Apart from that, that package does not orders of magnitude difference in brightness per mA. So use whatever you want.
The common 3.2V of white LEDs are close to the voltage of a LiPo, so you probaly won't be much more efficient with anything else than current limiting resistor. So mA in the LED equal mA drawn from the battery. To run the LED at 20mA for a year, you would thus need 20mA*24*365, so a 175Ah battery, or about 60 smartphone batteries or a car battery with an efficient buck converter.
You probably won't need 20mA, but even with 1mA, you are still at quite a big battery pack.
When you say biosphere, there should be light, shouldn't it? Perhaps you can use solar cells to charge during day? that would also be more in line of the biosphere idea.
yep,i thought that led, being too small it consume very very low amount of current, not 20mA.
And about the solar panel, i tought the same but then i also need a charger and maybe a step up convertor and all this stuff...
using a cr2 battery with ~900mA at 3V i need to have a have a drain of 104.1uA (0.1041mA) to keep it alive for 1 year, and if this little sh*t consume 20mA then i don't think there is anything that could