The worst part about the house originally was the stench in the garage! It smells to me like the previous owners kept their dogs in the garage and the smell of dog urine was awful. I did all the online research I could only to find a couple solutions so I called the City of Portland’s **free** Green Building Hotline and this was the response I got (Thanks Valerie!):
Here are some non-toxic things you can try. Muriatic acid (hydrochloric acid) is frequently used to clean concrete and brick industrially due to its corrosiveness. The porosity of the concrete can be a hindrance to getting smells out.
Enzymatic cleaners on the market – natural pet stores
1. Nature’s Miracle and Out Spot! The enzymes take care of the bacteria and smell.
From Nature’s Miracle page for concrete application: “Saturate the area to be treated with Nature’s Miracle and then saturate a bath towel with the product as well and lay it over the treated area. Allow the towel to remain in place until it’s totally dry.”
1- Listerine mouth wash will remove urine odors. Dilute with two parts water and spray or pour it on the problem area and let it sit for several hours. Wash off with hose.
2- You can try undiluted Hydrogen Peroxide. Work in with a brush and let it dry, then wash off.
3- Create a baking soda and water paste. Rub it into the area and apply distilled white vinegar over it (it will foam). Blot this up with newspapers, and repeat up to two times. Wash off with hose. It will smell like vinegar for a short time, but the urine smell should not come back.
I chose to use the muriatic acid (hydrochloric acid), because it sounded the most natural and the most potent. Some websites call muriatic acid “super stomach acid”.
I used a paint roller with a long extension and I let the acid sit for awhile before I washed it off with a power washer attachment to a hose. Treat this product like paint, event applications -more product on the roller is not better in this case. Whenever I dripped the muriatic acid onto the floor in a little excess, I now have a super white spot. I would do it all over again except the hose attachment. I would recommend using an actual power washer to wash the acid off.