Member of engineering association proweps GmbH (proweps.com)
Biogas is produced in anaerobic digestion plants from organic waste. The composition of biogas depends on the type of organic waste that is treated, and the methane concentration of biogas can vary between 55 and 75 Vol.-%. The other essential component in biogas is CO2 with a concentration in a range of 24-44 Vol.-%. There are still up to 2 Vol.-% other components in biogas such as oxygen, nitrogen and hydrogen.
It’s basically advisable to use substrates that produce during anaerobic digestion process biogas with the highest possible methane content. The energetic recovery of biogas can be carried out in various ways e.g. for the generation of electricity and heat in CHP-plants. But biogas utilization in CHP plants makes only sense if the produced heat can also be used. Otherwise the energy efficiency and the economics of biogas utilization is poor. Therefore, the most economical type of biogas utilization must be reviewed and defined for each project.
In many projects it makes sense to further process biogas by separating CO2 and to produce bio natural gas, or so called biomethane. With an efficient biogas upgrading technology > 99% of the methane contained in the biogas is obtained and the biomethane produced usually has a methane concentration higher than 98 %. This makes biomethane a quality comparable to natural gas.
On the market, various biogas upgrading technologies are available. A biogas upgrading technology includes mainly following components:
1. Biogas cleaning
2. Pressure adjustment
4. Biomethane drying
5. Exhaust gas treatment
The quality requirements for the composition of biomethane are already or are currently being regulated by law in many countries. Thus, the general conditions for the design of the biogas upgrading systems are clear.
Biomethane can be fed into natural gas networks and taken back from other locations for optimal energy recovery:
The different technical steps of the value chain from biogas to biomethane production and grid injection into natural gas grid:
A very interesting option is also the use of biomethane as fuel for vehicles (buses, cars, trucks, ships) to substitute the use of fossil fuels as diesel. Thus, not only the emissions of CO2 but also of other pollutants as fine dust, nitrogen oxides are drastically reduced. Fuel types are either bio-CNG (compressed biomethane) or bio-LNG (liquified biomethane). Bio-CNG is traditionally used for cars and buses whereas bio-LNG is used for heavy duty trucks and ships.
Our activities include the planning of new plants as well as integration of biogas upgrading plants in existing anaerobic digestion plants.
We support our customers in the planning and realization of biogas upgrading systems in many ways. These include:
• Feasibility studies for technology selection
• Clarifications of interfaces to anaerobic digestion plant and to natural gas grid operator
• Tender documents for technology procurement
• Supplier bid evaluation
• Preparation of documents for approval procedures
• Supervision of installation and commissioning