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Overview of bio energy technologies

Production and application of biogas

Biogas is a gaseous product of processing bioorganic material by anaerobic microorganisms in the absence of oxygen, and consists of methane (50-70%) and carbon dioxide (30-50%), as well as a certain amount of various impurities, for example, hydrogen sulfide and water [1]. Today, biogas production is an intensively developing area of ​​biomass processing in all regions of the world, although it is significantly inferior to modern methods of using solid biomass and liquid biofuel, and many times inferior to traditional wood combustion. According to [2], in 2018 a little more than 33 Mtoe (about 36.5 Bcm) of biogas was produced in the world. Smaller, but comparable values ​​for biogas production are given in other sources, for example, in [3]. More than half of the total biogas is produced in Europe, with China and the United States being other important producers. The total capacity of biogas production in Europe in 2018, according to [4], exceeded 11GW. A higher value of European production in 2018 was given by IRENA [5] – 12.8 GW (18.3 GW globally). However, it should be borne in mind that the production of biogas in China and other Asian countries is mainly concentrated in small households, so it is difficult to account precisely for the total capacity, and especially the volume of biogas production. Germany is the world leader in this technology by a significant margin; however, after a peak in 2016, biogas production in this country has stabilized and even slightly decreased.

Figures 1 and 2. Biogas plants. Left ordberga Biogas Plant, Sweden. Right –  BTS Biogas plant, Tuscany, Italy.

Considering that the total volume of natural gas production in the world in 2018 amounted to 3325.8 Mtoe or approximately 3868 Bcm [6], then the share of biogas currently covers approximately 1% of this amount. Of course, this is an insignificant contribution to the total energy consumption; however, it is necessary to take into account several important components related to biogas production firstly, it is the implementation of a useful transformation of a permanently renewable resource, and not the irreversible extraction of fossil fuels; secondly, when utilizing biomass in the process of biogas production the release of methane into the atmosphere, as the most aggressive greenhouse gas, is prevented; thirdly, the potential for biogas production that has not yet been realized is many times higher, which is especially important for some densely populated regions of the world. For example, according to calculations made in [7] and [8] only in China is the potential for biogas production between 150 and 350 Bcm. According to [1], in the USA, the potential for methane production using lignocellulosic biomass resources can reach 4.2 Tcf (about 120 Bcm) per year, which will replace 46% of natural gas in the power sector and 100% in the transport sector. At the same time, in 2018, according to estimates [9], only 270 Bcf (7.65 Bcm) was collected at 352 gas landfills in the United States (which is the main resource for biogas production in the country).The global potential for energy crops and organic waste is estimated at 36-48 EJ (860-1146 Mtoe) [10]. In [11], the potential for the use of biogas (agriculture and waste) on a global scale is estimated at 1000 Bcm, for China at 274 and for EU-27 at 78 Bcm. In [2], the global potential of biogas is estimated at a volume significantly exceeding 550 Mtoe. In the same paper, as well as in [12], detailed data on the potential for biogas production in the world are given, depending on the type of feedstock and by region. Thus, even according to the most conservative estimates, biogas obtained from various types of biomass in the future can compete with conventional and unconventional types of natural gas.

Biogas is used to produce heat and electricity, as well as biomethane, which is enriched biogas by removing most of the hydrocarbon dioxide and harmful impurities, and which is the most promising environmentally-friendly transport fuel. Most often, biogas is sent to Combined Heat and Power (CHP) units. This process achieves 40% electrical efficiency and 50% heat efficiency, 10% energy losses with exhaust gases [13].

Figures 3 and 4 show the data on the growth of the total capacity for biogas production in the world and the growth in electricity generation, as well as the top 10 countries for the production of electricity from biogas.

Figures 3 and 4. Left – Biogas capacity growth and electricity production in 2010-2018; Right – Top-10 countries by biogas electricity production in the world, 2018, GWth

Source: Based on Data from  IRENA (2020),  Renewable  Energy  Statistics  2020, International  Renewable  Energy  Agency (IRENA), Abu Dhabi

The raw material for biogas production is a wide range of bioorganic waste agriculture residues, sewage sludge, animal manure from Livestock Operations, municipal waste, as well as special energy crops (energy crops). Each of these raw materials has its own energy value. The greatest yield of biogas after anaerobic treatment can be obtained from cereals, rapeseed and molasses [12]. Among various types of manure, fresh chicken manure has the highest energy value, and to a lesser extent cattle and pig manure. The variety of raw materials for biogas production is a great advantage of this technology and allows production to be organized relying solely on local raw materials and taking into account the characteristics of local infrastructure. For example, in Europe – Austria, Slovakia, Slovenia, Latvia, Czech Republic and Croatia, the main raw materials for biogas production are energy crops, in Belgium, Finland, Romania and the UK - organic waste, and in Greece, Estonia and Portugal  sewage sludge [13]. The leading biogas producers in Europe, Germany and Italy have less advantage of one or another type of raw material. Energy crops, sewage sludge and Animal manure from Livestock Operations are widely used here.
The main method of biogas production is anaerobic decomposition. The process includes a multistage digestion of biomass by means of anaerobic bacteria without oxygen in a special reactor, mainly in two temperature ranges – between 35-40oС and 55-60oС. During this process, several complex biochemical reactions occur, such as hydrolysis, acidogenesis, acetogenesis, and finally, metanogenesis, which actually produces biogas [12]. The degree and rate of decomposition of  organic matter depends on its "digestibility" and can be enhanced by the combined use of specially-selected species [14].
There are several types of industrial reactors for biogas production [15], differing in scale, degree of centralization, configuration, level of consumption of methane-generating sources, methods of mixing, heating, substrate loading, etc. There are also two main processes of anaerobic fermentation
wet-type and conditionally dry. The Continuous Stirred Tank Reactor, with side heating, and where mixing of the substrate is provided by mixers, has become widely used on farms. Above the reactor there is a sealed gas-holder made from gas-tight polymer materials, which can be conical or spherical. In some cases, gas-holders are installed separately and made of steel. The decomposition of biomass occurs in the mesophilic mode at temperatures of 33-40oC with a degree of decomposition of 70-75% [16].

Figures 5 and 6. Biogas plants with cone gas-holder. Left - Sweden, right – Austria.

A schematic diagram of the wet process for biogas production is shown in Fig. 7. The diagram shows the joint use of manure and energy crops as a raw material. The supply of the substrate to the reactor is provided by an inclined auger. Tubular heaters are displayed on the walls of the reactor, in the upper part there is a cone-shaped gasholder for collecting gas. The option of mixed tanks in series, as well as the combined production of heat and electricity from the obtained biogas, is presented.

Figure 7. Schematic principle of biogas production

1. Energy crops  1aAnimal manure  2. Preliminary pit  3. Chopper  4. Primary digester  4a. Mixer  4b. Heating units  4c. Pipes (gas and liquid)  5. Secondary digester  5a. Gas holder  6. Gas generator  7. Fermented residues  7a. Separator   7b. Transportable dry fermented residue (fertilizers)  7c. Water reservoir  7d. Water for irrigation  8. Heat exchangers  9. Heating system  10. Electricity supply  11. Heat supply for heating elements 

Some countries, for example China, have adopted special programs for the construction of small reactors for households in rural areas, taking into account the characteristics of the local resource base, climatic conditions and available options for operation [17].

The main regulating technological factors that determine the efficiency of anaerobic decomposition in a reactor are primarily the type of raw material, the degree of its preparation, temperature, humidity, acidity level, and the presence of provoking additives.

In addition to the wet method of production, the dry method has become widespread, in which the biomass placed in a metal container is not mixed, but only irrigated with a techno-solution that seeps through the substrate layer, providing anaerobic decomposition of the biomass. Loading of raw materials is carried out by conventional loaders or even by trucks, then the container with biomass is sealed and irrigation and heating are turned on. Anaerobic bacteria digest biomass and produce biogas. Once used, the solution is pumped into a special container for reuse. The biogas generated is accumulated in a gas-holder and is purified. The main processes of biogas production, including the dry method, can be seen in more detail in the Zorg Biogas advertising video [16].

Figures 8 and 9. On the left - communications for collecting biogas and mixing the substrate. On the right is a biogas electricity generator. Gussing,  Austria.

Recently, due to the improvement or new application of previously known technologies, it became possible to use lignocellulosic biomass as a feedstock, which opens up unprecedented opportunities for biogas production in terms of the resource base. However, the feedstock must undergo a steam explosion. This process includes saturation of the crushed lignocellulosic biomass with water while heating under pressure until conditions for the formation of superheated steam are created. After rapid depressurization, the resulting steam grinds the fibres to a state suitable for use in biogas reactors [17]. Steam explosion has previously been used in the production of cellulosic ethanol. Of course, this process requires serious additional costs and is not always justified.

The final stage of biogas processing usually involves the removal of hydrogen sulfide, moisture and other contaminants. However, for biomethane production, biogas is subjected to deeper purification and enrichment, i.e. reduction of CO2 content to the level corresponding to natural gas. The most commonly used methods are water scrubbing, chemical scrubbing, and pressure swing adsorption [19]. Membrane technologies have proven themselves well, when the gas is passed through materials with selective permeability, for example, through special polymers, which allows for the separation of carbon dioxide and methane. Cryogenic separation is also possible.

Figures 10 and 11.  Jordberga Biogas Plant, Sweden

The main advantage of the applied technologies for biogas production is their sufficient diversity, which allows the use of available local raw materials in regional climatic conditions. Biogas reactors can be extremely simple for small households, designed for limited production of thermal energy and the simplest digestates or, conversely, large-scale and centralized for the production of electricity or biomethane. The variety of end products is also an important advantage for operating in an ever-changing commercial market.

In [13], the main barriers to increasing biogas production are noted, among which, first of all, the "Existence, stability and reliability of the framework and support scheme (s)" stands out. At the same time, it is emphasized that the need for such a support scheme is associated with relatively high investment costs, which according to [13], may amount to 2,700 €/(Nm3/hr). With operating and maintenance costs of 270 €/(Nm3/hr) per year, the payback period of projects can be quite long. Other important barriers to the development of biogas production include administrative procedures and access to finance.

Biogas plants

According to estimates [12], there are about 50 million biogas enterprises in the world, of course, primarily in the form of micro-scale. Most of them are concentrated in China (over 40 million) and India - about 5 million. There are several hundred thousand micro biogas plants in Nepal and Vietnam, and more than ten thousand in many Asian countries, including Indonesia, Bangladesh, Cambodia[17].

Fig 12 shows a map with the largest enterprises with a division by the type of raw materials used, as well as with a display of the patent activity of countries by the number of patents received and patent applications filed by their residents for 10 years from 2008 to 2017.

Figure 12. Examples of the largest biogas production facilities with a display of patent activity of countries in the field of biogas technologies

The largest biogas farms are concentrated in Germany, such as Klarsee Biogas Park with a capacity of 20 MWe.
A list of biogas production facilities in the United States with accompanying information can be found in [20], and biomethane production facilities in Europe on the map presented in [21]. According to the latest research, in 2020 the number of biomethane plants in Europe exceeded 700, of which more than 30% are concentrated in Germany. France and Great Britain are among the major biomethane producers.

Figures 13 and 14. Left - Delivery of biomass for processing, Jordberga Biogas Plant, Sweden. Right - biomethane filling station, Norrkoping Biogas Plant, Sweden.

Detailed information on the state of biogas production in different countries of the world can be found in [22].

Biogas. Research and innovations

Biogas and biomethane production is the subject of intensive scientific and engineering research. Below is a brief statistical analysis of inventive activity in the field of biogas production over the past 10 years (2010 -2019), based on a patent selection of nearly 2,000 patents prepared by residents of 46 countries and issued in 46 patent offices worldwide.

During the period under review, the largest number of patents was granted by the Chinese Patent Office CNIPA, as well as by the American USPTO. In total, these two offices have issued about 50% of the patents. Other popular patent jurisdictions, included in the top 10 included Korean, Japanese, Russian, German, Australian, South African and French. The share of other offices was less than 10% (Figure 15).  
Residents of China, Germany and the United States dominated the intellectual property register, having received more than 1100 patents together, or 60% of the total number of patents (Fig. 16).

Figures 15 and 16. Top 10 patent offices in the world by the number of patents issued in 2010-2019 (left) and top 10 countries whose residents received the largest number of patents in 2010-2019 (right), %

Source: Advanced Energy Technologies

 Canadian Intellectual Property Office; CIPC (ZA)– Companies and Intellectual Property Commission; CNIPA (CN)  National Intellectual Property Administration; DPMA (DE) – German Patent and Trade Mark Office; EPO – European Patent Organization; INPI (FR)– National Institute of Industrial Property; JPO (JP) – Industrial Property Office (Japan); KIPO (KR)  Korean Intellectual Property Office; Rospatent (RU)  Federal Service for Intellectual Property (Russia); IP Australia (AU) – IP Australia; USPTO (US) – United States Patent and Trademark Office

The largest number of patents was aimed at technical solutions for primary processing, as well as operations for pre-treatment of feedstock and finishing treatment (Fig. 17).

Figure 18 shows the distribution of patents by the number of technical, organizational and environmental problems mentioned in them, the solution of which was addressed by the inventors. Other inventors were interested in the problems of low efficiency of main processes and low efficiency of product treatment, problems of high operating costs (OPEX/Poor performance) and problems of environmental and social impact of biogas production technologies.

Figures 17 and 18. Distribution of patents by technology elements (left) and problems (right), %

Source: Advanced Energy Technologies

– Additional equipment, substances; CD – Methods of control and diagnostics; COS – Chemistry and other substances; CS – Capture and separation; CUW  Capture, utilization of solid, liquid and gaseous wastes; FS  Feeding systems; FT – Finishing treatment;  PP – Primary processing; PTF – Pre-treatment of feedstock; PTG – Processing technologies in general; SE  Secondary equipment; ST – Storage & transportation

 Administrative and organizational problems; ESI Environmental and social impact; HCD High CAPEX / Development; HCE High CAPEX / Equipment; HCG High costs in general; HOP High OPEX / Poor performance; HOR High OPEX / Repair and replacement; HOU High OPEX / Utilization; LEG Low efficiency in general; LEMP Low efficiency of main processes; LEPT Low efficiency of product treatment; LEVF Low efficiency / Variety of feedstock; UP Unclear problem

The top 10 leading applicants who received the largest number of patents during the period under review included BEKON Energy Technologies GmbH &Co. (Germany), KG, Evonik Degussa GmbH (Germany), Agraferm Technologies AG (Germany), KOMPOFERM GMBH (Germany), DGE GmbH (Germany), Nalco Company (USA), Evonik Fibres Gmbh (Australia), Novozymes A/S (Denmark), and two research organizations – Jiaxing Vocational Technical College (China), and the Institute for Electrification of Agriculture (VIESH) (Russia).  Each of these applicants received between 15 and 23 invention patents.

Figures 19 and 20 show the interests of these applicants in terms of the regions of patenting and elements of the technological chain of biogas production.

Figure 19. Distribution of patents of the leading applicants among patent offices of the world, %

Source: Advanced Energy Technologies

Canadian Intellectual Property Office; CIPC (ZA) Companies and Intellectual Property Commission; CNIPA (CN) – National Intellectual Property Administration; DPMA (DE) – German Patent and Trade Mark Office; EPO - European Patent Organization; INPI (FR) – National Institute of Industrial Property; JPO (JP) – Industrial Property Office (Japan); KIPO (KR) – Korean Intellectual Property Office; Rospatent (RU) – Federal Service for Intellectual Property (Russia); IP Australia (AU) – IP Australia; USPTO (US) – United States Patent and Trademark Office; IMPI (MX) – Mexican Institute of Industrial Property; APO (AT)– The Austrian Patent Office; EAPO  Eurasian Patent Organization; INPI (BR) National Institute of Industrial Property; OMPIC (MA) – Moroccan Industrial and Commercial Property Office; UIPV (UA) – Ministry of Economic Development and Trade of Ukraine; ZIS (RS) Intellectual Property Office of the Republic of Serbia

Each of the top 10 patent applicants  focused mainly on the technological operations of finishing treatment (including the processing of biogas to biomethane) and the primary processing.

Figure 20. Distribution of patents of the leading applicants by technological element, %

Source: Advanced Energy Technologies

 Additional equipment, substances; CD  Methods of control and diagnostics; COS  Chemistry and other substances; CS  Capture and separation; CUW  Capture, utilization of solid, liquid and gaseous wastes; FS  Feeding systems; FT  Finishing treatment;  PP  Primary processing; PTF  Pre-treatment of feedstock; PTG Processing technologies in general; SE  Secondary equipment; ST  Storage & transportation

The largest number of patents 117 – was found in groups of identical unified indicators, including "Low efficiency of main processes" and "Primary processing" and "device" as a type of technical solution.

The most popular International Patent Classification (IPC) index groups were: C12M01
– Apparatus for enzymology or microbiology; B01D53 – Separation of gases or vapors; Recovering vapors of volatile solvents from gases; Chemical or biological purification of waste gases and C02F11 Treatment of sludge; Devices thereof. Their combined share was over 38%.

Biogas. Development trends

Most of the forecasts for the development of biogas production are optimistic and assume a significant increase in this production over the next two decades. Thus, according to the restrained Stated Policies Scenario, [2] an increase in biogas production is predicted in the world by 2040 to a level exceeding about 150 Mtoe, and according to the optimistic Sustainable Development Scenario up to 300 Mtoe. On the other hand, in [13] in 28 EU countries it is assumed that biogas production will increase by 2030 according to different scenarios to a relatively modest range of 28-40 Mtoe, which is interesting given that Europe is currently the main biogas producer. Another study [19] examined the prospects for biomethane production in the countries of the European Union. Here, the authors were less constrained in their assessments they predicted an increase in biomethane production almost 10 times higher than the current level – up to 18 Bcm, which will be about 10% of the projected imports of natural gas.

Biogas. References

[1] Biogas Potential in the United States (PDF) / National Renewable Energy Laboratory /
[2] Outlook for biogas and biomethane: Prospects for organic growth / Fuel report — March 2020 / © OECD / IEA 2018, IEA Publishing, Licence: / International Energy Agency /
[3] Statista /
[4] EBA Statistical report 2019: European Overview / European Biogas Association /
[5] IRENA (2020), Renewable Energy Statistics 2020, International Renewable Energy Agency (IRENA), Abu Dhabi /
[6] BP Statistical Review of World Energy 2019 (PDF) /
[7] Opportunity and challenge of Biogas market in China (PDF) / Ostasiatischer Verein /
[8] Biogas Production in China:  current status and future development (PDF) / Dr.Xiujin Li / Build A Biogas Plant /
[9] Biomass explained, Landfill gas and biogas / U.S. Energy Information Administration , November 12, 2019 /
[10] New WBA Factsheet: Global biomass potential towards 2035 / 2016 March 03 / World Bioenergy Association /
[11] Biogas – An important renewable energy source (PDF) / WBA fact sheet / World Bioenergy Association /
[12] Global Potential of Biogas (PDF) / World Biogas Association /
[13] Biogas beyond 2020 final report (PDF) /
[14] How does anaerobic digestion work? / United States Environmental Protection Agency /
[15] Anaerobic digester types / Wikipedia /
[17] What Could China Give to and Take from OtherCountries in Terms of the Development of the Biogas Industry? / Lei Zheng, Jingang Chen, Mingyue Zhao, Shikun Cheng, Li-Pang Wang, Heinz-Peter Mang and Zifu Li / Sustainability 2020,12, 1490 ; doi:10.3390/su12041490 /
[18] Steam explosion / Wikipedia /
[19] Review of technologies for biomethane production and assessment of Eu transport share in 2030 / M. Prussi. M. Padella, M. Conton. E. D. Postma, L. Lonza / Journal of Cleaner Production Volume 222, 10 June 2019, Pages 565-572 /
[20] Biogas Project / American Biogas Council /
[21] European Biomethane Map / Gas Infrastructure Europe /
[22] IEA Bioenergy Task 37 Country Reports Summary 2015 / IEA Bioenergy /