The Health and Safety Executive have recently reported that a company which produces electricity from food waste by anaerobic digestion, has been fined more than £300,000 after an explosion caused two employees to suffer life changing injuries.
What Is Anaerobic Digestion?
Anaerobic Digestion is a natural biological process where organic material, from, in this instance, food waste, is broken down by bacteria.
It is similar process to composting but differs in that it takes place in sealed, oxygen-free tanks to produce biogas (methane) that can be used to generate electricity and heat.
Currently, much of the UK’s biodegradable waste is sent to landfill, where it breaks down to release methane which is then released into the atmosphere.
Understanding Methane
Methane is a molecule composed of one atom of carbon and four atoms of hydrogen: CH₄. It is the most abundant of the reactive trace gases, those formed and/or degraded by chemical reactions in the atmosphere.
CH₄ is the main component of natural gas. It is invisible and odourless but often associated with a strong smell, because the main natural process generating this gas is fermentation of organic matter. When we “smell natural gas” at home, it’s the result of a harmless additive included by gas providers to help detect gas leaks.
Methane is highly flammable. Its flammability range in air is 5–16% by volume. This means that if we have an atmosphere which is 95% air and 5% methane, and a spark is added, then it’s extremely likely that there will be an explosion.
The Incident: What Happened
On 20 September 2017, at the company in question, two workers were using a grinder to cut and replace pipework at the top of an 11-metre-high metal tank containing waste slurry. They were working in a mobile elevating work platform (MEWP) and were not using harnesses.
Sparks from the grinder ignited flammable gas (methane) causing the tank to explode. The metal tank the two men were working on was projected high into the air before crashing to the ground nine seconds later.
The Injuries
One worker was flung out of the MEWP into the air and landed on the ground in the slurry around the tank with serious back, neck and torso injuries. The other worker was thrown into the air and landed back in the basket of the MEWP. Following the incident, his leg was amputated, and he is now in a wheelchair.
HSE’s Statement
After the prosecution the HSE stated:
“This incident resulted from fundamental and multiple failings by the company to properly manage its health and safety risks.
These included failing to ensure that the design, installation and use of the tanks were safe; failing to carry out risk assessments; failing to put in place a safe system of work; and failing to train and supervise employees.”
Recurring Safety Failings We Still See Today
After over thirty years of training users of compressed and liquefied gases we still come across organisations who:
- Don’t have risk assessments covering all areas where gases are handled, stored or used
- Don’t have detailed method statements or systems of work covering the safe use of gas cylinders
- Don’t have detailed inspection regimes covering gas control equipment (regulators etc)
- Fail to utilise hot work permits
- Fail to train their staff in the safe handling, storage and use of gases
Need Help With Gas Safety?
If you believe that your organisation may require some assistance with any of the above bullet points or other compressed gas safety training, then please contact us on 01270 758890 or email us at admin@gassafeconsultants.co.uk.
