The multi-fuel reactor at SINTEF Energy Research has been designed to handle different biomass feedstocks and to transform them into energy and energy products in different ways. It is flexible with respect to the thermal conversion method (combustion, gasification or pyrolysis) and the composition of the inlet gas, from inert gas to only e.g. oxygen or steam. The reactor temperature and the inlet gas temperature can be well controlled. The multi-fuel reactor was originally built only for batch experiments, i.e. macro TGA studies. However, it has been redesigned, allowing now also continuous (fuel-feeding) operation. Several improvements have been introduced during the last years to develop the multi-fuel reactor. This makes it possible to carry out experiments suited for a wide range of applications.