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Nowadays, the anaerobic digestion of organic wastes to produce renewable energy is a reality in many countries. Many feedstocks can be processed by anaerobic digestion to produce biogas, however, anaerobic digestion of single substrates can have drawbacks that could be eliminated by the anaerobic co-digestion of their mixtures (two or more). In this paper, the anaerobic co-digestion of maize silage and red chicory (radicchio) waste is presented. Several batch anaerobic biodegradability tests were performed in order to compare the methane production of the blend with those of the two substrates digested separately. The methane production was modelled by a first order kinetic model, focusing on the initial substrate solubilization. The specific methane productions of maize silage and red chicory as single substrates were 0.346 L CH4 g-1 ODM and 0.326 L CH4 g-1 ODM. The first solubilization rate constants (ksol) were 0.231 d-1 for the digestion of maize silage, and 0.389 d-1 for the radicchio waste. Two parameters representing the relative changes in specific methane production and solubilization rate were calculated in order to evaluate the synergistic effects due to co-digestion of studied substrates. Results showed that blending the two substrates enhanced the performances of the AD process, mainly with respect to biogas production kinetics with low increments in the ultimate methane potential. [ABSTRACT FROM AUTHOR]

In the food industry, the brewing sector holds a strategic economic position: in the year 2013, the beer production of the EU-28 was equal to 383,553,000 hL. The brewing process includes chemical and biochemical reactions and solid-liquid separations, involving the generation of various residues and by-products, among which the major two fractions are brewer's spent grain (BSG), and exhausted brewery yeast (BY). Although until today their main use has been for animal feed, in recent years, several studies have investigated the application of anaerobic digestion in order to revalue the brewery wastes. In this work, specific methane production (SMP) and first-order solubilisation (disintegration + hydrolysis) rates (Ksol ) for BSG and BY were evaluated. Biomethanation tests were performed in 5-L fed-batch stirred reactors at several substrate/inoculum ratios. The obtained SMP ranged from 0.255 L CH4 g-1 COD for exhausted brewery yeast to 0.284 L CH4 g-1 COD for brewer's spent grain. The estimated ksol values ranged from 0.224 d-1 for BSG to 0.659 d-1 for BY. [ABSTRACT FROM AUTHOR]

In this study, an experimental setup for the evaluation of a two-stage anaerobic digestion has been developed: a laboratory-scale apparatus was assembled employing solid potatoes as energy crops. Two coupled 5-litre batch-fed stirred reactors, one for the hydrolytic-acidogenic step and one for the acetogenic-methanogenic step, kept at mesophilic temperature (308.1 K), were adopted. Evaluated in the first acidogenic reactor was the influence of fermentative yeast (Saccharomyces cerevisiae) on the degree of hydrolysation and on the acidification rate of the vegetable substrate. All runs were performed without the addition of chemicals. Samples of hydrolysed substrate were sent to the second methanogenic bioreactor, fed with an industrial anaerobic sludge and selected lyophilized anaerobic bacteria, in order to evaluate the methane yield of the produced biogas and the specific methanogenic activity (SMA). The whole procedure was repeated simulating an anaerobic sequencing batch reactor (ASBR) process. [ABSTRACT FROM AUTHOR]