A farm owner has been fined £145,000 for serious safety failings following a fatal accident at work involving a worker who was exposed to deadly hydrogen sulphide gas. The owner pleaded guilty to breaches of the Health and Safety at Work etc. Act 1974 at the Dorchester Crown Court. The worker had died after lifting the roof of a digester tank at an anaerobic digestion (AD) plant in Dorset.

A digester tank is a sealed unit which contains organic matter and bacteria. The bacteria, acting without oxygen, breaks down the organic matter and produces a mix of methane and carbon dioxide known as ‘biogas’. When sulphur-based matter decays it naturally produces hydrogen sulphide gas. This gas is toxic and highly flammable. If a large concentration is inhaled it can cause collapse and even death.

The man and his colleague had opened the tank to free a stirring mechanism when they lost consciousness. Despite his colleague returning to consciousness and raising the alarm, the worker was pronounced dead at the scene. Two paramedics and a further 2 farm workers were affected by the fumes.

An investigation by the Health and Safety Executive (HSE) revealed that there were several unsafe practices used at the AD plant. Workers had not been trained to properly remove the roof of the digester tank. HSE inspector Annette Walker commented that the risks related to the toxic hydrogen sulphide gas were “well known”.

The inspector also added: “What has happened at that farm demonstrates the important of having safe systems of work in place, particularly for maintenance and repair work where the risk of exposure is likely to be highest.”

Most shockingly of all, the investigation revealed that an incident of a worker losing consciousness at the same plant in the previous year had not been reported. Had this been dealt with correctly at the time, safety procedures would have been in place to possibly prevent this fatal accident.