We all know the mantra "Reduce, Reuse Recycle" but how many of us really put that into practice in our daily lives? Sure, it is easy to buy a soda and recycle the bottle, and it feels a lot better to recycle than to throw it in the trash, but we often forget that Reduce and Reuse come before Recycle. Can you live without the soda? Can you give the bottle new life and reuse it instead of throwing it in the bin?
These are the types of questions that gardeners have been asking for centuries -- how can I get the most out of my garden with the least amount of input? This means taking the output and turning it into input -- For example, turning straw from your grain harvest into baskets to winnow the grain with, or using manure from cows to fertilize the fields on which you grow their hay.
Although hydroponics is generally very efficient on resources, there can be a lot of waste involved. In Ebb & Flow systems, the entire reservoir must be emptied out periodically and replenished with clean water. This is essential for plant health, and still uses less water per plant than most traditional gardens, but still, what a waste! You can use this water on your grass, houseplants, or soil garden if you have one, but there are other ways to reduce waste as well. Aeroponics systems are incredibly water efficient. They spray a fine mist directly on to the root of the plant, and often collect any runoff and reuse it. Aquaponics systems are the most water efficient by far -- once you fill them up, the water is recycled indefinitely, plus you have the added bonus of a fish harvest every few months.
Aquaponics isn't the only way to add animals into your system, though. Rabbits, ducks, and worms can be used instead of or in addition to fish to add nutrients (thereby saving on producing, packaging and transporting artificial fertilizers) to your hydro solution.
Another big energy hog is lighting and cooling your system. If you have outdoor space I would highly suggest using it as much as possible, to reduce electricity use and cost. Otherwise, think about combining lighting and cooling systems with a hood vent. These cool the air directly under the lights, allowing you to get the plants closer for greater growth and reducing the overall energy used to cool the system.