CLEAN, het RIVM-landbouwmodel deel I: modelstructuur, versie 1.0

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In this report the first version of the model CLEAN is presented. CLEAN stands for Crops, Livestock and Emissions from Agriculture in the Netherlands. The model has been developed as part of the project EXPECT (EXPloring Environmental Consequences for Tomorrow) by a team of agricultural specialists, model builders and computer programmers at RIVM and the Agricultural University of Wageningen. The model is designed to function in the EXPECT system for construction of agricultural policy scenarios. The eutrophication issue has been the leading theme in the design of CLEAN 1.0. The manure production is calculated from development of the livestock numbers and the excretion rates per livestock category. The model distinguishes volume of manure and nitrogen, phosphate and potassium content. To calculate the total excretion and NH3 emissions, the differences between livestock on pastureland and in stables and between various manure storage systems are recognized in the model. The model allows simulation of manure distribution over crop classes which are linked to soil type and groundwaterlevel classes. The first step to assess the amount allocated to the local crops, in accordance with fertilization standards. Next, surplusses are allocated within the region, in line with an acceptance level by farmers for external manure. And the last step is to export remaining surplusses to regions with a demand for manure, or to manure processing plants or abroad. The allocation follows a transport cost minimization algorithm. Subsequently, the model calculates the NH3 emissions resulting from stables, manure storage and manure application to the land, and the additional chemical fertilizer application with the associated NH3 emissions.