More than an explosion hazard
Methane in biogas can form flammable mixtures. Carbon dioxide and hydrogen sulphide may also be present, creating asphyxiation or toxic hazards. Composition depends on the process and incoming materials; it should not be assumed that all gas produced always has exactly the same characteristics.
The assessment covered by Explosive atmospheres is complemented by mechanical, electrical and thermal risks. Pumps, agitators and conveyors can entangle people, while hot pipes and equipment can cause burns. Tanks and lagoons introduce falls and drowning hazards, even where a surface appears stable enough to support a person.
Control process deviations
Design needs to consider leaks, abnormal pressure, equipment failures and loss of auxiliary services. Instruments, alarms and protective devices require maintenance and checks appropriate to their functions. The presence of a relief valve alone does not establish that an overpressure scenario remains controlled throughout operation.
Material storage, transfer and digestate management require suitable containment and access. A spill can affect workers, drains and surrounding areas. Changes to feedstock or capacity should be reviewed for their effects on the process, emissions and working conditions before they become routine operating arrangements.
Maintenance and equipment access
Unblocking a pump or repairing an agitator requires consideration of energy, pressure and material entering from other parts of the plant. The intervention must be coordinated with operations and use a procedure that controls these connections. Stopping equipment through a control screen is not equivalent to safe isolation.
Tanks, pits and similar enclosures may contain hazardous atmospheres even when partly empty. Entry should be avoided where an alternative exists; necessary entry requires a specific confined-space system of work. Assessment includes supervision, equipment and rescue arrangements, never an improvised entry to assist a colleague.
Organise the response
Employees and contractors need to understand alarms, restricted areas, responsible contacts and expected actions. Work producing sparks or heat requires specific ignition-risk controls. Ventilation alone does not authorise any repair on equipment or pipework that has contained biogas or remains connected to the process.
The emergency plan needs current information about equipment, gases, access and technical contacts. Loss of containment and subsequent recovery should also be anticipated. Overseas references offer technical guidance; environmental permits and occupational safety obligations must be determined for the installation’s own location and activities.
