A method of preparing a mixture of brewer's spent grain from different compositions of brewer's spent grain having different nutritional composition, flavour and colour, and wherein the mixture of brewer's spent grain is having a composition corresponding to a requested user input, the method comprises; - providing a plurality of receptacles, each receptacle comprises a brewer's spent grain, where the brewer's spent grain comprises independently of each other: ∘ one or more nutrients, a flavour and a colour; - providing a database storing information of the content of nutrients, flavour and colour of the brewer's spent grains present in the receptacles; - providing input means adapted to receive an input from a user of a mixture of brewer's spent grain to be obtained by the method, wherein the input from a user to the input means is one or more selected from the following groups of inputs: a requested colour, a requested flavour, a requested nutrient content; - providing one or more delivery devices each comprising a metering device or weighting cells, said delivery devices are adapted to deliver from the receptacles a metered or weighed amount of the brewer's spent grain to a container, to form a mixture of brewer's spent grain; - providing a controller being adapted by suitable software instructions to retrieve from the database information of the content of nutrients, flavour and colour in the brewer's spent grain present in the receptacles and retrieve data of the user input from the input means, and wherein the controller is a programmable processor cooperating with a memory storing data and instructions, and wherein once the amount of nutrients, colour and/or flavour are known by the controller 6, it determines the amounts of brewer's spent grain to be delivered from the receptacles corresponding to the use input; - wherein the controller determines the amount of each of the brewer's spent grain to be delivered from the receptacles to the container on basis of said user input and the information from the database, - and wherein the controller is being adapted to control the one or more delivery device(s) to deliver individually into the container the metered or weighed amount of brewer's spent grain determined by the controller to be delivered from a receptacle to the the container. - providing a plurality of receptacles, each receptacle comprises a brewer's spent grain, where the brewer's spent grain comprises independently of each other: ∘ one or more nutrients, a flavour and a colour; ∘ one or more nutrients, a flavour and a colour; - providing a database storing information of the content of nutrients, flavour and colour of the brewer's spent grains present in the receptacles; - providing input means adapted to receive an input from a user of a mixture of brewer's spent grain to be obtained by the method, wherein the input from a user to the input means is one or more selected from the following groups of inputs: a requested colour, a requested flavour, a requested nutrient content; - providing one or more delivery devices each comprising a metering device or weighting cells, said delivery devices are adapted to deliver from the receptacles a metered or weighed amount of the brewer's spent grain to a container, to form a mixture of brewer's spent grain; - providing a controller being adapted by suitable software instructions to retrieve from the database information of the content of nutrients, flavour and colour in the brewer's spent grain present in the receptacles and retrieve data of the user input from the input means, and wherein the controller is a programmable processor cooperating with a memory storing data and instructions, and wherein once the amount of nutrients, colour and/or flavour are known by the controller 6, it determines the amounts of brewer's spent grain to be delivered from the receptacles corresponding to the use input; - wherein the controller determines the amount of each of the brewer's spent grain to be delivered from the receptacles to the container on basis of said user input and the information from the database, - and wherein the controller is being adapted to control the one or more delivery device(s) to deliver individually into the container the metered or weighed amount of brewer's spent grain determined by the controller to be delivered from a receptacle to the the container.