Technical and Legal Challenges in the Energetic Utilization of Household-Produced Biogas in the European Market

Abstract

In accordance with the EU Landfill Directive, by 2035, EU countries must reduce the amount of municipal waste sent to landfills to 10% or less of the total municipal waste generated. To achieve this, it is necessary to implement recycling measures, including composting organic waste. Another way to utilize organic waste generated in households is through anaerobic digestion, which produces biogas, a renewable energy source. Biogas production from biodegradable waste generated in households occurs in both industrial facilities and household biogas installations. Producing biogas in household installations offers the advantage of generating and using biogas at the same location where the waste is produced, reducing the need to transport bio-based materials to a storage site. This approach reduces costs and the environmental footprint associated with transporting waste to industrial facilities and subsequently transporting biogas to municipal (domestic) consumers. Although this solution appears optimal in many respects, the current technical and legal environment limits the development of the household biogas production market in EU countries. This article highlights the technical and legal aspects of safely using biogas from household installations (e.g., certification of gas equipment) and legal aspects (such as restrictions on the number of energy sources), which significantly limits the growth of this sector.

1. Introduction

The history of biogas used for energy purposes dates back to the 19th century, when Jean-Louis Mouras developed the concept of anaerobic digestion, and Louis Pasteur suggested that biogas could be used for heating and lighting. However, broader adoption of biogas technology for energy production occurred during World War II, driven by the search for alternative energy sources due to its shortages [1]. In the following decades, biogas lost its competitiveness to cheaper and more readily available fossil fuels.

The resurgence of biogas as an energy carrier occurred at the beginning of the 21st century, partly due to entry into force of the Directive 2009/73/EC of the European Parliament and the Council of 13 July 2009, which established common rules for the internal gas market in the EU. The directive required Member States to allow biogas into national gas systems on non-discriminatory terms, provided the biogas met the quality requirements for the fuel being transported [2].

The late 20th and early 21st centuries marked a period of dynamic investment in various European countries in injecting biogas into gas networks—either on a limited or unlimited basis—and in developing local biogas grids [3,4,5,6,7,8,9]. Injecting untreated biogas (not upgraded to biomethane) into the grid posed technical challenges (e.g., contaminants affecting network performance) and faced public acceptance hurdles. Nonetheless, efforts continued on social, political, and technical fronts to popularize biogas and increase its share in the energy mix. Additionally, the development of the biogas market in Europe encounters significant legal and regulatory barriers. Fragmented regulations among Member States, diverse financial support mechanisms, and complex administrative procedures considerably hinder investments, especially for smaller household-scale installations [10,11]. This regulatory diversity leads to challenges in biogas certification, a lack of uniform quality standards, and uneven competition in the market, necessitating the creation of coherent EU-wide solutions [12,13].

The technical strengthening of biogas’s role in the energy market was achieved through the widespread adoption of technologies for upgrading biogas to biomethane. Between 2011 and 2022, the number of operational biomethane plants in Europe grew from fewer than 200 to over 1000 [14]. However, upgrading biogas to biomethane entails significant additional costs, ranging from €0.6 to €1.24 per kWh [15]. These costs may significantly limit the development of the biogas market, particularly in countries with lower GDP, due to the additional financial outlays required for converting biogas to biomethane. These high capital requirements, combined with regulatory uncertainty and the absence of stable financial support mechanisms, create considerable barriers to market development. In particular, policy instability and the lack of predictable legal frameworks significantly increase financial risks for prosumers and small businesses, discouraging investment and slowing the overall growth of the sector [10,12].

Consequently, even the most optimistic forecasts for biomethane upgrading predict that only 60% of biogas will be utilized in this way by 2030 [16].

Alongside advancements in biogas upgrading technologies, policy directions have shifted to emphasize reducing fossil fuel use and promoting renewable fuels. Key documents in this area include the “RED II Directive”. The EU’s goals set forth in this directive indirectly influence biogas production, requiring renewable energy to account for at least 32% of total energy consumption and renewable energy in transport fuels to reach 14% by 2030 [17].

Currently, biogas production is also part of the circular economy [18,19,20] and occupies a central role in new strategies under the European Green Deal, such as the EU Methane Strategy [21], the Energy System Integration Strategy [17], and the “Farm to Fork” Strategy [22]. Moreover, the recently proposed framework for decarbonizing the EU gas market establishes principles for easier integration of biomethane into gas networks, alongside legislative proposals to reduce methane emissions in the energy sector.

Despite the dynamic growth in the number of installations and the increasing potential of biomethane, fully realizing the sector’s possibilities requires organizing and harmonizing the legal system and support at the EU level. The lack of coherent legislative and regulatory frameworks remains one of the primary technical and economic limitations for the development of household-produced biogas [10,11].

These actions have led to the combined production of biogas and biomethane in Europe exceeding 191 TWh of energy in 2020, with expectations to double by 2030 and reach over 1000 TWh by 2050. Europe’s high availability of biodegradable substrates provides a biomethane potential of 1350 TWh [23], making Europe the leading biogas producer (Figure 1) [24].

In addition to the mature markets in Europe and the United States, the biomethane market is developing in Brazil, Canada, China, and India [25].

Approximately two-thirds of the biogas produced globally is used for electricity and heat generation, around 30% is consumed by the residential sector, while a small remaining portion is upgraded to biomethane, injected into the gas grid, or used as fuel [26]. Biogas is typically utilized near its production site for electricity and heat generation, which minimizes transmission losses and maximizes overall energy efficiency [27]. The electricity produced is often consumed locally or can be fed into the grid, contributing to decentralized energy systems and enhancing local energy security [28].

Most analyses of biogas and biomethane production and utilization focus on industrial-scale solutions [29,30,31,32,33,34]. However, household biogas production and its use at the generation site present a viable alternative, particularly in rural or off-grid areas [35,36,37,38,39]. This is feasible because, unlike other biofuels, biogas production is relatively simple and can be carried out under various conditions with comparatively low capital investment [40,41,42]. Furthermore, household biogas systems enable direct management of organic waste streams, reducing environmental pollution and contributing to circular economy goals [43].

Such solutions are widely implemented in Africa and Asia, where the SNV organization installed approximately 52,000 household biogas plants across 14 countries between 2020 and 2021 [44]. These projects have demonstrated improvements in public health by reducing indoor air pollution from traditional biomass cooking methods [45], as well as socioeconomic benefits by lowering fuel costs and generating nutrient-rich digestate for agriculture [46]. Additionally, efforts to promote and enhance the efficiency of household biogas production are supported by institutions like Montana State University (MSU) and the City of Bozeman through projects funded by the U.S. Environmental Protection Agency [47,48].

Although biogas is increasingly seen as a promising renewable energy source, small-scale, household biogas systems within the European Union still receive relatively little attention. Most existing research focuses on large industrial plants, often overlooking the everyday challenges faced by individuals or small communities interested in producing and using biogas locally. Issues such as unclear regulations, complicated administrative procedures, and the absence of consistent certification standards make it difficult for these smaller systems to develop. There is also a lack of comprehensive data on the number of household biogas installations operating across Europe, along with limited information about social programs designed to raise public awareness of such solutions [11]. Notably, the role of household biogas plants in meeting energy needs is mainly discussed in the context of energy shortages and the lack of energy self-sufficiency in Ukraine due to ongoing military conflict [49]. This underscores the potential of decentralized biogas systems as resilient, community-level energy sources that can enhance energy security, particularly in times of crisis [50].

Household biogas plants are considered clean and environmentally friendly technologies that can help rural communities meet their energy needs for lighting, cooking, and electricity [51]. They contribute to improved living conditions, reduced reliance on fossil fuels, and lower greenhouse gas emissions compared to traditional biomass usage [52]. Due to their technical, socio-economic, and environmental benefits, these systems should gain wider acceptance and popularity within the EU [11]. However, successful deployment depends on overcoming legal, technical, and social barriers that currently hinder the sector’s development [10].

The main goal of our manuscript is to identify and highlight the technical and legal barriers that hinder the safe and lawful use of biogas from small-scale, household-level installations in EU countries. In particular, we focus on systems utilizing kitchen and green waste generated by households or small farms as feedstock, which represent an underutilized resource with high potential for sustainable energy generation and waste management [53].

2. Materials and Methods

This review focused on EU-level legislation, particularly in areas where implementation of specific provisions into national laws was required. The analysis of legal acts was complemented by an examination of relevant technical documents, primarily standards issued by the CEN. The above databases were searched using the keywords shown in Figure 2. The authors’ extensive experience in the relevant energy, gas and biogas industry, as well as their in-depth knowledge of the subject underline in the article, were also drawn on.

When analyzing and comparing the legal and technical frameworks in different regions of the world, the identification of technical barriers considered the geographical and social conditions that may affect the adoption and popularity of solutions for household-scale biogas production and utilization.

The review encompassed the entire value chain of biogas produced under household conditions (Figure 2), including the availability of raw materials, the fermentation process, biogas purification, final utilization of the obtained biogas, and options for managing by-products.

For each element of the value chain in biogas production, a review was conducted by searching for information using the following keywords:

• Availability of substrates for biogas production: “food waste”, “bio waste”, “food waste produced in Europe”
• Biogas production: “household biogas production”, “optimal temperature for biogas production”, “anaerobic digestion psychrophilic”, “temperature in Europe”
• Biogas purification: “water content in biogas”, “hydrogen sulfide content in biogas”, “biogas desulfurization”
• Biogas storage: “biogas storage”, “domestic biogas storage”, “biogas bag”, “biogas tank”
• Biogas utilization: “biogas cooker”, “biogas devices”, “appliances burning biogas”, “biogas fuel”
• Utilization of by-products: “biogas by-products”, digestate, “bio-fertilizer”.

Each search process involved reviewing academic articles, scientific papers, industry reports, and other sources to gather relevant data about each stage of the biogas value chain. To ensure the selection of high-quality and relevant documents, the authors applied specific inclusion and exclusion criteria. The inclusion criteria encompassed peer-reviewed articles published in the last ten years, studies focusing on bio waste biogas production value chain, articles available in English, and papers providing detailed methodological descriptions. The exclusion criteria ruled out non-peer-reviewed articles and grey literature, studies published more than ten years ago (unless they are seminal works), articles not available in full text, and documents not directly related to the topic.

3. Results

This chapter presents the results of the review concerning the individual elements of the value chain for biogas produced under household conditions, taking into account legal and technical aspects as well as geographical conditions.

3.1. Availability of Substrates for Biogas Production

One of the primary EU-level legal acts concerning waste management is Directive 2008/98/EC of the European Parliament and of the Council of 19 November 2008 on waste and repealing certain Directives [54]. This directive establishes measures to protect the environment and human health by preventing and reducing the adverse impacts of waste generation and management, as well as by improving resource use efficiency.

The directive [54] defines “bio-waste” as biodegradable waste from gardens and parks, food and kitchen waste from households, restaurants, catering services, and retail, as well as comparable waste from food processing plants. According to Article 22 of the directive, Member States should promote:

• the separate collection of bio-waste for composting and fermentation,
• the treatment of bio-waste in ways that ensure a high level of environmental protection,
• the use of environmentally safe materials produced from bio-waste.

The directive explicitly identifies composting as an appropriate method for managing bio-waste but does not provide a similar focus on biogas production from such waste. However, some recommendations adopted by the “European Citizens’ Panel on Food Waste” suggest that while preventing food waste remains the priority, the life cycle of food waste should follow this hierarchy: consumption by humans, consumption by animals, conversion into biofuels, and finally, composting [55].

EU documents also highlight that anaerobic digestion offers higher recovery efficiency for biodegradable waste. Energy recovery from residual waste, ensuring no energy is wasted, is considered an essential element of biodegradable waste recycling systems [37]. Therefore, anaerobic digestion with energy recovery from biogas, combined with using digested waste to produce compost, emerges as a particularly viable method. This approach aligns with the life-cycle concept by reducing greenhouse gas emissions, improving soil quality through compost, and recovering energy from biogas [56].

The abundance of substrates for biogas production in household-scale biogas plants is evidenced by data in [57], which reports that nearly 59 million tons of food (equivalent to 131 kg per capita) is wasted annually in the EU, with over half of this food waste (53%) originating from households. The availability of biodegradable waste from unused food in various countries around the world varies significantly, ranging from approximately 7 kg per capita per year in Romania to 86.5 kg per capita per year in South Korea (Figure 3).

Although in some European countries the level of food waste is lower than in countries on other continents, even in these cases, the availability of substrates for household biogas production should not pose a limitation to the development of household biogas production technologies. This is especially true considering that food waste is not the only substrate used for biogas production in households. Another potential resource is green waste (code 20 02 01), such as mown grass, leaves, and similar materials.

Considering the availability of biodegradable waste, including:

• Municipal waste segregated and collected selectively, such as biodegradable kitchen waste (20 01 08), and
• Waste from gardens and parks (including cemeteries), biodegradable waste (20 02 01),

As well as the legal regulations governing the management of such waste in the EU, the authors of the article believe that the limitations in the development of biogas market from household production do not stem from issues related to the acquisition of substrates for biogas production.

3.2. Biogas Production

At the EU level, there are no regulations specifically addressing household biogas production. However, technical aspects related to the design and operation production systems of household biogas are outlined in EN ISO 23590:2021 [59]. This standard is a European adoption of the international ISO standard with the same title and number. The acceptance of this ISO standard by the European Committee for Standardization (CEN) highlights the significance of household biogas production in Europe.

According to EN ISO 23590:2021, a household biogas plant should include the following components [59]:

• biomass inlet,
• digester,
• biogas storage,
• biogas outlet,
• biogas transfer system,
• digestate outlet,
• hydrogen sulfide filter to reduce hydrogen sulfide content from a minimum of 50 ppm (v/v) to a maximum of 100 ppm (v/v),
• disinfection unit (optional, depending on local regulations),
• an excess biogas release valve that automatically opens at pressures exceeding 20% of the system’s regular working pressure,
• a manual biogas shutoff valve, parallel to the automatic excess biogas release valve, connected to the biogas storage.

The EN ISO 23590 standard recommends placing the digester outdoors or in a well-ventilated area where air exchange occurs at least five times per hour. This recommendation is particularly critical for regions with significant variations in average monthly temperatures (

Table 1. Average monthly air temperatures in European countries (based on [60]).

Country	City	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Albania	Tirana	6.7	7.8	10.0	13.4	18.0	21.6	24.0	23.8	20.7	16.0	11.7	8.1
Andorra	Andorra la Vella	2.2	3.5	5.8	7.5	11.5	15.4	18.8	18.5	14.9	10.3	5.7	3.0
Austria	Vienna	0.3	1.5	5.7	10.7	15.7	18.7	20.8	20.2	15.4	10.2	5.1	1.1
Belarus	Minsk	−4.5	−4.4	0.0	7.2	13.3	16.4	18.5	17.5	12.1	6.6	0.6	−3.4
Belgium	Brussels	3.3	3.7	6.8	9.8	13.6	16.2	18.4	18.0	14.9	11.1	6.8	3.9
Bosnia and Herzegovina	Sarajevo	−0.5	1.4	5.7	10.0	14.8	17.7	19.7	19.7	15.3	11.0	5.4	0.9
Bulgaria	Sofia	−0.5	1.1	5.4	10.6	15.4	18.9	21.2	21.0	16.5	11.3	5.1	0.7
Croatia	Zagreb	0.3	2.3	6.4	10.7	15.8	18.8	20.6	20.1	15.9	10.5	5.0	1.4
Cyprus	Nicosia	10.6	10.6	13.1	17.1	22.3	26.9	29.7	29.4	26.2	22.3	16.3	12.0
Czech Republic	Prague	−1.4	−0.4	3.6	8.4	13.4	16.1	18.2	17.8	13.5	8.5	3.1	−0.3
Denmark	Copenhagen	1.4	1.4	3.5	7.7	12.5	15.6	18.1	17.7	13.9	9.8	5.5	2.5
Estonia	Tallinn	−2.9	−3.6	−0.6	4.8	10.2	14.5	17.6	16.5	12.0	6.5	2.0	−0.9
Finland	Helsinki	−3.9	−4.7	−1.3	3.9	10.2	14.6	17.8	16.3	11.5	6.6	1.6	−2.0
France	Paris	4.9	5.6	8.8	11.4	15.1	18.2	20.4	20.2	16.9	12.9	8.1	5.4
Germany	Berlin	0.6	2.3	5.1	10.2	14.8	17.9	20.3	19.7	15.3	10.5	6.0	1.3
Greece	Athens	10.2	10.9	13.2	16.9	21.8	26.6	29.3	29.3	25.0	20.1	15.5	11.5
Hungary	Budapest	0.4	2.3	6.1	12.0	16.6	19.7	21.5	21.2	16.9	11.8	5.4	1.8
Iceland	Reykjavík	−0.5	0.4	0.5	2.9	6.3	9.0	10.6	10.3	7.4	4.4	1.1	−0.2
Ireland	Dublin	5.3	5.3	6.8	8.3	10.9	13.6	15.6	15.3	13.4	10.5	7.4	5.6
Italy	Rome	7.5	8.2	10.2	12.6	17.2	21.1	24.1	24.5	20.8	16.4	11.4	8.4
Latvia	Riga	−4.7	−4.2	0.5	5.1	11.4	15.5	16.9	16.2	12.0	7.4	2.1	−2.3
Liechtenstein	Vaduz	0.8	2.1	6.3	9.9	14.4	17.1	19.0	18.4	14.9	10.9	5.2	1.9
Lithuania	Vilnius	−3.9	−3.1	0.9	7.6	13.0	16.4	18.7	17.9	13.0	7.0	1.8	−2.2
Luxembourg	Luxembourg	0.8	1.6	5.2	8.7	13.0	15.9	18.2	17.7	13.9	9.5	4.7	1.8
Malta	Valletta	12.8	12.8	13.3	15.6	18.9	22.8	26.1	26.7	23.9	21.1	17.2	13.9
Moldova	Chișinău	−1.9	−0.8	3.7	10.4	16.5	19.9	22.1	21.7	16.3	10.5	4.1	−0.6
Monaco	Monaco	10.2	10.2	12.0	13.8	17.5	20.9	23.8	24.2	21.1	17.9	13.8	11.2
Montenegro	Podgorica	5.0	6.8	10.0	13.9	19.0	22.8	26.0	25.6	21.4	15.9	10.5	6.5
Netherlands	Amsterdam	3.4	3.5	6.1	9.1	12.9	15.4	17.6	17.5	14.7	11.0	7.1	4.0
North Macedonia	Skopje	0.1	2.6	7.6	12.1	17.3	21.5	23.8	23.8	18.8	13.1	6.5	1.7
Norway	Oslo	−4.3	−4.0	−0.2	4.5	10.8	15.2	16.4	15.2	10.8	6.3	0.7	−3.1
Poland	Warsaw	−1.8	−0.6	2.8	8.7	14.2	17.0	19.2	18.3	13.5	8.5	3.3	−0.7
Portugal	Lisbon	11.6	12.7	14.9	15.9	18.0	21.2	23.1	23.5	22.1	18.8	15.0	12.4
Romania	Bucharest	−1.3	0.4	5.4	11.2	16.8	20.6	22.5	22.0	16.9	11.0	4.7	0.2
Russia	Moscow	−6.5	−6.7	−1.0	6.7	13.2	17.0	19.2	17.0	11.3	5.6	−1.2	−5.2
San Marino	San Marino	2.7	4.2	6.4	10.1	14.6	18.5	21.3	21.4	17.8	12.8	8.0	4.2
Serbia	Belgrade	1.4	3.1	7.6	12.9	18.1	21.0	23.0	22.7	18.0	12.9	7.1	2.7
Slovakia	Bratislava	0.3	1.9	6.1	11.7	16.2	20.2	22.0	21.5	16.2	10.7	5.7	1.1
Slovenia	Ljubljana	0.3	1.9	6.5	10.8	15.8	19.1	21.3	20.6	16.0	11.2	5.6	1.2
Spain	Barcelona	11.3	11.3	13.1	15.1	18.1	21.9	24.7	25.2	22.4	19.1	14.4	11.9
Sweden	Stockholm	−2.8	−3.0	0.1	4.6	10.7	15.6	17.2	16.2	11.9	7.5	2.6	−1.0
Switzerland	Zürich	0.3	1.3	5.3	8.8	13.3	16.4	18.6	18.0	14.1	9.9	4.4	1.4
Turkey	Istanbul	5.7	5.7	7.0	11.1	15.7	20.4	22.9	23.1	19.8	15.6	11.5	8.0
Ukraine	Kyiv	−3.5	−3.0	1.8	9.3	15.5	18.5	20.5	19.7	14.2	8.4	1.9	−2.3
United Kingdom	London	5.2	5.3	7.6	9.9	13.3	16.5	18.7	18.5	15.7	12.0	8.0	5.5

).

In general, anaerobic digestion systems operate at three optimal temperature ranges: psychrophilic (<20 °C), mesophilic (20–43 °C, with 35–37 °C considered optimal), and thermophilic (50–60 °C, optimal at 55 °C) [61]. At psychrophilic temperatures (<20 °C), anaerobic digestion produces less methane compared to mesophilic conditions. For psychrophilic anaerobic digestion (PAD) to be successful, investigation of cold-adapted microbial consortia involved in methane production is critical [37].

Given the average monthly temperatures in various parts of Europe, it appears that the only feasible anaerobic digestion process for household biogas plants is one occurring under psychrophilic conditions. Research on anaerobic digestion under psychrophilic conditions has challenged the notion that temperature fluctuations pose a significant challenge to the process in cold regions. While such fluctuations do affect the structure and activity of microbial populations, leading to decreased biogas yield, this can be mitigated by utilizing psychrophilic microorganisms. These microorganisms have an optimal growth temperature of 15 °C and a maximum growth temperature of 20 °C [62,63].

Notably, some psychrophilic microorganisms, due to their adaptive mechanisms, can grow at sub-zero temperatures and even produce methane under such conditions [64]. Considering the optimal growth temperature for psychrophilic microorganisms is approximately 15 °C, and their growth can be inhibited at temperatures above 20 °C, average monthly temperatures across European countries were analyzed to distinguish three periods for each country (Figure 4):

• Optimal period: Average monthly temperatures between 10 and 20 °C, conducive to efficient biogas production.
• Low-temperature period: Average monthly temperatures below 10 °C, during which biogas production may be less intensive.
• High-temperature period: Average monthly temperatures above 20 °C, during which biogas production may also be less intensive due to inhibited microbial growth.

In European countries, the average monthly temperatures are optimal for anaerobic digestion processes using psychrophilic microorganisms for about 5 months per year. This period is shortest in Iceland, lasting only 2 months, and longest in countries such as Monaco, Portugal, and Spain, where it lasts 8 months. In 24 of the 45 analyzed countries (Albania, Austria, Bulgaria, Croatia, Cyprus, France, Germany, Greece, Hungary, Italy, Malta, Moldova, Monaco, Montenegro, North Macedonia, Portugal, Romania, San Marino, Serbia, Slovakia, Slovenia, Spain, Turkey, Ukraine), periods occur where the average monthly temperatures exceed 20 °C. In these countries, the process should be conducted using psychotrophic organisms for part of the year.

Meanwhile, in 39 countries (Albania, Andorra, Austria, Belarus, Belgium, Bosnia and Herzegovina, Bulgaria, Croatia, Czech Republic, Denmark, Estonia, Finland, France, Germany, Hungary, Iceland, Ireland, Italy, Latvia, Liechtenstein, Lithuania, Luxembourg, Moldova, Montenegro, Netherlands, North Macedonia, Norway, Poland, Romania, Russia, San Marino, Serbia, Slovakia, Slovenia, Sweden, Switzerland, Turkey, Ukraine, United Kingdom), the average monthly temperatures drop below 10 °C for a period of 3 to 10 months. These conditions allow for the anaerobic digestion process using psychrophilic organisms, although the process may be less efficient.

The possibility of effectively conducting the anaerobic digestion process at temperatures not exceeding 20 °C means that, even when positioning the biogas plant outside the building or in unheated well-ventilated rooms, in accordance with the EN ISO 23590 standard, the European climate does not pose a barrier to the development of household biogas plants.

Table 2. Biogas production in EU countries (literature-informed estimates).

Country	Estimated Production (Million m3/Year)	Confidence	Notes	References
Austria	300–700	High	Mature farm & upgrading sector.	[65,66]
Belgium	200–500	Medium	Regional variation (Flanders strong).	[65,66]
Bulgaria	5–50	Low	Small sector, agricultural potential.	[65,67]
Croatia	20–80	Low–Medium	Growing farm/industrial AD.	[65]
Cyprus	<5	Low	Very small/pilot scale.	[65]
Czechia	50–200	Medium	Mixed farm & industrial plants.	[65]
Denmark	400–900	High	Strong AD + upgrading (manure + crops).	[65,66]
Estonia	5–30	Low	Small but some industrial sites.	[65,67]
Finland	70–250	Medium	Biogas + growing biomethane.	[65,66]
France	600–1800	High	Rapid growth; many farm & industrial plants.	[65,66]
Germany	1500–3500	High	Historically the largest EU biogas producer.	[65,66]
Greece	10–80	Low–Medium	Growing projects, food waste potential.	[65,67]
Hungary	20–100	Medium	Expanding AD capacity.	[65,67]
Ireland	30–120	Medium	Slurry-based AD + emerging upgrading.	[65,66]
Italy	500–1200	High	Long tradition of agricultural AD.	[65,66]
Latvia	5–30	Low	Small sector, some food industry plants.	[65,67]
Lithuania	10–70	Low–Medium	Growing number of sites.	[65]
Luxembourg	<5	Low	Very small national activity.	[65]
Malta	<1	Low	Negligible/pilot only.	[65]
Netherlands	300–800	High	Strong co-digestion & upgrading cluster.	[65,66]
Poland	150–600	Medium	Rapid growth potential; figures variable by source.	[65,67]
Portugal	10–80	Low–Medium	Increasing interest in OFMSW and agriculture.	[65,67]
Romania	5–50	Low	Underdeveloped despite agricultural base.	[65,67]
Slovakia	10–60	Low–Medium	Several medium sites.	[65]
Slovenia	10–50	Low–Medium	Small country but active small AD.	[65]
Spain	150–500	Medium	Increasing projects; historically modest.	[65]
Sweden	400–900	High	Large biomethane upgrading for transport.	[65]

Note: UK excluded—not EU; Units: million m³ raw biogas produced per year (approximate ranges). Legend (confidence): High = strong, consistent published numbers exist; Medium = available but variable; Low = scarce/mostly pilot activity.

presents estimated annual biogas production across EU member states, expressed in million cubic meters (m³) of raw biogas per year [65,66,67].

As shown in Table 2, countries such as Germany, France, Italy, Denmark, and Sweden stand out as high-confidence and high-volume producers, with mature anaerobic digestion (AD) sectors and significant upgrading capacity [65,66]. Austria and the Netherlands also demonstrate strong, well-documented production supported by agricultural and industrial biogas development [65,66].

At the medium-confidence level, countries including Czechia, Ireland, Spain, Finland, and Poland show notable but more variable estimates, reflecting diverse data sources and regional differences [65,67]. Meanwhile, several smaller or newer markets—such as Cyprus, Malta, Luxembourg, Estonia, and Latvia—remain at pilot or low-activity stages, with limited available statistics [65,67].

Overall, the figures highlight a strong core of biogas-producing countries with established agricultural and industrial AD sectors, alongside a number of emerging markets with untapped potential, particularly in Eastern and Southern Europe [65,66,67]. The confidence ratings reflect the quality and consistency of available data, with “High” indicating robust and reliable estimates, “Medium” indicating moderate variability, and “Low” signifying scarce or uncertain information [65].

In Europe, domestic biogas systems are more widely adopted in countries with strong renewable energy policies, technological readiness, and rural agricultural practices. Germany, Denmark, and Sweden lead in this area, with the systems providing households with a reliable and sustainable source of energy. However, the adoption of domestic biogas systems in other countries like the UK, France, and Italy is still emerging, with financial and infrastructural barriers limiting their widespread use [7,65,66,67,68,69,70]. Most domestic systems are small-scale, providing energy for cooking, heating, and sometimes electricity. They are most common in rural areas with access to organic waste. Usually used technology are the anaerobic digestion is the core technology, converting organic waste into biogas. The process results in methane-rich gas, which can be used for household energy needs, and the digestate is typically used as a fertilizer.

In countries with a strong emphasis on sustainability and renewable energy (e.g., Germany, Denmark, and Sweden), biogas adoption is higher, particularly in rural areas where waste is abundant. In countries like the UK and France, adoption is slower due to higher costs and less policy focus on domestic systems. Countries like Germany, Denmark, and Sweden have strong policy frameworks and incentives supporting the installation of domestic biogas systems, while other countries are still developing these policies [65,66,67,68,69,70].

In Poland, the biogas sector is growing. However, it still lags behind the European leaders. As of 2022, there were around 383 biogas plants in operation in the country, with a total installed capacity of more than 280 MW. The majority of these are agricultural plants that process waste from agricultural and livestock production. Backyard biogas plants are becoming increasingly popular. This is especially true in rural areas where the availability of organic raw materials is high. Support programs and an increase in environmental awareness are encouraging investment in this type of solution [66,67,68,69,70,71,72,73,74,75].

In Romania, small farms generate significant amounts of bio-waste. Projects have introduced household biogas installations that convert this waste into biogas for cooking, water heating, or electricity production. The residual byproduct serves as a nutrient-rich organic fertilizer, enhancing soil fertility [68,71,74,75].

The adoption of domestic biogas systems varies across European countries, influenced by factors such as government incentives, technological infrastructure, and public awareness. In some regions, initiatives have been launched to promote the use of biogas for household applications, aiming to enhance energy independence and reduce waste [3,7,65,66,69,71].

Utilizing domestic biogas systems offers several advantages, including reduced reliance on fossil fuels, decreased greenhouse gas emissions, and improved waste management. Additionally, the digestate produced can be used as an organic fertilizer, contributing to sustainable agriculture practices. Despite their benefits, the widespread adoption of domestic biogas systems faces challenges such as high initial investment costs, maintenance requirements, and the need for public education on system operation and benefits [7,66,68,70,74,75].

Domestic biogas systems represent a promising solution for sustainable energy production and waste management in Europe. Despite some challenges, ongoing technological advancements, policy support, and increased awareness can drive further adoption, contributing to a cleaner and more energy-secure future.

This type of activity has at least several positive impacts, including:

• provides a sustainable source of energy for cooking, heating and electricity generation, reducing dependence on fossil fuels.
• helps manage kitchen waste, animal feces and agricultural residues, reducing landfill use and associated emissions.
• significantly reduces methane emissions from decomposing organic waste, helping to mitigate climate change.
• households using biogas save on energy costs and can benefit from government subsidies and incentives.

On the other hand, challenges associated with this activity include:

• high initial investment costs,
• maintenance requirements, and
• the need to educate the public about how the system works and its benefits.

To enhance the adoption of domestic biogas systems in Europe, several measures can be considered [65,67,68,69,70,71]:

• Strengthening financial incentives and subsidies to lower installation costs.
• Providing technical training and support for users to ensure efficient system operation.
• Enhancing research and development for more efficient and compact biogas technologies.
• Promoting awareness campaigns to educate the public on the benefits of biogas systems.
• Encouraging policy harmonization across European nations to support a wider adoption.

However, a significant limitation for biogas production on a household scale in Europe is the low availability of commercial, ready-made solutions for biogas production. Commercial manufacturers of such solutions often lack trade representatives in European countries and frequently do not offer shipping of their products to Europe. This situation means that potential consumers interested in purchasing ready-made household biogas plant solutions are not protected by European regulations, including those related to warranties. In addition, the devices they purchase do not have a CE mark. The CE mark indicates that a given product has been tested by the manufacturer and found to meet EU health, safety and environmental protection requirements. The mark is required for products manufactured anywhere in the world and placed on the market in the EU.

Paradoxically, the most challenging product to utilize in a household biogas plant is biogas itself, due solely to legal restrictions, which apply only within the European Economic Area. According to Article 4 of the Regulation (EU) 2016/426 of the European Parliament and the Council of 9 March 2016 on appliances burning gaseous fuels, which repealed Directive 2009/142/EC, Member States must notify the European Commission and other Member States of the types of gases and their corresponding supply pressures used within their territory. This means that for an appliance designed to burn a specific type of fuel to be placed on the market, the fuel itself must be officially registered. However, biogas as a fuel has not been registered by any EU Member State.

The exclusion of biogas from the European market for household users appears entirely unjustified, especially given that such options exist in other parts of the world, including highly developed countries such as the United States.

Moreover, this restriction contradicts climate protection efforts and initiatives by national authorities, such as the Polish Ministry of Climate and Environment, which has introduced legal regulations for constructing direct biogas pipelines and local biogas networks.

However, creating a legal framework for local biogas networks will not yield positive outcomes for the sector if individual consumers cannot connect to these networks due to a lack of access to appliances capable of utilizing biogas as a fuel.

Summary of Household Biogas Production in the EU

Although there are currently no dedicated EU regulations specifically targeting household biogas production, the technical framework is outlined in EN ISO 23590:2021, a standard adopted by CEN that defines the design, installation, operation, maintenance, and safety requirements for household biogas systems. This reflects growing recognition of the technology’s potential within the European context.

Household biogas adoption is most advanced in countries such as Germany, Denmark, and Sweden, driven by supportive renewable energy policies, rural infrastructure, and technological readiness. Emerging interest is visible in Poland and Romania, while countries like the UK, France, and Italy show slower uptake due to financial constraints and infrastructural challenges. Most systems serve small-scale energy needs—cooking, heating, and occasionally electricity generation—while the by-product, digestate, is commonly used as organic fertilizer.

The environmental and economic benefits of household biogas include reduced reliance on fossil fuels, lower greenhouse gas emissions, improved organic waste management, and potential cost savings. Despite these advantages, wider adoption is hindered by barriers such as high initial investment costs, maintenance requirements, low public awareness, and the absence of certified, CE-marked plug-and-play units. Nevertheless, household biogas production holds significant potential to contribute to the EU’s climate neutrality goals by enabling decentralized, sustainable energy generation and promoting circular waste management at the local level.

A critical legal limitation remains the absence of biogas as a registered household fuel in EU law, preventing appliances from being certified for its use. This regulatory gap not only slows market development but also undermines broader EU climate and energy objectives. At the same time, integrating household biogas systems with other renewable energy sources and smart grid technologies could significantly enhance energy efficiency and flexibility, fostering more resilient and adaptive local energy networks. Moreover, further socio-economic research is needed to better understand user motivations, barriers, and the long-term viability of household biogas solutions, which would enable the development of targeted policies and support measures to effectively promote their wider adoption.

To support the expansion of household biogas systems, the following measures are recommended:

• increased financial incentives and subsidies for small-scale installations,
• expanded technical training and user support,
• investment in R&D for compact, efficient technologies,
• public awareness and education campaigns,
• harmonization of EU legislation, particularly in fuel registration and appliance certification,
• simplification of administrative procedures and reduction in approval times to encourage more users to invest,
• support for the development of local energy networks and community energy projects to promote cooperation and biogas sharing at the local level,
• promotion of circular economy business models that integrate energy production with waste recycling and resource recovery,

ongoing monitoring and evaluation of environmental and economic impacts to assess the effectiveness of support measures and guide future policy adjustments.

3.3. Biogas Purification

According to the EN ISO 23590 standard, biogas produced in a household biogas plant should be dried and purified to remove excessive hydrogen sulfide content [59]. However, the standard does not specify the method to be used for the biogas purification process. Water and hydrogen sulfide are the primary impurities in biogas, and their concentrations can vary widely (

Table 3. Content of selected pollutants in biogas.

Pollutant	Min	Max	References
Water	2% v/v	10% v/v	[76,77,78,79]
Hydrogen sulfide	20 ppm (v/v)	55,000 ppm (v/v)	[78,80,81,82,83,84,85,86,87]

).

Raw biogas at temperatures between 40 and 50 °C is saturated with water vapor, which means the dew point of the unsaturated biogas falls within this temperature range. Cooling the biogas results in the removal of a significant portion of the moisture. The simplest method for drying biogas is cooling it down. This process allows for drying the biogas to a level where the dew point temperature of water is 0.5 °C (at 1 atm pressure), and the water content does not exceed 100 mg/m³ [88,89,90].

Hydrogen sulfide is always present in biogas when the substrate used for biogas production contains sulfur. However, the concentration of hydrogen sulfide can vary depending on the raw material from which the biogas is produced. Hydrogen sulfide is formed under anaerobic conditions during the biodegradation of organic compounds, primarily proteins containing sulfur amino acids (methionine and cysteine), but also during the reduction in anionic forms present in the raw material. The concentration of hydrogen sulfide in raw agricultural biogas can vary widely, ranging from a few tens of ppm to as high as 5.5%, although most literature indicates that the hydrogen sulfide content should not exceed 2% before desulfurization.

Methods to remove H₂S from biogas can be categorized into three groups: biological desulfurization, absorption into a liquid solution (e.g., water), and adsorption onto a solid absorbent (iron sponge, iron oxide pellets, activated carbon) [91,92]. Due to cost and simplicity, the most suitable solutions for household biogas systems involve desulfurization processes using liquid or solid sorbents. The use of appropriate sorbents can reduce hydrogen sulfide content by as much as 98% [92]. While biological desulfurization methods can also be effective, they tend to be more complex and costly, making them less practical for small-scale household installations. In contrast, absorption and adsorption techniques offer simpler and more affordable options. It is important to emphasize that the effectiveness of these methods relies on regular monitoring and timely replacement of sorbents to ensure optimal hydrogen sulfide removal. Proper maintenance not only enhances the longevity and safety of the biogas system but also makes these technologies practical and accessible for everyday household use. Therefore, the ability to effectively and cost-efficiently prepare biogas through drying and desulfurization does not pose a technical barrier to the utilization of biogas produced on a small scale in household biogas plants.

The level of hydrogen sulfide in biogas is significantly higher than in natural gas. Therefore, in order for biogas to be used safely in commercially available appliances, it should be purified to levels permissible in gas (see

Table 4. Requirements of EN/CE Standards on Sulfur in Combustion Gas [93,94].

Parameter	Maximum Limit	Notes
Total sulfur (excluding odorant)	11 mg/m3 (up to 20 mg/m3 in exceptions)	Reference at 15 °C; prevents SO2 emissions and corrosion
H2S + COS (as sulfur)	5 mg/m3	Protects against toxic gas and corrosion
Mercaptan sulfur (excluding odorant)	6 mg/m3	Avoids excessive odorant interference and corrosion

).

According to the European standards on natural gas quality for safe combustion use (EN 16726:2015+A1:2018 and draft prEN 16726:2024) [93,94], strict limits are set on the sulfur and water content of natural gas in order to ensure safe operation of combustion appliances, durability of infrastructure, and interoperability across EU gas markets. These limits are essential to prevent corrosion in pipelines and appliances, minimize SO₂ emissions during combustion, and protect catalytic systems (e.g., in vehicles running on CNG or biomethane). The specified limits provide a framework for the safe and efficient use of combustion devices across the EU. By harmonizing gas quality requirements, the standards facilitate cross-border gas transmission without the need for local adaptation of combustion appliances. This ensures both safety and interoperability of the European gas market.

Most devices available on the European market are adapted to burn H-type natural gas, which is the most common type of gas in the region.

3.4. Biogas Storage

At the European level, issues related to the storage of biogas in household systems are not regulated. The technical aspects of how biogas from household biogas plants should be stored safely and efficiently are not detailed in the EN ISO 23590 standard either [40]. The standard merely recommends that “the materials used in the construction of the digester and the biogas storage chamber shall be such that they do not impart any color, odor, or toxic effect and do not contaminate the biomass slurry”. The materials used in the construction of a Household Biogas System (HBS) should [59]:

• be compatible with a biogas environment,
• have a tensile strength not less than 12 N/mm²,
• have a gas permeability of less than 350 cm/m²/d/bar of methane,
• not be hazardous to the user.

Additionally, the biogas digester internal and external surfaces and the biogas storage shall be free of hidden internal defects such as air bubbles, pits and metallic or other foreign materials.

This means that biogas can be stored both in steel pressure vessels and flexible polymeric low-pressure tanks. Solutions can also be used in which biogas is temporarily stored in the fermentation chamber and then directly used to power gas devices. However, this solution may generate problems associated with low gas flow during the operation of the device [31,95]. In the case of pressure vessels, an additional component for the household biogas system would be a gas compressor. Such a solution significantly increases the cost of producing a household biogas plant and raises the complexity of its subsequent operation. For these reasons, optimal solutions for storing biogas produced in household biogas plants are flexible polymeric tanks. Similarly to Household Biogas Systems the availability of dedicated flexible tanks for biogas storage on the European market is limited.

Summary:

At the European level, there are currently no specific regulations dedicated exclusively to biogas storage in household biogas systems. The EN ISO 23590 standard offers general guidance on suitable construction materials, emphasizing that they must be compatible with biogas, non-toxic, odorless, and free from contaminants that could affect the biomass slurry. Additionally, these materials should possess a tensile strength of at least 12 N/mm² and exhibit low gas permeability (less than 350 cm³/m²/day/bar of methane). It is also essential that the surfaces of digesters and storage tanks are free from defects such as air bubbles or foreign inclusions to ensure system integrity and safety.

In terms of biogas storage options, two main types are prevalent: steel pressure vessels and flexible polymeric low-pressure tanks. Steel vessels typically require gas compressors, which add to both the cost and technical complexity of the system, making them less suitable for small-scale household applications. Conversely, flexible polymeric tanks are considered more optimal for household use due to their simplicity, cost-effectiveness, and ease of installation. Despite their advantages, the availability of dedicated flexible biogas storage tanks on the European market remains limited, representing a potential barrier to wider adoption.

To facilitate the growth of household biogas systems, increasing the availability and affordability of appropriate storage solutions, along with further standardization and certification, would be beneficial.

3.5. Biogas Utilization

Although biogas produced in Household Biogas Systems is primarily used for cooking, this information mostly refers to solutions applied outside of Europe [87]. The use of biogas in this way seems to be hindered in Europe due to legal regulations both at the European level and some local provisions. A limitation at the EU level may be the fact that, according to Regulation (EU) 2016/426 of the European Parliament and of the Council of 9 March 2016 on appliances burning gaseous fuels and repealing Directive 2009/142/EC [95], the regulation covers appliances and equipment that are new to the EU market at the time they are placed to the market. This means that these are either new appliances and equipment produced by a manufacturer based in the EU, or new or used appliances and equipment brought from a third country, and it applies to all forms of supply, including distance selling [96]. According to Article 4 of this regulation [95], member states notify the Commission and other member states about the types of gases and the corresponding supply pressures used in their territory. This means that in order for a device designed to burn a particular type of fuel to be allowed on the market, the fuel must be appropriately notified. However, biogas as a fuel has not been notified by any EU member state.

Additionally, biogas is not classified as a gaseous fuel in the EN 437:2021-09 standard, “Test gases—Test pressures—Equipment categories” [96], which specifies the gases for testing, test pressures, and the categories of devices related to the use of gaseous fuels from the first, second, and third families. This standard serves as a reference document for other device-related standards. It contains recommendations for the gases and pressures to be used in testing appliances that burn gaseous fuels. The absence of biogas as a defined gaseous fuel in the EN 437:2021-09 standard means that devices cannot be tested for compliance with reference standards and, consequently, cannot be placed on the European market [97].

Industrial-scale biogas has similar physicochemical properties to gas from Group S, which is regionally used in Hungary. Therefore, it can be assumed, to a limited extent, that appliances designed for Group S gas can be safely used with industrial biogas. However, this assumption is not valid for biogas produced in Household Biogas Systems, as the biogas produced in these conditions is poorly desulfurized (with hydrogen sulfide content at around 50 ppm) and may also contain higher amounts of oxygen and carbon dioxide than Group S gas [59]. Given the potential variability of biogas produced in household settings, dependent on both the substrates and the conditions of the fermentation process, as well as the lack of continuous quality control of the produced gas, using appliances intended for Group S gas to burn biogas is not appropriate.

The mere design and production of an appliance capable of safely using biogas is not sufficient to bring it to market due to formal and legal barriers, which exclude biogas and its derivatives (excluding biomethane) from this part of the market intended for individual consumers. Importantly, biogas produced in a household biogas plant in Europe cannot currently be used in any combustion appliance (e.g., grills, gas stoves, boilers) that have been manufactured and/or approved for sale on the European market. Of course, the owner of a household biogas plant can use the fuel produced in it with appliances available on Asian or American markets, but such an appliance can only be imported to the EU by a private individual for personal use. This situation leads to several inconveniences and may have negative consequences for potential users, such as limiting rights related to the manufacturer’s warranty or issues related to insurance coverage, and the lack of CE marking.

Summary

The use of biogas from Household Biogas Systems (HBS) for cooking in Europe faces significant legal and regulatory barriers, unlike in other regions where it is more common. At the EU level, Regulation (EU) 2016/426 restricts the market placement of appliances that use biogas, as biogas is not recognized as a gaseous fuel in the EN 437:2021-09 standard. Without such recognition, appliances cannot be tested or approved for sale in the EU. Moreover, household-produced biogas differs in quality from industrial biogas and from Group S gas, making it unsuitable for existing approved appliances. As a result, household biogas cannot be legally used in any combustion device sold on the European market. While individuals could import compatible appliances from outside the EU for personal use, this carries drawbacks such as loss of warranty, potential insurance issues, and lack of CE marking.

3.6. Utilization of By-Products

A by-product of biogas production in Household Biogas Systems is digestate, which can be used as a bio-fertilizer. This product should be managed or disposed of in an environmentally safe manner. According to Regulation (EU) 2019/1009 of the European Parliament and of the Council of 5 June 2019, which lays down rules on the making available of EU fertilizing products on the market and amends Regulations (EC) No 1069/2009 and (EC) No 1107/2009, and repeals Regulation (EC) No 2003/2003 [97], and Commission Delegated Regulation (EU) 2022/1519 of 5 May 2022 amending Regulation (EU) 2019/1009 as regards the requirements applicable to EU fertilizing products containing inhibiting compounds and the post-processing of digestate [98], digestate can be used as a substrate for fertilizer production. Digestate from fermentation processes that can be used in fertilizer production includes:

• fresh crop digestate (CMC 4),
• digestate other than fresh crop digestate (CMC 5).

Digestate, other than fresh crop digestate (CMC 5), can be further separated into solid and liquid fractions before being used for fertilizer production. However, these regulations primarily concern industrial-scale applications.

In the same way, after separating the solid and liquid fractions of fermentation residues from household installations, they can be used as fertilizer in domestic applications.

Further possible solutions for the application of the digestate from fermentation processes only concern industrial scale. At an industrial scale, solid digestate can also be used for biochar production (a material with specific properties that can be used, for example, in wastewater treatment processes) [99]. Additionally, there are ongoing efforts to develop technologies for converting digestate into solid fuel after drying and pelletizing [100,101], though these technologies are currently only available at an industrial scale.

The effluent from biogas production can be directly used as a fertilizer in agriculture, as the anaerobic fermentation of organic matter results in easily absorbable nutrients such as nitrogen, phosphorus, and potassium, which are beneficial to plants [31]. The solid fraction of digestate can also serve as a fertilizer, containing significant amounts of organic matter and phosphorus, which can improve soil composition [102,103]. Furthermore, digestate can be converted into compost and then used as a growing medium for plants or for land regeneration [101].

The use of digestate as fertilizer or a substrate for composting is feasible both on an industrial scale and in small-scale household biogas systems. These solutions allow for the local management of digestate from HBS. However, it is important to ensure that the use of digestate as fertilizer complies with local regulations and best practices. The amount of digestate applied should be appropriate for the crops being grown, ensuring that nutrients are effectively absorbed by plants while minimizing the risk of runoff into nearby water sources. Additionally, the application of digestate should be carefully planned to avoid usage during heavy rainfall or when the soil is saturated with water [104].

Summary

Digestate, a by-product of biogas production in Household Biogas Systems (HBS), is a nutrient-rich material that can be used as a bio-fertilizer. According to EU regulations (Regulation (EU) 2019/1009 and Commission Delegated Regulation (EU) 2022/1519), digestate can be categorized as fresh crop digestate (CMC 4) or other digestate (CMC 5), and can be processed into solid or liquid fractions for fertilizer production. While these regulations primarily target industrial-scale applications, digestate use is also feasible at household scale. Digestate provides essential nutrients like nitrogen, phosphorus, and potassium, improving soil quality and crop yield. Proper use of digestate requires compliance with local agricultural and environmental regulations to avoid nutrient runoff and soil contamination.

4. Discussion

The use of biogas from Household Biogas Systems (HBS) for cooking in Europe faces significant legal and regulatory barriers, unlike in other regions where it is more common. At the EU level, Regulation (EU) 2016/426 restricts the market placement of appliances that use biogas, as biogas is not recognized as a gaseous fuel in the EN 437:2021-09 standard. Without such recognition, appliances cannot be tested or approved for sale in the EU. Moreover, household-produced biogas differs in quality from industrial biogas and from Group S gas, making it unsuitable for existing approved appliances. As a result, household biogas cannot be legally used in any combustion device sold on the European market. While individuals could import compatible appliances from outside the EU for personal use, this carries drawbacks such as loss of warranty, potential insurance issues, and lack of CE marking.

The concept of producing biogas directly in households from the waste generated within them offers many advantages and contributes to resource conservation. First and foremost, it helps reduce the transport of biodegradable waste, lowers the costs associated with upgrading biogas to biomethane, and decreases energy losses caused by the need to transport and distribute biomethane from production sites to end users [105,106,107]. This solution is particularly popular in areas where households have limited access to the gas grid. In such cases, biogas produced in HBS systems is used for cooking and provides a convenient alternative to more cumbersome solutions based on solid fuels (such as coal or wood) [107,108,109,110,111].

For European households, most of which have access to gas networks or electricity derived, at least in part, from renewable sources, the option of producing and using biogas for domestic purposes may seem less attractive. However, the ability to process biodegradable waste at the point of generation, while simultaneously obtaining renewable energy and fertilizer for plant cultivation, aligns with the principles of a circular economy and can serve as a factor promoting such solutions in European households. This approach also contributes to local sustainability by reducing the reliance on centralized energy systems and offering a decentralized, environmentally friendly energy source. Although the climate in Europe is less favorable for biogas production [112] than in African and certain Asian countries, which are leaders in household-scale biogas production [113,114], described in the literature research has confirmed that effective methanogenic fermentation can be carried out in psychrophilic conditions. This means that household biogas production in Europe is feasible and does not require costly modifications to the HBS system designs. Additionally, Europe has sufficient availability of substrates for household biogas production, particularly considering that biogas can be produced from two types of waste: biodegradable kitchen waste (20 01 08) and biodegradable garden and park waste (20 02 01).

The main factors contributing to the low popularity of biogas production in HBS systems in Europe are the lack of availability or low availability of ready-made HBS solutions and biogas storage tanks on the market. The need to import HBS systems from outside Europe can discourage potential users of such systems due to increased costs and limited consumer rights. Furthermore, the lack of availability of HBS systems in the European market may be due to the fact that biogas, in the context of its use in household appliances, is not treated on par with other gaseous fuels. The absence of biogas in the EN 437:2021-09 standard creates no formal pathway to introduce biogas-powered appliances into the European market [96]. As a result, the biogas produced in a domestic biogas plant is used only within the household. that produced it (only at the user’s own risk).

The environmental and economic benefits of household biogas include reduced reliance on fossil fuels, lower greenhouse gas emissions, improved organic waste management, and potential cost savings. Despite these advantages, wider adoption is hindered by barriers such as high initial investment costs, maintenance requirements, low public awareness, and the absence of certified, CE-marked plug-and-play units. Nevertheless, household biogas production holds significant potential to contribute to the EU’s climate neutrality goals by enabling decentralized, sustainable energy generation and promoting circular waste management at the local level.

A critical legal limitation remains the absence of biogas as a registered household fuel in EU law, preventing appliances from being certified for its use. This regulatory gap not only slows market development but also undermines broader EU climate and energy objectives. At the same time, integrating household biogas systems with other renewable energy sources and smart grid technologies could significantly enhance energy efficiency and flexibility, fostering more resilient and adaptive local energy networks. Moreover, further socio-economic research is needed to better understand user motivations, barriers, and the long-term viability of household biogas solutions, which would enable the development of targeted policies and support measures to effectively promote their wider adoption.

A review of the current state of the European market shows that several areas need to be addressed if technologies related to the utilization of household-produced biogas are to develop. The review also reveals that the energy-efficient use of household-produced biogas poses a challenge. The most significant challenges are:

• Regulatory exclusion:

  ▪

  Biogas is not classified as a recognized gaseous fuel under EN 437:2021-09 [96]

  ▪

  At the European level, there are currently no specific regulations dedicated exclusively to biogas storage in household biogas systems.

• Existing EU regulations mainly address industrial-scale digestate management, limiting clear guidelines for household-scale use.
• Market access restriction: Appliances using household biogas cannot be CE-certified or legally sold in the EU.
• Consumer risks:

  ▪

  use of imported non-CE appliances may void warranties, limit insurance coverage, and raise safety concerns.

  ▪

  risk of nutrient runoff or environmental contamination if digestate is applied improperly.

  ▪

  quality inconsistency: Household biogas often contains higher impurities (e.g., H₂S, CO₂) and variable composition.

• Need for appropriate planning of digestate application timing and quantities to protect soil and water quality.
• Limited availability of small-scale technologies for digestate processing (e.g., drying, pelletizing).

To support the expansion of household biogas systems, the following measures are recommended:

• Harmonization of EU legislation, particularly in fuel registration and appliance certification, e.g.,:

  ▪

  advocate for updating EN 437 to include biogas as a testable gaseous fuel,

  ▪

  develop EU-wide quality standards for household biogas to ensure safety and compatibility.

• Promote education for household biogas users, e.g., by:

  ▪

  develop tailored guidelines and best practices for household-scale digestate use and management,

  ▪

  expanded technical training and user support,

  ▪

  public awareness and education campaigns,

  ▪

  information on safe and effective digestate application to crops.

• Investment in R&D for compact, efficient technologies:

  ▪

  encourage innovation and market development for small-scale digestate processing technologies,

  ▪

  support research into low-cost purification technologies to stabilize gas quality,

  ▪

  encourage pilot regulatory programs allowing certified appliances for household biogas use,

  ▪

  increased financial incentives and subsidies for small-scale installations,

  ▪

  simplification of administrative procedures and reduction in approval times to encourage more users to invest,

  ▪

  increasing the availability and affordability of appropriate storage solutions, along with further standardization and certification,

  ▪

  support for the development of local energy networks and community energy projects to promote cooperation and biogas sharing at the local level,

  ▪

  promotion of circular economy business models that integrate energy production with waste recycling and resource recovery.

5. Conclusions

Based on the conducted review, it can be concluded that despite the high potential for biogas production, including in household systems, the development of this sector in Europe remains limited, primarily due to legal and regulatory constraints. The primary barrier to the widespread adoption of household biogas production and the use of biogas produced on an industrial scale by domestic (municipal) consumers is the fact that biogas is not treated on par with other gaseous fuels, both fossil (natural gas) and renewable (biomethane). The failure to classify biogas as a distinct category of gaseous fuel, for example, in the EN 437:2021-09 standard [96], prevents the introduction of gas appliances designed for this fuel into the European market.

However, the inclusion of biogas as one of the gaseous fuels in the EN 437:2021-09 standard [96] would require, in the first instance, the determination of the quality requirements and specifications for this fuel. This may also necessitate additional research to identify how typical impurities contained in biogas could affect gas appliances, including during prolonged use. Without addressing these issues, the integration of biogas into the European gas appliance market remains a challenge, limiting its broader adoption, particularly in household applications. Although EU energy policies promote renewable energy sources, no EU country has reported biogas as a fuel. Therefore, it is important that one of the EU Member States first notifies the European Commission about the use of biogas as a fuel, paving the way for its inclusion in the EN 437 standard [96]. The formal recognition of biogas as a gaseous fuel in EU standards would not only facilitate market entry for biogas appliances but also stimulate investments and innovation in this sector, contributing significantly to the EU’s renewable energy and climate neutrality goals. Moreover, fostering international collaboration and sharing best practices could accelerate the harmonization of regulations and technological solutions across Member States. In parallel, increasing public awareness and technical training on household biogas technologies will be essential to support widespread adoption and safe use.