Investigation about the biomethane potential of winery wastes

The wine industry represents one of the most important agro-industrial activities in Mediterranean area. Particularly, in Italy, every year, about 40 millions hectolitre of wine is produced, generating a big yield of organic residual as grape marcs and stalks. Today only the grape marcs are valorised in the distillery for alcohol extraction, but the winery’s remuneration for this product is relatively low in respect of transportation’s costs. Furthermore, not valorised winery waste are spread on the land or land filled, generating a strong environmental impact and representing cost for the company. In order to reduce both the effects, an energy valorisation of winery organic residual has been investigated. Experiments have been carried out to evaluate bio-methane potential of white and red grape marcs and stalks produce in a winery in Latium (Italy). Preliminary tests carried out to evaluate a possible valorisation of the winery organic wastes for biogas production demonstrated as the utilization of grape marcs for bio-methane production is feasible. Starting from this experience a laboratory scale batch system, constituted by 8 reactors, was specifically set up in order to perform an in depth analyses of grape-waste-performance in respect of their possible utilisation as energy production (bio-gas) source. A continuous and systematic monitoring of gas production and digestate product characteristics, adopting specialised control hardware and software architectures, was developed in order to perform a continuous monitoring of the process parameters through the utilisation of specific sensors and dedicated logging software tools. The study of the correlations existing between chemical and physical index values (e.g. pH, COD, Ammonia) affecting the evolution of biological processes and biogas production, as well as the occurrence of possible inhibition phenomena, was also carried out. The results of this study have been finalised to build a “full controlled” pilot-scale unit, optimised in terms of digestion unit architecture, sensing probes characteristics, detected parameters collection and data acquisition sequence, to be systematically utilised to evaluate the performance of the proposed approach when applied to different grape marks coming from different “not pre-treated” species of vitis vinifera wastes. Finally the research was also addressed to identify possible solutions for an optimal re-utilization of digestate as resulting form the conversion process.