Anaerobic Fermentation of Substrate with High Nitrogen Content

This work focuses on anaerobic fermentation of synthetic substrate with high nitrogen content. An anaerobic continuously stirred tank reactor was gradually loaded with synthetic substrate, and the first inhibition was observed on day 110 when the SBP decreased by 20 %. Another significant change was observed on day 135, when SBP dropped to 122 L kg–1 COD. At the same time, a gas washing bottle with hydrochloric acid was connected to capture ammonia from recirculated biogas. With this arrangement, a slight increase in the SBP production to 150 L kg–1 COD was observed. On day 164, the gas washing bottle was changed to two gas washing bottles with fritted discs. After ten days, a significant increase in SBP, to 320 L kg–1 COD, was observed, indicating that the system began to overcome inhibition. From these results, it can be concluded that this method is effective in mitigating ammonia inhibition. This work is licensed under a Creative Commons Attribution 4.0 International License

Increased biogas production from lignocellulosic biomass by soaking in water

Received: November 24th, 2022 ; Accepted: April 2nd, 2023 ; Published: April 11th, 2023 ; Correspondence: [email protected] to its large production worldwide, lignocellulosic biomass represents a substrate with great potential to produce biogas. However, this type of biomass is characterized by a complex and solid structure, which is difficult to decompose by anaerobic microorganisms. Applying the correct pre-treatment method can increase its biodegradability. Lignocellulosic substrate was pre-treated by soaking in water for one day at room temperature to increase biogas production and monitoring of long-term operation of laboratory models of anaerobic reactors for anaerobic digestion of such pre-treated maize waste was employed. Monitoring results in two reactors, R1 with biogas produced from a substrate soaked in water for one day and R0 with the production of biogas from a substrate mixed with water just before dosing into the reactor, were compared showing positive effect of the pre-treatment method. This was expressed by higher values of biogas production and higher methane content in biogas from the substrate soaked in water for one day. The achieved specific biogas productions during four different phases of reactor operation in reactor R1 were in the range of 190–335 mL g-1 of VS (volatile solids) and 101–221 mL g-1 of VS in reactor R0. Methane content of biogas during reactor operation was 49.3–55.2% in reactor R1 and 42.5–45.5% in reactor R0. During long-term operation of another reactor, pre-treated maize waste was used as a co-substrate for maize silage, in the ratio of 1:1 based on VS of the substrates proving as a suitable co-substrate for maize silage, as the achieved average value of specific biogas production during reactor operation at OLR (organic loading rate) = 1.75 kg VS m-3 d-1 was 510 mL g-1 of VS and during first 67 days at OLR = 2 kg VS m-3 d-1 it was 454 mL g-1 of VS

Biogas Production in Municipal Wastewater Treatment Plants – Current Status in EU with a Focus on the Slovak Republic

The presented contribution reviews actual status of biogas production in the European countries with a focus on the Slovak municipal WWTPs. In 49 monitored Slovak WWTPs (out of 520) the anaerobic digestion with biogas production is operated. The total volume of digestion tanks is about 195 000 m3 but the total daily biogas production is only approx. 55 000 m3 d–1. From a technological point of view, the digestion tanks have sufficient space for considerable increase of biogas production. The increase can be achieved by the choice and dosing of external organic sources that could bring significant energy – economic contribution to WWTP operation without technological process adaptation (plant oils, fats, organic materials, etc.) or with a small technological process adaptation (food residues, food and agricultural products and wastes). The contribution describes the actual load parameters of digestion tanks, specific biogas production, electrical power capacity, and production on the Slovak WWTP obtained on the basis of a questionnaire from Slovak Water Companies