If any composting experts want to check out the link, I've put it below. I know a lot about coffee, but not much about the science behind composting so if something in the description gives you any ideas let me know!!
This is from the companies site.
Patrick guides every single batch of coffee from start to finish. He oversees the purchase of the top 1% of the crop – typically from the small high-altitude farms known as “fazendas” from the Equatorial regions of South America– including Brazil, Coast Rica, Guatemala. and micro roasting the beans to ensure consistency behind the unique flavor. His favorite bean is the Guatemalan Huehuetenango
So what makes it so good for your soil? The areas they source their beans from do not use any Herbicides or insecticides per the requirements of being "Fazendas" The regulations for these are like the Appellation de Control of France for wine making.
The other factor is that freshly ground beans retain far more of the good things coffee beans contain. Once they are ground, degradation begins immediately so the closer to time of grind means more of the goodness is still around. (This is why vaccume packing is such a big deal with coffee, they are trying to keep the goodness in as much as possible.) This degradation begins as soon as the roasted beans cool, coffee companies do everything they can to keep their beans as fresh as possible so you get a wonderful product to sip. The Ideal is to buy your beans green, roast them in small batches, grind as soon as cool enough to grind properly, brew and drink. Not many folks have all the equipment to do this, which is why we search for the best we can buy where ever we are.
Free, and also plentiful. Those are the two qualities I look for in my coffee grounds.
When you see how coffee is produced, it's hard to imagine that any insecticides or herbicides would ever make it from the farm to your garden. I lived in a coffee producing region of Africa for years, and have seen how it's grown. First, most farmers aren't using much by way of chemical inputs. A bit of fertilizer at the start of growing season, but not much thereafter. I don't remember anyone spraying for bugs, or anyone using a herbicide. It's a relatively pest free tree. So from the start, the end product (coffee) isn't exposed to much if any harmful chemicals.
Once the ripe berries were picked, they were placed in baskets to soak in the stream. That would loosen the husk around the been. They would run the semi-fermented berries through a de-husking machine and the raw beans would be separated from the husk. At that point, anything that might have been sprayed on the tree and berry would be long gone --- washed, fermented and husked away. Those beans were set on mats to dry in the hot sun for a week or more. Again, further breaking down what ever chemicals might be present.
Then the raw beans are roasted, further breaking down whatever chemicals might have been hitch-hiking. hot water is run through the coffee grounds. And finally, it makes its way to your compost pile to undergo further fermentation and microbial attack.
Would there even be a fraction of a trace of harmful insecticides or herbicides that would make it through all that? All those steps along the way, particularly the fermentation, drying, roasting, grinding, brewing and then composting would seem to me to take care of whatever traces might remain. AND THEN --- it goes onto or into your soil, for further decomposition and "attack" by the microbial herd.
"Organic" coffee is a bit like "organic" avocados. Avocados don't need anything -- no fertilizer or insecticide is ever needed -- so buying an organic avocado is a rip-off if you are playing more than any normal avocado. Coffee is much the same, as far as I understand. Perhaps I'm wrong and I'm open to input and correction here, but having seen it grown and processed, I don't think that we are talking about Round-Up Ready GMO Corn, saturated in all the worst stuff Monsanto can create in their dark labs.
The important things are type of bean and growing conditions (atmosphere, soil, amount of shade and moisture both in ground and in the air) are the most important for flavor and body.
The other two major factors, how it is dried, and how it is roasted, which develop those flavor and body characteristics that come from the particular species (Arabica or Columbian, most of the world grows the Arabica species).
These factors are only important to the drinker of coffee not the user of spent grounds.
I've found that just about any store that provides brewed coffee for sale or free to customers will be happy for you to pick up their spent grounds.
Car dealerships, grocery stores and gas (mini-mart) stations are probably some of the least thought of places to get free grounds.
You might have to provide containers for them to put those in and they may want you to pick up daily, but compared to what you can get out of those free grounds, those are trifles.
I put up a fairly comprehensive post about spent coffee grounds way back.