Natural Gas + CCS Net Emissions Calculator
This calculator estimates the net CO2 emissions a natural gas power plant still releases after carbon capture is installed -- the residual climate impact that remains even when a strong capture system is running. It takes the plant's annual natural gas consumption and a capture rate, applies the EPA's standard emission factor for natural gas combustion, and reports the gross CO2 emissions, the captured CO2, and the net CO2 emissions that escape uncaptured. It pairs naturally with our CO2 Capture Cost Calculator for the cost side of running that capture equipment, and our Carbon Emissions Calculator for a direct comparison to an uncontrolled natural gas facility with no capture at all.
Representative of a large natural gas combined-cycle (NGCC) power plant. Check your facility's actual annual fuel consumption for a precise figure.
90% is a commonly cited capture rate target for post-combustion capture systems on natural gas plants.
(annual natural gas consumption (MMBtu/year) × 117) ÷ 2000
gross CO2 emissions (tons/year) × (capture rate (%) ÷ 100)
gross CO2 emissions (tons/year) − captured CO2 (tons/year)
This uses the EPA's standard emission factor of 117 lb CO2 per MMBtu of natural gas combusted. Actual facility emissions can vary slightly based on gas composition and combustion efficiency -- consult your facility's actual emissions monitoring data for regulatory or reporting purposes.
Results update live as you type. For planning and field-check estimates — always verify against applicable standards and equipment ratings.
How we calculate this →Even at a strong 90% capture rate, a natural gas plant with CCS still emits real CO2 -- in this example, 58,500 tons a year get through uncaptured, out of 585,000 tons gross. That remaining 10% isn't a rounding error: at gigawatt scale across a fleet of plants, uncaptured emissions from 'high capture' CCS facilities can still add up to a meaningful climate impact, which is exactly why some analysts push for higher capture rate requirements (95%+) in policy and permitting discussions, even though each additional percentage point of capture typically costs more to achieve.
How natural gas + CCS net emissions are calculated
This calculator estimates the net CO2 emissions a natural gas power plant still releases after carbon capture is installed, by converting annual fuel consumption into gross CO2 emissions with the EPA emission factor, then applying a capture rate to split that gross into captured and uncaptured (net) portions. Three quantities tie the calculation together.
Gross CO2 Emissions (tons/year) = (Annual Natural Gas Consumption (MMBtu/year) × 117) ÷ 2000. The EPA's standard emission factor for pipeline-quality natural gas combustion is 117 lb CO2 per MMBtu; multiplying annual fuel consumption by that factor gives gross CO2 in pounds, and dividing by 2000 converts pounds to short tons. At the defaults (10,000,000 MMBtu/year), that is (10,000,000 × 117) ÷ 2000 = 585,000 tons/year.
Captured CO2 (tons/year) = Gross CO2 Emissions (tons/year) × (Capture Rate (%) ÷ 100). The capture rate is the share of CO2 in the flue gas stream that the capture system actually removes; multiplying the gross emissions by that share gives the tonnage captured each year. At the defaults (585,000 tons/year and 90% capture rate), that is 585,000 × 0.90 = 526,500 tons/year.
Net CO2 Emissions (tons/year) = Gross CO2 Emissions (tons/year) − Captured CO2 (tons/year). Subtracting the captured tonnage from the gross leaves the CO2 that escapes uncaptured -- the plant's residual climate impact even with CCS running. At the defaults (585,000 − 526,500), that is 58,500 tons/year.
Two notes on the model. First, the 117 lb CO2/MMBtu emission factor is the EPA's published default for pipeline-quality natural gas combustion, based on the fuel's carbon content and standard combustion stoichiometry; actual facility emissions can vary slightly with gas composition and combustion efficiency, so the result is an estimate best replaced by facility-specific monitoring data for regulatory reporting. Second, this calculator covers combustion emissions at the power plant only -- it does not account for upstream methane leakage during natural gas extraction, processing, and pipeline transport, which is a separate and significant source of greenhouse gas emissions not captured by this tool. For the cost of running the capture equipment that produces these net emissions, see the CO2 Capture Cost Calculator; for a direct comparison to an uncontrolled natural gas facility with no capture at all, see the Carbon Emissions Calculator. Data sources: EPA standard natural gas combustion emission factor (117 lb CO2/MMBtu) from the EPA GHG Emission Factors Hub and AP-42; post-combustion capture rate targets (90% commonly cited, 95%+ in newer project targets) from DOE (Department of Energy), NETL (National Energy Technology Laboratory), and IEA (International Energy Agency) CCS technology assessments; net emissions and capture rate policy discussions from IPCC (Intergovernmental Panel on Climate Change) and IEAGHG technical reports. Verification: with defaults (10,000,000 MMBtu/year, 90% capture rate), Gross CO2 Emissions = 585,000 tons/year, Captured CO2 = 526,500 tons/year, Net CO2 Emissions = 58,500 tons/year.