*2.1. Biogas and Biomethane Boiler*

Steam is often used in industry as a heat transfer medium. In order to be able to provide steam safely and continuously, a complex plant structure consisting of burner, boiler, water treatment, condensate treatment and pumps is required, mostly economisers and, if necessary, other thermal apparatuses with the respective control technology are necessary [26]. The efficiency of a steam system depends on numerous factors due to its complexity. The main factors contributing to the reduction in efficiency are flue gas losses through the chimney, desalination and blow down losses during regeneration of the boiler water, radiation losses over the boiler surface and ventilation losses when starting the burner [27]. The part load efficiency of natural gas and Biogas and Biomethane Boiler (BGB) varies between 94% and 95% with an economiser. For substituting natural gas, biomethane or biogas can be used for firing the boilers. In case of biogas a specific burner is necessary. Biogas must be used at the place of production or in the immediate vicinity. Biomethane, on the other hand, is fed into the public gas grid. Biomethane is produced by upgrading biogas. In a number of process steps all components other than methane are separated from the gas mixture. Before being fed into the gas grid, further steps can be taken to achieve local feed-in requirements [28]. If biogas is not available, the switch to biomethane offers a convenient option for users of natural gas to reduce *CO*2,*<sup>e</sup>* emissions

regardless of the place of production of the biomethane. For this purpose the quantity of gas or energy withdrawn must be measured and balanced by the feed-in of biomethane into the grid.
