Nitrogen is a necessary element for crop and livestock growth, and protein intake is essential for a balanced human diet. This study examines efforts to improve nitrogen use efficiency (NUE) in agriculture, and reduce unintended losses of nitrogen (N) to the environment. The paper particularly looks at how it is possible to offset reactive nitrogen (Nr) and achieve so called nitrogen-neutrality.
The authors use the N footprint to quantify reactive nitrogen releases related to the food chain of a product.
Their conclusion is that the nitrogen-neutrality concept is a very useful one, and that it should be tested further. Compensation mechanisms or programs should be implemented and they should match the socio-economic setting of the entity that was responsible for the release of reactive nitrogen. Scientific progress on the standardization of the methods for the quantification of Nr releases and N offset also needs to continue.
We propose a novel indicator measuring one dimension of the sustainability of an entity in modern societies: Nitrogen-neutrality. N-neutrality strives to offset Nr releases an entity exerts on the environment from the release of reactive nitrogen (Nr) to the environment by reducing it and by offsetting the Nr releases elsewhere. N-neutrality also aims to increase awareness about the consequences of unintentional releases of nitrogen to the environment. N-neutrality is composed of two quantified elements: Nr released by an entity (e.g. on the basis of the N footprint) and Nr reduction from management and offset projects (N offset). It includes management strategies to reduce nitrogen losses before they occur (e.g., through energy conservation). Each of those elements faces specific challenges with regard to data availability and conceptual development. Impacts of Nr releases to the environment are manifold, and the impact profile of one unit of Nr release depends strongly on the compound released and the local susceptibility to Nr. As such, N-neutrality is more difficult to conceptualize and calculate than C-neutrality. We developed a workable conceptual framework for N-neutrality which was adapted for the 6th International Nitrogen Conference (N2013, Kampala, November 2013). Total N footprint of the surveyed meals at N2013 was 66 kg N. A total of US$ 3050 was collected from the participants and used to offset the conference's N footprint by supporting the UN Millennium Village cluster Ruhiira in South-Western Uganda. The concept needs further development in particular to better incorporate the spatio-temporal variability of impacts and to standardize the methods to quantify the required N offset to neutralize the Nr releases impact. Criteria for compensation projects need to be sharply defined to allow the development of a market for N offset certificates.
Leip, A., Leach, A., Musinguzi, P., Tumwesigye, T., Olupot, G., Tenywa, J. S., Mudiope, J., Hutton, O., Cordovil, C., Bekunda, M., Galloway, J., 2014, Nitrogen-neutrality: a step towards sustainability, Environ. Res. Lett. 9 115001 doi:10.1088/1748-9326/9/11/115001
For an overview of nitrogen issues in general you may want to have a look at the website of the International Nitrogen Initiative.