Use and the study of new renewables energies is imposed by the need to find alternatives to fossil fuels. The biomass is one of the most promising alternatives. Biomass can be classified according to its origin, the woody biomasses are currently the most widely used. There are other types of biomass such as biomass of agricultural origin and energy crops. Their abundance makes them serious candidates to provide alternative source of energy. The use of alternative biomasses has not been properly exploited and it is known that this use can generate different behaviors in the combustion devices with possible impacts in terms of polluting emissions. For these reasons, there is a need to study the effect of the nature and composition of the biomass on its emissions during combustion. In order to experimentally investigate the combustion of biomass, an experimental bench based on an instrumented domestic pellet boiler of 20kW has been set up with a control of the air and fuel inlets. Three biomasses have been used for this work, wood, miscanthus and straw. Gaseous and particulate pollutant emissions have been made in the smokes at the exhaust, for CO and NOx with a TESTO analyser, particle mass concentration with a PPS (DEKATY), particle size distributions with a Scanning Mobility Particle Sizer (SMPS, TSI). A CPMA (Cambustion) was set up in tandem. configuration with the SMPS to evaluate the effective density of particles produced during the biomass combustion. TEM images were made from the aerosol produced by the combustion of wood and miscanthus. Different parameters such as the feeding mode (pulsed or continuous), the air distribution within the furnace and the nature of the biomass are studied. The results obtained showed that CO emissions are strongly influenced by the feeding mode of the boiler. Particles and NOx can be less affected by this loading process. We were able to reduce the CO emissions of a conventional heater by about 40% by simply changing the feeding method. The impact of the position of air injection in the combustion chamber was also investigated. It was observed that small changes in the air distribution close to the fuel bed can have significant effects on the reduction of gaseous pollutant emissions. Also, the results obtained showed clear differences in the levels of gaseous emissions of the three types of biomasses, with wood being the lowest of the three. Finally, in terms of particulate emissions, there are clear differences in mass concentration and size distribution, MET images and effective density showed differences in the nature and shape of particles for miscanthus and wood biomasses.