Leave no trace? Seriously? We are climbers. We leave traces all over the place. Bolts, chalk, aggressive cleaning, trundling, "gardening" out cracks, trails, destroyed vegetation at the base of climbs, massive carbon footprints from driving and flying to destination crags, all of these things leave a trace.
Organic matter is a gray area for me. Sometimes i pack it out, sometimes I toss it. Although I am all for minimizing our impact on wild places, I just cannot get that worked up over an orange peel. YMMV.
Whether biodegradable or not, we as climbers should not be adding our waste to the environments with which we climb. We scoff at Leave No Trace and that's sad. We should be seeking to MINIMIZE our impact - although its impossible to mask our presence, we should be sensitive to what we leave behind. Orange Peels take about 6 months to decompose and Bananas about 3 months - but it only takes about 30 seconds to put it in your pack... Pretty straightforward