ABSTRACT
Research background: Wine production, which is considered a major sector in food industry, often involves the use of a large amount of resources. Moreover, wine making generates a large amount of grape pomace, which is generally used for low-value applications such as fertiliser and animal feed. The aim of the present research is to explore the possibility of improving the overall sustainability of traditional winemaking. Experimental approach: A zero-waste process was developed. It includes the production of white wine and the substantial valorisation of grape pomace, which is converted into solid biofuel, tartaric acid and concentrated grape extract as feedstock for industrial baker's yeast production. Results and conclusions: We estimate that a significant surplus of renewable energy of approx. 3 MJ/kg processed grapes can be obtained during this conversion. The suitability of grape extract as a potential substrate for industrial baker's yeast production was evaluated and the feasibility of a partial replacement of molasses (up to 30 %) was demonstrated. Novelty and scientific contribution: We present a circular economy approach for the conversion of winery biowaste into high-value resources such as feedstock and solid biofuel.
ABSTRACT
The anaerobic degradability of alcohol ethoxylates with various degrees of branching and several related substances was studied. Different inocula were employed in order to increase the probability of obtaining capable bacteria, and the degradation assays were fed with several small doses of the test substances in order to avoid inhibition by too high initial concentrations. Mineralization was quantified by monitoring the biogas production and inorganic carbon concentration in the liquid phase. Almost complete mineralization was achieved in the assays with linear alcohol ethoxylate, poly(ethylene glycol), dodecanol, 2-ethyl-hexanoic acid and 3-methyl-valeric acid. No significant degradation was detected in the assays with highly branched alcohol ethoxylate, 2-butyl-branched alcohol ethoxylate, alcohol alkoxylate, poly(propylene glycol) and iso-tridecanol. A 2-ethyl-branched alcohol ethoxylate was transformed to (2-ethyl-hexyloxy)-acetate, which was not further degraded. Apparently already the first step of anaerobic degradation of alcohol ethoxylates, the ethoxylate chain shortening, is sterically hindered by the alkyl branching. Alkyl branching in alcohol ethoxylates and the inclusion of propylene oxide units in alcohol alkoxylates seem to have a clearly more detrimental effect on anaerobic degradability than on aerobic degradability.
