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Precautions to be taken while handling Biogas

Anaerobic digestion systems and associated Substrate storage and handling present many safety hazards. Didask Bioenergy with its state of the art designs is concerned with safety from the very beginning of any digester project. Didask Bioenergy has excellent knowledge about and is sensitive to the safety needs of workers and visitors around a biogas system.

Safety First

Extreme caution is necessary when working with biogas. Adequate ventilation, appropriate precautions, good work practices, engineering controls, and adequate personal protective equipment minimize the dangers associated with biogas. Digester associated tasks and maintenance is performed in such a manner that nobody should enter confined spaces, including pits. Systems are initially designed so that confined space entry is not required to perform maintenance.

Biogas Hazards
Explosion & Fire

Methane constitutes 0% to 80% of biogas and forms an explosive mixture in air, the lower explosive limit being 5% methane and the upper limit 15% methane. Biogas mixtures containing more than 50 % methane are combustible, while lower percentages may support, or fuel, combustion. Hence, no naked flames should be used in the vicinity of a digester and electrical equipment must be of suitable "explosion proof" quality. Other sources of sparks are any iron or steel tools, power tools particularly motor comutators and brushes, normal electrical switches, mobile phones and static electricity. The other constituents of biogas namely Hydrogen sulfide and ammonia are also potentially explosive gases.

Negative pressure should never be allowed in a biogas system. Negative pressure occurs when the force created by the weight of the gases outside the biogas system is greater than the force inside the system. In normal operations the pressure inside the system should always be greater than the outside pressure. Negative pressure will pull air into the biogas system and the mixture of biogas and air might explode. If that does not happen, the oxygen in the air will kill the biogas bacteria and the gas production rate will drop.

When biogas is used at pressures below one column inch of water as measured on a pressure gauge, it is very likely that the flame will go out. Even though there is not much gas left in the system, biogas will continue to come out. Then the possibility of a spark or flame causing an explosion in the room or negative pressure pulling air into the biogas system causing an explosion in the system becomes a reality.

When opening a biogas digester for cleaning or repairing, no use of candles or cigarettes should be made. For light inside the digester, a flashlight should be used. Due to the explosion hazards, no open flames should be ever used near a digester. Equipment such as engines and electric generators should be such that a spark will not ignite the gas. Explosion-proof equipment and non-sparking tools should be used around digesters and biogas. No smoking should be permitted near the digester or related biogas lines and equipment.

If conducting a flammability test a small sample is taken well away from the main digester, or a flame trap is incorporated in the supply line, which is of a minimum 20 m length distance from the digester.

Asphyxiation or Suffocation

Asphyxiation or suffocation from biogas is of grave concern in an enclosed space where manure is stored. Even open-topped manure pits can generate methane at a sufficient rate to depilate the air above the manure and render the space oxygen-deficient.

Entry should be permitted to authorized personnel only, to a facility where manure is stored or where there is a suspected biogas leak as natural ventilation cannot be trusted to dilute the explosion hazard sufficiently. Airing out a facility does not impart safety, as some of the gases produced are heavier than air. If a person is found unconscious in such a facility, the personnel should not enter the facility; instead emergency services should be contacted so that firefighters equipped with self-contained breathing apparatus (SCBA) can safely retrieve the victim.

Disease

Animal manure contains bacteria, viruses and parasites. Biogas is generated by the anaerobic digestion of manure, which occurs because of the bacteria present in animal wastes, some of which can produce infection. When handling waste material, appropriate precautions should be taken by the usage of personal protective equipment to avoid contact with manure. Thorough washing after working around the digester is recommended. It is particularly recommended to wash hands before having food and or coming in contact with any mucous membranes or touching the eyes. Keeping the digester facility clean will reduce disease hazards as well as the spread of odors and fly populations in the digester facility.

Main Components of Biogas

Biogas consists mainly of 60% methane and 40% carbon dioxide, with low levels of hydrogen sulfide and other gases such as ammonia. Each of these gases can displace oxygen.

Methane

Methane is lighter than air and will collect toward the upper spaces of the storage area. It is explosive at 5% to 15% concentrations. While methane is not a toxic gas, it displaces air so that, in a confined space, it creates an oxygen-deficient atmosphere which can lead to breathlessness and suffocation.

Carbon Dioxide

Carbon dioxide is an odorless gas that is heavier than air. In a dormant space, carbon dioxide can layer near the floor. Slightly elevated levels of carbon dioxide increase heart rate and respiration rate. Higher levels displace oxygen supply in the bloodstream, which can cause unconsciousness and at times even death.

Hydrogen Sulfide

Hydrogen sulfide is a highly toxic gas that is heavier than air. At very low levels, it smells like rotten eggs and can produce eye irritation. At dangerous levels, it destroys the sense of smell and produces respiratory paralysis. Thus, at dangerous and very high levels, a person can literally drop dead and there would be no odor to warn of its presence.

Ammonia

Ammonia is a gas that is lighter than air, has a pungent odor, and can irritate the eyes and respiratory tract. Ammonia can displace oxygen in the bloodstream.

Precautions
Warnings regarding equipment usage

Failure to take heed of warnings cautioned by Didask’s Engineering team may result in serious injuries and at times even death.

Safety Walk-Through

A safety walk-through can help determine potential hazards and take preventative measures. It is intended to be used by plant managers or staffs who are responsible for the operations and maintenance of anaerobic digesters and their related processes. The walk –through provides an idea about the typical potential hazards for digester systems and the associated preventive measures can then be taken with the guidance from Didask’s Engineering team.

Gas Sensors

Explosion, suffocation, and poisonous gas hazards can be detected using gas sensors. Electronic sensors need testing regularly to ensure its accurate working, and these sensors may have a disposable component that needs periodic replacement.

Personal Protective Equipment

An area where manure is stored should never be entered without the appropriate personal protective equipment, which may include a self-contained breathing apparatus also known as SCBA.

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To create environmental sustainability and energy independence through the growth of the biogas industry thus reducing the dependence n fossil fuels.

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Biogas is the one of the only technologically fully established

renewable energy source that is capable of producing heat, steam, electricity, vehicle fuel and other valuable byproducts. It is, in the true sense of the word, a dynamic energy source. Biogas has become a fuel to be looked forward to. This growth has begun over the last two decades.

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