Capturing Renewable Natural Gas from Wastewater

Point Loma Wastewater Treatment Plant

Have you ever thought about what happens to the grease or cooking oil you use to cook your food?  It, along with other liquid waste, from our homes and businesses is sent to wastewater facilities to be treated. But at one plant here in San Diego, the process is taken a step further and produces a clean, renewable end result. 

Since 1963, the Point Loma Wastewater Treatment Plant has treated wastewater for more than two million residents – removing organic and inorganic materials from about 175 million gallons of wastewater each day before discharging it to the ocean. During this process, methane gas is produced in eight giant digesters and then captured and converted into clean, renewable natural gas that helps power the facility.

Clean, Renewable Natural Gas Powers Local Facilities

But what is unique about Point Loma Wastewater Treatment Plant is that some of the scrubbed methane gas – or renewable natural gas – is injected back into SDG&E’s gas pipeline system. That gas is being used to power a 2.8 megawatt (MW) fuel cell at the University of California, San Diego and another 1.4 MW fuel cell at San Diego’s South Bay Water Reclamation Plant.

Next Up: Dairy Biomethane

While this is a first of its kind project in the state and the only one in San Diego, our hope is that utilizing a natural gas transmission system to transport renewable natural gas like biomethane becomes standard practice in the near future. To facilitate this effort, in January, SDG&E along with other California utilities, issued a draft solicitation for dairy biomethane pilot projects under California Senate Bill 1383. Proposed projects must demonstrate an ability to capture and process dairy biogas to produce renewable natural gas, which can then be used to replace fossil fuel natural gas for generating electricity, home heating and vehicle fuel. Click here to read more.