We show, for a finitely generated partially cancellative torsion-free commutative monoid M , that K i (R) ∼ = K i (R[M ]) whenever i ≤ −d and R is a quasi-excellent Q-algebra of Krull dimension d ≥ 1. In particular, K i (R[M ]) = 0 for i < −d. This is a generalization of Weibel's K-dimension conjecture to monoid algebras. We show that this generalization fails for X[M ] if X is not an affine scheme. We also show that the Levine-Weibel Chow group of 0-cycles CH LW 0 (k[M ]) vanishes for any finitely generated commutative partially cancellative monoid M if k is an algebraically closed field. 0.1. Weibel's conjecture for monoid algebras. Recall that a famous conjecture of Weibel [36] asserts that if R is a commutative Noetherian ring of Krull dimension d, then K −d (R) ≃ K −d (R[t 1 , · · · , t n ]) and K i (R[t 1 , · · · , t n ]) = 0 for i < −d and n ≥ 0. An affirmative answer to this conjecture was obtained recently by Kerz, Strunk and Tamme [22]. For Noetherian rings containing Q, this was earlier solved by Cortiñas, Haesemeyer, Schlichting and Weibel [3] (see also [10], [23] and [38] for older results in positive characteristics).The main technical tool that goes into the proof of Weibel's conjecture in [22] is a pro-cdhdescent theorem for algebraic K-theory. However, the final step in the proof of the conjecture 2010 Mathematics Subject Classification. Primary 19D50; Secondary 13F15, 14F35.