Abstract A study was made on the performance of a fixed bed gas producer, using agricultural wastes as fuel and air as gasifying medium, and operated either as an up-draft or a downdraft reactor to supply producer gas to a converted oil-fired boiler. Up-draft operation, although achieving better thermal efficiencies, led to serious ash clinkering problems. Down-draft operation solved the problem of clinker formation on the grate at the expense, however, of slightly lower thermal efficiencies and reduced gasification rates.