Robert Clarke, 65, from Swallownest, and Joanna Nkusia, 35, of Saville Street, Dalton, Rotherham, were each fined £100 and ordered to pay £750 costs.
They were charged with environmental offences related to the running of two sites by their company, Used Tyre Exports.
The couple came to the attention of the authorities in March 2009 when an Environmental Agency officer visited their premises on Vicarage Road.
The inspector found around 4,000 worn tyres on the site - four times as many as the maximum 1,000 tyres they were permitted to store.
The couple agreed with the council that they would clear the site by May that year, but by then there were around 8,000 tyres on the site.
Following an anonymous complaint in January 2010, officers visited another site on Deep Lane, finding 5,000 to 7,300 old tyres. By the next time they visited, a month later, there were up to 9,500 tyres.
Paperwork obtained by the Environment Agency also showed two shipments of tyres to Cameroon in May and June 2009 when the couple did not have permission. Nkusia admitted she knew the limit on how many tyres she could store.
In their defence Nkusia claimed that the tyres had tread that is legal in the UK, so they were not classed as waste, but this was rejected by the court. Clarke said he simply helped out voluntarily but had no control in Used Tyre Exports’ waste operation.
The district judge found he was as responsible as Miss Nkusia.
The judge said he accepted the business had not brought them riches, and they would have been much better listening to the Environment Agency when they first visited.