SoCalGas and the DOE install the first biomethanation reactor system

Written By: Stratton Report
October 12, 2017

socalgas renewable gas

Recently, Southern California Gas Co announced the successful installation of a novel biomethanation reactor system that would be used to test power-to-gas technology at the U.S. Department of Energy’s National Renewable Energy Laboratory (NRE) in Golden, Colorado. The project is the first of its kind in the United States converting hydrogen generated from excess renewable power into pipeline quality methane for use in homes, businesses and in transportation.

According to the company, last month, researchers at NREL’s Energy Systems Integration Facility (ESIF) in Golden, Colorado, installed a 25-foot tall bioreactor system, which would be used to produce renewable natural gas from excess renewable electricity using archaea microorganisms that consume hydrogen and carbon dioxide and emit methane.

Jeff Reed, director of business strategy and advanced technology at SoCalGas, commented:

Power-to-gas technology can significantly increase the overall amount of renewable energy we use, by providing an economical method of storing excess solar-and wind-generated electricity. And this technology takes advantage of existing infrastructure, and can hold excess renewables for days, weeks or months to shift solar from day to night, address weather patterns and even seasonal patterns.

“Archaea are uniquely capable of handling fluctuating levels of hydrogen produced by electrolyzers as wind and solar generation systems cycle up and down,” said Kevin Harrison, senior engineer for NREL. “That’s in part why we believe this technology could provide a superior large-scale, cost-effective solution for storing excess renewable energy using our nation’s natural gas distribution system.”

According to a 2017 Lawrence Berkley National Lab study, by 2025, between 3,300 and 7,800 gigawatt-hours of excess solar and wind energy would be curtailed in California. If all that excess solar and wind energy were converted to methane through the biomethanation process and stored as renewable natural gas, it would provide enough renewable energy to heat 158,000 to 370,000 homes.

Per the company, the pilot project would be used to help assess the commercial viability of this power-to-gas approach to energy storage and provide insights into potential megawatt-scale system designs. The team would combine these insights with renewable energy resource data to identify optimal locations in California and the western half of the U.S. where this grid-scale energy storage would be the most beneficial and cost-effective.

Power-to-gas technology uses renewable electricity when prices are low—including times when renewable supply exceeds demand and would otherwise be wasted—to power an electrolyzer, which splits water to produce hydrogen, per Southern Gas Co. The hydrogen is then combined with carbon dioxide and fed to a biomethanation reactor where it is converted into renewable natural gas, or RNG, by special micro-organisms. RNG can be used in any application currently served by natural gas, from home appliances to industrial processes, heavy duty vehicle engines and power plants.

The research would also test how effectively the microbes convert hydrogen to methane and how efficiently the storable methane can be converted back to electricity. Tests would also examine the potential of power-to-gas technology to store large quantities of renewable energy for up to an entire year and how it compares in performance and cost to battery storage. Initial reports are expected beginning in 2018. The study is set to continue for several years.