<p>The efficiency of combustion of biogran organic fertilizer in a low-power boiler hot-water furnace has been investigated. It has been established that in the process of the boiler operation, intense fouling of its fire grate occurs, which increases its aerodynamic drag, reduces the consumption of primary air, decreases the active volume of the boiler combustion chamber and the boiler gross efficiency due to the significant increase in heat losses with chemical incompleteness of fertilizer combustion. A study of the elemental composition of biogran ash has shown that it contains a significant amount of oxides of alkaline earth and alkaline metals. Due to this, it is recommended that biogran be burnt together with wood biofuel at an optimal ratio of their components in a mixture, with this ratio being determined with account for the thermotechnical characteristics of these materials.</p>