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Additives for anaerobic digestion (AD) can play a significant role in optimizing the process by increasing biogas production, stabilizing the system, and improving digestate quality. The role of additives largely boils down to, among others, enhancing direct interspecies electron transfer (DIET) between microbial communities, resulting in improved syntrophic interactions, adsorption of toxic substances that may inhibit microbial activity, improving microbial activity, and increasing process stability and accelerating the decomposition of complex organic materials, thereby increasing the rate of hydrolysis. Through the aforementioned action, additives can significantly affect AD performance. The function of these materials varies, from enhancing microbial activity to maintaining optimal conditions and protecting the system from inhibitors. The choice of additives should be carefully tailored to the specific needs and conditions of the digester to maximize benefits and ensure sustainability. In light of these considerations, this paper characterizes the most commonly used additives and their combinations based on a comprehensive review of recent scientific publications, including a report on the results of conducted studies. The publication features chapters that describe carbon-based conductive materials, metal oxide nanomaterials, trace metal, and biological additives, including enzymes and microorganisms. It concludes with the chapters summarising reports on various additives and discussing their functional properties, as well as advantages and disadvantages. The presented review is a substantive and concise analysis of the latest knowledge on additives for the AD process. The application of additives in AD is characterized by great potential; hence, the subject matter is very current and future-oriented. [ABSTRACT FROM AUTHOR]

In recent years, Poland has seen a rapid increase in installed capacity in the renewable energy sources (RES) sector. This increase mainly concerns weather-dependent sources such as PV and wind installations, whose intermittent operation destabilizes the Polish power system (PPS). The solution to fluctuations in PPS operating parameters are stable and controllable RES sources, among which demand-driven biogas plants (with an energy storage in the form of biogas) have a special development potential. The aim of this paper was to describe the construction and principles of operation of peak biogas plants and to analyze the possibilities of including them in the operation of PPS. The paper shows the fundamental differences between the operation of typical biogas plants (producing electricity and heat continuously) and demand-driven biogas plants, in which biogas production takes place continuously, while electricity production occurs periodically, during the highest demand for power during the day. It was found that demand-driven biogas plants are a promising alternative to the previously used coal-fired units, battery energy storage units and pumped-storage power plants and in the future they may act as a stabilizer of the National Power System, achieving available electrical power of up to 11.1 GW. [ABSTRACT FROM AUTHOR]

The experiment consisted in monitoring the count of moulds and three selected Trichoderma sp. isolates (T1 - Trichoderma atroviride, T2 - Trichoderma harzianum, T3 - Trichoderma harzianum) in vegetable (onion and tomato) waste composted with additives (straw, pig manure). Additionally, the aim of the study was to determine the type of interaction occurring between autochthonous fungi isolated from composts after the end of the thermophilic phase and Trichoderma sp. strains applied in the experiment. Number of microorganisms was determined by the plate method, next the identification was confirmed. The rating scale developed by Mańka was used to determine the type of interactions occurring between microorganisms. The greatest count of moulds in onion waste composts was noted in the object which had simultaneously been inoculated with two strains T1 - T. atroviride and T3 - T. harzianum. The greatest count of moulds was noted in the tomato waste composts inoculated with T2 - T. harzianum strain. Microscope identification revealed that Penicillum sp., Rhizopus sp., Alternaria sp. and Mucor sp. strains were predominant in onion waste composts. In tomato waste composts Penicillium was the predominant genus, followed by Rhizopus. The test of antagonism revealed the inhibitory effect of Trichoderma isolates on most autochthonous strains of moulds. Tomato waste composts proved to be better substrates for the growth and development of Trichoderma sp. isolates. The results of the study show that vegetable waste can be used in agriculture as carriers of antagonistic microorganisms.

After entrance to EU in 2004, the management of sewage sludge has become more and more important problem for the new members. In Poland, one of the most promising technologies is composting process of sewage sludge with carbonaceous materials. However, the high price of typically used cereal straw forces the specialists to look for new and cheap materials used as donor of carbon and substrates creating good, porous structure of composted heap. This work presents the results of sewage sludge composting mixed with sawdust and maize straw used to create structure favorable for air exchange. The results show dynamic thermophilic phase of composting process in all cases where maize straw was used.

Celem badań była ocena stanu mikrobiologicznego (liczba bakterii heterotrofi cznych, promieniowców, pleśni) i biochemicznego (aktywność ureazy i fosfatazy kwaśnej) torfu z domieszką kompostów wytworzonych na bazie osadu ściekowego. Ponadto celem badań było wykazanie wpływu niniejszych podłoży na cechy morfologiczne szałwii błyszczącej (wysokość, liczba i długości pędów, liczba pąków i kwiatostanów, indeks zazielenienia (SPAD)). Komposty wyprodukowane z osadu ściekowego, słomy pszennej, kukurydzianej i łubinowej zmieszano z torfem w różnym udziale procentowym, od 25% do 75%.

Sewage sludge management is an important element of environmental protection. Composting and anaerobic digestion are the biological conversion methods for sewage sludge management. Mass and volume reduction is a result of a properly composted process. Solid fraction of digested pulp can be use as co-substrate, because it is good structural material. The aim of the study was to determine the possibility of composting sewage sludge with a solid fraction of digestate. The compost mix consisted of 25 kilograms of sewage sludge and 20 kilograms solid fraction of digestate in fresh mass. The experiment was carried out in laboratory conditions. Bioreactors of 165 dm3 volume were used. The experiment included two stages. Stage I took place in bioreactors and lasted until the cooling phase of the compost was complete. Stage II included compost maturation for a period of eight months (to 287 day of composting). The reduction of mass obtained at the end of Stage I amounted 30.2%. At the end of Stage II, it was 86.7% relative to the initial weight of the compost. The maximum value of temperature was 75.1°C. Studies have shown that sludge with a solid fraction of digestate can be a suitable substrate for composting with sewage sludge.

The aim of the study was to determine and analyse the costs of harvesting and storage of maize straw for biogas production. The investigations showed that it was the most economical to harvest maize straw with a self-loading wagon equipped with a cutting system and to store it in a field prism. The cost of this technology amounts to €12.5 per Mg d.m. The cost of maize straw harvest with a field chopper and storage in a flexible silo was the highest, amounts to €126.9 per Mg d.m. The research findings can be used for estimating the profitability of harvesting maize straw for energy production and other industrial purposes.

The aim of the study was to assess how the harvesting and ensilage technology influenced the quality of maize straw silages. The research findings showed that it was best to make maize straw silage in a flexible silo, whereas it was least favourable to make it in a film-covered field prism. The choice of the adequate ensilage method results in a high quality silage even if there is high content of dry matter in maize straw.

The paper presents the energy and economic comparison of two technologies of maize straw utilization: solid biofuel production (briquettes) and methane fermentation. The research experiments have shown that maize straw is the material which can be efficiently implemented in both technologies. Maize straw usage as briquettes can generate more energy (10.956 GJ Mg−1) than methane fermentation (9.74). In Europe, biogas is used in co-generation units for production of electric and heat energy. Due to higher price of electricity, economic profitability of maize straw usage for biogas production is over twice higher (182 USD) than in case of briquettes production (96 USD).