• Energy Research

Main goal of the study was present the results of some respirometric measurements of activated sludge biodegrading the substrate in the wastewater originated in selected sections of the dairy processing line. The following dairy production effluents were analyzed in the research: the pumping station wastewater (combined wastewater from all the sections of the dairy factory), the apparatus room wastewater, the butter section wastewater, the milk reception point wastewater, the cheese section wastewater and the cottage cheese section wastewater. Apart from that, sweet and sour whey, which are secondary products of hard cheese and cottage cheese production, respectively, was the subject of the research. The amount of organic matter being oxidized during a 5-day measurement session was calculated on 1g of the activated sludge biomass. The research was conducted at the temperature of 20 degrees C and 35 degrees C at the applied sludge loading rate of A'=0.2 g BOD g(-1) dry mass d(-1), which ensured complete biodegradation. The results indicated a correlation between a technological process of dairy processing, an ultimate outcome of which was the wastewater analyzed, and dairy wastewater biodegradability. The results confirmed that all dairy processing effluents can be treated together, with the exception of whey, whose complex biodegradation demands may cause too much burden to any wastewater treatment technological system and thus should be managed within a separate installation.

Production and consumption of confectionery products have increased worldwide, thus, effective management of wastewater produced is now an important issue. The confectionery high-load sewage was explored for biogas production in an innovative-design anaerobic reactor with labyrinth flow. The experimental studies were focused on determining the best technological parameters of anaerobic digestion for the effective removal of pollutants and obtaining high CH4 production efficiency. It was found that organic loading rate (OLR) of 5.0–6.0 g COD/L·d contributed to the highest CH4 generation of 94.7 ± 6.1 to 97.1 ± 5.1 L CH4/d, which corresponded to a high COD removal of 75.4 ± 1.5 to 75.0 ± 0.6%. Under such conditions the FOS/TAC ratio was below 0.4, indicating reactor stability, and pH was on the level of 7.15 ± 0.04 at OLR 5.0 g COD/L·d and 7.04 ± 0.07 at OLR 6.0 g COD/L·d.

To date, microwave radiation has been successfully used to support the chemical hydrolysis of organic substrates in the laboratory. There is a lack of studies on large-scale plants that would provide the basis for a reliable evaluation of this technology. The aim of the research was to determine the effectiveness of using microwave radiation to support the acidic and alkaline thermohydrolysis of lignocellulosic biomass prior to anaerobic digestion on a semi-industrial scale. Regardless of the pretreatment options, similar concentrations of dissolved organic compounds were observed, ranging from 99.0 ± 2.5 g/L to 115.0 ± 3.0 in the case of COD and from 33.9 ± 0.92 g/L to 38.2 ± 1.41 g/L for TOC. However, these values were more than twice as high as the values for the substrate without pretreatment. The degree of solubilisation was similar and ranged between 20 and 28% for both monitored indicators. The highest anaerobic digestion effects, ranging from 99 to 102 LCH4/kgFM, were achieved using a combined process consisting of 20 min of microwave heating, 0.10–0.20 g HCl/gTS dose, and alkaline thermohydrolysis. For the control sample, the value was only 78 LCH4/kgFM; for the other variants, it was between 79 and 94 LCH4/kgFM. The highest net energy gain of 3.51 kWh was achieved in the combined alkaline thermohydrolysis with NaOH doses between 0.10 and 0.20 g/gTS. The use of a prototype at the 5th technology readiness level made it possible to demonstrate that the strong technological effects of the thermohydrolysis process, as demonstrated in laboratory tests to date, do not allow for positive energy balance in most cases. This fact considerably limits the practical application of this type of solution.

Inexpensive carbon sources offering an alternative to glucose are searched for to reduce costs of docosahexaenoic acid production by microalgae. The use of waste glycerol seems substantiated and prospective in this case. The objective of this study was to determine the production yield of heterotrophic microalgae Schizochytrium sp. biomass and the efficiency of docosahexaenoic acid production in various types of cultures with waste glycerol. Cultivation conditions were optimized using the Plackett–Burman method and Response Surface Methodology. The highest technological performance was obtained in the fed-batch culture, where the concentration of Schizochytrium sp. biomass reached 103.44 ± 1.50 g/dm3, the lipid concentration in Schizochytrium sp. biomass was at 48.85 ± 0.81 g/dm3, and the docosahexaenoic acid concentration at 21.98 ± 0.36 g/dm3. The highest docosahexaenoic acid content, accounting for 61.76 ± 3.77% of total fatty acids, was determined in lipid bodies of the Schizochytrium sp. biomass produced in the batch culture, whereas the lowest one, accounting for 44.99 ± 2.12% of total fatty acids, in those of the biomass grown in the fed-batch culture.

Abstract Methane fermentation is a versatile and established technology that should be optimized at all stages, starting from biomass storage and ending at digestate management. A commonly used method of biomass storage is ensiling, and the methane production of the biomass is determined by the products of the ensiling fermentation. Therefore, this study determined the effect of fermentation stimulants, fermentation inhibitors and osmotic condition improvers on the methane production of Sida hermaphrodita silages. Methane production was highest (334.6 ± 8.1 L/kg VSadded) with silage prepared with molasses, which increased its content of carbohydrates and lowered its ammonium nitrogen content. Production of methane was also high with untreated plant (304.0 ± 10.1 L/kg VSadded). Methane production correlated with Methanosarcinaceae abundance in the sludge. Principal component analysis revealed that first principal component was strongly correlated with indicators related with ensiling performance. Ensiling had no effect on the hemicellulose content and lowered the pH of silage independent of the additive used.

Research to date has mainly focused on the properties and efficiency of the production of selected, individual types of biofuels from microalgae biomass. There are not enough studies investigating the efficiency of the production of all energy sources synthesised by these microorganisms in a single technological cycle. The aim of this research was to determine the possibilities and efficiency of the production of hydrogen, bio-oil, and methane in the continuous cycle of processing T. subcordiformis microalgae biomass. This study showed it was feasible to produce these three energy carriers, but the production protocol adopted was not necessarily valuable from the energy gain standpoint. The production of bio-oil was found to be the least viable process, as bio-oil energy value was only 1.3 kWh/MgTS. The most valuable single process for microalgae biomass conversion turned out to be methane fermentation. The highest specific gross energy gain was found after applying a protocol combining biomass production, hydrogen biosynthesis, and subsequent methane production from T. subcordiformis biomass, which yielded a total value of 1891.4 kWh/MgTS. The direct methane fermentation of T. subcordiformis biomass enabled energy production at 1769.8 kWh/MgTS.

Ultrasonic disintegration is one of the most interesting technologies among all known and described technologies for sewage sludge pre-treatment before the process of methane fermentation. This study was aimed at determining the effects of an innovative ultrasonic string disintegrator used for sewage sludge pre-treatment on the effectiveness of methane fermentation process. In this experiment, we used a device for disintegration of organic substrates, including sewage sludge, with the use ultrasonic waves. Its technical solution is protected by a patent no. P. 391477 – Device for destruction of tissue and cell structures of organic substrate. The volume of biogas produced ranged from 0.194±0.089 dm3/g o.d.m. at loading of 5.0 g o.d.m./dm3 and power of 50 W to 0.315±0.087 dm3/g o.d.m. at loading of 4.0 g o.d.m./dm3 and ultrasounds power of 125 W. The study demonstrated a positive effect of sewage sludge sonication on the percentage content of methane in biogas. Sewage sludge exposure to 125 W ultrasounds increased methane content in biogas to 68.3±2.5 % at tank loading of 3.0 g o.d.m./dm3.

This paper presents data on methane fermentation of algal biomass containing Chlorella sp. and Scenedesmus sp. The biomass was obtained from closed-culture photobioreactors. Before the process, the algae were subjected to low temperature and pressure pretreatment for 0.0, 0.5, 1.0 and 2.0 h. The prepared biomass was subjected to mesophilic methane fermentation. The amount and composition of the biogas formed in the process were determined. The amount of biogas produced was larger when the biomass was subjected to thermal preprocessing. The proportion of methane in the gas also increased. Extending the heating time beyond 1.0 h did not significantly improve the biogassing effects.

One of the most important factors in determining the profitable production of microalgae biomass is the use of a cost effective growth medium that is rich in nutrients. The objective of the study was to determine the possibility of using digestates from anaerobic digestion of different feedstock mixtures as the media for Scenedesmus sp. cultivation. A different liquid digestate composition was obtained in terms of organic compounds, phosphorus, and nitrogen concentrations, depending on the substrates used in the anaerobic digestion. It was found that the highest biomass production was obtained when using digestate from anaerobic digestion of the feedstock mainly composed of microalgae biomass, which was characterized by low organic compounds concentration. In this case, the average biomass concentration reached 2382 mg total solids/L. A lower Scenedesmus sp. biomass yield was obtained using digestate from anaerobic digester processing feedstock based on maize silage and cattle menure. In the variants of the study, it was also found that the increase in the initial concentration of ammonia nitrogen in the growth medium up to 160 mg/L significantly reduced the growth of Scenedesmus sp. The results indicated the possibility of a high ammonia nitrogen and orthophosphates removal from anaerobic digestates by Scenedesmus sp. microalgae. Phosphorus concentration in the cultivation medium is a limiting factor for the growth of Scenedesmus sp., thus phosphorus supplementation should be considered when using liquid digestate as the culture medium. The optimization model indicated that the volume of liquid digestate that was used for preparing the cultivation medium, the initial concentration of organic compounds, and the initial concentration of ammonia nitrogen had a significant impact on the production of Scenedesmus sp. biomass.