In this study, the application of hydrodynamic cavitation to improve the biodegradability of mature landfill leachate was investigated. Three configurations of cavitation device were examined and operational parameters of the process were selected. The study indicated that the orifice plate with a 3/10mm diameter conical concentric hole, characterized by the cavitation number of 0.033, is a reasonable choice to ensure the enhanced biodegradability of mature leachate. Using such a configuration and maintaining 30 recirculation passes through the cavitation zone at inlet pressure of 7 bar, the highest increase of biodegradability index (BI) of approximately 22% occurred, i.e., from the value of 0.046 to 0.056. The FT-IR/PAS analysis confirmed a degradation of refractory compounds that typically prevail in mature leachate. An evaluation of energy efficiency was made in terms of the actual consumed energy measured by using the Kyoritsu KEW6310 Power Quality Tester. A cavitational yield of 9.8 mg COD kJ(-1) was obtained for the optimum configuration and 30 recirculation passes. Regarding energy efficiency, the application of 10 cavitation cycles appeared to be the most profitable. This was due to an almost threefold higher cavitational yield of 27.5 mg COD kJ(-1). However, the preferable option should be selected by considering a satisfactory effect in the biodegradability enhancement.

Membrane techniques constitute an interesting alternative to conventional activated sludge systems (CAS). In membrane bioreactors (MBR), the biomass separated on membranes is retained independently of sludge sedimentation properties. As a consequence, a high biomass concentration as well as low food to microorganisms ratio can be obtained. Moreover, the development of a characteristic activated sludge population is stimulated by the specific conditions prevailing in MBRs. In the study, the operation and treatment efficiency of the MBR and CAS processes were examined and compared. Simulation was performed with the use of GPS-X software. The effluent quality obtained for the MBR system was either better or comparable to that of CAS. The most significant difference concerned the elimination of total suspended solids, which amounted to 99.8% in the MBR. Regarding nutrients, a low concentration of total phosphorus in the effluent from CAS and MBR was obtained (0.67 gP m⁻³ and 0.50 gP m⁻³, respectively). Greater differences were achieved in the case of total nitrogen. Although almost complete nitrification took place in both systems, a lower concentration of nitrate in the effluent from MBR in comparison to CAS, i.e., 11.2 gN m⁻³ and 14.1 gN m⁻³, respectively, allowed us to obtain a higher removal of total nitrogen (80.8% and 76.1%, respectively).

In the face of increasingly frequent natural disasters resulting from climate change and disruptions in the supply chains of energy resources, the demand for energy carriers based on locally sourced renewable resources is growing. Biomethane, derived from biomass and having multiple uses in the energy sector, fully meets these conditions. Analyses of the development and spatial distribution of biomethane production plants, the prevalence of methods of its production, and directions of applications, made on the basis of the data gained from official databases and research papers, are the main subjects of the paper. Additionally, the advantages and disadvantages of biomethane production, taking into account the results of the life cycle assessments, and the prospects for development of the biomethane market, facing regulatory and policy challenges, are considered. The results of the review indicate that biomethane production is currently concentrated in Europe and North America, which together generate over 80% of the globally produced biomethane. An exponential growth of the number of biomethane plants and their production capacities has been observed over the last decade. Assuming that the global strategies currently adopted and the resulting regional and national regulations on environmental and socio-economic policies are maintained, the further intensive development of the biomethane market will be expected in the near future.

Methane from environmentally friendly anaerobic digestion may be an alternative non-renewable source that is depleting. One of the substrates for that process may be lignocellulose-based materials. The article concerns comparing the environmental impact as well as technical and energy indicators of alternative ways of producing methane from the anaerobic digestion of Pennisetum hybrid. Five scenarios were analyzed: methane production from the anaerobic digestion of the raw grass, the grass subjected to alkaline pretreatment (with 2% NaOH solution at two temperatures), and the grass subjected to mechanical pretreatment (ground to obtain particle sizes <0.18 mm and 0.25–0.38 mm). Multi-criteria decision (MCA) analysis was carried out with the use of five indicators, including life cycle assessment results as well as methane production parameters, in order to optimize this sustainable way of bioenergy production. The purpose of this study was to identify the most cost-effective and environmentally friendly method of Pennisetum hybrid pretreatment in order to optimize the methane production process in terms of environmental, technical, and economic aspects. According to the obtained results, it was stated that the most advantageous solution for the majority of the analyzed indicators turned out to be the mechanical pretreatment with grinding the lignocellulosic biomass into a particle size <0.18 mm.

This study examined the influence of acid cheese whey (ACW) addition on the nitrogen and phosphorus release in the co-digestion with sewage sludge (SS). The laboratory installation consisted of two semi-flow anaerobic digesters operating under mesophilic conditions. The concentrations of total nitrogen (TN). total phosphorus (TP), NH4+-N and PO43--P in the feedstock and the digestate were determined together with the appropriate release factors. The results indicate that the co-digestion of SS with ACW did not cause a significant increase in the concentration of biogenic elements both in the reactor feedstock and the digestate. Lower concentration of total nitrogen and total phosphorus was achieved in the digestate, both in whey and reference runs, probably due to partial retention in the digesters due to the precipitation processes.