• There are many technologies available for ammonia reductions in Denmark. • Covering of storage and cooling are some of the cheaper measures analyzed. • Larger farms have lower costs per unit than smaller farms. • Setting BAT levels should be based on efficiency, affordability and cost-efficiency. The reduction of anthropogenic NH₃ emissions is essential for mitigating ecosystem eutrophication, limiting climate change driven by indirect nitrous oxide emissions, and improving human health. A key policy instrument in many countries is the implementation of emission standards based on Best Available Techniques (BAT), particularly in the context of livestock farm modernization and expansion. This study examines the Danish approach to defining BAT emission levels, which is based on three parameters: technological efficiency (emission reduction relative to a reference technology), affordability (increase in total production costs), and cost-effectiveness (cost per unit of NH₃ reduction). The analysis focuses on mitigation measures in growing–finishing pig (finisher pig) production as a case study. The results indicate that Denmark has access to a broader range of mitigation technologies compared to many other countries, including slurry cooling, slurry acidification, chemical and biological air scrubbers at varying intensities, and covering of slurry tanks. Multiple combinations of housing systems and technologies are identified that meet different parameter thresholds. Among these, slurry tank covers and slurry cooling emerge as the most cost-efficient options. From an affordability perspective, additional costs of up to 2% of total production costs (approximately €1.5 per pig) appear feasible; however, only a limited number of technologies meet this threshold. In terms of cost-effectiveness, several technologies can be implemented at costs below €5 per kg NH 3 -N, while a broader set remains viable below €10 per kg NH 3 -N. Overall, the Danish BAT framework achieves ammonia emission reductions exceeding 20% at costs below €13.4 per kg NH 3 -N. The analysis also highlights significant cost disparities between farm sizes, with smaller farms facing higher relative costs. This finding supports the continued use of a differentiated, two-tier BAT system. Finally, increasing estimates of welfare benefits associated with reduced ammonia emissions may justify stricter BAT requirements in the future; however, the determination of BAT levels ultimately remains a political decision.
Jacobsen et al. (Fri,) studied this question.