Appearing before St Albans magistrates in November, John Hibbert, of Hatfield, Hertfordshire, admitted dumping the containers, contrary to section 33(1)(a) of the Environmental Protection Act 1990. Sentencing was deferred until 2 February, when he was jailed.
The hazardous waste was derived from a process known as diesel stripping which involves "blackening" low-duty red diesel - a fuel for off-road use.
The case came to light when Mr Hibbert appeared as a witness for John Scott, a registered waste carrier who was prosecuted in September for allowing his vehicle to be used for the fly-tip on 13 June 2002.
Mr Scott was fined £300, plus a further £200 for failing to comply with a notice asking who was driving his vehicle at the time. He was also ordered to pay £500 costs and £1,000 compensation.
The court heard how a member of the public saw 14 containers dumped near a road at Wheathampstead. After witnessing a lorry leaving the site he noticed that four more containers had been dumped.
The emergency services were contacted due to the hazardous nature of the chemicals, which included diesel oil, sulphuric acid and contaminated charcoal.
Much of it had leaked out of the containers and had to be dug out of the ground in a two-week operation. The cost - £30,000 - was split evenly between the Agency and Lafarge, who owned an expired landfill site adjacent to the site.
On the same day as the fly-tip an Environment Agency officer questioned a man changing a lorry tyre by the side of a road in Hatfield.
A passing policeman stopped to assist when another man, Mr Scott, approached and admitted he owned the lorry. The lorry was the same one spotted at the fly-tip site.
During Mr Scott's court appearance, Mr Hibbert was called as a defence witness and inadvertently admitted under oath that he had driven the lorry involved in dumping the four containers.