Analysis of the main physical and chemical characteristics of the vine shoots of three vine varieties from Veneto (Italy)

In Italy the agricultural residues resulting from pruning of vineyards represent a potential energy resource, in particular for the Veneto region which is the second Italian region by vineyard area. This study is aimed at analyzing the main physical and chemical characteristics of vine shoots from the annual pruning of vineyards. This is for their possible use as wood chips in small-medium size power plants. International and European standards for the analysis of biofuels were used to determine the moisture content, heat value, ash content, micro and macro elemental and fibrous fraction (lignin, cellulose, hemicellulose and extractives). The samples were collected from three different vineyards in the Vicenza area. The varieties analyzed were Chardonnay, Glera and Merlot. For each variety, the three different components of vine shoots were compared: internode, node and pith, to investigate in which part of the vine shoot the greatest accumulation of metallic elements deriving from plant protection products occurs. The results show significant differences among the energy parameters of the three varieties and three vine shoot components. In particular, the pith shows low heat value and high ash content while the woody components are characterized by higher energy values. Analysis of the chemical elements showed a high content of Cu and Zn in the wood components, node and internode, causing the high ash content found. In particular, Cu content exceeds the limits set by the reference standard. As regards the analysis of the fibrous fraction, a high content of extractives was found in the pith. These extractives could be one of the explanations why the pith of the three varieties analyzed, especially in Chardonnay, have less lower heat value on dry basis (LHV0) values and high ash contents. On the contrary, the node and internode components have a higher content of cellulose, hemicellulose and lignin. Overall, the vine shoots analyzed have characteristics suitable for a possible energy use. However, due to the high ash and Cu content, according to EN ISO 17225-9:2021 standard these can only be used as wood chips for industrial purposes in large power plants.