where N 0 is the set of nonnegative integers and N 0 [x, x −1 ] is the semiring of Laurent polynomials with coefficients in N 0 . In this paper, we study various factorization properties of the additive structure of N 0 [α, α −1 ]. We characterize when N 0 [α, α −1 ] is atomic. Then we characterize when N 0 [α, α −1 ] satisfies the ascending chain condition on principal ideals in terms of certain well-studied factorization properties. Finally, we characterize when N 0 [α, α −1 ] satisfies the unique factorization property and show that, when this is not the case, N 0 [α, α −1 ] has infinite elasticity.