It followed local residents complaints to the Environment Agency about offensive smells coming from the companys Chertsey composting site.
WRG admitted to breaching conditions of its waste management licence by causing unnecessary odours from processing compost on May 17 last year. In addition to the fine, it was also ordered to pay costs of £2,612.34.
The site has been the subject of odour complaints in the past from residents in Lyne, Thorpe, Thorpe Green, Chertsey and Virginia Water. However, the Chertsey site is due to close later this year.
An agency inspection revealed failures in the companys plant and equipment had led to the odour complaints. Environment officers also found that the companys odour suppression system designed to neutralise the smell caused during the decomposing process as organic material breaks down into compost was not functioning.