A spill at Biogen’s anaerobic digestion site in Clapham was the result of the company not following its own procedures, Luton Magistrates Court heard yesterday June 18).
Claire Corfield, prosecuting for the Environment Agency, told the court there had been a series of errors on June 11 2012.
The company, which operates from Twinwoods Farm, Oakley Littlewood, Clapham, pleaded guilty to breaching its permit and was fined and ordered to pay costs totalling £8,700.
The company asked for a second offence concerning failing to report the incident without delay to be taken into consideration by the court.
Mrs Corfield told the court that on the day of the incident, electrical work was undertaken to the new separator situated between two digestate storage tanks. Following this work, a company operative turned an isolator switch back on re-starting the pumped transfer of digestate between the tanks.
The site manager was unaware of this and forgot to do his close down checks at the end of the day.
Later investigations showed that the company had failed to follow a number of its procedures including close down checks and had failed to follow the safe systems of work and control of change procedures which meant that the necessary risk assessments were not carried out before electrical work was done to the new separator.
In addition, the procedures were inadequate, as there was no written procedure for the transfer of digestate between storage tanks, there was no system of planned preventative maintenance and visual checks of underground pipes were sporadic and not recorded. Before the incident, the company had identified various pollution risks at the site, yet had failed to adequately address them.
The result was two separate spills which were spotted on CCTV by the head of plant operations, who was monitoring the site from home and alerted the site manager.
The site manager went to the site and reported back that a storage tank was overfilled and about 350 cubic metres of digestate (a nutrient-rich substance produced by anaerobic digestion that can be used as a fertiliser) had overflowed onto the ground and there was a separate spill of 20 cubic metres of raw waste. It appeared that the spills had been contained on site by the bund. No alarms had been triggered.
Biogen’s permit authorises the acceptance and treatment of 47,500 tonnes of combined food waste and pig slurry per year. It also requires a written management system to identify and minimise risks of pollution.
Mrs Corfield said that Environment Agency officers were alerted to the site the following day by a complaint of bad smells from a member of the public and found a large amount of digestate covering the base of the compound. A surface water outfall pipe, from the site and neighbouring pig unit, was discharging a black effluent into the adjacent ditch which smelt of digestate.
Downstream a dam had been built and the ditch was being cleaned up. Fifteen hours after the spills were discovered, the company reported the incident to the Agency.
A company representative told investigating officers that the company had discovered that an underground pipe had fractured resulting in the spill of raw waste and that a transfer pump between two storage tanks had been left running unattended. He said they had notified the Agency as soon as they realised there might be a link between the spill and the levels of ammonia in the outfall pipe.
Mrs Corfield told magistrates that the company has a previous conviction concerning a pollution incident at the same site which occurred in 2010 and involved the spill of 300 cubic metres of digestate.
In addition, a similar incident had occurred at another anaerobic digester plant at Westwood in 2010 when an alarm failed and 1 tonne of digestate had gone into a ditch.
Digestate has the potential to cause a high degree of environmental harm if it gets into watercourses.
Digestate from anaerobic digestion plants receiving food waste and slurry is likely to contain grossly polluting levels of biochemical oxygen demand and ammonia.
After the hearing, Environment Agency officer Rob Jamieson said: “This case demonstrates the potential for adverse environmental impact resulting from an inadequate environmental management system and the failure to apply the controls within the management system ully.”