Alternative use of tobacco stems as sustainable biofuel

Climate change, rising pollution and the fossil fuels depletion encourage many countries to push towards the introduction of renewable-based energy conversion systems. In particular, European Union energy policy gives a high priority on the increasing use of renewable energy sources because of their strong contribution to the diversification of energy supply, the improvement of energy security, the reduction of greenhouse gas emissions and the social and economic cohesion. Among renewables, biomass is currently the dominating energy source for multiple uses in heat and electricity sectors as well as in transport sector, even if the production sustainability of biomass has been questioned because of the competition with food crops. Therefore, novel non-food biomass resources need to be investigated. In particular, most plant residues of agro-industrial cultivation present a high concentrations of cellulose and thus they could be used as biofuel. Among these the tobacco stems have a high cellulose content (30-40% of dry matter). Tobacco is traditionally used for cigarettes and cigars manufacturing and after the drying process a great quantity of dry tobacco stems (up to 3 t/hectare) is treated as wastes. In this framework, the aim of the paper is to investigate the use of tobacco stems to feed a biomass boiler after a chipping process in order to obtain two advantages: the avoiding of the tobacco stems disposal costs for the agro-industrial company and the promoting the energy recovery from wastes. First of all, tobacco stems sampled out in an air-curing factory of South Italy crops have been characterized according to ASTM D5142 and ASTM D5373. The evaluation of the quantities of lignocellulose agricultural wastes in a form of tobacco stems and the cost of the chipping process has been conducted too. Then, biomass and natural gas fuelled boilers have been compared by means of an energy, environmental and economic analysis on simulative basis. Both systems satisfied the thermal energy demands of a multi-purpose condominium located in a cold Italian climatic zone. The analysis results have demonstrated that the good thermal properties of the chips made from tobacco stems as well as the relatively low price of the raw material (practically without market value), determine the competitive capability of these chips for heating applications.