How to Calculate Geothermal Lithium Brine Recovery Yield
Direct lithium extraction (DLE) projects in geothermal settings are racing from pilot to commercial scale. Investors, offtakers, and regulators all ask the same question: how many tonnes per day of lithium carbonate equivalent (LCE) will the facility produce under realistic operating conditions? This guide walks through a transparent mass-balance calculation that ties together brine flow, lithium concentration, recovery efficiency, and uptime into a defensible daily yield. The approach helps decision-makers compare field pilots, evaluate offtake readiness, and pressure-test economic models before committing capital.
The same discipline used to validate hydrogen storage mass balances in the hydrogen cavern cushion gas guide and to track embodied carbon using the battery passport carbon intensity calculator applies here: define every variable, keep units consistent, and document the operational assumptions behind each number.
Definition and boundary conditions
Recovery yield represents the mass of elemental lithium captured from produced brine and expressed as lithium carbonate equivalent per day. It captures hydrodynamic factors (flow rate), geochemical factors (lithium concentration), process factors (recovery efficiency), and operational factors (uptime). The boundary ends at the point where lithium carbonate or hydroxide leaves the polishing circuit; downstream crystallization or packaging losses are typically minimal but should be noted separately if material.
Unlike grade calculations for hard-rock ores, brine yield depends heavily on steady-state operations and fouling behavior. The formula assumes density near 1,000 kg/m³, appropriate for most geothermal brines after accounting for dissolved solids. If density deviates significantly, adjust volumetric-to-mass conversions accordingly.
Variables and units
Track each parameter with units that map to lab assays and flow meters:
- Q – Brine flow rate (m³/h).
- CLi – Lithium concentration (mg/L) from assay data.
- η – Overall lithium recovery efficiency across sorption, stripping, precipitation, and polishing (%).
- U – Operational uptime fraction of the day (0–1).
- mLi – Elemental lithium mass recovered per day (kg/day).
- mLCE – Lithium carbonate equivalent mass per day (metric tons/day), using the 5.323 stoichiometric multiplier.
Concentration reported in mg/L converts directly to kilograms when multiplied by volume in cubic meters: CLi × Q × 0.001 yields kilograms of lithium per hour assuming a density of 1,000 L per m³. The LCE factor converts elemental lithium to lithium carbonate by molecular weight ratios.
Formulas
The mass balance follows a short chain of multiplications:
Hourly lithium in feed = CLi × Q ÷ 1000 (kg/h)
Daily lithium = Hourly lithium × 24 × U (kg/day)
Recovered lithium = Daily lithium × η / 100 (kg/day)
LCE output = Recovered lithium × 5.323 ÷ 1000 (metric tons/day)
The calculation is deterministic and linear, making it easy to attribute differences between sites. Uptime reflects cleaning and maintenance; η reflects chemistry and process control. Multiplying by 5.323 assumes production of lithium carbonate. If the product is lithium hydroxide, use 5.88 instead and note the change in your documentation.
Step-by-step workflow
1. Validate flow and concentration inputs
Pull a representative week of flow meter data to confirm the average Q value and discard startup transients. Cross-check flow totals against produced brine volume used in heat balance calculations for the power plant. For CLi, use lab assays from multiple wells and depths; avoid single samples that might miss heterogeneity.
2. Set recovery efficiency
Recovery depends on sorbent selectivity, regeneration efficiency, and polishing losses. Use pilot plant data adjusted for temperature and scaling tendencies. If planning for a new resin or adsorbent, model best-case and conservative η scenarios to show the sensitivity of mLCE.
3. Determine uptime realistically
Uptime rarely hits 100% in geothermal environments. Include downtime for filter backwashing, reinjection pump maintenance, and scaling mitigation. Many operators start at 85–92% until fouling behavior stabilizes. Align uptime assumptions with the maintenance philosophy you apply in the immersion cooling heat rejection walkthrough, where thermal cleaning cycles similarly eat into productive hours.
4. Compute the daily yield
Run the formulas using the vetted Q, CLi, η, and U values. Record both elemental lithium and LCE so downstream marketers can communicate in the units buyers expect. If the product will be hydroxide, adjust the stoichiometric factor and explicitly note it in your communications.
5. Document uncertainty and monitoring
Provide ranges for each input based on lab variance and operational swings. During operations, track actual recovery against the calculated expectation and update η quarterly. Use deviation analysis to isolate whether brine grade, flow, or process steps drive any gap.
Validation and limits
Validate assays with certified labs and periodically rerun concentration tests to detect reservoir drift. Compare calculated yields to pilot plant production logs over multiple weeks to ensure the assumed η holds under fouling and temperature swings. If the measured yield consistently lags calculations, inspect resin breakthrough curves and reinjection chemistry for causes.
The calculation assumes steady-state operations and neglects solids handling losses during filter swaps. It also assumes brine density near water; high total dissolved solids can reduce volumetric throughput for fixed pump power. Extreme scaling can lower uptime well below modeled values—when that happens, recalc with lower U until mitigation is proven.
Embed: geothermal lithium recovery calculator
Input brine flow, lithium concentration, recovery efficiency, and uptime to estimate kilograms of lithium and metric tonnes of LCE produced per day.