The Passive Porous Tube Nutrient Delivery System is a plant growth technique developed for space applications that delivers a nutrient solution to the roots of plants via capillary action. The system was designed for use in microgravity. Current nutrient delivery techniques proposed for space involve the use of a medium for the roots to penetrate, such as arcilite. This new system utilizes a ceramic porous tube and water/nutrients bags connected in a loop. No electricity or moving parts are required. Instead, the nutrients are pumped in through a combination of capillary force and evapo-transpiration from the plant. The porous tube supplies the plants with the water and nutrients needed to germinate and grow. This system provides an autonomous plant growth apparatus that is simple to assemble, plant and harvest, minimizing the amount of intervention needed in micro-gravity.

Applications for the Passive Porous Tube Nutrient Delivery System may be home gardening, community gardens, vertical farming or green walls. The technique has been demonstrated to be a water conserving plant growth system (as opposed to most hydroponics systems) and this innovation allows its operation without external power inputs. Since this system uses no soil or soil substitutes it requires no regeneration of materials and is sustainable and reusable using simple cleaning techniques.