Offset Opportunities for Row–Crop Agriculture in the US Midwest: The Role of Nitrogen Fertilizer in Developing a Nitrous Oxide Reduction Protocol.

Current Federal legislation envisages a domestic offset market of up to 1.5 billion Mt of tradable carbon credits to meet the demand of the regulated industries unable to achieve their GHG emissions reduction targets.

The agriculture sector has been thought of as playing a major role in delivering these offset credits, by way of large–scale adoption and alteration of management practices that mitigate emissions, as compared to current scenarios.

However, despite significant potential for agricultural GHG mitigation, very few widely applicable, quantitative methodologies have been developed for programs and markets to meet this demand. To date, no protocols have been approved for N₂O emissions reduction. However, as N₂O is the major GHG emitted by US agriculture – accounting for ~70% of total US N₂O emissions, and with a GWP of ~300 – it is viewed as a ‘low hanging fruit’ for offset project development, due to the high CO₂ equivalent payback associated with its emission prevention.

Current understanding is that N fertilizer rate is a reliable predictor of N₂O emissions in US row–crop agriculture, with recent research indicating emissions can increase exponentially with increasing N fertilizer rate, contrary to the linear, default increase adopted by the IPCC. This divergence has significant environmental and economic implications for incentivizing reduced N fertilizer rate management, and generating emission reduction credits. Knowledge of trade–offs and synergies between N₂O emissions, N fertilizer rate, and crop yield is essential for informing management strategies that aim to reduce the agricultural N₂O burden without compromising productivity and economic return.

We present an empirically derived, transparent methodology that provides farmers with the economic and environmental incentives necessary for adopting reduced N rate practices, and is capable of generating emission reduction credits for cross sector trading. In doing so, we address controversial issues such as baseline, additionality, and permanence.