There is no algorithm. Indeed, the property that $Wh(G)$ is trivial is Markov that is there exists a finitely presented group (${\mathbb Z}$) with trivial $Wh$ and there exists a finitely presented group not embeddable into any group with trivial Wh (any finite non-trivial group).
Update Recall that Markov proved undecidability of every Markov property for semigroups (see http://iopscience.iop.org/0036-0279/19/3/M05/pdf/0036-0279_19_3_M05.pdf), and later Adyan and Rabin proved it for groups (see Lyndon and Schupp, Combinatorial group theory, Theorem 4.1, Chapter 4).