ANNOTATION: A tub grinder was employed to process debris discharged by a flail. The machine successfully passed the material through a 7.62 cm screen and discharged the reduced debris into a chip van for transport. It was found that fuel production is directly dependent upon the production of clean chips by the flail/chipper portion of the system and the available biomass of the stand. Clean chips were produced at 57 green tonnes/PMH with fuel yields of from 14 to 21 green tonnes/PMH. The usual disposal of flail residues is an additional cost charged to the clean chips; processing turns the residues into a positive cash flow.