The feeding of upgraded biogas (“biomethane”) into the natural gas grid offers an efficient and flexible energy solution, allowing the use of energy from biogas in areas located far away from where the energy is generated.
For the production of biomethane two kinds of technologies are available:
Typical feedstock for fermentation is animal manure, organic household waste, energy crops, food residues and food processing industries. As one result of the fermentative process, biogas emerges as a metabolite with a methane content of 50%-70%. This raw biogas needs to be upgraded before in can be injected into a natural gas grid. The upgrading mainly consists of drying the gas and removing hydrogen sulphide (H2S) as well as carbon dioxide (CO2).
The most common methods include gas pressure washing, pressure swing adsorption (PSA), as well as separation and permeation processes based on selexols and membranes. This is done up to a level that meets gas quality standards for natural gas which differ throughout Europe.
Typical biomass used is dry biomass, especially wood. Through gasification “syngas” is produced, which consists mainly of hydrogen (H2) and carbon monoxide (CO). After methanisation and gas cleaning a gas can be produced that meets the gas quality standards of the natural gas grid.
Fermentation is the technology applied most.
Biomethane can be used for any purpose currently satisfied by conventional natural gas. The most important fields are:
- heat generation
- cogeneration heat/power
- natural gas vehicles
Situation in the EU
Due to its multiple advantages biomethane is becoming more important on the political agenda and as a business opportunity in various EU Member States.
Biogas will significantly contribute to reaching the EC targets for renewable energies by 2020 with biogas feed-in representing a very efficient option and an attractive alternative to highly debated biofuels in the transportation sector.
The EC has asked Member States to take position in their Renewable Energy Actions Plans while also sustainability criteria apply for biomethane as vehicle fuel.