Turning Biosolids into Carbon Storage: Scaling Subsurface Injection at the TIRE Facility to Meet Los Angeles’ 2050 Population-Driven Emission Demands

Abstract The urgency of addressing global climate change, underscored by the 2015 Paris Agreement, coupled with Los Angeles's significant population expansion since 2000 (≈11.17%) and anticipated growth through 2050, necessitates the implementation of robust and scalable carbon removal strategies. This study assesses how expanded subsurface Biosolid Slurry Injection (BSI) at the Terminal Island Renewable Energy (TIRE) facility can offset the city's rising Carbon Dioxide (CO2) footprint. We correlate historical and forecasted population trends with injected volumes and reservoir capacity, presenting a unique city-scale roadmap for transforming Sewage Sludge (i.e., Biosolids) into a durable carbon sink. To derive a biosolids generation curve, population data spanning 2000 - 2050 were correlated with biosolid production at Los Angeles (LA) County. A life cycle carbon audit was conducted to quantify CO2 removal (CDR) per barrel injected. To evaluate the maximum injection capacity of the TIRE Facility, reservoir and wellbore simulations were performed across multiple operational scenarios. These included the base case, representing approximately 15% of the facility's current operational capacity, and the full capacity scenario at 100%. The full capacity scenario would be capable of accommodating all current and future regional biosolid sources driven by population growth, thereby supporting regional efforts to achieve emission reduction targets by 2050. The results demonstrate a linear correlation between Biosolid generation output and regional population growth, with an R2 value of 0.96. Currently, a single well at the TIRE facility sequesters approximately 0.3 million metric tons of CO2e annually, corresponding to a Biosolid injection of 150 US tons per day. This setup provides a CDR capacity of 4,684 Mt CO2e yr−1, representing only 15% of the Biosolid stream from Los Angeles County. Scaling up pumping capacity to two wells would enable full disposal of LA County's Biosolids, with an injection of 750 US tons daily, sequestering over 1 million Mt CO2e yr−1, and achieving a CDR capacity exceeding 30,000 Mt CO2e yr−1. Expanding to a seven-well configuration could accommodate regional Biosolid inputs of 7,774 US tons daily, resulting in a total GHG offset exceeding 11 million Mt CO2e yr−1, and a CDR capacity of approximately 154,442 Mt CO2e yr−1. These findings underscore the significant potential of the BSI system to meet regional and broader climate mitigation targets through scalable deployment. The analysis demonstrates the scalability and effectiveness of subsurface BSI technology as a viable strategy for meeting metropolitan-scale CDR targets. The findings confirm that BSI operations can be progressively expanded to align with long-term climate and urban development objectives. By integrating demographic projections with field proven BSI data, this work presents a unique, city scale roadmap for turning Biosolid into a durable carbon sink. The methodology links municipal Biosolid management and carbon storage engineering, offering a transferable framework for rapidly growing urban areas aiming for net zero emissions through existing infrastructure.