Biomethanation is a prospective biogas upgrading method to integrate renewable energy grid with existing biogas grid. Biomethane can directly substitute fossil natural gas and be used in all energy sectors. The selection of packing material for the ex-situ biomethanation in biotrickling filter reactors can be based on the physical and chemical characterization of the carrier material. The packing material selected for biotrickling filter reactors supports hydrogenotrophic methanogenic growth and thereby increases the area for H² mass transfer. Chemical components and melting temperature analysis of wood ash material are carried out to determine optimal parameters for producing wood ash filter material. Physical characteristics of new wood ash filter material such as volume-specific surface area (m² m⁻³), the external porosity (vol. %) and bulk density (kg m−3) are carried out to compare this material with other carrier materials that have been used in biotrickling filter reactors before.

Biomethanation is a prospective method to integrate a renewable solar or wind power grid with a biogas grid, where excess energy can be used to produce hydrogen for the biomethanation of the biogas to produce biomethane. The use of biotrickling filter reactors with appropriate carrier materials for biomethanation is essential for the immobilisation of hydrogenotrophic methanogens on the surface of the packing material. This study tested the suitability of filter materials made from woodchip ash (FA and CA) and glass waste (GF) for methanogenesis in biotrickling filter reactors using comparative performance analysis. The readily available and widely used expanded clay pallets (EC) and polyurethane foam (PUF) in biomethanation were used for comparison. The manometric method and BMP test are used to determine the rate of CH4 production. CH4 produced using filter materials decreases in the order GF>EC >PUF>FA>CA, respectively. The physical parameters of tested materials are compared to other filter materials commonly used in biomethanation applications. Glass foam (GF) that is made from glass waste showed the best biomethane production rate of 201.2 NmL/Lmaterial, as it has the best physical properties for methanogenesis in biotrickling filter reactors such as low volume density, high external porosity, and neutral pH. Ash waste recycling is related to its specific chemical properties, as it is alkaline and contains heavy metals that can leach out and negatively affect living organisms.

Syngas biomethanation has emerged as a promising technology for converting synthesis gas (CO, H2, and CO2) into renewable methane, offering a sustainable alternative to fossil-based natural gas. However, despite significant progress at the laboratory scale, the transition to industrial applications remains hindered by multiple challenges spanning microbial efficiency, reactor design, process optimization, and large-scale feasibility. At the fundamental level, mass transfer limitations significantly constrain the biological conversion of syngas, with poor gas-liquid diffusion of CO and H2 affecting microbial metabolism. Moreover, the adaptation of microbial consortia to varying syngas compositions remains insufficiently understood, particularly regarding the dominant pathways under mesophilic and thermophilic conditions. Reactor design further exacerbates these challenges, with current configurations (continuous stirred-tank reactors, packed bed reactors, and membrane bioreactors) struggling to achieve efficient syngas conversion at high productivity rates. Process parameters such as temperature, H2/CO ratio, and trace element supplementation also require fine-tuning to enhance methane yields while maintaining process stability. While small-scale experiments have demonstrated promising results, scaling up remains a major hurdle due to economic constraints, reactor operational challenges, and the need for reliable feedstock supply. Additionally, the integration of syngas biomethanation with existing energy infrastructure, including power-to-gas technologies and anaerobic digestion systems, requires further investigation to ensure economic viability and process efficiency. This review systematically explores these multi-scale challenges, from bench-scale research to commercial deployment, highlighting key research gaps and potential strategies to accelerate the transition of syngas biomethanation from laboratory studies to industrial reality.

This article reviews state-of-the-art microdroplet technological solutions for screening microorganisms mutant and GMO strains. Microorganisms used in the production of various products – single-cell protein, single-cell oil, enzymes, pigments and other bioactive compounds – can always be improved and their properties enhanced to increase the production of products of interest, to simplify microbial cultivation process, improve efficiency or adapted strains to use cheaper raw materials such as agroindustrial by-products. Microorganisms can be improved using either classical mutagenesis techniques or genetic engineering methods. Regardless of the selected method for mutant or GMO creation, during the process most promising microorganism strains must be selected, which is usually a slow and labour-intensive process. The use of microdroplets is a promising technological solution to speed up strain selection. This review looks at the latest developments in microdroplet technology, compares their variations, and identifies future prospects.

This study presents an analysis of key elements of biobutanol production, including feedstock selection, pre-treatment methods, and microorganism strains. Using laboratory experiments, we evaluated the ability of different microorganisms to convert various agricultural and industrial by-products into biobutanol. We tested three microorganism strains: C. acetobutylicum DSM 792, C. beijerinckii DSM 6423, and C. saccharoperbutylacetonicum DSM 14923. The results showed that biodiesel production residues, various agricultural hydrolysates, yeast residues, and milk processing residues were the most suitable feedstocks for biobutanol production. In addition, the authors explored different pre-treatment methods, such as microbial and chemical hydrolysis, to enhance the efficiency of biobutanol production. Our findings provide valuable insights for optimizing biobutanol production processes in line with sustainable and cost-effective production principles.