The initiative at InBev's brewery in Magor was supported by the Unite union and the Carbon Trust.
The project was driven by employees at all levels who worked with other departments to identify areas for energy and resource savings.
The brewery has cut carbon emissions and water use by nearly half "an impressive statistic" from a company that used 35,000m3 of water per day and produced 50t of carbon dioxide, according to the Welsh Assembly environment minister Jane Davidson.
"The work carried out to reduce energy consumption and carbon emissions at this brewery is truly impressive ... it has resulted in millions of pound savings for the company," added Davidson. "I know that the project has engaged, and relied upon people from all levels of the organisation to identify where energy savings can be made, and I am sure this has been key to its success."