Bricks, Masonry, Asphalt and Concrete - Cleaning Concrete Patio

Hello,
My patio seems to get a runoff from the black shingles of an overhang that is making it look dirty. A few years ago, I used a chemical and deck brush and it looked better afterwards. But now I need to clean it again and I am hesitant in using any chemical because my lawn is now picture perfect and the flow of any chemical will get on parts of the lawn through gravity.
I have a pressure washer and intend to just use that as a cleaner. What brand sealer is best to use so that it stays cleaner for a much longer time?

If you Google nontoxic concrete cleaners, there are many. Orange Oil Concentrate (not the watered-down orange-whatever products you see on TV) is used industrially to clean and degrease concrete floors. By buying the concentrate you can use full strength or water down to desired strength for many household cleaning chores. It can also be used as a foliar spray of insects on plants. It contains raw oil of citrus peels.

http://www.agorganics.com/products/Orange-Oil-Concentrate-Qt-Medina/12/173.html

A penetrating concrete sealer can be used to seal the patio. Behr has one that penetrates to 1/2"--Concrete and Masonry Waterproofer.

http://www.behr.com/images/productgroup/98001_251004.jpg
Photo Credit: Behr

Learn more here: http://www.behr.com/behrx/act/view/products_detail?prodGroupId=10&catName=Concrete%2FMasonry+Waterproofers&catId=6

Thanks,
I'll do a search for non toxic cleaners for concrete.

Thought I give an update on my cleaning the patio.

While in the concrete section of home depot, I found a product by Quickrite that is a non toxic cleaner. I applied it and scrubed away and can see the foam change color. But when I rinsed it, I could still see the dark material that was imbedded in the concrete. So I tried another application and got the same results.
Then I got the pressure washer out and was I surprised how easily it got into the concrete to remove the imbedded dark material. Now the patio looks almost new.
When I get the chance, I am going to see if it does the same job without using a cleaner.