Don: Today we're broadcasting from an undisclosed public restroom here at the radio      station. [TOILET FLUSH] And what better way to introduce today's topic: Is it      better to flush toilet paper or throw it away?

Yaël: Yuck--well, I certainly hope it's better to flush.

D: Well, here's a hint. Most sewage ends up either in a septic system or in a sewage      treatment plant.

Y: Let's see. In either case, bacteria process the organic waste and decompose it, and      at the same time decompose the cellulose fibers that make up toilet paper. And      these bacteria release carbon dioxide as a byproduct--and that's a greenhouse gas.      On the other hand, in landfills, once the oxygen is gone, garbage-eating bacteria take      over that don't require oxygen. But this process produces methane, which has about      twenty times more global warming potential than carbon dioxide. So, from this      perspective, it's clearly better to flush.

D: Except that many sewage treatment plants use a similar process to degrade the solids      that settle out of the wastewater. And because degradation happens faster in moist      environments, this process may actually release more methane compared to landfills,      where moisture is limited to avoid contaminating ground water. So it isn't really clear      whether landfills or sewage treatment plants release more harmful gasses.

Y: So if it isn't about the environment, what is it about?

D: It's about sanitation. Flushing is way more sanitary than carting used toilet paper to      the local landfill.

Y: What a relief. Still, you brought me into this restroom just to tell me that it's okay to      flush toilet paper?

D: Pretty much.  

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