Green Waste to Renewable Natural Gas by PyroBioMethane

Producing renewable natural gas and value-added co-products from green waste

Anaergia Services


Carlsbad, CA

Recipient Location


Senate District


Assembly District



Amount Spent



Project Status

Project Result

The project was completed November 2015. The final report is awaiting publication. The project showed that the co-digestion of sludge with bio-oil produced from the pyrolysis of biosolids improves digester performance by increasing biogas production and solids destruction. By using this co-digestion process, a typical wastewater treatment plant could increase its biogas production by 30 percent.

The Issue

Green waste, such as leaves, yard trimmings, and tree trimmings, account for roughly 10-20 percent of the 35 million tons of waste disposed in landfills per year. California's municipal wastewater treatment plants generate 800,000 tons per year of biosolids, of which two-thirds are added to soil for nutrients, and one-third is landfilled. Landfilling and land application of biosolids is not sustainable due to their potential impacts to public health and the environment. There is a need to cost effectively address both of these waste streams.

Project Innovation

This agreement demonstrated that bio-oil generated from a low temperature pyrolysis process called PyroBioMethane (PBM) and undigested biosolids sourced from municipal wastewater treatment plants can be converted into biogas without adversely impacting the anaerobic digestion process. The amount of biogas generated with the bio-oil was greater that from the anaerobic digestion of sludge alone. Biogas can be upgraded to renewable natural gas (RNG), which can be used to fuel vehicles. The project also demonstrated that condensing the nutrients generated from the PBM process resulted in a high value biochar fertilizer that can be used to improve soil quality.

Project Benefits

Co-digestion of sludge and biosolids bio-oil at a ratio expected at a typical wastewater treatment plant and pyrolyzing indigenous sludge resulted in a 25% increase in the biogas production rate and a 5-10% increase in volatile solids destruction as compared to anaerobic digestion of sewage sludge alone, indicating the biogas production potential of biosolids bio-oil is greater than that of sludge and improves efficiency of the anaerobic digestion process.

Lower Costs


Concentration of nutrients and mass reduction enhance the value of the solid end product and offer savings to transportation and hauling of solid residuals from wastewater treatment plants.

Environmental & Public Health

Environmental Sustainability

Low temperature pyrolysis is an effective approach to convert municipal sludge biosolids from wastewater treatment plants (WWTPs) and green waste into biomethane for power or fuel production in anaerobic digesters. Undigested biosolids and green waste can be converted into high-value biochar fertilizer.

Key Project Members

Project Member

Juan Josse

Match Partners


Anaergia Services


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