Polylactide (PLA) as a Cell Carrier in Mesophilic Anaerobic Digestion—A New Strategy in the Management of PLA

The management of waste polylactide (PLA) in various solutions of thermophilic anaerobic digestion (AD) is problematic and often uneconomical. This paper proposes a different approach to the use of PLA in mesophilic AD, used more commonly on the industrial scale, which consists of assigning the function of a microbial carrier to the biopolymer. The study involved the testing of waste wafers and waste wafers and cheese in a co-substrate system, combined with digested sewage sludge. The experiment was conducted on a laboratory scale, in a batch bioreactor mode. They were used as test samples and as samples with the addition of a carrier: WF—control and WFC—control; WF + PLA and WFC + PLA. The main objective of the study was to verify the impact of PLA in the granular (PLAG) and powder (PLAP) forms on the stability and efficiency of the process. The results of the analysis of physicochemical properties of the carriers, including the critical thermal analysis by differential scanning calorimetry (DSC), as well as the amount of cellular biomass of Bacillus amyloliquefaciens obtained in a culture with the addition of the tested PLAG and PLAP, confirmed that PLA can be an effective cell carrier in mesophilic AD. The addition of PLAG produced better results for bacterial proliferation than the addition of powdered PLA. The highest level of dehydrogenase activity was maintained in the WFC + PLAG system. An increase in the volume of the methane produced for the samples digested with the PLA granules carrier was registered in the study. It went up by c.a. 26% for WF, from 356.11 m3 Mg−1 VS (WF—control) to 448.84 m3 Mg−1 VS (WF + PLAG), and for WFC, from 413.46 m3 Mg−1 VS, (WFC—control) to 519.98 m3 Mg−1 VS (WFC + PLAG)

The Use of Lignin as a Microbial Carrier in the Co-Digestion of Cheese and Wafer Waste

The aim of the article was to present the effects of lignin grafted with polyvinylpyrrolidone (PVP) as a microbial carrier in anaerobic co-digestion (AcoD) of cheese (CE) and wafer waste (WF). Individual samples of waste cheese and wafers were also tested. The PVP modifier was used to improve the adhesive properties of the carrier surface. Lignin is a natural biopolymer which exhibits all the properties of a good carrier, including nontoxicity, biocompatibility, porosity, and thermal stability. Moreover, the analysis of the zeta potential of lignin and lignin combined with PVP showed their high electrokinetic stability within a wide pH range, that is, 4–11. The AcoD process was conducted under mesophilic conditions in a laboratory by means of anaerobic batch reactors. Monitoring with two standard parameters: pH and the VFA/TA ratio (volatile fatty acids-to-total alkalinity ratio) proved that the process was stable in all the samples tested. The high share of N–NH4+ in TKN (total Kjeldahl nitrogen), which exceeded 90% for WF+CE and CE at the last phases of the process, proved the effective conversion of nitrogen forms. The microbiological analyses showed that eubacteria proliferated intensively and the dehydrogenase activity increased in the samples containing the carrier, especially in the system with two co-substrates (WF+CE/lignin) and in the waste cheese sample (CE/lignin). The biogas production increased from 1102.00 m3 Mg−1 VS (volatile solids) to 1257.38 m3 Mg−1 VS in the WF+CE/lignin sample, and from 881.26 m3 Mg−1 VS to 989.65 m3 Mg−1 VS in the CE/lignin sample. The research results showed that the cell immobilization on lignin had very positive effect on the anaerobic digestion process

Kraft Lignin Grafted with Polyvinylpyrrolidone as a Novel Microbial Carrier in Biogas Production

The objective of this study was to verify the effect of kraft lignin as a microbial carrier on biogas/methane yield. An anaerobic co-digestion test process was carried out, in which confectionery waste was used with sewage sludge. At the first stage of the study pure lignin and lignin combined with polyvinylpyrrolidone (PVP) were subjected to an extensive physicochemical analysis. Their morphology, dispersion and adsorption properties were determined. The two materials were also subjected to thermal, spectroscopic and elementary analysis. The anaerobic digestion of the two substrates was carried out with and without the addition of the carrier, under mesophilic conditions and in periodic operation. The monitoring and analysis of the two essential parameters, i.e., pH and volatile fatty acids/total alkalinity (VFA/TA) ratio, revealed that the process was stable in both tests. Microbial and biochemical analyses showed intensified proliferation of eubacteria and increased dehydrogenase activity in samples prepared with the lignin + PVP material. The cell count increased by 46% in the stuffed wafers (WAF) + sewage sludge (SS) variant with the carrier, whereas the enzyme activity increased by 43%. Cell immobilisation noticeably improved the process efficiency. The biogas production increased from 722 m3 Mg−1 VS to 850 m3 Mg−1 VS (VS ⁻ volatile solids), whereas the methane production increased from 428 m3 Mg−1 VS to 503 m3 Mg−1 VS (by about 18%). The research proved that lignin could be used as a very effective microbial carrier in anaerobic digestion (AD)

Production efficiency of Poland farm-scale biogas plants: A case study

This paper provides the analysis of results of biogas and methane yield for: maize silage (MS), pig slurry (PS), waste potatoes (WP) and sugar beet pulp (SB). The results show that maize silage is the most energy substrate (among the samples tested), providing a cumulative methane yield from 595 to 631 m-3 Mg VS (VS – volatile solids). The study was carried out in a laboratory scale using anaerobic batch reactors, at controlled (mesophilic) temperature and pH conditions. This paper is Part I of a report of an experiment carried out, in the laboratory scale and in the commercial scale (in parallel) The purpose of the experiment was to verify differences in biomethane yields of the same materials in the two scales. Moreover, this paper is an introduction to a presentation of the method to determine the biochemical methane potential correction coefficient (BMPCC), the details of which will be explained in Part II

Dimension Reduction of Digital Image Descriptors in Neural Identification of Damaged Malting Barley Grains

The paper covers the problem of determination of defects and contamination in malting barley grains. The analysis of the problem indicated that although several attempts have been made, there are still no effective methods of identification of the quality of barley grains, such as the use of information technology, including intelligent sensors (currently, quality assessment of grain is performed manually). The aim of the study was the construction of a reduced set of the most important graphic descriptors from machine-collected digital images, important in the process of neural evaluation of the quality of BOJOS variety malting barley. Grains were sorted into three size fractions and seed images were collected. As a large number of graphic descriptors implied difficulties in the development and operation of neural classifiers, a PCA (Principal Component Analysis) statistical method of reducing empirical data contained in the analyzed set was applied. The grain quality expressed by an optimal set of transformed descriptors was modelled using artificial neural networks (ANN). The input layer consisted of eight neurons with a linear Postsynaptic Function (PSP) and a linear activation function. The one hidden layer was composed of sigmoid neurons having a linear PSP function and a logistic activation function. One sigmoid neuron was the output of the network. The results obtained show that neural identification of digital images with application of Principal Component Analysis (PCA) combined with neural classification is an effective tool supporting the process of rapid and reliable quality assessment of BOJOS malting barley grains

The Influence of the Process of Sugar Beet Storage on Its Biochemical Methane Potential

The manner of storage of sugar beets largely influences their physical and chemical properties, which may subsequently determine their biochemical methane potential. In this study, samples of fresh sugar beets as well as beets stored in two ways—in airtight conditions and in an open-air container—were tested. In both cases, measurements were taken on specific dates, i.e., after 4, 8, 16 and 32 weeks of storage. A decrease in pH was observed in all samples, with the lowest decrease occurring in hermetically stored samples. The lowest pH value of 3.71 was obtained for sugar beets stored in an open-air container after 32 weeks of storage. During storage, a gradual decrease in total solids was also recorded along with accompanying losses of organic matter, more significant in the case of storage in an open-air container. In subsequent storage periods, the biogas/methane production efficiency differed slightly for both methods. The highest volume of biogas was obtained for fresh sugar beets—148.23 mL·g−1 fresh matter (FM)—and subsequently in the 8th and 16th weeks of storage: 139.35 mL·g−1 FM (H—airtight conditions) and 144.14 mL·g−1 FM (O—open-air container), and 147.58 H mL·g−1 FM (H) and 148.22 mL·g−1 FM (O), respectively. The storage period affected the time of anaerobic decomposition of the organic matter—fresh sugar beets took the longest to ferment (26 days), while the material stored for 32 weeks took the shortest to ferment. In the experiment, the content of selected organic compounds in individual samples, i.e., sugar, methanol, ethanol, lactic acid and acetic acid, was also analysed. Within these results, significant differences were found between the samples stored using the two different methods. A high content of sugar, methanol, ethanol and other chemical compounds in the “O” materials showed the hydrolysis and acidogenesis processes taking place in an open-air container, with the participation of catalytic microorganisms

Use of Confectionery Waste in Biogas Production by the Anaerobic Digestion Process

It was the objective of this study to verify the efficiency and stability of anaerobic digestion (AD) for selected confectionery waste, including chocolate bars (CB), wafers (W), and filled wafers (FW), by inoculation with digested cattle slurry and maize silage pulp. Information in the literature on biogas yield for these materials and on their usefulness as substrate in biogas plants remains to be scarce. Owing to its chemical structure, including the significant content of carbon-rich carbohydrates and fat, the confectionery waste has a high biomethane potential. An analysis of the AD process indicates differences in the fluctuations of the pH values of three test samples. In comparison with W and FW, CB tended to show slightly more reduced pH values in the first step of the process; moreover an increase in the content of volatile fatty acids (VFA) was recorded. In the case of FW, the biogas production process showed the highest stability. Differences in the decomposition dynamics for the three types of test waste were accounted for by their different carbohydrate contents and also different biodegradabilities of specific compounds. The highest efficiency of the AD process was obtained for the filled wafers, where the biogas volumes, including methane, were 684.79 m3 Mg−1 VS and 506.32 m3 Mg−1 VS, respectively. A comparable volume of biogas (673.48 m3 Mg−1 VS) and a lower volume of methane (407.46 m3 Mg−1 VS) were obtained for chocolate bars. The lowest volumes among the three test material types, i.e., 496.78 m3 Mg−1 VS (biogas) and 317.42 m3 Mg−1 VS (methane), were obtained for wafers. This article also proposes a method of estimation of the biochemical methane potential (theoretical BMP) based on the chemical equations of degradation of sugar, fats, and proteins and known biochemical composition (expressed in grams)

Methods of Handling the Cup Plant (<i>Silphium perfoliatum</i> L.) for Energy Production

The aim of the study was to determine the possibilities of using cup plants (Silphium perfoliatum L.) to generate energy. The energy balances of the combustion and anaerobic digestion were compared. The research showed that cup plants could be used as a raw material for solid fuel and for anaerobic digestion. An energy balance simulation showed that electricity could be generated through the anaerobic digestion of cup plants. The following amounts could be generated in the anaerobic digestion process: 1069 kWhe from 1 Mg of the raw material fragmented with an impact mill, 738.8 kWhe from 1 Mg of the raw material extruded at a temperature of 150 °C, and as much as 850.1 kWhe from 1 Mg of the raw material extruded at 175 °C. The energy balance of the combustion of biofuel in the form of cup plant pellets showed that 858.28 kWht could be generated from 1 Mg of the raw material. The combustion of solid biofuel generated a relatively low amount of heat in comparison with the expected amount of heat from a biogas-powered cogeneration system due to the high energy consumption of the processes of drying and agglomeration of the raw material for the production of pellets

Methods of Handling the Cup Plant (Silphium perfoliatum L.) for Energy Production

The aim of the study was to determine the possibilities of using cup plants (Silphium perfoliatum L.) to generate energy. The energy balances of the combustion and anaerobic digestion were compared. The research showed that cup plants could be used as a raw material for solid fuel and for anaerobic digestion. An energy balance simulation showed that electricity could be generated through the anaerobic digestion of cup plants. The following amounts could be generated in the anaerobic digestion process: 1069 kWhe from 1 Mg of the raw material fragmented with an impact mill, 738.8 kWhe from 1 Mg of the raw material extruded at a temperature of 150 &deg;C, and as much as 850.1 kWhe from 1 Mg of the raw material extruded at 175 &deg;C. The energy balance of the combustion of biofuel in the form of cup plant pellets showed that 858.28 kWht could be generated from 1 Mg of the raw material. The combustion of solid biofuel generated a relatively low amount of heat in comparison with the expected amount of heat from a biogas-powered cogeneration system due to the high energy consumption of the processes of drying and agglomeration of the raw material for the production of pellets