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Biogas production is the most important and promising alternative for replacing fossil fuels in an environmentally friendly manner. Along with the many renewable energy sources available, biogas production occupies an irreplaceable position due to the undeniable availability of biomass and the need to manage agro-commercial waste. The article reviews the current state of technology used in the production of biogas for selected European examples in terms of methane fermentation efficiency and actual energy production. The novelty of the article is its description of innovative trends that have great potential to play an important role in this field in the near future. The development of the biogas industry in Europe is evident, although the dynamics vary from country to country. Different models are presented, which are based on the different types of feedstock used for biogas production and the proportion of substrates used in co-digesters. Of course, Germany is the undisputed pioneer in the use of this renewable energy source. Nevertheless, the efforts to improve energy self-reliance and environmental impacts are reflected in the growing number of operational biogas plants in other European countries, which provides hope for rapid progress toward the complete abolition of the conventional exploitation of fossil fuels.

In small German farms, there is a technically usable potential of cattle manure and pig manure ranging from 153 to 187 million tons of fresh matter per year. Since 2021 and 2023, new incentives under the Renewable Energy Sources Act (EEG) have been promoting biogas production in small farms. These incentives, applicable to biogas plants up to 150 kWel, include direct compensations for plants up to 100 kWel and market premiums for those up to 150 kWel. A small biogas plant made of textile materials was designed for both pilot and full-scale applications. Compared to conventional concrete biogas reactors, these textile-based reactors offer a simplified construction and operation, eliminating the need for specialized civil engineering. The primary objective of this research is to demonstrate the process engineering feasibility of biogas reactors based on textile materials for small farm biogas plants (30 to 75 kWel). Another goal is to design the construction method in such a way that this type of system can be built by farmers themselves after type testing on site. Operational insights were gathered from the laboratory plant with a 300-L digester volume, using cattle manure and clover grass silage. To adapt the system to the biogas reactor made of textile materials, the reactor was designed without a stirrer. These insights were considered in the design and approval procedure of the full-sized demonstration biogas plant made of textile materials. The full-size demonstration plant digesters underwent an approval procedure from local authorities, featuring treatment volumes of 120 m3 for the main biogas reactor and 550 m3 for the digestate reactor in an earth basin style. This new type of biogas plant could be built in small farms for self-sufficiency in electrical and thermal energy or for treating sewage sludge in small-scale communal wastewater treatment and biogas plants.

In the past decade, agricultural biogas plants have become one of the key tools driving the energy transition in rural areas. Nevertheless, their development in Poland still lags behind that in Western European countries, suggesting the existence of barriers that go beyond technological or regulatory issues. This study aims to examine how Polish farmers perceive the risks and expected benefits associated with investing in biogas plants and which of these perceptions influence their willingness to invest. The research was conducted in the second quarter of 2025 among farmers planning to build micro biogas plants as well as owners of existing biogas facilities. Geographic Information System (GIS) tools were also used in selecting respondents and identifying potential investment sites, helping to pinpoint areas with favorable spatial and environmental conditions. The findings show that both current and prospective biogas plant operators view complex legal requirements, social risk, and financial uncertainty as the main obstacles. However, both groups are primarily motivated by the desire for on-farm energy self-sufficiency and the environmental benefits of improved agricultural waste management. Owners of operational installations—particularly small and medium-sized ones—tend to rate all categories of risk significantly lower than prospective investors, suggesting that practical experience and knowledge-sharing can effectively alleviate perceived risks related to renewable energy investments.

The article presents a model for finding the most suitable locations for setting up micro-biogas plants (<50 kW), which represent an efficient way of processing organic waste in small local communities. The input parameters of the model, which was made with GIS tools, were the number of farms and heads of large livestock with their locations, the number of food establishments and their collected food waste and waste fat. We tested the case study model in the Gorenjska region in Slovenia. The result of processing the input data in the model are four locations in three municipalities Naklo 1, Naklo 2, Kranj and Cerklje. We evaluated the locations with economic indicators net present value (NPV), internal rate of return (IRR) and discounted payback period (DPP). With sensitivity analysis, we investigated the impact of increasing investment costs, decreasing energy prices and different scenarios with adding corn silage to the anaerobic process. Location Naklo 1 has NPV 31,410.26 €, IRR 10.53% and DPP 22 years, Naklo 2 has NPV −58,808.91 € and DPP of more than 25 years, location Kranj has NPV 140,313.00 €, IRR 13.07% and DPP 16 years, location Cerklje has NPV −43,026.82 € and DPP of more than 25 years.

The use of individual biogas plants can be a means of solving many energy-environmental and financial-economic problems. The article aims to assess the prerequisites and consequences of using biogas plants at the macro and micro levels to search for opportunities to reduce the cost of their installation and make them more affordable for individual farms. The need for the use of biogas plants by farms is determined by the fact that these farms have a raw material base; the growing cost of energy resources pushes them to search for new sources of profit. At the micro level, the costs of biogas plants in the conditions of companies and individual farms in the Slovak Republic are evaluated. At the macro level, the aggravation of energy and agricultural problems and the need to transition to green technologies require a comprehensive approach to their solution. The article investigated the cost of purchasing and operating biogas plants based on a private company’s data. It assessed the cost of the construction of a biogas plant and more. The analysis of biogas plant operation results showed that its purchase and use by a farm can be financially unprofitable but bring significant benefits in the energy, environmental, and social dimensions.

The study aimed to assess the most efficient solution of raw material management in selected biogas plants into the concept of circular economy and evaluate the most efficient solution of raw material management in selected biogas plants due to the quality and quantity of the feed and the final product obtained, which is biogas, as well at the closed circulation (circular economy). The study evaluated two agricultural biogas plants on a real scale and one at the sewage treatment plant (in real scale) in northeastern Poland. A year-long study showed that in technical terms, the best work efficiency is achieved by agricultural biogas plants processing: silage, manure, apple pomace, potato pulp (biogas plant No. 1), followed by biogas plant No. 3 processing chicken manure, decoction, cattle manure, poultry slaughterhouse waste (sewage sludge, flotate, feathers), and finally, the lowest efficiency biogas plant was No. 2, the sewage treatment plant, which stabilized sewage sludge in the methane fermentation process. Moreover, based on the results, it was found that agricultural biogas gives the best efficiency in energy production from 1 ton of feed.

Biodegradable waste from households, companies, and gastronomy is not utilized in large Polish agglomerations for the production of biogas. Determining the biogas production potential in a selected agglomeration will enable the implementation of circular economy goals and sustainable development objectives. Once appropriate odor neutrality standards are met, biogas plants could be constructed around large cities, supplying both energy and heating systems to nearby housing estates or production facilities. This article aims to assess the potential of biodegradable municipal waste collected in a large city for the production of energy in specialized municipal biogas plants. The following analytical study focuses on Krakow and its surrounding municipalities. Because of its geographical location, Krakow is exposed to smog, and every action limiting the usage of carbon-based materials for heating will have a positive impact on the air quality. A biogas plant powered by municipal waste would present a viable opportunity to limit urban smog. It is also crucial that a biogas plant can store energy as it is equipped with methane tanks. Both renewable and other energy sources are still awaiting functional technical solutions that would allow for optimal energy storage.

This paper presents an analysis of selected parameters of biogas, formed as a result of methane fermentation, during the start-up of a biogas installation, using water, liquid manure, corn silage and inoculated sludge as substrates. Moreover, the dependencies between the type and amount of the supplied substrate and the obtained parameters of biogas and fermentation mass are presented and explained. During 59 days after the start of the biogas plant operation, the methane content increased to a maximum of about 62%. Finally, after about 80 days, the methane content stabilized at a constant level of about 55%. CO2 content increased from about 6% (day 32) to about 46% (day 84), with a clear linear correlation between carbon dioxide and methane content. Oxygen content decreased from about 18% (day 32) to about 0.3% (day 84) as the resulting gases displaced air from the reactor, and there was also a linear correlation between oxygen and methane content. The hydrogen sulfide content decreased from about 76 ppm (day 32) to about 0 ppm (day 47), after which, in a clear power correlation to the methane content, it maximally increased to 890 ppm (day 61). However, for the sake of safe engine operation, the desulfurization plant was started on day 63, which resulted in a H2S concentration below 50 ppm on day 74 of the experiment. The final hydrogen sulfide content was 9 ppm on day 84 of the biogas plant start-up.

Circular economy, clean technologies, and renewable energy are key to climate protection and modern environmental technology. Recovering water and valuable minerals from the liquid fraction of digestate is in line with this strategy. Digestate, a byproduct of anaerobic methane fermentation in biogas plants, is a potential source of water, minerals for fertilizers, and energy rather than waste. This study examined digestate from municipal and agricultural biogas plants and highlights the need for research on both due to their differences. The use of membrane techniques for water recovery from liquid digestate offers an innovative alternative to conventional methods. This study used standalone membrane filtration and an integrated system to produce water suitable for agricultural use. Ceramic membranes with cut-offs of 1, 5, 15, and 50 kDa and polymeric membranes of polyethersulfone and regenerated cellulose with cut-offs of 10 and 30 kDa were tested. The results showed that the membrane material significantly affects the transport and separation properties. Higher cut-off values increased permeate flux across all membranes. Ceramic membranes were more susceptible to fouling in standalone ultrafiltration, but were more effective in purifying digestate than polymeric membranes. The best results were obtained with a ceramic membrane with a 1 kDa cut-off (for example, for the integrated process and the municipal digestate, the retention rates of COD, BOD5 and DOC were 69%, 62%, and 75%, respectively).

Italy is one of the leading nations in the biogas sector. Agricultural, landfill, sewage and manure substrates are converted into biogas using anaerobic digestion and, then, into electricity and heat by means of properly arranged internal combustion engines. In this study, after an overview of the European context, the authors present the Italian biogas sector status in terms of development trends and factors that favour/block biogas spread. Despite the fact that biogas is a renewable fuel and a consolidate technology, it is mandatory to examine its real costs, biogas composition and engine combustion products. For this purpose, in the present work, the authors selected six in-operation biogas plants fed by different substrates, investigate plants construction and operation costs and measure both biogas and engine emissions compositions. Biogas status analysis shows a high growth rate until the end of 2012 due to generous Government subsidies while, after supports reduction, a continuous depletion of biogas installations is observed. Alongside the development, established supports overlook also the plant size as well as the cost. In fact, the most widespread plant nameplate electric power is 1 MW while its construction cost ranges between 4.2–4.8 millions of Euros. Real on-site measurements show variable biogas composition while engine emissions are comparable with the natural gas ones.