The firm at the centre of an ongoing smells row has been handed a penalty of almost £25,000.
Omega Proteins, of Swalesmoor Road, Halifax, admitted twice failing to comply with environmental permit conditions.
The offences occurred in April 2010 after environment officers responded to nearby residents’ complaints of foul stenches.
Zara Pedelty, prosecuting on behalf of Calderdale Council, said an environmental officer visited the site on April 12 to find a strong smell of rotting animal meat.
He returned next day with another officer to find decomposing animal carcasses being scraped off the ground by a digger and pushed into a shed.
Calderdale magistrates heard the shed was so full the door would not close, leaving a gap of one metre between the door and the ground. Officers also found a total of 21 skips, of which 10 did not adequately contain the decaying meat.
Two of the skips were leaking, with liquid sitting on the yard floor.
Another skip was overflowing with carcasses and several more were uncovered so that animal by-products could be seen.
The firm had already been given a caution in January 2010 following a breach in August 2009.
Rob Rode, defending, said an incinerator had broken down which had caused a backlog of material, and that one member of staff had been dismissed for gross misconduct following the incident.
The magistrates described the lack of maintenance of the skips as “deplorable” and said the incidents occurred because of a system failure rather than one person’s mistake.
A spokesman for Leo Group, which owns Omega Proteins, said: “The two charges related to a breach of permit when skips were inadvertently left temporarily uncovered on site in April 2010.
“This was a matter of simple human error and not a deliberate action.
“However, as the company is liable for the actions of its employees, we pleaded guilty at the earliest opportunity so as not to waste any court time and money.
“It was an unfortunate incident and one that had not occurred before nor been repeated since.
Graham Fawthrop, speaking on behalf of the Swalesmoor Action Group, said: “This evidence in court is the tip of the iceberg.
“Residents of Queensbury and the surrounding districts have been complaining frequently especially over the last few years about the stench from this facility and the spillages over our roads from the Leo group wagons.
“It’s making Queensbury and the surrounding district a regular stinking hole which we should not have to suffer if they were to operate good working practices, which was evidently not the case.”
The company was ordered to pay a fine of £20,000 and £4,500 in legal costs.