I’m a huge coffee drinker as well, and I go through the same scenario as you. Winter hits and I don’t walk my happy ass outside, through crotch high snow to the composters. I use to save it and every time it turned into a trich farm. There’s been times I’ve forgotten about a cup in the garage and when I discovered it, sure as shit, Trichoderma was growing on the liquid surface.
Your right, it is very beneficial for the garden. It doesn’t have any properties that fight botyritis directly, however it does initiate the SAR (systemic acquired resistance) in plants, which when combined with other microbes dramatically enhance growth, resistance to disease, pests and environmental stress. Specific strains of trichoderma will enhance root development much more than any endo/ecto mycorhizal. Those strains are Verdes, Koningii, Harzianum.
If your up for a good read, that’s a good place to start with Trichoderma.
If your serious about organic cultivation I’d recommend you read up on the microbial loop of soil born organisms. It helps tremendously to grasp an understanding of how organic works.
I’ve been a soil grower for going on 21yrs and been formulating my substrates from scratch for about 15 of it. Once you get it going, it only gets better and better. I’ve been recycling my soil for 2 decades now and to me, its worth more than gold.
If you have the time or the motivation, get a worm farm going, they love coffee grounds and fresh vermi castings are far more superior to any you can buy. Furthermore you can enrich the quality of your castings with an array of different inputs.
Lastly check out bokashi composting. Winter time isn’t the best for outdoor composters, but indoor bokashi composting is an ideal solution to that. When spring returns, now you’ve got a shit load of “pre chewed” parent material that can be buried in the soil, thrown into a composter or fed to the worm farm. And as a bonus, the lechate that’s produced from the bokashi durring fermentation is an exceptional fertilizer, immediately available to the roots and foliar spray. Additionally it’s probiotic and aids in plant and soil health. Flaculative anerobes are one of nature’s best kept secrets. KNF and JADAM operate on these principles.