Photos: Pumping gas from manure to PG&E

When Pacific Gas & Electric on Tuesday starts pumping methane from a farm in the Fresno, Calif., area, it'll be relying on machinery like this that converts manure into a useful gas. This marks the first time that manure-generated gas will get sold across pipelines in the state.

It takes a few steps to transform manure into methane. First, the manure has to sit in a lagoon and get broken down by microbes. The gas released then needs to be processed and purified. The unit pictured here removes hydrogen sulfide, which could corrode pipelines, from the biogas.