Introduction of The API Compendium of Greenhouse

The API Compendium of Greenhouse Gas Emissions Estimation Methodologies for the Oil and Natural Gas Industry (known as the API Compendium was released to initiate to study, evaluate and do the comparison of other greenhouse gas estimation methodologies and protocols. The American Petroleum Institute including its many member companies is already implementing action plans to address greenhouse gas (GHG) along with its policy issues (Shires, Loughran, Jones, & Hopkins, 2009).

The main objective the API compendium is to promote the application of standardized and consistent methodologies for the estimation of greenhouse gas from the operations of oil and gas industries (referred to as O & G industries). This API compendium includes techniques for calculations and emission factors which will be used to estimate the GHG emission for oil and gas industries.

The API compendium presents and demonstrates the use of the estimation methods for almost every harmful or injurious gas that is released during the operation of oil and gas industries. The other pollutants are as below;

CO2 = carbon dioxide

CH4 = methane

N2O = nitrous oxide

HFC = hydro-fluorocarbons

PFC = per-fluorocarbons

SF6 = sulfur hexafluoride

CO2e = carbon dioxide equivalent

 The prescribed method includes the method for the estimation of carbon dioxide, nitrous oxide, methane, hydro-fluorocarbons, sulfur hexafluoride, per-fluorocarbons. These methods include almost all the emission sources together with vented, combustion, fugitive. The API has provided the user with decision trees for the easiness in selecting the technique for the estimation or calculation, based on the kind of the material, availability of data and the accuracy required.

2: Emission sources of The API Compendium of Greenhouse

 In the oil and gas industry, the emission of greenhouse gas takes place from one of the following sources. The first type of source is combustion sources. These type of sources include both types of types of equipment, either these are stationary or mobile equipment. The second type of sources includes process emissions and vented sources. Then there are fugitive sources. The fourth type of sources is indirect sources. Some pieces of equipment may emit GHG under more than one class. For example, a compressor emits under fugitive emissions under the pressurized condition, during maintenance, these emit under vented emissions and during normal operations they emit under combustion emissions (Reay, 2007).

Greenhouse gas emission by gas of The API Compendium

2.1 Combustion of The API Compendium of Greenhouse

The combustion includes the formation of the CO2 as a result of the oxidation of carbon Combustion is a chemical process to produce heat and light fuel combines with the oxygen let’s take an example to explain combustion Burning wood in a fire. In this reaction carbohydrates in wood react with the oxygen as a result water and carbon dioxide is form. It also generates the energy. This type of phenomena can be seen in most of the stationary equipment like heaters, burners, boilers, flares engines and incinerators. Sometimes methane CH4 ma also releases in exhaust gases due to incomplete combustion it is impossible that combustion is completely done so carbon monoxide, hydrogen and even carbon may also release. (Glassman, A, Yetter, & Glumac, 2014).

2.2  Process Emissions and Vented Sources of The API Compendium of Greenhouse

These sources occur as a result of release from normal operations, Turnaround activities, emergency events, maintenance, and many other non-routine events. The sources include in this are condensate, crude oil, storage tanks for oil and gas products, loading sources and racks. These also include some equipment like pneumatic devices and chemical injection pumps that release greenhouse gases. These mainly emit CH4 and potentially CO2.

The process vents come in a subcategory of the vented sources. These are the sources that produce emissions due to the chemical transformation or some processing steps. Dehydration, hydrogen plants and gas sweetening catalytic cracking units and naphtha reformers are the examples of these type process vents. GHG emissions may be caused during the startup of equipment. FCC (Fluid Catalytic Cracking) is the most significant conversion processes utilize in the petroleum refineries. It is used for the high molecular weight of the hydrocarbons factions of the heavy crude oil into the more valuable gasoline products. The portion of the heavy crude oil is the feedstock of the FCC, which has initial boiling point around about 340  with the higher atmospheric pressure. The portion of the heavy crude oil is normally referred for the heavy gas and the vacuum gas oil. In the process of the FCC feedstock is heated as a high temperature as well as moderate pressure plus into contact hot powered catalyst.

2.3  Fugitive Sources of The API Compendium of Greenhouse

The unintentional releases from the equipment leaks and piping components at sealed surfaces are considered as fugitive emissions. These also include the leaks in the underground pipeline. These are usually leaks of low volume from sealed surfaces. Some specific fugitive emissions source types include seals, rotating surfaces and mechanical joints.

2.4 Indirect Sources of The API Compendium of Greenhouse

These emissions are the result of activities of combustion of fuels, more precisely hydrocarbon fuels, for the generation of electricity steam, heat, or for the cooling where this energy is purchased or imported. Indirect emission is a critical test and is a mind boggling region, yet we anticipate that 84% of multinationals will take a gander at methods for diminishing their roundabout emanations inside the following three years. Right now is an ideal opportunity to begin assessing how this will influence your business - as it will assume an expanding job in buying choices and in money related and chance arranging. It will likewise be a key factor in recognizing brands, building notorieties and improving buyer devotion.3.  Emissions estimation methods of The API Compendium of Greenhouse

There are the following emissions estimation methods which are used for the emissions sources as given below;

Direct Measurement

Emission Factors

Mass balance

Engineering Calculation  

 Direct measurement is is obtained form the emission sources, by using the variety of methods including the source testing, continuous emission monitoring system (CEMS). The Emission factors relate the amount of the emission from the given piece of the equipment of the activity of the equipment .  

Please put together a table comparing the quantification methodologies used for GHG estimation in each protocol/standard. For instance, see the table below (just for your reference). Alternatively, you can create a workbook in Excel and list all emissions sources and categories with the respective calculation methodologies for the three (3) GHG we estimate (CO2, CH4, and N2O). In preparing this workbook, please keep in mind the most commonly used emissions determination methodologies for emissions sources such as internal combustion engines:

Continuous Emissions Monitoring System Or CEMS

Predictive Emissions Monitoring System Or PEMS

Measured—Stack Test Data

Portable Analyzer Test Data

Vendor-Supplied Emission Factors

Ap-42 Emission Factors

Source Category Emission Model 

Mass Balance

Engineering Judgment 

3.1  Combustion emissions estimation methods of The API Compendium of Greenhouse

These methods include combustion emission from mobile and stationary sources, flares and other many miscellaneous sources. These methods are applicable to any fuel-based combustion source.

Usually the companies used three “Tiers for emission calculations depending on data availability and the different levels of complexity.  

Following are some of the methods that can be used to estimate the combustion Emissions.

Prepare a table summarizing data required to collect for all combustion sources (see below)

3.1.1    Estimating Fuel Consumption Data from Energy Output or Volumetric Flow

In this compendium, the energy input has been used as the basis for the estimation of combustion emissions. The reliability of the approach is due to the mass rates or fuel combustion volumes. The actual fuel data is possible for consumption should be used according to this API compendium.

This method is further categorized in the types based on the type and source of the data that we are using for the emission estimation. In the first method we use equipment data for the estimation of fuel usage. In another method, if we are provided with the input of fuel then we will calculate the energy input by conversion of the volumetric flow rate.

3.1.2    Conversion between Gross and Net Heating Value of The API Compendium of Greenhouse

In this method, we simply imply IPCC’s convention, and the emission factors reported on the basis of lower heating value converted to higher heating value. In this method, we multiply the lower heating values with a factor (the factor selection depends upon the type of fuel) to convert it to higher heating value.

3.1.3    Fuel Combustion Emissions Estimated from Fuel Composition and Usage

In this method we estimate the emissions by considering the combustion of the fuel. In this, we apply a material balance. It is the most reliable method for the emission estimation. Factor of Emission, potential of global warming, rate of mass emission, maximum uncontrolled emission, maximum uncontrolled carbon dioxide equivalent, pollution control efficiency as well as mass emission rate maximum control.  We use the data of fuel usage and the carbon analysis of fuel.  The estimation of CO2 emission is purely based on the 100% oxidation of the carbon present in the fuel. The API compendium estimates methane gas emission on the basis of emission factors.

In this first we calculate the carbon content percentage by using the following formula.

3.1.4    Fuel Combustion Emissions Estimated on a Fuel Basis for Stationary Sources

This method is implied if the carbon analysis of fuel is not provided. In this case, we use the average composition of the fuel. We can also different type of available default values for the implication of this method. First of all, we can use the average composition of the fuel available by default. Then we can also make use of the carbon dioxide values for the estimation of carbon dioxide emissions.

3.1.5    Emissions Estimated on an Equipment Basis for Stationary Sources

For the implication of this method, we have to be provided with the fuel usage for specific equipment like turbine, engine, boiler etc. some other greenhouse gas estimation methods give the factors for CO2 emissions for stationary combustion on the basis of the equipment.

 But these factors are not consistent with the methods provided in the API compendium. As early mentioned the API compendium’s methods are purely based on the 100% oxidation of the carbon o the fuel.

3.2       Process and Vented Emissions Estimation Methods of The API Compendium of Greenhouse

There are a number of sources for vented emissions, associated with the operations of the oil and gas industry. These emissions may be a result of vents and non-fired stacks. These sources are very specific about the type of the operations. That's why this method subcategorized according to the type of the process.

3.2.1    Gas Treatment Processes of The API Compendium of Greenhouse

These processes may include the emissions from glycol dehydrators or glycol pumps. Some of the other equipment is which will be responsible for these emissions are desiccant dehydrators, sulfur, and acid gas removal units and other alternatives for the glycol dehydrators.

The rational estimating procedures are used for the gas treatment process. To better estimates the gas treatments for the gas emission rational procedures is developed which is used either in the plant specific data, and the more general data. This procedure is evaluating by using the full scale data from the 16 treatment facilities.

3.2.2    Refinery Processes Vents of The API Compendium of Greenhouse

These include some specialized process vents that are emitting GHG in refineries. Some of these are linked with the regeneration of the catalytic reformer and catalytic cracking. Some other emissions are used to from catalytic cracking units, fluid coking units, coking units delayed, units  of catalytic reforming, units  of coke calcining, asphalt blowing operations, blow down systems, storage tanks, equipment leaks, loading operations, flares, as well as sulfur recovery plants the Petroleum Refineries Sector also reports process emissions. The by-products include the processes like hydrogen plant, cokers (Flexi cokers, fluid cokers and delayed cokers) and other catalyst regenerators.

The Catalytic cracking is the estimation procedures for the Refineries process of vents, which is used in the petroleum refineries.  Catalytic cracking units plus the fluid coking units by the rated capacities less than the 10,000 could find the coke burn factor plus the carbon content of coke.

3.2.3    Cold Process Vents of The API Compendium of Greenhouse

These vents are related to vents released by the emissions without any combustion. Due to this, these sources mostly contain methane emission more than carbon dioxide. The main sources for these vents usually include small and miscellaneous downstream and upstream.

Due to a variance of the sources that can be considered as cold vents, se we can’t calculate the emission of methane or carbon dioxide by using some default values. But, we can use general material balance approach to estimate the concentrations and vent emissions.

Where;

Ex is the emission of the any component in unit mass, in unit time.

VR= Volume of combustion components per unit of heat content

VT= Volumetric flow rate of fuel

Fx = Volume of combustion components resulting from combustion

n= Index for measurement period.

Molecular weight of pollutant “x”

3.3       Fugitive Emission Estimation Methods of The API Compendium of Greenhouse

These emission methods refer to the estimation of the emissions from the leaks in the equipment. It is obvious that if any equipment is pressurized then it will definitely have the possibility of leakage. The sources of leakage on involve flanges, valve, seals and any other related equipment. Sometime the fugitive emissions could be from sources of no-point operations. Such examples are pits, wastewater treatment, ponds, and impoundments.

Average SOCMI “Synthetic Organic Chemical Manufacturing Industry “leak –no leak estimations procedures are used to estimate the fugitive emissions. Fugitive emissions involve the process of eth equipment leaks, flanges, valves for the process of emission and the treatment facilities.

3.3.1    Equipment Leaks of The API Compendium of Greenhouse

There are a number of sources in the oil and gas industry that are considered as sources for fugitive emissions. The equipment leaks include leaks from flanges, valve, pump seals and relief valves. There are the following three methods or approaches for greenhouse fugitive. The first method is Average emission factor and the second is Correlation equations and the last technique is screening value range. The recommended approaches for greenhouse gas fugitive equipment can be listed or graded on the basis of accuracy and data requirements. To calculate fugitive emissions only the Average Emission Factor Technique might be used when an Inspection as well as at the facility Maintenance Program is not in place as well as reliable site-specific screening data are not accessible. In the event that an Inspection and Maintenance Program is set up at the office and solid site-particular screening information are accessible, the Correlation Equation Method can be utilized to figure the criminal emanations. Oil and Gas Production offices may utilize the Correlation Equations what's more, Factors for Refineries and Marketing Terminal. To calculate the fugitive emissions the third method Screening value range Method this is based on two specific levels of leaks. These factors can be of equipment level, component level, facility level, and component level approach for measurement. PART 2

4.         Emission categories for O&G business activities of The API Compendium of Greenhouse

For the convenience of the companies in this API compendium, the oil and gas industries are categorized for the idea of describing applicable methodologies for the emission estimation.

These industries can be categorized as follows;

4.1       Conventional Exploration and Production of The API Compendium of Greenhouse

In this category, we extract the petroleum from the underground reservoir. The reservoir can be located offshore or onshore. This is because the natural gas can be produced from the same well. The exploration process mainly informs different geophysical and geological tests and surveys. The main components of the emissions are CO2, N2O, and CH4.  The sources of the combustion for these types of industries generally are, boilers, dehydrators, heaters, flares, fire pumps, turbine electric generators etc.

There are a number of steps that are included in the production of oils or gas.  There are numbers of steps that are implicated for the production. The most important method is the separation process. Also, the wellhead may have a vent to discharge casing head gas. It could be a source of both methane and carbon dioxide gas.

4.2       Oil Sands and Heavy Oil Upgrading

This category includes the extraction of heavy oil from sand deposits, by the unconventional means. Oils sands are mixtures of sand, clay, water, bitumen naturally. There are certain methods to separate the bitumen from sand deposits. Some of the methods are in-situ recovery, surface mining, and extraction. After that, the bitumen is upgraded by removing carbon and by adding some amount of hydrogen and synthetic crude oil is produced (Gray, 2015).

4.3       Gas Processing of The API Compendium of Greenhouse

In this segment, only processing operations are included. In the processing of gas, we recover high-value liquid products from the gas stream. Process vents from gas sweetening, dehydration, pneumatic devices, and many other non-routine activities can result in the emission of methane gas. Combustion sources such as heaters, engines, boilers, and flares may result in carbon dioxide emission (Kidnay, Parrish, & McCartney, 2011).

4.4       Carbon Capture and Geological Storage of The API Compendium of Greenhouse

 These storages refer to the chains of the processes that are used to collect the gas stream of carbon dioxide. In this step of capturing the carbon dioxide gas is separated from other gaseous products. Then it is compressed to facilitate the transportation. In these operations the combustions and indirect emissions also the fugitive and vented emissions can result from equipment which is used as a part of the process of capture.

4.5       Natural Gas Storage and LNG Operations of The API Compendium of Greenhouse

These facilities are used for the storage of the natural gas that is produced usually in summer. It is usually done to deliver the gas during the time of peak demand. In this, the first the gas is liquefied by a super cooling process and then stored in tanks with heavy insulations.

For fugitive sources and LNG, vents are not fully developed for the methane emissions. The LNG systems are designed in such a way to avoid the contact with outside air. When the methane is vaporized, the emission factors those are applicable to the storage of natural gas through operations (Mokhatab, Mak, Valappil, & Wood, 2013).

4.6       Refining of The API Compendium of Greenhouse

This segment in API compendium consists of almost all the refinery sits that include both crude and finished products for example gasoline. It includes many distillation steps that split petroleum hydrocarbons into the boiling rangers with narrow spacing. There are a number of process vents that can contribute to greenhouse gas emission. Fugitive methane gas emissions can result from the components and piping associated with refining processes. Some of the process vents include catalytic crackers for fluids, regenerators and boiler vets (Fahim, Al-Sahhaf, & Elkilani, 2009).

References of The API Compendium of Greenhouse

Fahim, M. A., Al-Sahhaf, T. A., & Elkilani, A. (2009). Fundamentals of Petroleum Refining. Elsevier.

Glassman, I., A, R., Yetter, & Glumac, N. G. (2014). Combustion. Academic Press.

Gray, M. R. (2015). Upgrading Oilsands Bitumen and Heavy Oil. The University of Alberta.

Kidnay, A. J., Parrish, W. R., & McCartney, D. G. (2011). Fundamentals of Natural Gas Processing. CRC Press.

Mokhatab, S., Mak, J. Y., Valappil, J. V., & Wood, D. A. (2013). Handbook of Liquefied Natural Gas. Gulf Professional Publishing.

Reay, D. (2007). Greenhouse Gas Sinks. CABI.

Shires, T. M., Loughran, C. J., Jones, S., & Hopkins, E. (2009). Compendium of greenhouse gas emissions methodologies for the oil and natural gas industry. URS Corporation for the American Petroleum Institute (API). API, Washington DC.