What is a good non-toxic ant killer?

Orange Guard is a good nontoxic ant killer and repellent, notes PETA. The active ingredient in Orange Guard is d-Limonene, which is extracted from orange peels.

PETA recommends spraying Orange Guard around the home, but not directly on ants, because it destroys their respiratory systems and suffocates them. Cream of tartar and strongly scented spices placed around openings where ants enter the home also serve as non-toxic ways to keep ants out of the home. Recommended ant-repelling spices include cinnamon, coffee grounds, lemon juice and zest, chili pepper, peppermint and clove. Planting mint close to a home's foundation also repels ants.