Seed germination and risks of using the invasive plant Eichhornia crassipes (Mart.) Solms-Laub. (water hyacinth) for composting, ovine feeding and biogas production

Water hyacinth (Eichhornia crassipes (Mart.) Solms-Laub.) is an invasive aquatic weed that has one of the highest growth indices of vascular plants, producing large amounts of biomass. Its use for composting, livestock feed and biogas production has been proposed as a management strategy for its control. The work presented here is an assessment of the potential spread of water hyacinth due to the release of seeds from the by-products of some of these manufacturing processes. We tested experimentally if the seeds were destroyed or did not lose germinability when they had passed through the gut of sheep, remained in compost piles or been used in biogas bioreactors. We made optical and electronic microscopic observations, and calculated retrieval and germination percentages of the seeds subjected to these treatments. After having passed through the gut of sheep, the anatomical organization of the seed was completely destroyed, only 30.50 ± 5.83% of the seeds were retrieved and the germinability was null (0 ± 0%). The biogas production and compost-treated seeds both had retrieval percentages of 100 ± 0% and germination values of 1.00 ± 0.57 and 3.50 ± 0.96% respectively, with several anatomical damages. The use for compost or biogas production as a management strategy to control this pest is not completely safe from an environmental perspective and the selected management option should focus on sheep fodder production.