Evaluation of the biogas productivity potential of some Italian agro-industrial biomasses.

Batch trials were carried out to asses the biogas productivity potential of rice and barley straw, grape stalks, grape marcs, maize drying up residues, tomato skins and seeds, and whey. Trials were carried out in 2l glass digesters kept in a thermostate controlled room at 40 degrees C for 40days. The most productive biomasses, in terms of specific methane yield, were the whey and the maize drying up residues. Their specific methane yields were 501 and 317l(N) CH(4) *kgSV(-1), respectively. Barley and rice straw gave a specific methane yield of 229 and 195l(N) *kgVS(-1). Similar result was also obtained from tomato skins and seeds. Grape stalks and grape marcs produced lowest amounts of specific methane, respectively, 98 and 116l(N) CH(4) *kgSV(-1). According to trial results and considering the availability of examined biomasses in Italy, it is possible to estimate their total energetic potential close to a value of 21,900TJ *year(-1). This energetic potential value is equal to that obtainable from the anaerobic digestion of about 6.5 million tons of maize silage.