The dairy and meat industries generate thousands of tons of organic waste and by-products each year, making them two of the least environmentally sustainable sectors. Typical waste includes not only processing by-products such as curds but also commercial products that are defective or unsaleable due to expiration or damaged packaging. This study aimed to evaluate the methanogenic potential of a mixture of 80% inedible curds and 20% expired sausages, as a substrate, using two continuously stirred tank reactors (CSTR). The reactors were fed daily with increasing doses of the 80–20% mixture and an organic loading rate ranging from 0.31 gVS/litre/day at the beginning of the trials to 7.20 gVS/litre/day toward the end. The produced biogas was continuously analysed from both quantitative and qualitative point of view. Also, the process was continuously monitored by withdrawing samples from each reactor during the whole process, to analyse their physical–chemical parameters, including pH, total solids (TS), total volatile solids (TVS), chemical oxygen demand (COD), ammonium nitrogen (NH4⁺-N), total Kjeldahl nitrogen (TKN) and total volatile fatty acids (VFA). The results of this study show a promising increase in biogas production with the increase in feed. In terms of biogas production, organic waste from the dairy and meat industry shows the potential to be exploited as a substrate to produce biomethane. Indeed, in this study, biomethane cumulative production reached 410.86 NL_CH4∙gTVS⁻¹ using an 8 L capacity reactor filled up to 6 L. This makes the tested by-products usable as a renewable energy source in the future, particularly within a circular economy approach, helping to mitigate the effects of global warming and addressing sustainable development goals.

This study explores AnMBR technology as a promising method for treating wastewater from the meat-processing industry by analysing its characteristics and impact under continuous feeding. The solids were retained, utilising an ultrafiltration membrane with a pore size of 0.2 µm, and the efficacy of reducing the organic load was evaluated. Although the COD removal rate decreased from 100% at an OLR of 0.71 g/(L*d) to 73% at an OLR of 2.2 g/(L*d), maximum methane yields were achieved at the highest OLR, 292.9 Nm³/t (COD) and 397.8 Nm³/t (VS) per loaded organics and 353.1 Nm³/t (COD) and 518.7 Nm³/t (VS) per removed organics. An analysis of the microbial community was performed at the end of the experiment to assess the effects of the process and the substrate on its composition. The AnMBR system effectively converts meat-processing wastewater into biogas, maintaining high yields and reducing the loss of dissolved methane in the permeate, thanks to a temperature of 37 °C and high salt levels. AnMBR enables rapid start-up, efficient COD removal, and high biogas yields, making it suitable for treating industrial wastewater with high organic loads, enhancing biogas production, and reducing methane loss. Challenges such as high salt and phosphate levels present opportunities for a wider use in nutrient recovery and water reclamation.

Poly(3-hydroxybutyrate) (PHB) is a biobased and biodegradable polymer with properties comparable to polypropylene and therefore has the potential to replace conventional plastics. PHB is intracellularly accumulated by prokaryotic organisms. For the cells PHB functions manly as carbon and energy source, but all possible functions of PHB are still not known. Synechocystis (cyanobacteria) accumulates PHB using light as energy and CO₂ as carbon source. The main trigger for PHB accumulation in cyanobacteria is nitrogen and phosphorous depletion with simultaneous surplus of carbon and energy. For the above reasons, obtaining knowledge about external factors influencing PHB accumulation is of highest interest. This study compares the effect of continuous light exposure and day/night (16/8 h) cycles on selected physiology parameters of three Synechocystis strains. We show that continuous illumination at moderate light intensities leads to an increased PHB accumulation in Synechocystis salina CCALA 192 (max. 14.2% CDW – cell dry weight) compared to day/night cycles (3.7% CDW). In addition to PHB content, glycogen and cell size increased, while cell density and cell viability decreased. The results offer new approaches for further studies to gain deeper insights into the role of PHB in cyanobacteria to obtain bioplastics in a more sustainable and environmentally friendly way.

Shows an overview of the integrated biogas purification and nutrient recovery system. The diagram illustrates the coupling of a two-stage biological desulfurization unit with a hollow-fiber membrane contactor. Biogas containing H₂S enters the first scrubber, is oxidized to H₂SO₄, and the biologically produced acid reacts with NH₃ recovered from the effluent to form ammonium sulfate ((NH₄)₂SO₄), demonstrating simultaneous gas purification and nutrient recovery. This study presents a novel integrated system for biogas purification and nutrient recovery, combining biological desulfurization with ammonia recovery using a hollow-fiber membrane contactor. Designed for anaerobic treatment of nitrogen- and sulfur-rich wastes, the system enables simultaneous hydrogen sulfide (H2S) removal and ammonium sulfate production, improving environmental performance and resource recovery. A two-stage desulfurization unit scrubbed and biologically oxidized H2S to sulfuric acid under controlled oxygen supply. The acid was neutralized by ammonia extracted from the biogas effluent through a hydrophobic membrane, forming ammonium sulfate without chemical additives. The system achieved over 95% H2S removal, with outlet concentrations below 35 ppm, and accumulated up to 12.5 g/L (0.095 mol/L) ammonium sulfate. Operation remained stable over several months at pH 3.0, with mass balance and ion analyses confirming efficient sulfur conversion. Microbial analysis identified Acidithiobacillus and Alicyclobacillus as dominant sulfur oxidizers. Compared with conventional systems, the two-stage design avoided sulfur clogging and biogas dilution. This robust, scalable process couples gas purification with nutrient recovery, producing a concentrated fertilizer solution while minimizing chemical use and supporting circular resource utilization.

Overview of the combination of an anaerobic membrane bioreactor with integrated ultrafiltration and the downstream ammonia removal using reverse osmosis or nanofiltration. RO exhibits higher energy consumption and better retention performance, while NF shows significantly lower energy consumption but also poorer retention performance. Nanofiltration (NF) is an energy-efficient alternative to reverse osmosis (RO) for partial ammonia removal and nutrient recovery. Within the EC SYMSITES project, this study evaluated NF performance for treating anaerobic membrane bioreactor effluents from meat-processing wastewater. Pilot-scale experiments were conducted at 20°C and 4–18 bar using spiral-wound NF and RO modules. The DuraSlick NF2540 membrane treated real effluents with conductivities up to 27 mS cm−1 and ammonium nitrogen concentrations up to 2,200 mg L−1. Ammonia retention increased with pressure for both membranes. NF achieved 60–80% ammonium rejection at 10 bar and pH ≈ 6 with significantly lower energy demand, while RO exceeded 95% rejection but at reduced flux. Acidification improved NH4− rejection due to the shift of the ammonia–ammonium equilibrium, although further pH reduction to 4.5 provided limited additional benefit while increasing chemical consumption. Ionic composition also affected performance: multivalent anions enhanced rejection, whereas monovalent salts reduced selectivity. NF removal efficiencies were consistent with literature values for complex effluents, but NF alone cannot meet stringent reuse limits. Overall, NF is a cost- and energy-efficient option for partial ammonia removal and is best combined with complementary treatment processes to achieve stricter standards.