Investigating a Composting Management System for Brown Algae (Sargassum fluitans and Sargassum natans)

Seaweed biomass, typically green algae species, such as kelp, have been used as a fertilizer for plant growth for centuries. The brown algae that becomes beached along the Gulf shores, known as Sargassum, acts the same way to replenish the nutrients required by coastal flora along the Texas coast.  In 2011, Sargassum fluitans Børgesen was added to the Global Invasive Species Database, while Sargassum natans Gaillon remains undocumented by the database.  Research from Texas State University has shown positive results of Sargassum used as a feedstock in large-scale composting.  Even without treatment to remove salt or other possible contaminants, Sargassum can be a simple feedstock in the production of organic soil amendments such as compost.  Compost is the natural process of breaking down organic matter into a usable, waste-free product and is increasingly used as a waste management system.  This project examines large-scale compost management of Sargassum fluitans and Sargassum natans (brown algae, or Sargassum, collectively) as a method that can be replicated locally near the communities that are burdened by the plant as well as investigates the limits that a compost management system has when using Sargassum as a feed stock to create a marketable byproduct for use in agriculture, horticulture and related markets.  Three recipes were used with the Sargassum, pairing it up with other common, and not so common, feedstocks found in the organic waste stream such as fish carcasses, palm leaves, manure and food waste.  The compost was managed over a period of 8 weeks until it was cured before final testing.  Samples were sent to Pennsylvania State University for compost quality testing where they used the U.S. Compost Council’s Seal of Testing Approval (STA) Program to analyze for various characteristics of the composite samples of the compost, including pH, soluble salt content (dS/m), stability, nutrient content and pathogens. Results of the project will be presented.