Experimental and theoretical studies of butanol biodegradation under transient (periodic) operation are reported. A concise two-phase model of the process has been proposed. The expression of the kinetics of odour biodegradation in the solid phase using the equation R-i = muq(i)(n)/(k(m) + q(i)), with n = 1.5, appeared to be critical to obtain the process accurate portrayed in a broad range of operating variables.