Can I just whir together my coffee grounds, eggshells and banana peels ( or other fruit/veg) and work into soil en masse? Is there a limit? I live in a planned retirement community - no place at all to compost.
Amending Soil With Kitchen by Products
Certified GKH Gardening Expert
Those three happen to be just fine to add to soil as it is. They will break down without too much issue. I would not put much else besides these to avoid a fungal issue. There isn't a whole lot that I would recommend putting in without composting, but you will be fine to use these items.