Wood biomass recovery from chestnut orchards: results from a case study.

Sweet chestnut has been for many centuries essential to human diet in large areas of Southern Europe. Its cultivation was abandoned in the last century, but is at present under restoration for socioeconomic reasons, representing also an opportunity for allocating woody residues to the energy sector. A little is known from the literature about sweet chestnut pruning, and the aim of the study was to assess the biomass yield and quality, the productivity and costs of the system as well as its energetic balance between inputs and outputs. The yield of recovered wood material amounted to between 22.3 tonnes of dry matter per hectare (t_dw ha⁻¹) and 33.3 t_dw ha⁻¹. Time consumption for pruning has been related to trees’ DBH, so detecting a linear relationship, although weak, between tree size and the time spent for maintenance. Productivity expressed as t_dw per hour varied according to the site and the operating systems adopted accordingly. Costs for the whole chain, excluding transport to the plant facility amounted to 113 or to 430 € t_dw⁻¹ depending on the terrain relief and the presence of an underbrush to be cleaned. Wood chips distribution in size classes provided a material unsuitable for non-industrial due to the percentage of oversize particles, probably due to the high presence of twigs. The energy ratio resulted of 30:1 and 21:1 for the two sites. Transportation had the main impact in terms of energy, followed by extraction and chipping phases. [ABSTRACT FROM AUTHOR]