of high levels of salinity.

“Since pre-washing of the seaweed did not impact the final compost produced in terms of improved quality, future studies may also attempt to identify the maximum amount and proper ratios of sargassum that can be used as a feedstock for compost creation,” said Jen Sembera, one of the researchers.

The study used 12 cubic yards of sargassum as feedstock mixed with food waste and wood chips to create 72 cubic yards of workable matter. From this, the researchers derived 25 cubic yards of stabilized compost. From that, they were able to test the quality of the resulting compost, and discovered sargassum-based compost was of either equal or higher quality than traditional or commonly sought compost; therefore its use in this manner proves to be a sensible way to manage the presence of this invasive species.

“When the amount of sargassum that arrives on the shoreline exceeds the amount that can be integrated into dunes, the biomass can be used as a feedstock to create compost valuable to the horticultural industry,” said researcher Erica Meier. “The compost may even be considered a ‘boutique’ compost product due to the incorporation of seaweed, since seaweed has been marketed to horticulturalists as a liquid fertilizer.”

Sembra, Meier and Tina Waliczek dedicated months assembling data along Texas beaches communities. The results of their study are illustrated in their article entitled Composting as an alternative management strategy for sargassum drifts on coastlines, published in HortTechnology, published by the American Society for Horticulture Science (ASHS). The article is available at http://horttech.ashspublications.org/content/28/1/80.abstract

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5 Comments on "High quality compost made from sargassum"

  1. Dr. Evelyn Weekes | July 21, 2020 at 11:56 pm | Reply

    What about the grave problem of inorganic arsenic in Sargassum that presents health and safety hazards and related cancer threats? Along with the tests for salt level in the finished compost can you say what the inorganic arsenic levels were in the seaweed? Would be grateful to know as this threat is what is preventing many people from using the seaweed in compost or fertilizer.
    The connection with all this inorganic arsenic from compost and fertilizers made using sargassum also goes to its runoff in coastal and marine ecosystems endangering our fish food security if indeed the finished compost or fertilizer has significant levels of inorganic arsenic. Your comments will be greatly appreciated.

    • I will try to get answers to your questions.
      Thank you for your comment.

      • Mike Williams | August 3, 2021 at 12:30 pm | Reply

        The levels of arsenic in sargasso are so low it is insignificant. Possibly in cases where it is concentrated ie mounded there could be elevated levels of arsenic leached but that has not been studied sufficiently to conclude that there re deleterious effects. Not enough to stop using sargasso as a compost. This is what I have found.

    • Chris Boulicault | August 5, 2021 at 12:59 pm | Reply

      Arsenic level is going down after composting, not endangering human health anymore. Sargassums are an issue on-shore but off-shore, it is an habitat for fish (like mahi mahi) and provide a excellent ecosystem, even for Co2 level. Marine ecosystem are more endagering by over fishing, cruise, and acidity pollution than by sargassum.

  2. I have seen multiple news reports, over the past few years, reflecting high levels of ecoli contamination in the Gulf of Mexico. Where is the safety data regarding that? Not to mention the agricultural industry is generally not organic and prefer to use large quantities of synthetic fertilizers, so using compost made from plant material that has absorbed high amounts of synthetic fertilizer (not to mention the synthetic pesticides and herbicides) should prevent the product from being OMRI listed. While the additional benefit sounds good in theory, I wouldn’t use it in my garden.

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