AnneMarie Luijendijk, ‘Sacred Scriptures as Trash: Biblical Papyri from Oxyrhynchus’, Vigiliae Christianae 64 (2010), 217-254.
Here is the abstract:
Most New Testament papyri with a known provenance were found at the site of the ancient Egyptian city of Oxyrhynchus, or more precisely: on that city's rubbish mounds. The fact that sacred scriptures were discarded as garbage is surprising in view of the holiness of Christian biblical manuscripts, intrinsically and physically. Yet the trash aspect of provenance has never been adequately problematized or studied. Taking a social-historical and garbological approach, this article demonstrates that at Oxyrhynchus in antiquity entire manuscripts with biblical writings were deliberately discarded by Christians themselves, unrelated to persecution and issues of canonicity.The basic claim is that 'studying the praxis of discarding manuscripts provides social information on Christian communities and their habits towards holy scriptures' (p. 218). There is some general discussion of Oxyrhynchus and the manuscripts of the Christian scriptures that have been recovered from the rubbish dumps of that site (pp. 221-228). There is an introduction to 'A garbological approach' - the academic study of garbology (Wikipedia also has an introduction) (pp. 228-231). She then presses the tension between early Christian reverence for Scripture generally and their own Gospel manuscripts particularly (examples on pp. 231-236) and their disposal as trash (as distinct from the possibly more respectful/reverential disposal by burial, pp. 236-240).
AML argues that Christians did dispose of their Scriptures as trash (it was not deposited by persecutors, since that called for burning, pp. 240-241); that they did so while regarding them as Sacred Scripture (pp. 241-243); and that although often only fragments survive the likelihood is that they were discarded as whole copies (pp. 243-245): 'these manuscripts either deteriorated (further) on the trash heap, which may explain their present fragmentary state, or they had been torn up before they were discarded' (p. 244). She doesn't so much explain how or why this was done - the evidence of the final stages of usage is rarely very clear - but insists that it is an interesting datum:
'despite all the evidence for the physical holiness of Christian manuscripts, at Oxyrhynchus in late antiquity Christians deliberately discarded entire manuscripts with sacred scriptures as trash'. (p. 250).An appendix provides brief notes on NT manuscripts which appear to have been discarded as a whole: P115; P5; P13; P70; P77