Digestate mechanical separation in industrial conditions: Efficiency profiles and fertilising potential.

The growing number of biogas plants has resulted in problems with the digestate management. In the studies carried out in industrial conditions in the biogas plant fed with sugar beet pulp, the influence of the decanter centrifuge operating parameters such as the retention time and differential speed on the effectiveness of digestate mechanical separation was evaluated. During the studies, the impact of the addition of cationic polyacrylamide flocculants with different charge density on the liquid and solid fraction composition was also determined. It was shown that the dry matter and organic matter concentrations in the solid fraction were about 88.80 g/kg FM and 66.20% DM, respectively and in the liquid fraction 25.50 g/kg FM and 77.00% DM after the centrifugation of the digestate without flocculant at an optimal retention time of 225 s and differential speed of 4 rpm. The removal efficiency of dry matter and organic matter was 32.00% and 39.39%. The best separation results were obtained centrifuging the digestate with addition of 20 g/kg DM flocculant with a charge density of 80%. The flocculant addition increased the removal efficiency of dry matter and organic matter in comparison to centrifugation without flocculant by 49.60% and 46.86%, respectively. After centrifugation and flocculation, about 60.83% of nitrogen, 74.55% of potassium and 33.23% of phosphorus remained in the liquid fraction. The liquid fraction contained lower concentrations of nickel, lead, cadmium and chromium in comparison to solid fraction.

High-throughput sequencing approach in analysis of microbial communities colonizing natural gas pipelines.

This study provides a deep modern insight into the phylogenetic diversity among bacterial consortia found in working and nonworking high-methane natural gas pipelines located in Poland. The working pipeline was characterized by lower biodiversity (140-154 bacterial genera from 22 to 23 classes, depending on the source of the debris) in comparison to the off-gas pipeline (169 bacterial genera from 23 classes). The sediment recovered from the working pipeline contained mostly DNA identified as belonging to the phylum Firmicutes (66.4%-45.9% operational taxonomic units [OTUs]), predominantly Bacillus (41.4%-31.1% OTUs) followed by Lysinibacillus (2.6%-1.5% OTUs) and Clostridium (2.4%-1.8% OTUs). In the nonworking pipeline, Proteobacteria (46.8% OTUs) and Cyanobacteria (27.8% OTUs) were dominant. Over 30% of the Proteobacteria sequences showed homologies to Gammaproteobacteria, with Pseudomonas (7.1%), Enhydrobacter (2.1%), Stenotrophomonas (0.5%), and Haempohilus (0.4%) among the others. Differences were noted in terms of the chemical compositions of deposits originating from the working and nonworking gas pipelines. The deposits from the nonworking gas pipeline contained iron, as well as carbon (42.58%), sulphur (15.27%), and oxygen (15.32%). This composition can be linked to both the quantity and type of the resident microorganisms. The presence of a considerable amount of silicon (17.42%), and of aluminum, potassium, calcium, and magnesium at detectable levels, may likewise affect the metabolic activity of the resident consortia in the working gas pipeline. All the analyzed sediments included both bacteria known for causing and intensifying corrosion (e.g., Pseudomonas, Desulfovibrio, Shewanella, Serratia) and bacteria that can protect the surface of pipelines against deterioration (e.g., Bacillus). Biocorrosion is not related to a single mechanism or one species of microorganism, but results from the multidirectional activity of multiple microbial communities. The analysis presented here of the state of the microbiome in a gas pipeline during the real gas transport is a particularly valuable element of this work.

Effect of Different Sugar Beet Pulp Pretreatments on Biogas Production Efficiency.

The objective of this study was to determine the effect of different sugar beet pulp (SBP) pretreatments on biogas yield from anaerobic digestion. SBP was subjected to grinding, thermal-pressure processing, enzymatic hydrolysis, or combination of these pretreatments. It was observed that grinding of SBP to 2.5-mm particles resulted in the cumulative biogas productivity of 617.2 mL/g volatile solids (VS), which was 20.2 % higher compared to the biogas yield from the not pretreated SBP, and comparable to that from not ground, enzymatically hydrolyzed SBP. The highest cumulative biogas productivity, 898.7 mL/g VS, was obtained from the ground, thermal-pressure pretreated and enzymatically hydrolyzed SBP. The latter pretreatment variant enabled to achieve the highest glucose concentration (24.765 mg/mL) in the enzymatic hydrolysates. The analysis of energy balance showed that the increase in the number of SBP pretreatment operations significantly reduced the gain of electric energy.

Effect of enzymatic pretreatment on anaerobic co-digestion of sugar beet pulp silage and vinasse.

Results of sugar beet pulp silage (SBPS) and vinasse (mixed in weight ratios of 3:1, 1:1 and 1:3, respectively) co-fermentation, obtained in this study, provide evidence that addition of too high amount of vinasse into the SBPS decreases biogas yields. The highest biogas productivity (598.1mL/g VS) was achieved at the SBPS-vinasse ratio of 3:1 (w/w). Biogas yields from separately fermented SBPS and vinasse were by 13% and 28.6% lower, respectively. It was found that enzymatic pretreatment of SBPS before methane fermentation that caused partial degradation of component polysaccharides, considerably increased biogas production. The highest biogas yield (765.5mL/g VS) was obtained from enzymatic digests of SBPS-vinasse (3:1) blend (27.9% more than from fermentation of the counterpart blend, which was not treated with enzymes). The simulation of potential biogas production from all the aforementioned mixtures using the Gompertz equation showed fair fit to the experimental results.