Biomass residues adjacent forest roads in two different forest species (Fagus sylvativa and Pinus brutia): quantities and evaluation of their biogas production potential

Abstract

In this study the quantity of biomass residues accumulated at a low-altitude Mediterranean forest (pinus and fagus clusters) were evaluated under field conditions. Samples of fresh and dry leaves (litter) were digested in batch anaerobic reactors to evaluate their biogas production potential. The quantity of pine needles and fagus leaves accumulated onto the forest carpet was on average 670 and 1440 g/m2, respectively and they were characterized by a low moisture content (10-11%). The biogas production potential was 100 and 150 L/kg volatile solids for pinus and fagus litter respectively (compared to 140 and 300 L/kg VS for the fresh pine needles and fagus leaves). The data from both field and laboratory studies were used to calculate the biogas yield per km of forest road, if the collected biomass is disposed of to an anaerobic digestion facility. The conceptual model applied revealed that it is possible to recover up to 500 and 1000 m3 CH4 / km, from the pinus and fagus clusters respectively. Concluding, pine needles and fagus leaves are important resources and can be efficiently used for energy production in anaerobic digestion facilities.