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Natural gas from your sewage

Pima County makes methane from your poop
Posted at 6:58 PM, Oct 21, 2021
and last updated 2021-10-21 21:58:45-04

TUCSON, Ariz. (KGUN) — Something you can’t wait to flush down the toilet could be a boost for clean energy, and Pima County’s budget. Pima County just cut the ribbon on a system to turn wastewater into natural gas.

This is a story a third grader could appreciate but adults could find something to appreciate too. Third graders love jokes about well, farts, and part of that gas is something called methane. When Pima County collects sewage from a large swath of the county, it’s able to extract enough methane to be a valuable source of energy.

What you flush down the toilet has a good chance of ending up at the pipes, pumps and tanks of Pima County’s Tres Rios Treatment Center.

There it basically gets digested.

Your own digestion can create methane gas. We usually call methane natural gas. Sewage digestion creates natural gas too. The plant’s been burning the methane so it won’t build up and explode but new equipment lets Pima County collect the gas, clean and concentrate it, and sell it to Southwest Gas.

Southwest Gas CEO John Hester says, “It was a very important project for us, renewable natural gas or as we talked about biogas today, is a big priority for Southwest Gas because natural gas usage across the country has helped reduce greenhouse gas emissions and to be able to get an increasing portion with biogas as part of our portfolio is something Southwest Gas is very interested in.”

Pima County says in one year, the plant can turn what you’ve been flushing away into the energy equivalent of more than 175 million gallons of gasoline or diesel.

Burning methane still puts carbon dioxide into the air but with 30 percent less CO2 than from gasoline or diesel.

That cleaner burn means Southwest Gas plans to sell the methane in California where clean air credits mean extra money can flow into Pima County’s budget.

Assistant Pima County Wastewater director Jeff Prevatt says, “This is projected to make probably about $2 million to $3 million a year that will come back to the Department, and with that revenue source that'll help us decrease and minimize future rate increases and help us reduce increases in cost is to keep costs down for our ratepayers .”

And the gas from this plant is a renewable resource as long as you continue…doing your part.