[hnmullany]

Methane and nitrous oxide emissions from these piles would likely be rather high, potentially negating any carbon sequestration benefits

[ckrapu]

This is definitely true.

My hope would be that the thawed region would be a very thin shell overall, so the overall emissions as a fraction of total stored mass would be relatively low. Can you think of any ways to minimize anoxic activity in the thermally active area?

[aqme28]

Methane would be extremeley high. The core of the pile might be frozen, but the unfrozen region would be anoxic and decomposing.