Renewable Natural Gas Production from Woody Biomass via Gasification and Fluidized-Bed Methanation
Demonstrating conversion of woody biomass into renewable natural gas for cost-effective pipeline injection.
The Regents of the University of California, on behalf of the San Diego campus
Recipient
La Jolla, CA
Recipient Location
38th
Senate District
77th
Assembly District
$1,000,000
Amount Spent
Completed
Project Status
Project Result
Numerous improvements to the fast internally-circulating fluidized bed gasifier were completed to allow for precise sampling of the producer gas. New producer gas cleanup methods, including a chilled biodiesel scrubber, were developed and implemented to remove water and tars from the producer gas; a critical step before methanatoion can occur. A methanation reactor was constructed and tested to prove that methane could be produced via the fluidized bed methanation method. Finally, a techno-economic analysis was performed showing significant cost reduction for producing RNG via fluidized-bed methanation compared to conventional fixed-bed methods. Key next steps for the technology include additional catalyst research to determine optimal methanation catalysts and a pilot-scale demonstration to prove the technology can be scaled-up while maintaining the same performance characteristics.
The Issue
California has 32 million bone dry tons of sustainable undeveloped biomass equivalent to 512 trillion BTUs a year. A large portion of this biomass could be economically converted to renewable natural gas (RNG) by methanation, but the cost of the produced RNG is high. The leading cause of the high costs of the methanation process, as with many other fuel synthesis processes, is the deactivation of catalysts. While the effect of trace contaminants on catalysts is known, the detailed measurement and characterization of these trace contaminants is often not performed. This leads to inadequate gas cleanup and early catalyst deactivation.
Project Innovation
This project developed, through lab and pilot-scale testing, a novel bioenergy pathway to convert woody biomass into renewable natural gas (RNG) via fluidized bed methanation for cost-effective pipeline injection. A fast internally circulating fluidized bed (FICFB) gasifier was used to convert biomass to producer gas with high efficiency. Researchers developed and tested new methods for the measurement of trace contaminants in the product gas. New gas cleanup methods were tested on producer gas with contaminants measured before and after gas cleanup. The trace contaminants in the cleaned gas were evaluated to determine if they are suitable for methanation catalysts. The project then tested these catalysts in a fluidized bed methanation experiment. Finally, technical and economic analysis was performed for a full-scale (60 MW RNG) facility with the intent to scale-up for future projects.
Project Benefits
Conversion of woody biomass to renewable natural gas is a first-of-its-kind demonstration in California and may prove to be a viable pathway to convert forest waste into renewable energy. Given unprecedented tree mortality rates in California, there is an urgent need to test and demonstrate forest waste-to-energy pathways. The project also demonstrated fluidized-bed methanation for the first time in the U.S., a process more efficient than conventional fixed-bed methanation.
Affordability
This project demonstrated a low-cost bioenergy pathway that converts woody biomass into RNG. Techno-economic analysis indicates that a full-scale facility would produce RNG at approximately $8/therm. Although this is two to three times the price of natural gas, it is competitive with RNG produced from other biogas sources, such as anaerobic digester gas.
Environmental Sustainability
Results from this project can help design and commercialize a full-scale woody biomass to renewable natural gas facility. Such a facility would result in decreased impacts to climate change by decreasing dependence on fossil natural gas and by reducing harmful environmental emissions (namely black carbon) associated with wildfires.
Safety
This project demonstrated a bioenergy pathway that could ultimately harness the growing supply of dead trees. Dead trees present a large wildfire risk as they are dry and more prone to catch fire. Utilizing these trees for bioenergy could aid in reducing wildfire risk, increasing safety for surrounding communities.
Energy Security
Successful commercialization of this technology will result in decreased dependence on fossil natural gas by introducing a new renewable natural gas pathway.
Key Project Members
Lynelle Gehrke
Subrecipients
The Regents of the University of California, on behalf of the Davis Campus
West Biofuels, LLC
Match Partners
The Regents of the University of California, on behalf of the Davis Campus
Sacramento Municipal Utility District
West Biofuels, LLC
