Genus bounds in right-angled Artin groups

We show that, in any right-angled Artin group whose defining graph has chromatic number k, every non-trivial element has stable commutator length at least 1/(6k). Secondly, if the defining graph does not contain triangles, then every non-trivial element has stable commutator length at least 1/20. These results are obtained via an elementary geometric argument based on earlier work of Culler.