Stewart Brown, aged 69, of Fernwood Close, Forest Town, was found guilty of failing to take reasonable care for the health and safety of others, who might be affected by his acts or omissions at work.
He was cleared of two counts of gross negligence manslaughter over the deaths of 19-year-old Nathan Walker and Gavin Rawson, 35.
The men died in December 2016 following the incident at Greenfeeds, Normanton, Leicestershire.
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The company produced bio-fuel and pig feed from recycled products which were then delivered using road haulage tankers.
The court heard that on the afternoon of December 22, 2016, Mr Walker, a member of yard staff at the company, climbed into a tanker to clean it after it was found the tanker could not be fully emptied of the pig feed.
Tragically, he got into difficulties and when he shouted for help, Mr Rawson dashed over to help.
He climbed inside the tanker and tried to haul Mr Walker to safety, but both men became overcome by the fumes and collapsed.
They were found face down in the liquid after a saw was used to cut holes in the tanker. They were pulled out and resuscitation attempted, but both died at the scene.
A post-mortem examination concluded they died as a result of drowning in the animal feed.
Health and safety
An investigation by Leicestershire Police and the Health and Safety Executive found Greenfeeds had no adequate health and safety procedures in place to govern the cleaning of their tankers.
A method of cleaning the tankers which involved an employee entering the tanker with a power washer while another acted as a spotter and held the hose pipe connected to the power wash had been allowed to develop at the company.
The cleaning of the tanker on December 22, 2016, had been carried out at the direction of Gillian Leivers, who owned the company with her husband Ian, and Brown, the transport manager in charge of the yard.
Leicestershire Police said the cleaning method had no proper risk assessment, there was no method statement for entering the tanker or for getting someone out and no provision of breathing apparatus or personal protection equipment.
Enquiries found staff had raised concerns regarding the dangerousness of the cleaning method, but they had been ignored.
Following a six-week trial at Leicester Crown Court, Greenfeeds, which admitted failing to ensure the health and safety of its employers, was found guilty of two counts of corporate manslaughter.
Gillian Leivers, 60, of Fosse Road, Newark, was also found guilty of two counts of gross negligence manslaughter and both her and husband Ian, 59, were found guilty, as Greenfeeds directors, of a Health and Safety breach in that the company’s offence was attributable to their neglect.
They have all now been sentenced for their part in the tragedy.
Brown was jailed for a year, suspended for two years, while Ian Leivers was jailed for 20 months and banned from being a company director for 10 years.
Gillian Leivers was jailed for 13 years and banned from being a company director for 15 years, while Greenfeeds, which is now in liquidation, was fined a total of £2 million.