Today after another answering machine plea, Mark-the-Engineer of the landfill called me back. Our trash goes to a "Sanitary Landfill" which means it is compacted rather than incinerated, and isolated from the water table. I unfortunately forgot to ask about methane reclamation, but this is usually used in cities where the capped landfill may be used as an industrial park or golf course. I'll start entering my data into the calculator to see what it looks like, and I'll call back to verify that there is no methane recovery.
As for the missing data - for landfill-bound trash I have 4 recent years of the coveted 18 - the landfill records the tonnage by the hauling company, not by the source. I believe our hauling company is Athens/Hocking Recycling Center, but I'll have to check my notes and maybe call Ed Newman back. If I provide the landfill with a hauling company, they can give me annual tonnage brought by them. That hauling company would be another data source possibility. Recycling data on the other hand is far more complete.