Energy invested in organic agriculture: An assessment focusing on nitrogen circularity

To achieve sustainable development, agriculture must secure food supply while reducing its dependence on non-renewable resources and minimizing environmental impacts. Organic farming, which excludes industrial fertilizers and pesticides, offers a promising pathway to meet these goals as agrochemicals are energy-intensive inputs and potential causes of environmental degradations. However, the current literature lacks integrative modeling frameworks that support energy analysis in agricultural systems. To address this gap, we have developed a modeling approach that combines nitrogen and energy flows to assess food productivity and balance between energy invested and recovery from residues. We assess various configurations of organic systems. Our findings indicate that increasing the proportion of grassland in low land productivity systems reduces food yield but improves the energy balance significantly. Conversely, as grain-fed livestock production increases, food productivity decreases sharply and also the energy balance degrades. To address this, increases in livestock production should be paired with improved manure recovery and nitrogen use efficiency. Furthermore, enhancing crop nitrogen use efficiency and recycling manure and biowaste can double food and energy productivity from residues with only modest additional energy costs, as long as nitrogen circularity is well-designed. We explore challenges and opportunities to promote nitrogen circularity between agricultural land, livestock and urban areas. Key steps to advance sustainable organic agriculture and reduce fossil fuel dependence include minimizing feed-food competition, recovering energy from agricultural residues, and enhancing nitrogen use efficiency through effective management of nitrogen transfer systems.