Apr 19, 2023Liked by Aaron Smith

Aaron, great article! AD is undoubtedly expensive for the industry to deploy. I can appreciate with your focus on the LCFS, that your analysis up to this point has been focused on methane avoidance and the GHG benefits. However, methane avoidance is not the only environmental value these systems generate. For farmers, digesters are a tool to manage crop residues, stabilize nutrients, and create a more efficient nutrient management systems. This certainty has environmental value in the form of lower infield N20 and CH4 emissions, as well as fewer nitrate leaving through waterways. Is there any interest in attempting to quantify the additional environmental benefits these system provide, outside of just avoiding CH4 from manure?

Thank you and keep up the great work!

Expand full comment

Great article and accurate analysis on the cost and GHG policy benefits. Thanks for taking the time to accurately document this important topic.

The benefit side of the analysis is even less due to updated analysis on methane gas. Methane gas is a potent GHG as measured in the laboratory as a single gas. But in the atmosphere methane is a dilute and weak GHG gas due to competition with water vapor and CO2 absorbing most of the long wave infra-red energy.

More up-to-date analysis on GHG gases is finding 89% of global warming due to water vapor, 10% due to CO2, Methane 0.004% and 0.005% due to Nitrogen Dioxide. These NASA satellite-based observations were reported in a recent article The Impact of CO2, H2O and Other “Greenhouse Gases” on Equilibrium Earth Temperatures. The science and math on methane absorption is described in this article; Methane: The Irrelevant Greenhouse Gas – Watts Up With That?

Expand full comment

Your data and analysis are greatly appreciated. Have you factored the Investment Tax Credit (ITC) for dairy biogas under the recent so-call Inflation Reduction Act (IRA)? That credit will be 30% to 50% of the capital cost for a digester project. Monetization of the ITC has been greatly simplified under the IRA and ought to be a significant subsidy for construction.

Expand full comment