A gasifier

There is disclosed a gasifier (500) comprising: a gasification chamber (518); a feedstock inlet (520) opening into the gasification chamber (518) for introducing feedstock material and primary combustible gas; a gas outlet (523) opening into the gasification chamber; and a flow path between the feedstock inlet (520) and the gas outlet (523) which passes through the gasification chamber (518), a portion of the flow path having an upwards component within the gasification chamber so that particulate material entrained in the primary combustible gas separates from the primary combustible gas and falls towards the bed of feedstock material. There is also disclosed a gasifier (500) comprising: a chamber wall (510) defining a gasification chamber (518); an ash grate (526) disposed in the gasification chamber (518); and a rotary crusher (532) disposed in the gasification chamber (518) above the ash grate (532) and provided with at least one crushing element (536); wherein in use rotation of the crusher causes agglomerated feedstock material in the bed to break apart between the crushing element and an opposing surface.