32 having a similar configuration as the upstream screw tunnel the downstream screw tunnel dispenses to an output belt conveyor 34 the output belt conveyor has an overlying blade 36 which levels the feedstock an oven 40 surrounds all but the upstream end of the input belt conveyor and downstream end of the output belt conveyor feedstock traveling on the input belt conveyor 22 is levelled by blade 24 the material then drops into upstream screw tunnel 26 this screw tunnel rotates to roll the feedstock and feed it downstream at the downstream end of the upstream screw tunnel the feedstock drops to the middle belt conveyor 28 where it is levelled by blade 30 and conveyed into downstream screw tunnel 32 the downstream screw tunnel rotates to roll the feedstock and convey it to output belt conveyor 34 where the feedstock is levelled by blade 36 and then dispensed from the oven conveyor by repeatedly conveying rolling and levelling the feedstock at elevated temperatures in the oven conveyor the feedstock is dried and evaporation of mercury in the feedstock is promoted returning to fig1 there are air uptakes 13 15 21 and 51 associated with each of pre shredder 12 shredder 14 oven conveyer 20 and a sieve 50 respectively each of the air uptakes feed ultimately to a cyclone 46 with air uptakes 13 and 15 feeding to the cyclone through a particulate filter 37 a vacuum source 44 draws.