Previously asked and answered:

Scrypt:
We chose scrypt for a couple reasons. First, scrypt asic mining will reduce power consumption considerably for mining in the future. The second reason it has a good, stable history.

As to the power problem: The amount of mining ultimately would be fairly miniscule to the scale of the problem at hand. Global CO2 emissions are clocking over 31 GT annually. Let's take a look at bitcoin: obviously considered to be power-hog, but it's only 0.03% of the grid (I've read this elsewhere, if there is a better number, let me know). Electric power generation contributes 25% of the total global CO2 emissions, so 0.0003 * 0.25 * 31 GT = 2.3 MT of annual CO2 emissions coming from bitcoin's existence, or 0.0075% of all CO2 emissions. Now, we are all hopeful greencoin will become a great coin, and even if it did, I doubt it would be using substantially more power than bitcoin. If greencoin was capable of onlining green energy to even a 1% reduction in global electric power emissions, it means the coin reduces 33X more carbon than is produced by miners. At a 10% global reduction, it's over 300X and so on. Additionally, miners have an incentive to go green on their rigs because they get mined coins AND produced coins. Bitcoin doesn't offer this additional incentive. This is all before you even begin to account for the trade-offs that might actually work in cryptos' favor as an alternative payment system, for example, the energy needed to send payments in more traditional banking ways also uses power (servers, etc), and bitcoin might actually be net "greener."

And to add to the answer, now that we are merged-mined, only the most valuable coins in the merge should be assigned the power allocation since miners are basically receiving the smaller value coins as a bonus. In a way, we've latched on to these other coins like DOGE that will be mined anyways, so there is negligible additional carbon output as a result. Certainly, in the future IF greencoin were to become quite valuable, then we would have a power use responsibility however, and at that time, the above answer would apply anyhow.