I have been saving 3 liter pop bottles to store water for emergencies. Next I'll use some to grow and sequester algae; thus removing CO2 from the atmosphere. I'll add a bit of fertilizer to the 3 liters of water, and bubble air through the mixture. Algae will grow in sunlight. I can leave it in the bottle permanently, or use it to fertilize the yard.. If I grow spirulina or chlorella, it may be eaten or sold. Some fish eat algae, and insects such as mealworms can eat spirulina or chlorella, I think.