New technology could potentially double RNG production
LOS ANGELES—This spring, Southern California Gas Company made public its vision to be the cleanest natural gas utility in North America, delivering affordable and increasingly renewable energy to its customers. In support of that goal and its potential statewide benefits, the California Energy Commission has awarded the company a $3 million grant to fund the next phase of development of a new technology that doubles the amount of renewable energy created from decomposing organic matter at wastewater treatment plants.
The new process is known as hydrothermal processing, or HTP. It is capable of reducing greenhouse gas emissions by three times that of traditional anaerobic digestion, while incurring roughly half the cost, according to SoCalGas. Data suggests that the state’s existing organic waste could produce enough renewable natural gas to meet the needs of 2.3 million homes.
HTP is highly efficient, using heat and pressure to capture nearly 90 percent of the waste energy while requiring only 14 percent of the energy for processing, said the utility. It is also remarkably straightforward technology. Corinne Drennan, a bioenergy technologies researcher at the Department of Energy’s Pacific Northwest National Laboratory, noted, “The reactor is literally a hot, pressurized tube.”
Despite that simplicity, developing HTP required an innovative approach that has spanned a number of years. “We’ve really accelerated hydrothermal conversion technology over the last seven years to create a continuous, scalable process [that] allows the use of wet wastes, like sewage sludge, without the need to dry it first,” Drennan said.
SoCalGas plans to put HTP to work at a pilot project at the Central Contra Costa Sanitary District Wastewater Treatment Plant in Martinez, California. Funding is coming from the utility, the CEC and private sources. “We’re excited to see HTP piloted … at an actual waste treatment plant,” Drennan said.
If the pilot proves as successful as expected, HTP will be just the latest tool aiding SoCalGas’ strategy to replace 20 percent of its traditional natural gas supply with renewable natural gas by 2030. According to the utility, research has shown that such a move would lower emissions equal to retrofitting every building in the state to run on electric-only energy, at a fraction of the cost.