Biogas an all-rounder

Conquering the Gas Grid

Injecting biogas into the natural gas grid is a state-of-the-art process.

The gas grid is the ideal way of getting biogas to the consumer.

Biogas is a versatile energy source. It can be burned in the motors of CHP plants to produce electricity and heat, as is already the case in more than 5,000 biogas plants in Germany. Biogas can also be processed to upgrade it to the quality of natural gas. This can be done using various chemical-physical purification processes, which essentially involve removing carbon dioxide and hydrogen sulphide from the raw biogas.

The product of this is a biogenic gas with a methane content of 96 to 99 percent. This gas is very similar to natural gas, and is therefore suitable for injection into the natural gas grid. Called biomethane, it has the advantage that it is not a fossil fuel, and is therefore renewable. It is produced from energy crops and grass as well as liquid and solid manure, which are fermented in biogas plants.

Diverse applications

Injecting biomethane into the natural gas grid is wise wherever waste heat from a CHP plant cannot be used in a biogas plant. To make injection into the grid viable, the biogas plant merely has to produce a minimum amount of gas. The presence of a suitable gas line near the plant is also important.

Once injected into the natural gas grid, the biomethane is withdrawn at another location, for conversion into electricity and heat in a CHP plant some distance from the biogas plant. It can also be used for gas-fired central heating in detached homes or apartment blocks. Another option is to use the biomethane for filling gas-driven vehicles at natural gas/biogas filling stations, enabling CO₂ -neutral mobility.

Pure biomethane

Germany currently has two biogas filling stations for pure biomethane fuel. The first was built in Jameln/Wendland, in Lower Saxony, and the second is located near a sewage treatment plant in Bottrop, in the Ruhr area of North Rhine Westphalia. A third is soon to be taken into operation in Dannenberg/Wendland. Of around 900 natural gas filling stations in Germany, over 100 offer a blend of natural gas and biomethane containing up to 20 percent biomethane.

A total of 70 biogas plants will be injecting into the natural gas grid by the end of 2010, the first of which went into operation at the end of 2006. The total biogas processing capacity will then be around 50,000 standard cubic metres per hour. A capacity of 8,000 full load hours per processing plant will therefore allow around 400 million cubic metres of biomethane per year to be injected into the natural gas grid.

This only equates to 0.4 percent of annual natural gas consumption in Germany. However, the German government’s objective is to cover ten percent of natural gas consumption from biomethane by 2030. This is an ambitious target, as it will require approximately 120 biogas plants capable of injecting biomethane into the grid to be built each year. The fermentation power plants necessary for this would correspond to a plant size with an electrical power output of one to two megawatts.

Injection quality unproblematic

At the current construction speed of biogas injection plants, this objective is unattainable. There are too many obstacles to injection, many of which have been created by the gas industry, despite the fact that injection does not cause quality problems. For this reason, the German Biogas Association has long been calling for a Renewable Gas Injection Law (EGE), which would regulate unhindered access to the gas grid at fixed feed-in tariffs for biomethane. Only then can the objectives set by the German government be reached and climate protection goals be fulfilled.