What are the best and 100% safest thing I can use to get rid of bird poop stains on cement? I place their food on a tray which has 2 bowls on top and bird seeds in it. This is placed under porch so food doesn't get wet. I just bought a ground feeder which I will receive in a month since they have to make it. I will put this under porch because where I live it rains slanted sometimes so food will still get wet somehow. I want to get rid of the bird crap stains just using this 100% safe non-toxic chemical and a water hose.