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Bioenergy – energy in many forms

For EnBW, bioenergy represents another step toward effective climate action. In addition to the already high percentage of emission-free electricity generated from hydropower and wind power, bioenergy is also playing an increasingly important role: EnBW is generating electricity and heat in biomass power plants and offering its customers biomethane as a renewable alternative to natural gas.

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Electricity and heat from bioenergy

Bioenergy is obtained from biomass, which is composed of plants, biowaste, wood or manure. Bioenergy is the all-rounder among the various renewable energy sources because it provides eco-friendly electricity, heat and fuel.

Biomass can essentially be classified into solid, liquid and gaseous biomass.

  • Solid biomass, such as wood or straw, is used as a fuel for combustion to generate electricity and heat in the private, municipal and industrial sectors.
  • Liquid biomass is mainly obtained from the oils of plants like rapeseed, palm trees or sunflowers, before being used in road transport and in combined heat and power plants.
  • Gaseous biomass, or biogas, is obtained by fermenting biowaste, crops such as corn, and plant or animal waste. Biogas is generally converted into electricity and heat in combined heat and power plants. However, it can also be upgraded into biomethane and fed into the natural gas grid.

Unlike coal, oil and natural gas, biomass is classed as a renewable raw material, and the bioenergy produced from it has an excellent carbon footprint: When biomass, biogas or biomethane is burned, only as much CO₂ is released into the atmosphere as was removed from it during plant growth.

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How biogas is made

Biomass is a term that covers crops like corn, vegetable matter, organic waste and animal waste such as dung and manure. These materials are fermented by bacteria in a digester.

This process produces a biogas mixture, which is collected in the “dome” of the digester. It also produces digestate, which is then made available to the agricultural sector again for use as a virtually odorless fertilizer.

The biogas mixture can be used in the place where it was produced by burning it in a combined heat and power plant (CHP) to generate electricity and heat.

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Biomethane: “upgraded” biogas

Instead of converting it into electricity and heat in a combined heat and power plant, the biogas can also be purified into biomethane at a gas upgrading plant. This involves removing the hydrogen sulfide, carbon dioxide and trace gases, ultimately producing a product that contains more than 96 percent methane.

Upgrading biogas and feeding it into the natural gas grid can significantly increase the usage efficiency of this versatile energy source in many cases. If biogas is used in a combined heat and power plant, around one third will be used to generate electricity, depending on the output and design, while around two thirds will produce heat, which often cannot be fully used in the biogas plant’s rural location.

If biogas is fed into the natural gas grid as upgraded biomethane, it can be transported to consumers in this form in line with demand and used in full.

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The largest producer of biomethane in Baden-Württemberg

EnBW is the largest producer of biomethane in Baden-Württemberg, operating five biomethane plants at the following sites:

  • Laupheim-Burgrieden (owned by Erdgas Südwest GmbH)
  • Blaufelden-Emmertsbühl (owned by EnBW AG)
  • Riedlingen (owned by Erdgas Südwest GmbH)
  • Geislingen-Türkheim (owned by EnBW AG)
  • Weikersheim (owned by EnBW AG)

Across these five plants, we can produce up to 160 million kWh of biomethane annually – enough to supply at least 8,000 households with biomethane. We offer our environmentally conscious customers our upgraded biomethane in various product forms.

You ask – we answer

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Biogas is obtained by fermenting biomass in airtight tanks, so-called digesters, anaerobically using microorganisms (bacteria). The resulting raw biogas is collected in the “dome” of the digester. It is then either converted into green electricity and heat on-site in a CHP (combined heat and power plant) or upgraded to produce biomethane.

How is biogas made?

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Biomethane is a renewable alternative to fossil fuel natural gas. Biogas is firstly needed in order to be able to produce biomethane. In a biogas upgrading plant, the biogas is then “purified” to remove the carbon dioxide, water vapor and hydrogen sulfide. Once upgraded, it has the quality of natural gas and can be fed into the existing natural gas grid.

What is biomethane?

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Biomethane can be transported to consumers via the existing natural gas grid. Its potential uses range from power generation and heat generation to use as a fuel for natural gas vehicles. Compared to other renewable energy sources, biomethane has the advantage that it is well-suited to storage and can therefore generate electricity and heat flexibly in line with demand.

What can biomethane be used for?

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The biomass fermentation process produces biogas on the one hand, but also digestate. However, this should by no means to be described as “waste” because it can be reused by farmers. It is firstly stored in the digestate storage facility before being made available again to the agricultural sector as a virtually odorless fertilizer. This high-quality organic fertilizer can supplement and, in most cases, completely replace the mineral fertilizer normally needed, which is obtained from ores, salts, gas and oil.

What happens to the “waste” generated during biomethane production?

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EnBW is already working with scientists from the University of Hohenheim and the Karlsruhe Institute of Technology (KIT) to conduct research into alternatives forms of biomass. In the course of this collaboration, various cultivation scenarios with a plant mix that can be economically converted into biogas have already been identified for Baden-Württemberg. Playing a key role in these scenarios is strip cropping as part of a special crop rotation system in conjunction with permanent crops. The potential is currently being determined on the basis of a field trial in the Biberach region with the involvement of farmers. EnBW is continuing to research new ways of making even greater use of waste material for biogas production.

Is it conceivable to use other energy crops to produce biomethane as well?

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Biomethane represents part of our commitment to a sustainable, climate-friendly energy supply. There is certainly still a great deal of development potential, but it will also reach its environmental and economic limits at some point. That is why we are focusing on expanding capacity for various renewable energy sources by investing in wind and hydropower, for example.

Why is EnBW producing biomethane?

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Our biomethane is produced in two ways. On the one hand, production is based on the fermentation of biowaste. In this sense, all residual materials classified as organic waste in the Biowaste Ordinance are considered biowaste. These include kitchen scraps, overstocked food and many other kinds of waste. Yet it is also obtained from energy crops such as corn in the form of wholecrop silage (the entire corn plant chopped), cereals in the same form, green waste from meadows and fields, and manure.

What materials does EnBW use to produce biomethane?

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There are no costs for you when switching to biomethane. You only pay the costs set out in your usual tariff, which are made up of the price of gas, among other things. Immediately after being processed, the biomethane is fed into the existing natural gas grid and can be used to generate heat in existing appliances such as a gas condensing boiler. No expensive conversions or special heating systems are required.

How much does it cost to switch to biomethane?

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For EnBW customers, there is our Biomethane 10 tariff, where 10% biomethane is added to the natural gas. To change your gas supplier and check availability for where you live, or to find out more information, visit our biomethane tariff pages.

How can I obtain biomethane?