I would love to dispose of my offerings outside, but I can’t unless they are liquid libations (sometimes even then). What that means is that when they come off the altar, I am forced to throw them away. I know I’m not the only one, so, if you’re interested, here’s how I deal with it. I devised a small prayer, and I take a moment to hold the offering and say it before it’s thrown away.
“With respect this [offering] was given to [god], and with that same respect I dispose of it to make room for more offerings in his/her/their name.”
I think this can be adapted to a lot of different gifts, gods, and situations. “Respect” can be replaced or added to as needed/wanted, etc. etc.