The aim of the present paper is to compare the combustion results of two solid biofuels suitable for industrial applications: olive tree pruning (OTP) pellets and sunflower husk (SH) pellets. The former derives from the thin prunings, along with the leaves, whereas the latter derives as a byproduct from the sunflower oil extraction industries. The combustion was performed in operating conditions at two industrial fixed bed biomass boilers (1.16 MWth capacity each) with a common flue gas stack used for greenhouse heating. Combustion tests were performed at the industrial boiler for two consecutive days. During the first day, the OTP pellets were combusted and monitored for emissions, whereas in the second day the reference fuel that is normally used in the plant (SH pellets) was monitored. While combusting OTP pellets, the boiler's performance was found to exhibit a slightly worse, leading to a decrease of 3.5% points of the boiler efficiency compared to SH pellets. Lower emissions of CO and NOx were also observed for OTP pellets, while the ash formation exhibited signs of reduced slagging. Dust emissions were high for both fuels, indicating that particle emission abatement equipment should be installed at the facility. (C) 2021 Elsevier Ltd. All rights reserved.