Community-Powered Sustainability: North Torrey Pines Anaerobic Digester

Anaerobic digestion is a process through which bacteria break down organic matter in the absence of oxygen. Anaerobic digestion for biogas production takes place in a sealed vessel called a reactor, which is designed and constructed in various shapes and sizes specific to the site and feedstock conditions. These reactors contain complex microbial communities that break down (or digest) the waste and produce biogas and digestate (the solid and liquid material end-products of the AD process) which is discharged from the digester. ^[1]

Pre-consumer food waste is collected from the Sixth College Restaurants and fed into the digester. The system is monitored daily and adjusted as needed to make sure the bacteria are properly breaking down the food waste. Two end products are created: renewable biogas, and liquid fertilizer. The biogas will be pumped up to the roof to fuel the outdoor fireplace. The liquid fertilizer will be given to campus community gardens, and Landscape Services to be used on-site as a soil fertilizer.

This anaerobic digester supports our university Zero Waste and Carbon Neutrality goals. Through this system, we expect to divert up to 960 pounds of food waste per week, or 25 tons per year! This will conserve approximately 3.6 metric tons of carbon dioxide equivalent annually, the equivalent of 405 gallons of gasoline. ^[2][3]

1. It’s located in Sixth College/North Torrey Pines Living Learning Neighborhood, at the south-west corner of Mosaic Building.