The NUFER (NUtrient flows in Food chains, Environment and Resources use) model quantifies nitrogen (N) and phosphorus (P) flows in food chains and nutrient use efficiencies. In NUFER, the food chain consists of four main compartments: crop production, animal production, food processing, and household consumption (see Figure below). N and P cycling is modelled within and across these compartments, which includes nutrient imports to and exports from the compartments. For example, nutrient imports to crop production are synthetic and organic fertilisers, and exports are crop yields and losses of N and P to the environment. Nutrient losses to the environment include N losses to air (such as ammonia, nitrous oxide), and N and P losses to water systems (through leaching, for example).