Prioritizing the valorization strategies of an invasive fern (Azolla) in a wetland

Wetlands play a vital role as one of the most important natural habitats on our planet. However, the survival of wetlands is threatened by various issues, including the arrival of invasive and non-native aquatic ferns. In this regard, Azolla filiculoides has become a serious problem for the Anzali wetland. The valorization of Azolla can contribute to the establishment of a collection system for this invasive fern, which can consequently reduce the harmful impact of this fern on the wetland, and it can be considered as a free and available source of biomass. Therefore, a fuzzy analytical hierarchy process was applied to rank the valorization strategies of this invasive fern. In the first step, four evaluation criteria (technical, economic, social, and environmental) and six valorization strategies were identified for the analysis through a literature review and expert opinions. The valorization strategies for Azolla were: 1) no collection, 2) collection and landfilling, 3) direct use as livestock and poultry feed, 4) composting, 5) biogas generation, and 6) biodiesel generation. The results revealed that the economic criterion had the highest priority for Azolla valorization, followed by environmental, technical, and social criteria, respectively. Regarding the valorization strategies, biodiesel was identified with the highest priority according to economic and social criteria, and biogas was the strategy with highest priority based on the environmental and technical criteria. In overall, biodiesel, biogas, and composting were ranked as the most appropriate valorization strategies for Azolla in the investigated wetland, respectively. Implementation of the identified valorization strategies can potentially promote the circular economy at the regional level and reduce the adverse effects of the invasive fern on the wetland ecosystem.