Methane Reduction through Algal Bloom Mitigation in Aquatic Ecosystems

The proposed methodology applies to project activities that reduce methane emissions by mitigating harmful algal blooms (HABs) in open freshwater bodies, including the application of algicides containing heavy metals.

Eutrophic events occur due to point and non-point source loading of nutrients (phosphorus and nitrogen). Excess nutrient levels cause dense algae blooms and negatively impact ecosystem health (water quality, habitat loss, biotic community structure) and access to and cost of clean drinking water. Toxic algal (cyanobacteria) blooms are strongly correlated with increased methane and nitrous oxide emissions. Algaecides alleviate issues associated with algae by directly killing standing biomass.

The methodology idea note was rejected by Verra, as per Section 3.1.6(3) of the VCS Methodology Development and Review Process, v4.4 (PDF). The decision was based on:

• Low climate change mitigation potential compared to other proposals
• Potential unmitigable environmental and regulatory risks associated with applying algicides and the accumulation of heavy metals in bottom sediment due to reoccurring treatment
• Uncertainty associated with the resuspension of nutrient-laden sediment and its impact on water quality. Reversal of legacy nutrients associated with bottom sediment may lead to additional eutrophic events.

Methodology Development ID# M0369.