Toward the scale-up of agro-food feed mixture for biogas production

Olive oil and dairy production are among the most important and widespread agro-food activities in southern Italy and particularly in the Puglia region. According to a territorial survey of the Puglia region, the related wastes, olive pomace (OP), olive mill wastewater (OMWW) and whey milk are very abundant (741,000 tons/year) and represent potential sources of contamination for the land and aquifers; however, these wastes also represent an interesting feedstock for biogas production through anaerobic digestion. OP,OMWWand wheymilk are high in organic content (100 g/l, 65 g/l and 60 g/l, respectively), are acidic (with pH values between 3.5 and 5.5), and have high total solid percentage concentrations (30% (w/w), <5% (w/w) and 5% (w/w), respectively). In this study, the results of two experimental campaigns, both conducted at Asja Ambiente’s research center in Ceglie Messapica (Italy) are reported. In the first campaign, different waste mixtures obtained from OP, OMWW and whey milk were fed into a 45-L anaerobic reactor to evaluate their biogas yields. In the second campaign, a combination of whey milk and OP was fed into an anaerobic pilot plant with a volume of 1.6 m3. In the case of feed composed of 25% (w/w) OP and 75% (w/w) whey, a Chemical Oxygen Demand (COD) reduction of 64% and a biogas production of approximately 1.3 L/L day were obtained, which correspond to 0.013 Lbiogas/gTSin. This performance is potentially able to cover 0.015% of Puglia’s yearly total demand for energy.