Stobart Energy, a subsidiary, will provide 270,000 tonnes of waste wood a year for 15 years to a yet-to-be built energy plant in Tilbury Port, Essex.
The £175m contract between the Group and Tilbury Green Power will begin in March 2017.
The Danish construction company Burmeister & Wain Scandinavian Contractor A/S will build the biomass facility.
The plant will produce 40MW of energy a year, enough for 70,000 homes, and will create 50 full-time jobs upon construction.
Stobart Rail will also be constructing its own £7.5m waste wood processing facility next to the plant.
Stobart Group has finalised similar supply contracts in Rotherdam, Margam in South Wales, and Widnes in Cheshire since late November 2014. The Tilbury Port deal pushed the Group to the completion of its supply goal of two million tonnes of biomass per year by 2017-2018.