Nitrogen Management for Carbon Credit.

Since the 1970s, more than 800 environmental markets have operated throughout the US. More recently, carbon markets have been proposed as a mechanism to help reduce agricultural emissions of the greenhouse gases (GHGs) carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O). Offset credits generated by reducing these emissions through management actions on farms are increasingly attractive to regulatory bodies looking at ‘off-site’ mitigation as an effective way to compensate for environmental damage. Agricultural ‘carbon credits’ are currently traded on several US markets, including the Verified Carbon Standard (VCS), Climate Action Reserve (CAR), and American Carbon Registry (ACR). Regional (RGGI and WCI) and state (California) markets also exist or will likely do so in the near future.

 Nitrous oxide is the major GHG emitted by US agriculture accounting for ~70% of total US N₂O emissions. With a GWP of ~300 it is a ‘low hanging fruit’ for offset project development, due to the high CO₂ equivalent (CO₂e) payback associated with its emission prevention. In a win-win-win scenario, farmers through adoption of nitrogen best management practices (N-BMPs) can reduce the agricultural footprint of this potent GHG, decrease levels of other reactive N species in the environment, and play a major role in delivering carbon credits to regulated industries, while receiving financial compensation for doing so.

 Here, we present an overview of current and developing protocols that use N-BMPs on cropped farmland as their driver for N₂O emissions reductions and offset credit generation. We place an emphasis on our methodology that uses N fertilizer rate as a robust predictor of N₂O emissions, and was developed from empirical data from trials conducted on commercial farmer fields under corn-soybean rotations in the Midwest. We discuss this work in the context of controversial issues that continue to vex offset project development in agriculture, such as baseline evaluation, additionality, and broad applicability.