The Environment Agency prosecuted the business for sending waste such as used nappies and food packaging to China. The export of unsorted household recycling waste from the UK to China has been banned since 2006.
After a three-week trial, a jury at Wood Green Crown court found Biffa guilty of two breaches of the law in May and June 2015.
While paper can legally be sent to China, heavily contaminated other waste cannot. The jury did not accept Biffa’s version of events that the consignments leaving its depot in Edmonton four years ago complied with the law because they comprised of waste paper.
Investigators gathered evidence at Felixstowe port that clearly identified the contents of seven 25-tonne containers bound for China as including glass, plastics, electrical items and metal.
Environment Agency officers searching the cargo found items ranging from women’s underwear, shoes and socks to plastic bottles, metal pipes, video tape, toiletries and electric cable.
The nappies and sanitary towels gave off a pungent “vomit-like” smell, according to Environment Agency officers.
Jurors heard that Biffa used two brokers to act as intermediaries to manage the deal to send the waste to two delivery sites in Shenzhen and Guangdong on the South China Sea coast.
The first broker took up a request from a Chinese client in April 2015 to arrange shipment of 5,863 tonnes of mixed waste paper by contacting Biffa. A price of around £350,000 was agreed for the export, due to take place the following month.
At the same time, Biffa agreed with a second broker to ship 4,992 tonnes of mixed paper in a contract worth almost £290,000.
The Environment Agency prevented any of the seven containers from leaving Felixstowe.
Sarah Mills, an enforcement manager whose team investigated the breaches for the Environment Agency, said: “Our officers found anything and everything in Biffa’s containers at Felixstowe. They were marked as waste paper, but contained a totally unacceptable level of contamination with other waste.
“The regulations around shipment of waste were brought in to stop the West merely passing the problem to other countries. It was commonplace in the 1970s and 1980s for developed nations to send vast amounts of waste abroad.
“The waste contained offensive material likely to have been discarded by the receiving country, at great risk and cost to the environment and people.”
Sentencing has been deferred until 27 September and the court was told the Environment Agency and Biffa had agreed a figure of £9,912 to be paid for proceeds of crime.
Biffa said it was "very disappointed" with the outcome of the case and that it is "considering its position and grounds for appeal".
“At the time of the case we supplied a vital raw material to China to be recycled in an environmentally sound manner as an alternative to forestry,” the company said in a statement.
“The materials we supplied commanded market-leading prices and met both international industry and customer standards.”
Speaking to BBC Radio 5 Live’s Wake Up to Money programme yesterday (26 June), Recycling Association chief executive Simon Ellin said: “One of the big problems we have with the judgement is that we have repeatedly asked the Environment Agency to work with industry to develop quantitative standards so that we know where we stand.
“The rules pertaining to export are so vague and so undefined that we don’t know what the rule is and what the law is. I’ve been in the industry 30 years and I still couldn’t tell you what an acceptable specification for export of material is.
“This exact same material, with exactly the same spec, is going into UK mills with no problem whatsoever and the Agency are not interested in that at all, it’s just the obsession with the material that’s exported.”