The historical version of drain tile was a f@ggot drain, consisting of wood bundles, laid in the bottom of a trench, then covered over.
I have buried a lot of wood in my backyard , with similar aims.
I've also made char directly directly in a trench, quenched it and added wood before burying it.
As for fired clay, it certianly shows its value in hydroponics.
I wonder if high fired clay would work, toilets are free.
The broken pieces would be sharp, so they should be tumbled, to protect future hands.