Systems and methods associated with biomass decomposition are generally described. Certain embodiments are related to adjusting a flow rate of a fluid comprising oxygen into a reactor in which biomass is decomposed. The adjustment may be made, at least in part, based upon a measurement of a characteristic of the reactor and/or a characteristic of the biomass. Certain embodiments are related to cooling at least partially decomposed biomass. The biomass may be cooled by flowing a gas over an outlet conduit in which the biomass is cooled, and then directing the gas to a reactor after it has flowed over the outlet conduit. Certain embodiments are related to systems comprising a reactor and an outlet conduit configured such that greater than or equal to 75% of its axially projected cross-sectional area is occupied by a conveyor. Certain embodiments are related to systems comprising a reactor comprising an elongated compartment having a longitudinal axis arranged substantially vertically and an outlet conduit comprising a conveyor.