I have a small vegetable garden 30' x 20'. We burn hardwoods in our insert & have wood ash. Could I mix our coffee grinds with the wood ash to counteract the ph?
coffee grounds are NOT noticeably acidic - an excess of wood ash in soil that doesn't need it is very counterproductive
As Bill noted, coffee grounds (used) aren't very acidic. They are acidic before being brewed, but once brewed tend to be near neutral in pH.
Wood ash is fine to add to the soil as an amendment as long as you understand you are adding both alkalinity and potassium.
Some areas have soils with excessive potassium levels, make sure yours isn't one of them or you are doing more harm than good.
Wood ash is best used on soils where a pH raise and potassium source are both desired. If only one is desired, I would recomend an alternative.
Having said that, the potassium and pH changes aren't dramatic unless the amount of ash is very high. If you simply wish to have a means of disposing of the ash, then it is fine to scatter it thinly around the lawn and gardens.
In other words, don't be afraid to give it back to the earth, but don't dump it repeatedly in the same small area unless you want to raise pH and potassium levels over the course of a few years in that area.
Even though the University of Tennessee says that 50 percent of Tennessee soils need some lime you need to have you soil tested by them before adding wood ash to determine if some is needed and how much would be needed to adjust the pH of your soil. Contact your local office about soil tests and keep in mind that fall, not spring, is the best time to adjust the soils pH.
Here is a link that might be useful: UT CES
I add reasonable amounts of wood ash to my compost pile without noticible problems. Large amounts would likely slow composting down and give some funky effects, but composting seems to counteract the pH effects of some amount of wood ash and likely stabilizes K in the humus.
I have acidic soil and apply it to the lawn sparingly several times during the growing seasons. Too much at once would cause a wild pH swing. A little at a time slows the use of it as it's effect is pretty fast-acting, but short- term compared to say pelletized lime.