Various techniques are disclosed for pretreating municipal solid waste (MSW) and other biomass-containing feedstocks that may be of a poorer quality and consequently more difficult, or even impossible, to convert to higher value liquid products (e.g., transportation fuels) using conventional processes. Such conventional processes may otherwise be satisfactory for the conversion of the biomass portion of the feedstock alone. The pretreatment of biomass-containing feedstocks may generally include steps carried out prior to a hydropyrolysis step and optionally further steps, in order to change one or more characteristics of the feedstock, rendering it more easily upgradable.