XII Международная студенческая научная конференция Студенческий научный форум - 2020

Introduction

A precondition for use of biogas as a fuel is its processing to form biomethane (also known as bio natural gas). In chemical terms, biomethane is de-facto identical with natural gas and is fed into the natural-gas grid. This grid makes an outstandingly ex­tensive infrastructure available: there are opportunities to link up to sources across large areas of Germany; at the same time the grid is connected with underground storage facilities. This enables stored bio­methane to be deployed flexibly where the demand for energy is present. The biometh­ane can also be used not only for electricity and heating, but also as a fuel.

The quantity of biogas facilities in Germany has by now risen to 8,100, more than 180 of which produce biomethane (status: end of 2016). However, the treatment of the biogas, so as to form methane, involves re­source commitment in terms of technology and energy. This is worth it, for instance, in those cases where there are not enough takers for the energy produced at the bio­gas facility’s location. A methane-producer can conclude an agreement for supply of product with a mineral-oil trader or a fuel station operator. It is not necessary to be neighbors in terms of location, the fuel station operator obtains normal (bio-)natu­ral gas from its grid, yet pays the biometh­ane producer that feeds-in the correspond­ing quantity of biomethane at its specific location.

The Federal Government has anchored the Gas Grid Access Ordinance (Gasnetz­zugangsverordnung) in legislation, as a prerequisite for feeding biomethane into the natural-gas grid. This ordinance not only created the legislative framework but also defined goals. It provides for the feeding-in of biomethane to rise to 6 bn. m3 annually by 2020. As a comparison: in 2013 over 50 m. m3 were used as fuel.

Raw materials

The starting substance for biomethane is biogas: in Germany this is mainly obtained by fermentation of energy plants, liquid manure and solid manure, but also from organic waste material sourced from in­dustry and private households. Around a half of the substrates used are renewable substances (52 %), followed by animal ex­crement, at 43 %, and biogenic waste and recycled material, at 5 %. Maize dominates among the renewable resources, at 73 %. The Federal Ministry of Agriculture is pro­viding support to the search for sustainable alternatives to maize, in various projects (http://energiepflanzen.fnr.de). Scien­tists are examining new systems of cultiva­tion and crop rotation, and also numerous interesting old and new energy crops. In plant-breeding projects, highly-promising candidates are made ready, in terms of culti­vation, for their task as energy supplier.

For the production of biomethane as a fuel, the use of waste materials and recycled ma­terials is particularly interesting. Low GHG emissions make a case that favors this source as an option.

Tab. 1. YIELD OF RAW MATERIALS, ANNUAL YIELD OF BIOGAS AND METHANE

Manufacture The biogas produced by fermentation contains a substantial proportion of carbon dioxide, alongside a methane content of 50–75 %. Added to this are small quantities of hydrogen sulphide and other trace gases. Yet it is only the methane (CH4) that is usable as a fuel: in chemical terms it is identical with natural gas. Thus, separation of the methane from other constituent elements of biogas is decisive. In Germany there are currently five different treatment procedures used in practice. These include PSA (pressure swing adsorption), compressed water washing, physical and chemical washing (e. g. amine washing), and the membrane separation procedure.

These procedures allow the methane content in the biogas to be increased to up to 98 %. The orientation point for this level of methane content is the respective methane concentration in the gas grid at the place where the product is fed-in. The degrees of concentration range from 80 % (so-called L-Gas from Lower Saxony, the Netherlands and the North Sea) up to 98 % (H-Gas sourced from Russia).

Properties and quality of the fuel Biomethane or natural gas are stored in a pressurized tank at 200 bar and sold at specialized fuel pumps. It is a mandatory requirement to state natural gas prices and biomethane prices at fuel-stations, based on mass and denominated in kg. The energy-content of a kilogram of methane ap-proximately corresponds to that of 1.5 l of petrol or 1.3 l of diesel.

To guarantee uniform quality, bringing bio­methane and natural gas into circulation as a fuel is tied to compliance with the norm DIN 51624. Subject to this prerequisite, natural gas and biomethane can be mixed in any ratio.

New natural-gas vehicles are usually biva­lent, i. e. equipped with an additional petrol tank, so that there are no losses sustained in terms of vehicle range or problems arising from a lack of gas fuel stations.

Market presence/use

In the year 2015, biomethane-natural-gas mixtures were able to be tanked throughout Germany in various mix ratios at over 300 fuel stations. Of these, 150 fuel stations were already offering pure biomethane. In 2015, sales rose to 38 m. kg or respectively 53 m. m3.

Thanks to politicians’ efforts and to initia­tives by the industry, in future natural gas and biomethane are to play a larger role in the mobility sector; the aim is a 4 % share for natural gas and biomethane in German fuel consumption. This goal is ambitious be­cause it amounts to a factor-of-10 increase compared to the figure for 2015. The aim is also for the number of suitable vehicles in use to grow, to a total of 1.4 m. vehicles. At present there are no more than 98,000 natural-gas-powered vehicles on German roads, of which 80,000 are cars. They have a network of more than 900 natural-gas fuel stations available to them. Yet biomethane is obtainable not only at the network of natu­ral-gas fuel stations; there are also biometh­ane service stations directly at biogas facil­ities. In 2006 the first of these biomethane fuel stations was established in Wendland.

A reduced energy-tax rate applies to natural gas and biomethane until the end of 2018, namely 1.39 EUR-ct per kilowatt-hour. If biomethane is credited against the biofuels quota, however, the full tax rate must be paid. Yet because the prices for biometh­ane are still above the natural-gas prices, quota-trading for biomethane sourced from recycled material is an important mechanism used for biomethane sales.

Biomethane is an alternative, not solely for cars and small transporters; to an increasing degree, urban buses, vehicle fleets serving municipalities and also commercial vehicles are gas-powered. While the comparative­ly low vehicle range is problematic in the transport sector, buses and municipal vehi­cles can typically use the company-internal fuel-station at their operational base. First concepts tested in agriculture show that combined diesel-biomethane operation is possible with tractors. A two-tank system, similar to that used for vegetable-oil fuel, serves for starting up and switching off the vehicle using diesel fuel. The degree to which these concepts can be economically viable for farmers in the future, depends on the tractor’s area of operation and on the fi­nancial support provided.

Tab. 2. SALES OF BIOMETHANE AS FUEL

Environmental aspects

A key advantage of biomethane compared to diesel and petrol is the reduced level of pollutant emissions. By using bio natural gas in buses and municipal vehicle fleets, emissions of soot and particles attributable to transport can be substantially reduced in our inner urban areas.

Depending on the raw material used, the GHG emissions for biomethane vary. The use of recycled and waste material has a positive effect because only emissions from transport and from processing are includ­ed in the balance. Overall, GHG savings of 60–80 % are possible. On this basis, even taking into account various mixtures of sub­strate, the target value of 50 % GHG sav­ing for 2018 can be reached. After all, for natural-gas-biomethane mixtures (80:20), the GHG saving still amounts to 30 % com­pared to petrol fuels or diesel fuels. taking into account various mixtures of sub­strate, the target value of 50 % GHG sav­ing for 2018 can be reached. After all, for natural-gas-biomethane mixtures (80:20), the GHG saving still amounts to 30 % com­pared to petrol fuels or diesel fuels.

Picture № 1 - GHG REDUCTION POTENTIAL USING BIOMETHANE & BIOMETHANE-NATURAL GAS (NG) MIXTURES

Picture № 2 - WTW GREENHOUSE-GAS EMISSIONS – CARS: 2012

At present, the Biofuels Sustainability Ordi­nance includes no standard value for GHG saving attained by biomethane sourced from energy plants; accordingly, in this case the producers must make their own calcula­tion, using the predetermined methodology. However, the European Commission has already announced a corresponding addi­tion to the list of standard values. The two graphics (see Pages 39 and 40), based on various studies, give points of reference on the GHG savings.

References

Agentur für Erneuerbare Energien (AEE):

www.unendlich-viel-energie.de

Bundesministerium für Ernährung und Landwirtschaft (BMEL):

www.bmel.de

Bundesministerium für Wirtschaft und Energie (BMWi):

www.bmwi.de

Bundesverband der deutschen Bioethanolwirtschaft e. V. (BDBe):

www.bdbe.de

Clean Energy Partnership (CEP):

www.cleanenergypartnership.de

Deutsches Biomasseforschungszentrum gGmbH (DBFZ):

www.dbfz.de

Karlsruher Institut für Technologie (KIT) – bioliq-Verfahren:

www.bioliq.de

Technologie- und Förderzentrum TFZ:

www.tfz.bayern.de

Union zur Förderung von Oel- und Proteinpflanzen e. V. (UFOP):

www.ufop.de

Verband der Deutschen Biokraftstoffindustrie e. V. (VDB):

www.biokraftstoffverband.de

Verband der ölsaatenverarbeitenden Industrie in Deutschland e. V. (OVID):

www.ovid-verband.de

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