Cost-effective options for increased closing of the carbon, nitrogen and phosphorous cycle (Pcycles)

Nitrogen (N) and phosphorus (P) are essential elements for life, but inefficient use, associated with losses of N and P to the air (only N) and water (N and P), causes various environmental problems, including: (i) loss of biodiversity, due to eutrophication and acidification of terrestrial and aquatic ecosystems, (ii) negative impacts on human health, due to groundwater contamination by nitrate leaching and to secondary particles induced by ammonia emission and (iii) contribution to the global greenhouse effect through the emission of nitrous oxide. In addition, unused N and P in our food end up in the sewer via human excrements and disappear from the cycle via incineration of sewage sludge, at the cost of energy use for chemical N fixation and depleting the earth rock-phosphate pool.

In a previous project, we made a first evaluation of different options to close the P-cycle with the related costs. In this project we aim to study the effectiveness of different options to close the N and P-cycle across farm and regional scale, while also accounting for the related effects on the C cycle and the emissions of greenhouse gases (GHG). Note in this context that the N cycle cannot be fully closed, due to inevitable losses by ammonia emission, denitrification and nitrate leaching. It would be better to say “reducing N and P leakages up to an environmentally acceptable level”, but for sake of convention we keep the wording closing the N and P cycle.


In this project we aim to study the effectiveness of different options to close the N and P cycle on farm- and regional (provincial) scale in the Netherlands and the effect of these options on the national N and P flows. The focus is on an evaluation of cost-effective options for closing of the N and P cycle by: (i) increased N and P use efficiencies from soil to crop and from feed to animal product,  (ii) enhanced recycling of P in waste to reduce P mining, (iii) recovery of N and P, from animal manure and biosolids (e.g. compost, sewage sludge), including the local use and export of N and P fertilizers thus produced and (iv ) dietary changes.

The evaluation will be connected to the related flows of carbon (C), available in manure and waste, by assessing the effects of different options on the C input and C balance. Additionally, the land-sea exchange of N and P will be studied under various options of mariculture in coastal waters. The evaluation will be made by considering the wish of farmers (in view of soil quality) and of policy makers (4 promille initiative) to maintain and preferably increase the soil organic carbon (SOC) level in view of carbon sequestration. Apart from C, N and P, the various measures will also be evaluated in terms of greenhouse gases (GHG; CO2, CH4 and N2O) emissions from animal housing systems and soils in Dutch agriculture. The emissions by manure treatment and transport and by machinery use will not be included. Estimates of and-sea exchange of N and P will be included.