Is burning trash or used toilet paper OK?

We do not advocate burning toilet paper. Plan ahead to pack the toilet paper out—in a plastic bag—with you. This will leave the least impact on the area. Otherwise, use as little as possible and bury it deeply in the cathole. Attempts to burn toilet paper at the site are not recommended. It rarely burns completely, and has been the cause of wildfires. “Natural” toilet paper such as grass, sticks, and snow can be surprisingly effective, and should always be buried deeply in the hole. Always pack out feminine hygiene products because they decompose slowly and attract animals. We do advocate packing out used TP but still give folks an out if they’re too disgusted by the mere thought of it, i.e. bury it deeply in the cathole.
We never recommend burning trash regardless of the length of trip. We recommend repackaging food (and other items that could generate trash) before the trip to ensure the least amount of garbage and trash will be hauled into the backcountry, thereby mitigating the need to burn trash. The reason we don’t recommend burning trash is that it generally takes a hot fire to completely burn trash to ash, which presents its own set of issues. Additionally, partially burned trash and food is usually a magnet for scavenging wildlife, which can lead to wildlife becoming habituated to human foods, i.e. animals lose their fear of humans and seek them out to obtain food. When this occurs, wildlife almost always loses in the end.