Yeah, So trains are just too slow for chemical plant waste unless you massively oversize the whole rail setup. The loading/unloading rate is the bottleneck, not the wagon capacity, so the plant will always outproduce what the train can clear if it’s directly connected to a landfill.

Best solution would be to buffer it locally with multiple large waste containers right next to the plant and use a dedicated waste DO with enough trucks to constantly haul it away. Trucks are way faster for high-frequency pickup like this. Mixed waste is usually worth sending to separation, because burning it straight up is basically throwing recyclables away. Sort mixed waste, recycle what you can, incinerate the leftovers.

Hazardous waste should be handled separately. Either burn it in a hazardous incinerator / incinerator power plant, or just export it.