Column: Electric dreams turn into a nightmare for battery metals
A sector that was once racing to build new supply has been closing mines and deferring projects as low prices bite into the cost curve.
The City of Roseville, in California, will start powering its trash and recycling trucks with renewable natural gas (RNG) derived from the digestion of organic waste.
In a media release, the city announced that the expansion project of the regional Pleasant Grove Wastewater Treatment Plant (PGWWTP) will grow the facility’s capacity from 9.5 million gallons to 12 million gallons of wastewater treated per day. As part of this initiative, Roseville has developed an energy recovery system to transform the plant into a waste-to-energy facility capable of producing RNG fuel.
“We have come full circle with managing our integrated utility service to benefit our community,” Roseville’s environmental utilities director, Richard D. Plecker, said in a statement. “Through this project, we have the opportunity to generate environmentally beneficial by-products, mitigate the impacts of climate change, comply with regulatory obligations, and safeguard the interests of our ratepayers by stabilizing fuel costs for our solid waste fleet.”
To go ahead with the plan, the city installed two new anaerobic digesters at the plant to stabilize wastewater solids generated in the treatment process and generate a sustainable fuel source.
A receiving facility was constructed to accept high-strength organic waste (fats, oils, and greases) directly into the anaerobic digesters, maximizing digester gas production for RNG conversion and diverting up to 12,000 tons of high-strength organic waste per year from landfill. Four microturbine cogeneration units produce electricity to help power the gas conversion process and provide heat for the anaerobic digesters.
By running its solid waste collection fleet of approximately 47 trucks via a new on-site RNG fueling facility and ceasing diesel use, Roseville expects to reduce greenhouse gas emissions by about 7,000 metric tons of CO2 equivalents per year, equal to planting more than 270,000 trees. It will also earn credits through the Low Carbon Fuel Standard program as it lowers NOx emissions by five metric tons per year.
In addition to the prior, by generating electricity with microturbines, the initiative became eligible for the Clean Water State Revolving Fund Green Project Reserve, which incentivizes proposals that address water or energy efficiency and reduces costs for utility customers.
“We applaud the city for its vision and follow-through in transforming its wastewater treatment process into a highly sustainable, energy-efficient operation,” said Adam Ross, president of environmental engineering and construction services firm Brown and Caldwell, which was hired for the job.
“Our team is honored to help position Roseville as a model waste-to-energy pioneer by improving the environmental and financial sustainability of the Pleasant Grove Wastewater Treatment Plant.”
