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 the pruning of
vineyards represent a potential energy Source, in particular for the
Veneto region, which is the second Italian region by vineyard area.
This study is aimed at analysing the main physical and chemical
characteristics of vine shoots from the annual pruning of vineyards.
This for use them 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, heating
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 analysed 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 most significant 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 heating value and high ash content,
while higher energy values characterise the woody components.
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 explain why the pith of the three
varieties analysed, especially in Chardonnay, have lower heating
value on dry basis (LHV0) values and high ash contents.
On the contrary, the node and internode components have a
higher cellulose, hemicellulose, and lignin content. Overall, the
vine shoots analysed have characteristics suitable for possible
energy use. However, according to EN ISO 17225-9:2021 standard,
these can only be used as wood chips for industrial purposes
in large power plants due to the high ash and Cu content.