According to the definition of “biomass” given in the Directive 2009/28/EC (at its Article 2), our attention was recently focused on the assessment and quantification of the biomethane potential (BMP) of: 1) some agricultural residues having a peculiar relevance at Italian national scale, i.e. grape-seeds and plum-stones; 2) a flowering plant, scientifically classified as Isatis Tinctoria L., widely used for the indigo blue colour extraction in the Urbino dukedom (Marche Region) during the Renaissance epoch. Concerning the Isatis Tinctoria L., our research intention is to consider innovative options for its re-evaluation, including the potential bioenergy recovery. The anaerobic digestion tests on the selected substrates were performed in batch mode and at mesophilic conditions. A lab-scale system representing a variant of the Owen et al. serum-bottle technique (Owen et al., 1979) was employed in these experiments. A digested sludge from the anaerobic digestion treatment stage of a large wastewater treatment plant was used as the inoculum. The feeding mixtures were prepared observing some precise inoculum to substrate (I/S) ratios on volatile solids (VS) basis. The specific methane yield (SMY) values (expressed as Nml gVS-1), obtained for the aforementioned residues, resulted not so strictly dependent on the I/S ratio as highly connected with the peculiar biochemical composition of the feeding materials. For instance, concerning the grape-seeds, a I/S ratio of 1 gave arise to an higher methane production yield respect to a I/S ratio of 0.5, probably because of a major presence of bacteria in the inoculum providing a more efficient biochemical degradation of the grape-seed oils. On the contrary, a I/S ratio of 0.5 improved appreciably the methane yields of the plum-stones, rather than the I/S of 1. The increasing of the substrate concentration, indeed, could ensure a broader availability of organic substrates for the bacteria, considering that plum-stone is noticeably characterized by a higher lignin content. Within an integrated research approach, interesting chemical-physical characterizations of the final digestates were also carried out. In particular: 1) moisture and loss on ignition (LOI) analyses were executed to evaluate volatile and fixed solids; 2) chemical (calcium carbonate, elemental analysis C, N, H, S and IR spectroscopy) and thermal (differential thermal analysis and thermogravimetric analysis DTA/TGA) analyses were performed on the digestate solid component. They will be properly discussed in the paper and compared and critically evaluated with the obtained methane yields.
Combined BMP tests and digestate characterisation of peculiar agricultural substrates in Italy
TATANO, FABIO;
2012
Abstract
According to the definition of “biomass” given in the Directive 2009/28/EC (at its Article 2), our attention was recently focused on the assessment and quantification of the biomethane potential (BMP) of: 1) some agricultural residues having a peculiar relevance at Italian national scale, i.e. grape-seeds and plum-stones; 2) a flowering plant, scientifically classified as Isatis Tinctoria L., widely used for the indigo blue colour extraction in the Urbino dukedom (Marche Region) during the Renaissance epoch. Concerning the Isatis Tinctoria L., our research intention is to consider innovative options for its re-evaluation, including the potential bioenergy recovery. The anaerobic digestion tests on the selected substrates were performed in batch mode and at mesophilic conditions. A lab-scale system representing a variant of the Owen et al. serum-bottle technique (Owen et al., 1979) was employed in these experiments. A digested sludge from the anaerobic digestion treatment stage of a large wastewater treatment plant was used as the inoculum. The feeding mixtures were prepared observing some precise inoculum to substrate (I/S) ratios on volatile solids (VS) basis. The specific methane yield (SMY) values (expressed as Nml gVS-1), obtained for the aforementioned residues, resulted not so strictly dependent on the I/S ratio as highly connected with the peculiar biochemical composition of the feeding materials. For instance, concerning the grape-seeds, a I/S ratio of 1 gave arise to an higher methane production yield respect to a I/S ratio of 0.5, probably because of a major presence of bacteria in the inoculum providing a more efficient biochemical degradation of the grape-seed oils. On the contrary, a I/S ratio of 0.5 improved appreciably the methane yields of the plum-stones, rather than the I/S of 1. The increasing of the substrate concentration, indeed, could ensure a broader availability of organic substrates for the bacteria, considering that plum-stone is noticeably characterized by a higher lignin content. Within an integrated research approach, interesting chemical-physical characterizations of the final digestates were also carried out. In particular: 1) moisture and loss on ignition (LOI) analyses were executed to evaluate volatile and fixed solids; 2) chemical (calcium carbonate, elemental analysis C, N, H, S and IR spectroscopy) and thermal (differential thermal analysis and thermogravimetric analysis DTA/TGA) analyses were performed on the digestate solid component. They will be properly discussed in the paper and compared and critically evaluated with the obtained methane yields.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
