The Road to COP Webinar Series: Organic Amendments and Nitrogen Circularity: Pathways to Climate-Relevant Adoption
Moderator: Maria Luz Cayuela, researcher at CEBAS-CSIC and iN-Net Climate Working Group member
About the Series: The Road to COP Webinar Series is an initiative of the International Nitrogen Network (iN-Net) Climate Working Group, convening scientists, policymakers, and advocates to explore the often-overlooked role of nitrogen management in addressing the climate crisis.
Nitrogen pollution is one of the most consequential and least regulated environmental challenges of our time. Excess nitrogen in the environment causes air and water pollution and contributes to climate change. Yet, it remains on the margins of mainstream climate discourse. The Road to COP series exists to change that.
Each session brings together leading voices from across the scientific and advocacy communities to examine nitrogen as a climate solution: tracing its pathways through soils, atmospheres, and governance frameworks; identifying where mitigation opportunities are being missed; and building the cross-disciplinary fluency needed to carry these issues into negotiating rooms, national policies, and public debate.
The series takes its name from the global rhythm of UN climate negotiations — each edition building toward COP and the moments when ambition is tested and commitments are made. By convening across disciplinary and sectoral lines, we aim to ensure that nitrogen is not an afterthought in those conversations, but a central thread.
About this Session: Humans now fix roughly as much nitrogen artificially as all natural terrestrial processes combined, yet a substantial share of this reactive nitrogen is never captured within the food system. Instead, it is lost to air, soil, and water, where it drives greenhouse gas emissions, biodiversity loss, and water quality degradation. Closing this loop through the recovery and reuse of organic amendments (manures, composts, and other recycled nutrient sources) offers a promising pathway to reduce reliance on synthetic fertilizers while restoring nitrogen to productive use. Yet scaling these practices remains constrained by technical, economic, and policy barriers that limit adoption across different agricultural and environmental contexts.
In this session, Prof. Oene Oenema and Prof. Rebecca Ryals, two leading researchers who have extensively studied nitrogen recycling through organic amendments, will share their perspectives on improving nitrogen use efficiency, the mechanisms and trade-offs involved in recycling practices, and the critical research and policy gaps that must be addressed to move toward climate-relevant, large-scale adoption.
Prof. Oene Oenema (Wageningen University & Research & China Agricultural University) has made substantial contributions to understanding nitrogen recycling within agricultural systems, particularly through his work with the EU Nitrogen Expert Panel and the UNECE Task Force on Reactive Nitrogen. His research demonstrates that up to 80–90% of plant nitrogen can be recycled on-farm, and has shown that historical EU-27 livestock N excretion was comparable in magnitude to mineral fertilizer N inputs. More recently, his work on integrated nutrient management has demonstrated that combining manure recycling, precision fertilization, and legume expansion can substantially improve nutrient use efficiency while reducing environmental surpluses. This body of work underscores the scale and feasibility of closing nitrogen loops in agricultural systems, providing important context for framing sustainable, recycling-based approaches to nitrogen management.
Prof. Rebecca Ryals (University of California, Merced) has advanced the understanding of how organic waste recycling and compost amendments can improve nitrogen cycling while enhancing soil carbon storage. More recent work has extended this to biochar-compost co-amendments, showing that biochar co-compost improves nitrogen retention and reduces carbon emissions in cropping systems. She has also investigated how composting dairy manure with biochar substantially reduces methane emissions, highlighting the dual climate and nutrient-management benefits of integrating biochar into organic waste recycling pathways. This body of work provides key precedent for coupling biochar-based strategies with nitrogen recycling to achieve co-benefits in soil carbon storage and nutrient use efficiency.
Format: Zoom
When: Tuesday July 28th, 2026 from 9:00-10:00AM EST (15:00–16:00 CEST)
