Static methods are one per class, even if you create thousands of instance of that class all of them will see just one copy of your static method.
Now as per Spec you should not have static methods in your EJB, you should consider moving this as part of utility if you want it static, or else make it non static.
From the Spec:
EE.5.2.3 Annotations and Injection
As described in the following sections, a field or method of certain container-managed component classes may be annotated to request that an entry from the application component’s environment be injected into the class. Any of the types of resources described in this chapter may be injected. Injection may also be requested using entries in the deployment descriptor corresponding to each of these resource types. The field or method may have any access qualifier (public, private, etc.). For all classes except application client main classes, the fields or methods must not be static.