Cost per unit abated for selected nitrogen mitigation strategies on Irish farms

With the initial deadline identified by the Water Framework Directive (Directive 2000/60/EC) has passed in 2015 and new one set out in 2027, policymakers face increasing pressure to introduce new regulations to achieve water quality targets. Agriculture is one of the contributors of diffuse pollution entering watercourses and hence will come under pressure to further reduce pollutant loads. This paper describes a microsimulation model that allows the Cost per Unit Abated (CPUA) for six farm-level measures that could potentially reduce nitrate loss to water bodies from agricultural land on Irish dairy farms to be estimated. Results from this study indicate that almost all of the considered measures will lead to reductions in farm gross margins. However, some of these measures can be still implemented at acceptable cost-effectiveness ratios. Furthermore we observe variation in the ranking of the measures by CPUA across farms suggesting that a one-size-fits-all command-control approach may place unnecessary costs on some farms, where alternative policies may lead to N reduction at lower costs. Hence, focusing on the average CPUA across all farms, overlooks the heterogeneity of impacts across individual farms, potentially leading to sub-optimal policies being implemented.The authors acknowledge support from the Harmony project: High stAtus wateR bodies - Managing and Optimising Nutrients, funded by the Irish Department of Agriculture, Food and the Marine (DAFM) (RSF 13 S 488)