A process and apparatus for energy efficient remediation of soil contaminated with hydrocarbons, including desorbing the hydrocarbon contaminants from a bed of the soil by thermal desorption in a treated desorption chamber (20) and thereafter combusting the contaminants in a thermal oxidiser (30). The combustion air for the desorption chamber and the thermal oxidiser, and the desorbed contaminants prior to admission to said thermal oxidiser, are preheated by heat exchange (40) with offgases from the thermal oxidiser. The offgases are then rapidly quenched at below 200° C.