A study on the production of agricultural residues in Italy

Abstract

The Italian production of agricultural residues has been evaluated with a view to energy recovery through gasification. Two main categories of residues have been identified: the first, (A) is associated with the growing and collection of products with a nutritional value, whereas the second (B) includes the residues associated with the subsequent processing in order to obtain final products for commercialization. Category A, which comprises three further sub-categories: straw (A1); woody residues (A2); and stems and leaves (residues from vegetables, tobacco, sugar beet, (A3)), results in about 16.5 mt/yr. The average amount of straw (A1) is 11 mt/yr, of which about 60% is waste to be eliminated. Woody residues (A2) (mainly pruning off-cuts from vineyards and olive groves) are about 3.5 mt/yr (85% unused). Category A3 amounts to about 2 mt/yr (90% unused). Straw is available mainly in the northern part of the country, whereas the other two sub-categories are widely distributed in central and southern regions. The yields of category B are estimated at 4 mt/yr, of which more than 3 mt/yr are waste products from grape and olive processing. Other residues, such as rice, sunflower and soya-bean husks (about 0.65 mt/yr), almond and nut shells and fruit stones (about 0.2 mt/yr), although not widely available on a national scale, can be significant on a local basis. The total amount of unused agricultural residues is about 14.5 mt/yr, which, if completly exploited through gasification, can contribute as much as 7–10% to the current national electricity needs. The regions of Veneto, Puglia, Friuli, Lombardia and Emilia Romagna appear to be good candidates for electricity production, given the significant surface concentration of unused residues (105-55 t/km 2).