Seasonal variation of the biochemical methane potential of fruit and vegetable wastes produced in the Mediterranean area

Fruit and vegetable wastes produced massively in open markets are a suitable feedstock for biogas production and digestate of high fertilizing value. A first step of designing anaerobic digestion systems for treating these wastes efficiently is to study the impact of the seasonal variation on the biochemical methane potential. Moreover, during mechanical pretreatment applied to reduce the size of the waste mixtures, several fractions derive which affect the rate of the methane production as well as the ultimate methane yield. Fractionation of the chopped wastes through sieving resulted in fractions of different parts of wastes and size, affecting the initial rate and the ultimate methane yield. It was found that the smaller fraction yielded methane at an initial higher rate but at lower ultimate value than the larger fraction. These results were consistent in all waste mixtures chosen to represent the typical composition of the organic fraction of wastes generated in open market in autumn/winter, spring and summer. In all cases examined the BMP of these wastes varied between 360 and 527 ΝmL CH4 g VS-1 with an average value of 436±51 ΝmL CH4 g VS-1.