Small-scale biomass-fired cogeneration, pellet production or district heating: new criteria for selecting the most profitable solution

In this paper the possible use of heat surplus from a biomass-fired cogeneration unit, for treating a share of the biomass and produce a new and more performing fuel like pellet, is proposed and discussed. Such a fuel could be easily stored and then distributed, for a more widespread and diffused utilization close to the consumers, for heating purposes. This form of energy storage makes time and geographical shift of heat utilization possible, also in small-scale applications. A technical-economical comparison is carried out and discussed between the above mentioned system and a district heating supplied by a traditional biomass boiler, or a conventional chip-fired cogeneration plant without pellets production. The paper also focuses on the opportunities and challenges deriving from the energy use of a specific biomass resource: olive pomace. The technical feasibility and the economical profitability of different plant solutions are investigated. To a methodological contribution, related to the description and modeling of the proposed conversion processes, some case-studies are joined, based on efficiencies and costs suggested by the most recent literature and field tests.