Natural Resources Institute Finland (Luke) is requesting offers from suppliers for the procurement of laboratory scale biogas reactors. The procurement target is laboratory-scale continuously stirred tank reactors (CSTRs) for research purposes. Reactors must be suitable for studying process performance, especially the methane production and digestate quality, of anaerobic digestion of various types of biomass: slurries, sludges, manures, and also drier materials (plant biomass, food waste, etc.) as a co-feedstock. Equipment is needed for semi-continuous operation with manual feeding and digestate removal possible without opening the reactor or interrupting the process. Reactors must be equipped with adjustable stirring and temperature control; the heating mechanism must ensure a stable temperature. The requirement is for four (4) CSTR units.