Via carbon offsets, so they emit all the co2 up front and then hope the forests their partners plant are both real and will be properly managed for the next few decades.

They emit very little co2 up front. So little that they trivially reach carbon-negative with a small amount of carbon offsets.

Very little compared to the entire planet, sure. But what's the actual amount?

Sustainable Blockchain: Estimating the Carbon Footprint of Algorand’s Pure Proof-of-Stake

https://www.algorand.com/resources/blog/sustainable-blockcha...

Nope. Still worse than status quo + planting trees via partners, which is exactly what alogrand does...

You can install an algorand server on a desktop and measure it yourself. Try doing that with Visa, or Venmo, or [choose your own black box].