Disclosed is a method for acidifying animal manure (5). The method comprises the steps of:• adding and mixing an acidification agent (4) into a first portion of animal manure (5) in a process tank (2),• conveying a second portion of animal manure (5) to the process tank (2) and mixing it with the first portion to form an acidified mixture, and• removing a part of the acidified mixture from the process tank (2).Wherein the first portion it bigger than the second portion and bigger than the removed part of the acidified mixture.A plant (1) for acidification of animal manure (5) is also disclosed.