Failed undergraduate research project: does it belong in my CV?
I think for an undergraduate student, it is quite valuable to show that they have experience working on a diverse range of problems with different people, even if some of such projects do not lead to anything substantial.

Usually for grad school application and other fellowships there is an essay component. It may also be useful to mention such projects (briefly), and how such experience clarified your research interest/taught you how to do research/provided cross-disciplinary/cultural experience, etc. The exact messaging of course depends on what you think the program is looking for from the applicants.