The invention relates to a method for producing energy, comprising the steps of 1) Burning of fuel in an internal combustion engine thereby producing mechanical energy and a waste gas containing carbon dioxide and water vapor, 2) Reducing the carbon dioxide and water vapour waste gas components in an environment containing organic material into a synthesis gas which contains carbon dioxide and hydrogen, and 3) Feeding the synthesis gas produced in step 2 to the internal combustion engine. To produce methanol, a methanol synthesis is introduced between steps 2 and 3 of the method set forth above.