1. Biomethanation Projects and Industrial-Scale Facilities in Europe

• In contrast to the well-known biogas-based biomethanation projects, the BIOCO₂NVERT project aims to implement a biocatalytic P2M facility at one of the largest bioethanol plants of Europe. According to the description of the Innovation Land Lab, installation and commissioning are the next steps of the project ^[3][53]. The project started in 2018, and the cooperation partners are Klärgastechnik Deutschland GmbH, MicrobEnergy GmbH, PRG Precision Stirrer Gesellschaft GmbH, and Südzucker AG ^[4][54].
• The HYCAUNAIS project takes place in Saint-Florentin, France, and involves synthetic methane production with CO₂ from landfill gas through the development of biological methanation. The project started in 2018 and is being realized by five private and three public partners ^[5][6][55,56].
• The CarbonATE project in Austria and Switzerland focuses on the optimization of microbiological methanation by the development of enzymatic CO₂ capture process to prevent the microorganisms from harmful contaminants (e.g., N₂, O₂) of potential input gases (industrial exhaust gases) ^[7][8][57,58].

2. Key Topics of Future Implementation

2.1. Key Topic 1: The Role of Biomethanation in the Hydrogen Economy

Based on the short summaries of the listed projects (ca. 1–3 pages, 2501 total terms, 14,573 total tokens), the most common word is “hydrogen”. Similar influential words are “carbon dioxide” and “methane” (see Figure 1). This result refers to the importance of input factors in the biomethanation sector, and even though it is not particularly surprising, the relative dominance of hydrogen against the other key terms (e.g., methane, storage, biogas, natural gas) is conspicuous. Regarding the trend and advancements towards the hydrogen economy ^[35][85], the hydrogen orientation can be justified, but it can also be asked, for example, what could the role of biomethanation (biomethane or SNG production) be in the hydrogen economy? This might require further analysis later, based on other research results and EU policies.

Figure 1. Word cloud from biomethanation project descriptions.

In addition to taking a static “snapshot” of the content of the biomethanation project descriptions (Key topic 1), quantitative characteristics of the projects provide opportunities for deeper insights. The next section (Key topic 2) considers the size of the facility (indicated by the capacity of the electrolyzer), while after that, Key topic 3 analyzes trends according to the start of the project (year).

2.2. Key Topic 2: Opening New Ways besides Biogas Plants to Store More Renewable Electricity/Hydrogen

The terms that appeared at least 15 times in the project descriptions were analyzed according to the size of the biomethanation facility. It can show how the focus of the R&D&I activities changes (or does not change) with the deployment of larger facilities. Considering the lessons of the interpreting interviews as well, Figure 2 suggests the following:

Figure 2 . Appearance of the most common terms according to the size of the planned/implemented biomethanation facility. For example, the term “storage” appeared in project descriptions of biomethanation plants, which were 1.3 MW_el on average.

(a)

at the small scale, the focus is on the “efficiency” of the “process”, the “reactor” structure, the microorganisms (“archaea”), and the “biogas” input from “biogas plants”, which contains “carbon dioxide” to “convert” it into “methane”.

(b)

at the large scale, the emphasis is on the “volume” of “wind” or other “renewable energy” and the “production” of “methane”, which can be “fed” into the “natural gas” for “energy” “storage” purposes. (Words in quotation marks refer to the empirical data.)

The importance of the results shown by Figure 2 is that they interconnect the past and the future of biomethanation technology development from a purely technical aspect (without considering the time horizon, which is presented in the next section). Less abstractly, different issues are important at the small and large scales, and the gaps between these issues might generate new areas for research. Regarding the listed (a) and (b) points above, a step is missing between the efficient process in kW-scale with CO₂ from biogas and the purpose of storing high volumes of renewable electricity in the form of SNG in MW-scale. This missing step seems to be the sourcing of CO₂ in large volumes to develop multi-MW biomethanation plants. Accordingly, it is worth analyzing that if biogas plants cannot provide enough carbon dioxide for large-scale P2M plants ^[36][15], which could convert the vast volume of renewable electricity produced by wind or solar parks, what solutions can help to increase the capacity of biomethanation facilities to multi-MW_el level, which are needed in the future ^[9][59].

2.3. Key Topic 3: From Technology Development towards Achieving “Future” Benefits

The most common terms of the project descriptions may change according to the start year of the projects, not only their capacity. Accordingly, Figure 3 shows constellation plots of a hierarchical cluster analysis which might reveal some underlying structures (e.g., main terms of past and present; based on the 75 most common terms). Based on the collaborative interpretation with the interviewees, Figure 3 shows the following:

Figure 3. Constellation plots showing clusters of terms according to the project starts.

• From 2013 to 2016/2017, the emphasis was on “research” and “pilot” implementation; moreover, the fundamental characteristics of the process (e.g., using “excess” “solar” energy, “conversion” into “gas”, connection to the “grid”, and/or “biogas plants”).
• From 2016/2017 to 2020/2021, broader themes appeared, such as the “future” “potential” of the “technology” realized by a “company”, utilizing “renewable energy” and “electricity”, and producing “green methane”, “biomethane”, or other “fuels” that fit the “infrastructure” to fight “climate” change.

2.4. Key Topic 4: Future Project Planning in Line with Scientific Advancements and Policy Objectives

Based on the abstracts of the selected publications, a slightly different scheme can be seen on the word cloud than in the case of the biomethanation project descriptions. For example, while hydrogen and carbon dioxide are apparently important, carbon dioxide appears more often in case research papers, while hydrogen utilization appears more often in case of the project descriptions. Scientific research, however, deals more with the operative questions of the “system”, the “process”, or the “reactor”, while biomethanation project descriptions write about “using” the “technology” for “energy storage” and the “production” of methane.

Figure 4 shows the comparison of the most common terms of research papers, project descriptions, and EU policies. In line with the mentioned trends, carbon dioxide (N = 116), hydrogen (101), methane (92), system (79), and power-to-gas (77) were the most dominant in a quantitative sense, in case of the abstracts of research papers. Project descriptions were also focused on these three terms, but with others: hydrogen (104), methane (90), carbon dioxide (80), use (80), energy (77), and gas (77).

Figure 4. Comparing the word clouds of biomethanation project descriptions, P2M publications, and relevant EU policies.

In contrast to that, regarding the EU policies and strategies, the most common terms are energy (157), greenhouse gas emissions (88), economy (87), reduce (69), sectors (68), and sustainable (68). Accordingly, the main objective is to “reduce” the “greenhouse gas emissions” (GHG) through a “sustainable” “transition” with more “renewable energies”. The “economy” and increasing “competitiveness” in a “global” “environment”, however, is also important while fighting “climate change”. For example, the document called “A Clean Planet for All” by the European Commission refers to competitiveness already in its subtitle: “A European strategic long-term vision for a prosperous, modern, competitive and climate neutral economy” ^[37][47]. The European Green Deal “aims to transform the EU into a fair and prosperous society, with a modern, resource-efficient and competitive economy” (p. 2, ^[38][48]).

These results suggest that scientific research, industrial project development, and policies have common points, e.g., the GHG-reduction induces the scientific research on carbon capture and utilization (CCU) solutions and their industrial application at biomethanation facilities. These high-level interconnections, however, should be analyzed in-depth to identify how sectoral competitiveness can be supported in practice by new biomethanation facility development projects.