A method for destroying biosecurity hazards in quarantined materials and producing valuable products that are safe and have economic value in an apparatus including a continuous converter including a reaction chamber for a feed material, an inlet for supplying the feed material to an upstream end of the reaction chamber, an assembly for moving the feed material through the reaction chamber from the upstream end towards a downstream end of the reaction chamber, and a plurality of outlets for discharging the products from the reaction chamber, with the method including the steps of: (a) supplying a feed material including the quarantined materials and additional biomass to the inlet of the reaction chamber of the apparatus; (b) moving the feed material through the reaction chamber from the inlet to the downstream end of the chamber and exposing the feed material to a time-temperature profile within the chamber that destroys biosecurity hazards in the quarantined materials and dries and pyrolyses organic material in the feed material and releases water vapour and a volatile products gas phase from the feed material as the feed material moves through the chamber; (c) moving the water vapour phase and the volatile products gas phase produced by heating the feed material in step (b) through the reaction chamber in a direction counter to that of the feed material so that at least a part of the water vapour phase and the condensable components of the volatile products gas phase condense in cooler upstream sections of the reaction chamber and form liquid water and liquid oil, at least the liquid oil being carried forward in the reaction chamber by the feed material to the higher temperature regions of the reaction chamber and being progressively volatilised and cracked to a non-condensable gas; and (d) discharging (i) a gas product and (ii) a dried and pyrolysed solid carbon-containing product from the separate outlets of the chamber. (a) supplying a feed material including the quarantined materials and additional biomass to the inlet of the reaction chamber of the apparatus; (b) moving the feed material through the reaction chamber from the inlet to the downstream end of the chamber and exposing the feed material to a time-temperature profile within the chamber that destroys biosecurity hazards in the quarantined materials and dries and pyrolyses organic material in the feed material and releases water vapour and a volatile products gas phase from the feed material as the feed material moves through the chamber; (c) moving the water vapour phase and the volatile products gas phase produced by heating the feed material in step (b) through the reaction chamber in a direction counter to that of the feed material so that at least a part of the water vapour phase and the condensable components of the volatile products gas phase condense in cooler upstream sections of the reaction chamber and form liquid water and liquid oil, at least the liquid oil being carried forward in the reaction chamber by the feed material to the higher temperature regions of the reaction chamber and being progressively volatilised and cracked to a non-condensable gas; and (d) discharging (i) a gas product and (ii) a dried and pyrolysed solid carbon-containing product from the separate outlets of the chamber.