Disclosed herein are non-toxic antimicrobial compositions for cleaning, reducing the bioburden and substantially killing gram negative and positive bacteria on hard surfaces. The antimicrobial compositions comprise about 0.01% to about 4.0% by weight of one or more oils selected from the group comprising rosemary oil, tea tree oil, spearmint oil, peppermint oil, clove oil, lemongrass oil, cedar oil, and cinnamon oil and about 0.1% to about 4.0% by weight of one or more acids selected from the group comprising carboxylic acids, ascorbic acid, glutamic acid, fumaric acid, oxalic acid and malonic acid. In an embodiment of the invention, an alkali base such as sodium hydroxide or potassium hydroxide is added to the above antimicrobial solution to increase the pH of the antimicrobial solution to a range of about 2.0 to about 4.0 to effect a rapid reduction of the bioburden on the hard surfaces within 5 minutes.