Not that any of us would have any need for this usage, but coffee has such "odor neutralizing" properties that it has always been the habit of drug dealers to ship their wares packed with coffee to throw off the drug-sniffing dogs. Well, at least until the DEA people got wise to that. My grandmother always put her coffee grounds around the base of her plants. She claimed it kept the insects off.
While the amount of coffee grounds obtained from an individual household (even if you are big coffee drinkers) won't alter the pH of your garden much, if you can get the grounds from a commercial coffee enterprise such as a Starbucks, Dunkin' Donuts, etc., it IS a pretty good acidifier fertilizer for acid-loving plants. Caffeine is allegedly toxic to slugs and snails, too, if you have those problem critters. I add our grounds to my worm farm with other waste and they seem to survive fine on that combo.
I'm just as interested in coffee grounds helping to keep mosquitoes away and think I will try the coffee beans for this and also maybe put some coffee grounds in a spray bottle with water and let it set and then spray some on my skin to see if it repels those critters. Maybe my camera that I just fixed can capture some of those exciting moments when the mosquitoes retreat instead of trying to eat me alive.
I'm getting ready to lay grass seed down in some bare spots. I wonder if coffee grounds will benefit in some way. Maybe by keeping the birds away?
I don't think it could hurt, and may well help. I have been harvesting some of my compost from one of my bins and filling in low spots on my lawn, which means that I also have bare spots to cover.
I've never been much ofa farmer or one to grow much of anything, always relying on my local grocer me with all that stuff I did no grow. But, I wish I'd have thought of this eight years ago, I could have leveled my entire back yard with coffee grounds. I'm old and one foot in the grave, but maybe there's hope yet.