Certain types of algae can feed off of organic carbon as well as sunlight, and in the process produce carbohydrate energy for themselves as well as oxygen as a waste product.
Cajella’s lamps consist of algae-filled water along with a light and battery system. During the day the algae produce energy from sunlight that is then stored in the batteries. Then at night the energy is used to power the light. However, as the algae can also produce energy from carbon, sunlight isn’t required for the process to work. That means such lights can be placed where there is no natural light and the air will effectively be cleaned on a daily basis.
What isn’t discussed in the video is how much maintenance such a light needs. However, the good news is algae can also act as a biofuel once separated from the water, so even if the lights need a water change out every so often, the waste algae just forms another type of fuel where as the water can be recycled.