Composition and use of biogas
Methanization, namely the digestion of organic matter (decomposition of vegetal or animal matters) or of household waste without oxygen produces a gas called biogaz. This is a mixture of methane (CH4) (typically between 50 and 70%), carbon dioxide, hydrogen sulfide in low proportion (which is responsible for the smell of this gas) and of water vapor in variable concentrations . Biogas can be produced naturally in the atmosphere, particularly in swamps and wastelands. It is also artificially synthetized in digesters notably during waste water and sludges treatment. It is also found in the food industry.
The institutions have been focusing for several years on biogas as it is part - according to the international climatologists - of the global climate change of these last years. In France, since the release of the order of the 9th september 1997 order, the recycling of biogas in wastelands is mandatory. Biogas recycling is interesting for the ecology as it can be an alternative to fossil fuel power. Thus, the economic activity linked to biogas is under development: 214 production sites in 2012 against 848 at the end of 2013. If it is not recycled, it has to be burn by flaring. The main reasons for its recycling or removing are its toxicity, its explosivity and its large volume.
Biogas properties and effects on health
Because it is mainly composed of methane, biogas is a combustible gas, but it is also a toxic gas as there is a presence of hydrogen sulfide, and a corrosive gas too. The digestion process envolves bacterias and particles action that can lead to various effects on humans.
Eyes (conjunctivitis)and nose (colds) irritations, as well as nauseas are symptoms of high level exposure during a short period of time. A chronic exposure does not lead to death but to organ faillures like the brain (headache and chronic fatigue) or the digestive system (abdominal pains and nausea). When all basic precautions linked to the activity around this gas are taken, the risks for humans are quite inexistent.
Prevention and protection means against biogas
- As biogas is explosive, a 4-gas detector like the X-am 2500 portable gas detector enables biogas concentrations monitoring
- In order to get an accurate analysis of the biogas concentrations variations, the use of a specific equipment, a biogas analyzer, like the Biogas 5000 shall be prefered to a traditional gas detectors (fixed or portable) that will no be able to monitor such important concentrations
- As biogas contains very high H2S concentrations (sometimes up to 10.000 ppm) and asphixiant gases (such as CH4 or CO2), an air purifying protective mask is not suitable and it will be necessary to get an atmosphere supplying respiratory protective equipment (self-contained breathing apparatus or airline system)