Potential Availability of Wood Biomass from Urban Trees: Implications for the Sustainable Management of Maintenance Yards

Abstract

The current energy situation requires the effective utilization of all available resources, and residual wood biomass from urban forestry may represent an excellent opportunity for increasing the presence of short-range energy sources. In urban forestry management, two main operations can provide large amounts of wood biomass: The felling and pruning of trees. These operations are carried out with two principal techniques that differ in terms of mechanization intensity (i.e., accessing the trees’ crown with mechanized aerial lifts or utilizing ropes—tree-climbing). This study has investigated 18 felling and 15 pruning yards, carried out with aerial lifts (17 yards) or tree-climbing (16 yards), most of them located in the city of Rome (Italy), one of the greenest European capitals. The operations were sampled with time studies, and five elements of work time were measured from the beginning of work to the transport of the residual biomass to the loading point, using centesimal stopwatches and video recording. The total observation time amounted to 152.0 h. The total residual biomass was assessed. The cost calculation for each yard took into account fixed, variable, and labor costs. A set of variables for each yard (including several site characteristics, trees’ size, fuel consumption, carbon dioxide (CO2) emissions, energy consumption, costs of yards, biomass, and work times) was analyzed. This study can contribute to enhancing tree maintenance sustainability in urban sites and estimating the quantity of residual wood biomass obtainable from urban forestry maintenance in the city of Rome.