What is biogas?

Biogas is a mixture of gases produced by the fermentation of organic biomass. Organic waste like biodegradables, wood, manure, sewage sludge, corn, grass, etcetera is broken down by anaerobic micro-organisms. During this process a mixture of chemical compounds is released. This is a natural process and therefore these biogases are considered a renewable energy.

Composition

The main components of biogas are Methane CH4 and Carbon Dioxide CO2. They make up about 95% of the biogas mixture, but the composition of the components can differ. Other components of biogas are Nitrogen N2, Hydrogen H2, Hydrogen Sulfide H2S, and Oxygen O2. Of these components Hydrogen Sulfide gives biogas its typical, egg-like, smell. Depending on which materials are used for the fermentation process the composition of biogas differs. Like for instance household waste produces less Methane than wastewater sludge or agricultural waste. The gas created by household waste is richer in Carbon Dioxide. In general, the composition of biogas looks like this:

Methane:                           60-65%

Carbon Dioxide                 30-35%

Nitrogen                              0-5%

Hydrogen                           0-2%

Hydrogen Sulfide             0-2%

Oxygen                                0,5-1%

Since Methane and Carbon Dioxide are both strong greenhouse gasses, harvesting these gasses for energy has double the effect on the improvement of our environment. On the one hand these greenhouse gasses are not emitted into the ozone and on the other hand energy does not have to be generated by more conventional, polluting, energy sources, such as coal, lignite, petroleum, or natural gas. A win win situation for biogas!

Storage

Biogas is often generated in large tanks, called digesters or biogas plants. Here the composition of the biomass is mixed, stirred, and heated, to create an optimal environment for the micro-organisms. The digesters are sealed air tight, in order for the anaerobic fermentation to take place. The gases that are released  in this process are captured in these digesters. This happens in special made roofing systems. A double membrane made from Poly-Vinyl-Chloride (with a reinforced polyester textile) is fitted over the digesters. The inner membrane expands when the gas is produced, while the outer membrane is always kept on pressure. This membrane shields the inner membrane from the influences of the weather. Special air in- and outlets regulate the air pressure between the two membranes. These entire roofing systems is what Membrane Systems Europe BV, or MSE for short, specializes in!

When extracted it can either be stored, or directly generated into heat, electricity, or used as fuel. A current trend in  the Netherlands is the transitioning from biogas to green gas. This process requires upgrading the energy levels and some purification of the gas, in order to meet the standards for natural gas.

Rise of biogas

In 2018 the worldwide production of biogas was 1360 petajoule, 0,2% of our total energy consumption that year. The usage of biogas is rising however. In the Netherlands 12.5 petajoules were generated in 2019, while in 2020 this number rose to almost 14 petajoules. The energy transition is a very hot item these days and switching from fossil fuels to renewables is essential to reach the Paris Climate Agreements. The role of biogas in this process is getting bigger and bigger, and MSE is proud to be a part in reaching a greener future!