Fast pyrolysis of naturally produced water hyacinth was assessed through Emergy accounting approach. Two analyses were carried out to evaluate the influence of additional services and externalities on Emergy indicators for a pyrolysis plant unit able to process 1000 kg of dry biomass per hour. The initial approach was a traditional Emergy assessment in which financial fluxes and externalities were not considered. The second approach included taxes and fees of the Brazilian government, interests related to financing operations and assumes a reserve financial fund of 5% of the total investment as externalities cost. For the first evaluation, the renewability of 86% indicates that local and renewable resources mainly support the process and the Emergy Yield Ratio of 3.2 shows that the system has a potential contribution to the regional economy due to the local resources use. The inclusion of financial fluxes and externalities in the second evaluation reduces both renewability and Emergy Yield Ratio, whereas it increases the Emergy Investment Ratio which means a higher dependence on external resources. The second analysis allows portraying significant forces of the industrial and financial systems and the evaluation of the externalities' impact on the general system Emergy behavior. A comparison of the renewability of water hyacinth fast pyrolysis with other biofuels like soybean biodiesel and sugarcane ethanol indicates that the former is less dependent on fossil fuel resources, machinery and fertilizers. To complement the sustainability assessment provided by the Emergy method, a regular financial analysis for the second defined system was done. It shows that the system is financially attractive even with the accounting of additional costs. The results obtained in this study could be used as the maximum and minimum thresholds to subsidize regulatory policies for new economic activities in tropical wetlands involving natural resources exploitation and bio-industrial systems.532281-291