Gains of integrating sector-wise pollution regulation: The case of nitrogen in Danish crop production and aquaculture

- A Computable General Equilibrium model is extended with an externality market for nitrogen pollution permits.
- Economic gains of integrating independent regulation of agriculture and aquacultures into a common system are identified.
- Common regulation lead to socio-economic gains through reallocation of pollution permits between sectors.
- Common regulatory gains are larger than losses of stricter environmental policy that fulfill EU's Water Framework Directive.

This paper extends the Orani-G Computable General Equilibrium model with an externality market. The externality market is modelled with a limited number of pollution permits that are traded between representative firms in different sectors. The model is applied to identify the gains of a common nitrogen regulation system for Danish agriculture crop and aquaculture production. Common regulation across the two sectors is found to increase GDP by euro 32 million, corresponding to 2.2% of their initial GDP contribution. The direct effect in the two sectors is euro 39 million, where the spill-over effect is − 7 million. Full use of recirculation technology in aquaculture entails a further increase in GDP to 106 million. The introduction of a common regulatory system and recirculation technology, simultaneous with a reduction of the common nitrogen cap of 17.6%, corresponding to the current policy objectives, is found to increase GDP by 52 million, 4.1% of their initial contribution. Hence, introducing a common regulatory system and taking advantage of the new technology more than counterbalances the negative socio-economic effect of a cap reduction. The analysis points to the importance of introducing more coherent regulatory frameworks that include all polluters under the same regulatory system.