The Biogas is the gas produced by the fermentation of materials organic in the absence of oxygen . At the heart of the energy transition and the circular economy, it is also a source of local employment 1 . The anaerobic digestion occurs spontaneously (in marshes , rice fields, large tanks or tropical hydroelectric dams 2 , the discharges containing waste or organic materials (animal, plant, fungal or bacterial). It can cause artificially in digesters (in Particularly for treating sludge,
It is a renewable energy sources affecting the energy transition , and in France the roadmap of the Environmental Conference of September 2012 provides for the preparation of a national biogas plane , extending the “agro-ecological project” 3 launched December 2012, including an Energy Methane Autonomy Nitrogen plan (EMAA, launched on 29 March 2013). The 2014-2020 Waste Plan in preparation and future Biomass regional schemes will also help to improve the value of this resource.
Biogas, if it is purified, becomes biomethane (the renewable form of natural gas that is essentially composed of methane but also of butane , propane and other elements and is a fossil energy).
It depends on the composition of the gas produced by the fermentation: the more methane it contains , the more energy it has. For example, a fermentable material rich in C and H produces a biogas containing up to 90% methane, while cellulose , which is leaner in C and H, will produce a biogas with only 55% methane (and 45% carbon dioxide ) 4 .
Biogas is mainly composed of methane (50-70%), but also carbon dioxide (CO 2 ) and varying amounts of water vapor , hydrogen sulphide (H 2 S), and others Compounds (“contaminants”), particularly in landfill biogas 5 . Among the impurities are 4
- of siloxanes 4 ;
- of organochlorine (including vinyl chloride , dichloromethane , trichloromethane and tetrachloromethane which are substances carcinogenic 6 ;
- Sulfur compounds ( mercaptans ) 4 ;
- Nitrogen compounds (NH3 and NH2) 4 ;
- Hydrogen 4 ;
- Various fermentation intermediates ( alcohols , acids , esters, etc.) 4 ;
- Metals and metalloids 7
- and even some anaerobic microbes (optionally methanotrophic) 7 .
Its content depends on the duration and quality of the fermentation process, the type of plant and much of the nature of the fermentable material used (and in particular its proportions of carbon, hydrogen, oxygen and nitrogen or undesirable contaminants ).
The biogas can be purified to remove carbon dioxide and hydrogen sulphide, thus obtaining biomethane which can be injected into the natural gas distribution network . The refining process into biomethane, however sophisticated and expensive 8 but has a great deal of progress.
Biosynthesis process [ edit | Change the code ]
There are three ranges of biogas production, depending on the temperature.
- 15-25 ° C : psychrophilic
- 25-45 ° C : mesophilic
- 45-65 ° C : thermophilic
These are the digesters mesophilic that are most used (approx 38 ° C ) in temperate zones.
The recovery of biogas discharge is doubly interesting because methane released into the atmosphere is a gas greenhouse more potent than carbon dioxide (CO 2 ) produced by combustion.
Sources of biogas
Biogas is the result of methanisation or anaerobic digestion of fermentable wastes 9 . The most common sources of biogas come from voluntary or involuntary organic matter stocks:
- Cultures ;
- Discharges: their biogas content is more or less high depending on the sealing of the operating mode. * Selective collection of putrescible waste allows faster methanisation than in landfill using specific bioreactors (digesters) 9 ;
- Sludge from sewage treatment plants: methanization removes organic compounds and allows the station to be more or less autonomous in energy;
- Livestock effluents: regulations require that effluent storage equipment (slurry, manure) be compulsory for a capacity greater than 6 months. This storage time can be used for the methanisation of effluents. These include animal waste, but also other agricultural wastes: crop residues and silage, dairy effluents, market withdrawals, turf, etc. 10 ;
- Effluents from the agro-food industry can also be methanated. The main aim is to avoid the rejection of organic matter that is too rich, and can be accompanied by energy recovery;
- The bottom of lakes and marshes: biogas is produced naturally by the organic sediments that accumulate there. The use of Lake Kivu biogas was undertaken more than 40 years ago and is now being developed on a large scale.
Biogas in the world
World consumption of biogas (often in the form of biomethane ) would have increased by an average of 3.5% per year from 1965 to 2000, while overall primary energy demand increased on average by only 2.4% Year 11 . It could become a non-fossil fuel dominant xxi th century, as was the previous century oil and coal to xix th century 4 .
A report published in late 2015 by the EBA ( European Biogas Association or European Biogas Association ) shows that biogas production sites grew significantly counting 17 240 sites (+ 18% compared to 2013). The EBA estimates that 14.6 million European households are fueled by biogas. Germany is the European leader in the biogas market 12 .
In 2016, for biomethane injection into the grids, Germany is ahead of the other Member States by 2015, already 165 biomethane injection units (10 TWh / a ), ahead of Great Britain (50 sites and 2 TWh / A ), the Netherlands (25 sites and 0.9 TWh / a), far ahead of France. Denmark, Austria, Sweden and Switzerland all have between 10 and 20 production sites providing 130 to 360 GWh / year.
France has 19 sites and produces only 82 GWh / a. Spain and Italy do not allow or encourage injection into the network.
The holly erected and lying couch derived from Sarvache Hungary. These wild plants are 20% less productive than the corn and are considered only as a supplement to it 8 , 13 . Since 2012 the German law imposes a certain diversification of the crops (to reduce the place of the corn).
France and French-speaking countries
In France, the recovery of biogas discharge is mandatory since the decree of14 . This decree requires the search for solutions for energy recovery of biogas or its thermal destruction ( flaring ) in case of non-valorisation, in order to avoid olfactory nuisance and the environmental impact of methane. In France, in 2012, this landfill gas supplied more than 70% of the primary energy production from biogas in the country 15
An Atlas Bioenergy International and in France a biogas atlas annually update the map of industrial installations for the production / recovery of biogas (in the form of electricity, heat or direct injection into gas networks in French-speaking countries);
- In 2012, 241 production sites were listed (publication 2013), in 2013 they were 848 (publication 2014): 578 in France, 200 in Flanders & Wallonia, 32 in Switzerland, 25 in French-speaking Canada, 9 in Luxembourg and Mauritius and 3 in Tunisia.
The density of installation is highest in Belgium and Switzerland 16 . France hosted the Biogaz Europe fair in March 2015 in Nantes 17 .
- 2014 : Some small heat networks are already fueled by biogas, for example in Indre-et-Loire that of Pernay ( 1 000 inhabitants ), then in 2014 of Le Plessis-Gassot in Val-d’Oise with 23 homes Fueled by the gas from a garbage dump . The minister Ségolène Royal launched the 200 territories positive energy, and announced plans to appeal for 1500 projects of biogas in three years in rural areas 18.
- 2015 , installed capacity of the biogas sector is growing at a “steady pace” according to Ademe: “70 new methanisation units were installed in 2015, with a capacity of 20 MWe16. For 2016, forecasting is difficult because of a lack of visibility on electricity purchase rates that strongly impact the economic equilibrium of the units ” 19 . A national biogas committee was set up on March 24, 2014 20 to facilitate dialogue between the actors of the sector, through 4 working groups dedicated respectively to 1) the mechanisms supporting biogas (cogeneration purchase price). .), (2) reflections on facilitation procedures, (3) bio-fuel NGV,
- 2016-2018 . Within the framework of the SRADDETs and the implementation of the national biomass strategy (in preparation 22 ), the regions are preparing the drafting of a regional biomass scheme . In 2017, according to Valérie Borroni 23 , about 500 installations are installed in France at the beginning of 2017: 300 agricultural installations, less than 100 wastewater treatment plants, the rest being produced from household refuse by industrialists. A hundred old landfills also recover methane. They mainly produce electricity and heat, and – since 2011 – some thirty installations are injecting into the gas network 24 .
- Foresight :
In 2015, the Energy Transition Law sets a target of 10% of total gas consumption in 2030, deemed ambitious by the Syndicat des Energie Renewables (SER) and the French network managers (GRDF, GRTgaz, SPEGNN and TIGF) Which in 2016 counted only 19 injection sites in service in France (but 200 others, equivalent to 3.86 TWh are planned). As the share of this gas is 0.02% in 2016, it must be multiplied by 500. From 0.082 TWh in 2016, the sector expects to produce 1.7 TWh in 2018 and then 8 TWh in 2023.
100% “renewable” In 2050? According to the SER if all actors wanted it, in 2030, 56 TWh of biogas could be extracted from the methanisation of 130 million tons of raw material (sludge, effluent, waste, crops, etc.) to potentially supply 100% of national needs (400 to 550 TWh) in 2050. For this, the methane waste could provide 210 TWh, and the biomass gasification 160 to 280 TWh more. 20 to 35 TWh could come from hydrogen-methanation and 10 to 25 TWh from the fermentation of microalgae. Fos-sur-Mer wants to experiment with the Power-to-Gas approach, which aims at energy agility through the interconnection of smart grids of electricity and gas resources in order to better switch from one to the other as needed. The “gas mobility” could also complement the electric mobility (which does not apply to delivery trucks, garbage trucks, buses). Favorable factors include the redemption and / or injection tariff, an extension of existing contracts; The SER also proposes an exemption for consumers of “biomethane” from the energy climate contribution or the property tax for industrial methanisation units. “There is also mention of” biomethane carried “projects (ie compressed and transported by truck from the production site to an injection point in the network) 24 .
In 2013, about 50 farms in Switzerland produce biogas 25 .
Biogas consists mainly of methane (CH 4 ) that the greenhouse is very important. Its combustion produces carbon dioxide , which is also a greenhouse gas , but whose impact is less. Indeed, one kilogram of methane (CH 4 ) has a Global Warming Potential (GWP) over 100 years, 23 times higher than one kilogram of carbon dioxide .
Using biogas does not increase the greenhouse effect if the carbon produced ( methane and carbon dioxide ) has itself been previously absorbed by the plants from which this biogas is produced, when they are grown and if this uses In a short carbon cycle and if it does not contribute to the overexploitation of biomass (it only returns carbon that was recently removed from the atmosphere , unlike natural gas ).
As biofuel it has many advantages:
- Reduction of greenhouse gas emissions, as indicated above;
- Significant reduction of fine particulate emissions compared to diesel and gasoline;
- Reduction of certain microbes in agricultural effluents ( coliforms in particular 26 );
- Substitute for other exogenous energies (fossil and nuclear), a source of income for the farmer who saves on his energy costs and / or, increasingly sells his energy;
- Reduction of the carbon load of vegetable waste. Once digested, the waste is less harmful to the environment; The risk of biological or organic pollution is also greatly reduced, and the fermentation decreases the percentage of dry matter, which makes it possible to reduce the volume to be transported and spread;
- The manure is treated free of charge by or for farmers who recover it at the end of the cycle, after having produced methane, of better quality because it no longer “burns” plants, it is cleared of many pathogens and all the seeds of “weeds” that could hold 27 .
- It can also be injected into the natural gas network by means of purification 8 . It is the solution that offers the best energy efficiency, if the network is close enough to the point of production. This solution is now supported by network operators, who are even considering 100% green gas by 2050. In France, Afsset concluded in 2009 that the injection of clean biogas into the network did not pose a particular health problem 28 .
The uses of biogas
- Combustion in a gas engine or a small turbine, to generate electricity injected into the grid (more than 8,000 installations in Germany), and often heat in cogeneration , but trigeneration (cooling production) is possible;
- Thermoelectric power station, cement plant, collective boiler room, etc. When they exist near the source;
- Heating of greenhouses (with CO 2 enrichment );
- Fuel for NGV vehicles, in substitution for conventional fossil natural gas. It feeds captive fleets (buses, garbage trucks, service vehicles) (see biogas fuel ) or even individual vehicles ( Switzerland and Sweden );
- Reforming methane to form renewable hydrogen (called ” biohydrogen “) or to inject it into the grid (CO 2 , water, sulfur compounds must be extracted from the biogas to obtain a gas composed of more than 96% CH 4 substitutable for fossil natural gas). For other applications, a gas containing 60% methane is largely sufficient, so purifying it would be an unnecessary expense. It is then sufficient to remove the impurities presenting problems of pollution, corrosion or odor , sulfur compounds in particular.
The IFEU studies show that in Germany the use of biogas for local cogeneration with a gas engine is more efficient in terms of greenhouse effect, injection into networks and The necessary maintenance. However, this study estimates the energy supplied at the equivalent of 5,000 liters of fuel oil per hectare per year. Replace fossil fuels and nuclear power with biogas require almost the whole surface of Germany 29 .
The operating efficiency of a heat-electricity cogeneration is at best 70%, or 30% losses.
The use of heat is often seasonal and requires close proximity to users and the creation of a distribution network. It is also possible to provide cold by means of heat absorption processes. However, this use is limited to certain regions in France.
Injection is permitted and can achieve an operating efficiency of 90%. The consumption of gas is also seasonal, but in general it is possible to inject on the networks all year round, except in some cases, a few days or weeks in summer, where consumption is lower and therefore the network is saturated. By injection, the production of biomethane in summer finds an outlet that the heat of cogeneration does not always find.
Many projects are injected into France. For example, Fontainebleau, accompanied by the Ecole Supérieure des Mines, initiates a methanisation-injection of 30,000 tons per year of horse manure under the project name: EQUIMETH.
Worldwide, the use of biogas at the domestic level is widespread, particularly in Asia 30
In Mali , pilot projects were conducted in remote areas to measure how biogas could produce energy for domestic use in a sustainable way. Experience has shown that, with the training of local craftsmen who can take charge of the production of the necessary equipment (gasometer, digester) and the training of families in the maintenance of equipment, biogas can be a viable alternative to ” Use of woodfuels for cooking meals and improve living conditions by other energy inputs (including refrigeration). Pressure on wood resources decreased and the compost produced was used to fertilize soils.
Arti, a non-governmental organization in India, develops a simple 0.5 m 3 (raised) digester for the tropics, which uses kitchen waste (rich in starch and sugars) to produce biogas. 1 kg of waste produces 400 liters of biogas in 6 to 8 hours, which is enough for about 15 to 20 minutes of cooking 32 .
Biogasmax: waste energy for urban environmental transport
Biogasmax is a European project of the 6 th Framework Program for Research and Development FP6 – 6 th Framework Program (2000-2006) of the European Commission. It is part of Europe’s initiatives to reduce its dependence on fossil fuels. Based on existing experiences in Europe, it promotes techniques and achievements demonstrating the value of using biogas as a fuel for land transport, based on deposits available in urban areas in Europe.
This four- year project will prove technical reliability and pose the environmental, societal and financial benefits. On the basis of full-scale demonstrations, the project will optimize existing industrial processes and carry out research on new ones. In addition to its technical value, Biogasmax has a scouting function to reduce barriers to entry, be they technical, operational, institutional or regulatory. The knowledge gained will be disseminated throughout the European Union, especially in the new Member States.
In fact, this project does not start from a virgin situation; Its members are involved in innovative projects in this field, which have been for a long time for some. It is therefore a European project of proof and not of intention.
Biogasmax brings together cities such as Lille in France, Stockholm and Gothenburg in Sweden, Rome in Italy, Bern in Switzerland, Torun and Zielona Gora in Poland. The project has surrounded itself with advanced skills in Germany (ISET in Kassel for the biogas purification and concentration aspects, the University of Stuttgart for biomethane-fuel life cycle analysis), Transfer of skills, as well as a set of public and private partners in the countries concerned: mainly waste and energy management operators.
Most of the most successful experiments currently involving the use of biogas as fuel are represented within Biogasmax, which provides an extremely prolific communication and action framework.
Biogasmax represents a perspective of experiences: each city has located its own strategy and objectives as indicated on the project’s website (  [ archive ] ). An intense exchange takes place between the partners, which results in a number of results and technical reports made available on the Web. This visibility of the results is also accompanied by strategic documents on the evolution of biomethane (biogas adapted to engine carburization), its participation in taking climate change into account and helping it to be taken into account in urban metropolises . These exchanges, fruitful from the inside, spread to the whole of the community concerned,
With the acquisition of best practices, Biogasmax’s partners are able to federate the best participants and promote reflection and actions regarding this approach.
For more information on the European Biogasmax project, see Where News and downloads are regularly updated [ archive ] .
Following Biogasmax, the European program Biomethane Regions also promotes this energy