Greenhouse gases (GHGs)

Scope

EPA addresses the reduction of man-made emissions of greenhouse gases through various programs, including pre-construction permitting and operating permits. EPA also inventories greenhouse gas emissions from the largest sources in the U.S. through the Greenhouse Gas Reporting Program.

Regulatory citations

• 40 CFR 98 — Mandatory Greenhouse Gas Reporting

Key definitions

• Biodiesel: A mono-akyl ester derived from biomass and conforming to ASTM D6751–08, Standard Specification for Biodiesel Fuel Blend Stock (B100) for Middle Distillate Fuels.
• Biomass: Non-fossilized and biodegradable organic material originating from plants, animals or micro-organisms, including products, by-products, residues and waste from agriculture, forestry and related industries as well as the non-fossilized and biodegradable organic fractions of industrial and municipal wastes, including gases and liquids recovered from the decomposition of nonfossilized and biodegradable organic material.
• Blast furnace: A furnace that is located at an integrated iron and steel plant and is used for the production of molten iron from iron ore pellets and other iron bearing materials.
• Blendstocks: Petroleum products used for blending or compounding into finished motor gasoline. These include RBOB (reformulated blendstock for oxygenate blending) and CBOB (conventional blendstock for oxygenate blending), but exclude oxygenates, butane, and pentanes plus.
• Blowdown: The act of emptying or depressuring a vessel. This may also refer to the discarded material such as blowdown water from a boiler or cooling tower.
• Bulk natural gas liquid or NGL: Mixtures of hydrocarbons that have been separated from natural gas as liquids through the process of absorption, condensation, adsorption, or other methods. Generally, such liquids consist of ethane, propane, butanes, and pentanes plus. Bulk NGL is sold to fractionators or to refineries and petrochemical plants where the fractionation takes place.
• Carbon dioxide equivalent or CO2e: The number of metric tons of CO ₂  emissions with the same global warming potential as one metric ton of another greenhouse gas, and is calculated using Equation A–1 of this subpart.
• Carbon dioxide stream: Carbon dioxide that has been captured from an emission source (e.g. a power plant or other industrial facility) or extracted from a carbon dioxide production well plus incidental associated substances either derived from the source materials and the capture process or extracted with the carbon dioxide.
• Carbon share: Tthe percent of total mass that carbon represents in any product.
• CH4: Methane.
• CO2: Carbon dioxide.
• Continuous emission monitoring system or CEMS: The total quipment required to sample, analyze, measure, and provide, by means of readings recorded at least once every 15 minutes, a permanent record of gas concentrations, pollutant emission rates, or gas volumetric flow rates from stationary sources.
• Emergency generator: A stationary combustion device, such as a reciprocating internal combustion engine or turbine that serves solely as a secondary source of mechanical or electrical power whenever the primary energy supply is disrupted or discontinued during power outages or natural disasters that are beyond the control of the owner or operator of a facility. An emergency generator operates only during emergency situations, for trainingof personnel under simulated emergency conditions, as part of emergency demand response procedures, or for standard performance testing procedures as required by law or by the generator manufacturer. A generator that serves as a back-up power source under conditions of load shedding, peak shaving, power interruptions pursuant to an interruptible power service agreement, or scheduled facility maintenance shall not be considered an emergency generator.
• Ethane: A paraffinic hydrocarbon with molecular formula C ₂H ₆.
• Ethanol: means an anhydrous alcohol with molecular formula C ₂H ₅OH.
• Ethylene: An olefinic hydrocarbon with molecular formula C ₂H ₄.
• Feedstock: Raw material inputs to a process that are transformed by reaction, oxidation, or other chemical or physical methods into products and byproducts. Supplemental fuel burned to provide heat or thermal energy is not a feedstock.
• Flare: A combustion device, whether at ground level or elevated, that uses an open flame to burn combustible gases with combustion air provided by uncontrolled ambient air around the flame.
• Flowmeter: Aa device that measures the mass or volumetric rate of flow of a gas, liquid, or solid moving through an open or closed conduit (e.g. flowmeters include, but are not limited to, rotameters, turbine meters, coriolis meters, orifice meters, ultra-sonic flowmeters, and vortex flowmeters).
• Fossil fuel: Natural gas, petroleum, coal, or any form of solid, liquid, or gaseous fuel derived from such material, for purpose of creating useful heat.
• Fossil fuel-fired: Powered by combustion of fossil fuel, alone or in combination with any other fuel, regardless of the percentage of fossil fuel consumed.
• Fuel gas: Gas generated at a petroleum refinery or petrochemical plant and that is combusted separately or in any combination with any type of gas.
• Gas-fired unit: A stationary combustion unit that derives more than 50 percent of its annual heat input from the combustion of gaseous fuels, and the remainder of its annual heat input from the combustion of fuel oil or other liquid fuels.
• Gas monitor: An instrument that continuously measures the concentration of a particular gaseous species in the effluent of a stationary source.
• Gasification: The conversion of a solid or liquid raw material into a gas.
• Hydrofluorocarbons or HFCs: A class of GHGs consisting of hydrogen, fluorine, and carbon.
• Industrial greenhouse gases: Nitrous oxide or any fluorinated greenhouse gas.
• Landfill gas: Gas produced as a result of anaerobic decomposition of waste materials in the landfill. Landfill gas generally contains 40 to 60 percent methane on a dry basis, typically less than 1 percent non-methane organic chemicals, and the remainder being carbon dioxide.
• MMBtu: Million British thermal units.
• Municipal solid waste landfill or MSW landfill: An entire disposal facility in a contiguous geographical space where household waste is placed in or on land. An MSW landfill may also receive other types of RCRA Subtitle D wastes (40 CFR 257.2) such as commercial solid waste, nonhazardous sludge, conditionally exempt small quantity generator waste, and industrial solid waste. Portions of an MSW landfill may be separated by access roads, public roadways, or other public right-of-ways. An MSW landfill may be publicly or privately owned.
• N2O: Nitrous oxide.
• Natural gas: A naturally occurring mixture of hydrocarbon and non-hydrocarbon gases found in geologic formations beneath the earth’s surface, of which the principal constituent is methane. Natural gas may be field quality or pipeline quality.
• Natural gas liquids (NGLs): Those hydrocarbons in natural gas that are separated from the gas as liquids through the process of absorption, condensation, adsorption, or other methods. Generally, such liquids consist of ethane, propane, butanes, and pentanes plus. Bulk NGLs refers to mixtures of NGLs that are sold or delivered as undifferentiated product from natural gas processing plants.
• Oil-fired unit: A stationary combustion unit that derives more than 50 percent of its annual heat input from the combustion of fuel oil, and the remainder of its annual heat input from the combustion of natural gas or other gaseous fuels.
• Oxygenates: Substances which, when added to gasoline, increase the oxygen content of the gasoline. Common oxygenates are ethanol, methyl tertiary butyl ether (MTBE), ethyl tertiary butyl ether (ETBE), tertiary amyl methyl ether (TAME), diisopropyl ether (DIPE), and methanol
• Perfluorocarbons or PFCs: A class of greenhouse gases consisting on the molecular level of carbon and fluorine.
• Petrochemical: Methanol, acrylonitrile, ethylene, ethylene oxide, ethylene dichloride, and any form of carbon black.
• Petroleum product: All refined and semi-refined products that are produced at a refinery by processing crude oil and other petroleum-based feedstocks, including petroleum products derived from co-processing biomass and petroleum feedstock together, but not including plastics or plastic products. Petroleum products may be combusted for energy use, or they may be used either for non-energy processes or as non-energy products. The definition of petroleum product for importers and exporters excludes waxes.
• Process unit: The equipment assembled and connected by pipes and ducts to process raw materials and to manufacture either a final product or an intermediate used in the onsite production of other products. The process unit also includes the purification of recovered byproducts.
• Storage tank: A vessel (excluding sumps) that is designed to contain an accumulation of crude oil, condensate, intermediate hydrocarbon liquids, or produced water and that is constructed entirely of non-earthen materials (e.g., wood, concrete, steel, plastic) that provide structural support.
• Supplier: A producer, importer, or exporter in any supply category included in Table A-5 to this subpart, as defined by the corresponding subpart of this part.
• Trace concentrations: Concentrations of less than 0.1 percent by mass of the process stream.

Summary of requirements

• Stationary sources that are already covered by preconstruction, operating permits, or other air permits may also need to include greenhouse gas emissions in their permitting calculations.
• Large stationary sources in 41 industrial categories covered under the Greenhouse Gas Reporting Program need to track their greenhouse gas emissions and report them to EPA every year.