Methodology for In-situ Phycoremediation of Eutrophic River-estuary Systems

The proposed new methodology is based on the biological carbon sequestration of microalgae and biomass storage in riverbed sediment. The project activities are based on the in-situ bioremediation of eutrophic river-estuary systems using a microalgae-based consortium constituted by native microalgae. The idea is to emulate natural seasonal microalgal blooms with fast growth rates and high nutrient uptake, contributing to microalgal biomass production and accumulation. Once microalgal biomass aggregate and flocculate, microalgal cells sediment and accumulate in the riverbed, increasing soil organic carbon. The proposed new methodology applies to river-estuary systems in tropical and subtropic regions.

The methodology idea note was rejected by Verra, as per Section 3.1.6(3) of the VCS Methodology Development and Review Process, v4.3 (PDF). The decision was based on:

• The proposal’s low climate change mitigation potential compared to other proposals.
• Potential unmitigable environmental risks associated with algae blooms, the resuspension of nutrient-laden sediment, and the impact on water quality.
• Uncertainty related to the permanence of emission reductions due to insufficient supporting research on this application in freshwater environments.