The optimal carbon sequestration in agricultural soils: Do the dynamics of the physical process matter?

The Kyoto Protocol, which came into force in February 2005, allows countries to resort to 'supplementary activities', consisting particularly in carbon sequestration in agricultural soils. Existing papers studying the optimal carbon sequestration recognize the importance of the temporality of sequestration, but overlook the fact that it is an asymmetric dynamic process. This paper takes explicitly into account the temporality of sequestration. Its first contribution lies in the modelling of the asymmetry of the sequestration/de-sequestration process at a micro level, and of its consequences at a macro level. Its second contribution is empirical. We compute numerically the optimal path of sequestration/de-sequestration for specific damage and cost functions, and a calibration that mimics roughly the world conditions. We show that with these assumptions sequestration must be permanent, and that the error made when sequestration is supposed immediate can be very significant.