Biopolymers are a suitable alternative for the ongoing problem of plastic accumulation, even though commercialization is difficult, which is reflected in the price of the product. However, costs can ...be reduced if active sludge bacteria and cheap, accessible substrates such as waste brewer’s yeast are used. Waste brewer’s yeast is a rich source of carbon and nitrogen and is widespread as a substrate in various industries. Thus, the cultivation of active sludge bacteria was performed on waste brewers’ yeast to obtain biopolymers that can be used in 3D printing. FT-IR, TG, and DSC analyses of produced polymers were conducted after extraction, as well as biogas and biomethane potential tests. Results of cultivation under various conditions show that biopolymer content is extremely heterogeneous. However, during cultivation in SBR, signals at 1741.3, 1709.6, 1634.3, and 1238 cm−1 were detected. Further analyses are needed, but when said results are compared to those of consulted scientific articles, there is an indication that at least a small amount of PHA is present in biomass produced in SBR. Biopolymers produced in SBR were used as a material for the 3D printing of a cube. Moreover, testing of the physical properties (Young’s modulus) of a 3D-printed cube was performed. After conducting experiments, it can be concluded that said process, although time-consuming, achieved the goal of printing a stable and rigid 3D-printed cube made from biopolymers. Further optimization of said process should focus on more detailed microbial selection as well as biopolymer extraction. In that way, isolation, purification, and identification techniques will be improved, which could achieve higher biopolymer yield and, thus, make biopolymers more accessible in various industries.
Renewable energy sources are becoming increasingly important in the beverage and food industries. In the brewing industry, a significant percentage of the used raw materials finishes the process as ...secondary resource or waste. The research on the anaerobic digestion of brewer's yeast has been scarce until recent years. One of the reasons for this is its use as a secondary resource in the food industry and as cattle feed. Additionally, market value of brewer's yeast is higher than its energy value. Due to the increase of energy prices, brewer's yeast has become of interest as energy substrate despite its difficult degradability in anaerobic conditions. The anaerobic co-digestion of brewer's yeast and anaerobically treated brewery wastewater was studied using a pilot-scale anaerobic sequencing batch reactor (ASBR) seeded with granular biomass. The experiments showed very good and stable operation with an organic loading rate of up to 8.0 kg/(m
·day), and with a maximum achieved organic loading rate of 13.6 kg/(m
·day) in a single cycle. A specific biogas productivity of over 0.430 m
/kg of the total chemical oxygen demand (COD) inserted, and total COD removal efficiencies of over 90% were achieved. This study suggests that the brewer's yeast can be successfully digested in an ASBR without adverse effects on the biogas production from brewer's yeast/wastewater mixtures of up to 8% (by volume). By using the brewer's yeast in the ASBR process, the biogas production from brewery wastewater could be increased by 50%.
Anaerobic digestion, despite its preferable use as a treatment for high organic matter polluted waste streams, is susceptible to inhibitors, salt included. Therefore, two different experiments were ...conducted to observe the responses of bacterial and archaeal communities to hypersaline environments. In the first experiment, salt was added gradually, while in the second experiment, salt was added rapidly (so-called salt shocks were performed). The results of the gradual addition of salt showed a recovery of methane production after the salt concentration decreased. The NaCl concentration of 28.2 g/L seems to be the limit between stable operation and occurrence inhibition. The specific biogas production varied between 0.490 and 0.562 msup.3/kgsub.tCOD during the stepwise salt addition, depending on the salt concentration, while the maximal achieved COD removal was 79.8%. The results of the rapid salt addition showed good recovery of the bacterial community, while a reduction of salt-sensitive species was observed in the archaeal community. The trend of specific biogas production during rapid salt addition was stable with an average value of 0.590 msup.3/kgsub.tCOD, and it was observed that higher concentrations of up to 39.4 g/L of NaCl were tolerated. The maximum COD removal achieved during rapid salt addition was 83.1%. In conclusion, certain bacterial and archaeal communities were well-adapted to the hypersaline environment and remained active during the anaerobic digestion of substrates with high salt concentration.
The objective of this study was to determine the density of anaerobic granules on different heights of a full-scale Upflow Anaerobic Sludge Bed reactor. The density was defined through the settling ...velocities of anaerobic granules, measured in a full-scale Upflow Anaerobic Sludge Bed reactor. In this study, granular density was calculated with the measured settling velocities and developed mathematical model. The developed mathematical model is based on the Stokes model. In the experiment, granules were taken from different heights of an Upflow Anaerobic Sludge Bed reactor, from 0.6 to 7.6 m. The granules’ diameters varied between 1 and 5 mm. The granules were taken from six different heights through the reactor. The settling velocity of the active granules (with gas in the granule pore and on the surface of the granule) was measured first. After the active granules’ settling velocity measurement, the granules were placed in a vortex to obtain degassed granules (granules without any gas in the pores or on the surface), for which the settling velocities were also measured later. It is shown that granules’ densities at different heights are independent of the reactor height.
The brewery spent grain (BSG) represents approximately 85% of the total quantity of by-products from the brewing industry. The biogas production from the BSG has been the subject of several studies ...in recent years, due to relatively high energy consumption in the brewing process and due to the increasing energy costs. The biodegradability of raw and pre-treated BSG in a single-stage and two-stage solid-state anaerobic digestion (SS-AD) system was determined in this study. The results show that the BSG have a biogas potential of 120 L/kg(-1). In the single-stage system, the biogas yield obtained from raw BSG (87.4 L/kg(-1)) was almost equal to the yield obtained from the pre-treated BSG (89.1 L/kg(-1)), while the methane yield was 51.9 and 55.3 L/kg(-1) and the biodegradation was 62.0% and 62.2% for raw and pre-treated BSG, respectively. In two-stage SS-AD the pre-treated BSG showed better results, with the biogas yield of 103.2 L/kg(-1) and the biodegradation of 73.6%, while the biogas yield obtained from raw BSG was 89.1 L/kg(-1), with the biodegradation of 63.5%. In two-stage process the obtained methane yields from raw and pre-treated BSG were identical (58.7 L/kg(-1)).
Renewable energy sources are becoming increasingly important in the beverage and food industries. In the brewing industry, a significant percentage of the used raw materials finishes the process as ...secondary resource or waste. The research on the anaerobic digestion of brewer’s yeast has been scarce until recent years. One of the reasons for this is its use as a secondary resource in the food industry and as cattle feed. Additionally, market value of brewer’s yeast is higher than its energy value. Due to the increase of energy prices, brewer’s yeast has become of interest as energy substrate despite its difficult degradability in anaerobic conditions. The anaerobic co-digestion of brewer’s yeast and anaerobically treated brewery wastewater was studied using a pilot-scale anaerobic sequencing batch reactor (ASBR) seeded with granular biomass. The experiments showed very good and stable operation with an organic loading rate of up to 8.0 kg/(m3·day), and with a maximum achieved organic loading rate of 13.6 kg/(m3·day) in a single cycle. A specific biogas productivity of over 0.430 m3/kg of the total chemical oxygen demand (COD) inserted, and total COD removal efficiencies of over 90 % were achieved. This study suggests that the brewer’s yeast can be successfully digested in an ASBR without adverse effects on the biogas production from brewer’s yeast/wastewater mixtures of up to 8 % (by volume). By using the brewer’s yeast in the ASBR process, the biogas production from brewery wastewater could be increased by 50 %.
Upotreba obnovljivih izvora energije u proizvodnji pića i prehrambenoj industriji postaje sve značajnija. U pivarskoj industriji znatan postotak neiskorištenih sirovina proizvodnog procesa postaje ...sekundarna sirovina ili se zbrinjava kao otpad. Do nedavno se mali broj istraživača bavio anaerobnom digestijom pivskog kvasca. Osnovni razlog tome je iskorištavanje pivskog kvasca kao sekundarne sirovine u prehrambenoj industriji te kao stočne hrane. Osim toga, tržišna vrijednost pivskog kvasca veća je od njegove energetske vrijednosti. S druge strane, zbog povećanja cijene energije, pivski kvasac postaje sve zanimljiviji energetski izvor, unatoč teškoj razgradljivosti u anaerobnim uvjetima. U radu je istražena anaerobna razgradnja pivskog kvasca i otpadnih voda pivarske industrije u poluindustrijskom anaerobnom sekvencijskom kotlastom reaktoru (ASBR reaktor) uz primjenu granulirane biomase. Provedeni pokusi bili su uspješni, a proces je bio stabilan pri stupnju organskog opterećenja do 8,0 kg/(m3·dan), dok je maksimalni stupanj organskog opterećenja u jednom ciklusu bio 13,6 kg/(m3·dan). Postignuta je specifična proizvodnja bioplina od 0,430 m3/kg i učinkovitost uklanjanja ukupnog organskog opterećenja od preko 90 %. Ovo istraživanje je pokazalo da se pivski kvasac može učinkovito anaerobno razgraditi u ASBR reaktoru ako je volumni udjel pivskog kvasca u smjesi s otpadnim vodama pivarske industrije manji od 8 %. Osim toga, anaerobnom razgradnjom pivskog kvasca u ASBR reaktoru može se povećati proizvodnja bioplina iz otpadnih voda pivarske industrije za 50 %.
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