California Air Resources Board

Principal Investigator/Authors: Ermias Kebreab, Deanne Meyer, Jia Deng

Contractor: University of California, Davis

Sub-contractor: DNDC ART

Contract Number: 23RD031

Project Status: Active

Relevant CARB Programs: AB 32 Climate Change Scoping Plan, California Greenhouse Gas Emissions Inventory Program, Dairy and Livestock Greenhouse Gas Emissions Working Group, Short-Lived Climate Pollutants. California State Implementation Plans

Topic Areas: Greenhouse Gas Emission Inventory Program , Greenhouse Gas Inventory , Short-Lived Climate Pollutant Inventory, Particulate Matter (PM) , PM2.5, State Implementation Plans (SIPs), Agriculture, Modeling

Research Summary:

This project aims to improve the accuracy of methane (CH₄), nitrous oxide (N₂O), and ammonia (NH₃) emissions estimates from cattle by enhancing the California Dairy Emissions Model (CADEM). It incorporates both feed- and manure-based mitigation strategies, including the use of anti-methanogenic feed additives and improved manure management practices. By integrating a better understanding of rumen fermentation and manure processes, the updated model will provide more reliable estimates across various management scenarios. It will also include diet and manure management default values, sensitivity analysis, and expanded coverage for beef cattle, offering a practical tool to help producers, researchers, and policymakers reduce greenhouse gas emissions and support California’s climate goals.

Keywords: dairy cattle, methane, greenhouse gases, GHG, ammonia, emission sources, modeling