Heat of combustion

{{Short description|Amount of heat released by combustion of a quantity of substance}} The '''heating value''' (or '''energy value''', '''calorific value''', '''heat of combustion''') of a [[Chemical substance|substance]], usually a [[fuel]] or [[food]] (see [[food energy]]), is the amount of [[heat]] released during the [[combustion]] of a specified amount of it. The '''enthalpy of combustion''' is the same value expressed as an [[enthalpy]], where release of heat is described as negative number.

The ''calorific value'' is the total [[energy]] released as heat when a substance undergoes complete [[combustion]] with [[oxygen]] under [[standard temperature and pressure|standard conditions]]. The chemical reaction is typically a [[hydrocarbon]] or other organic molecule reacting with [[oxygen]] to form [[carbon dioxide]] and [[water]] and release heat. It may be expressed with the quantities:

* energy/[[mole (unit)|mole]] of fuel * energy/[[mass]] of fuel * energy/[[volume]] of the fuel

There are two kinds of heating values, called high(er) and low(er), depending on how much the products are allowed to cool and whether compounds like {{chem|H|2|O}} are allowed to condense. The high heat values are conventionally measured with a [[bomb calorimeter]]. Low heat values are calculated from high heat value test data. They may also be calculated as the difference between the [[standard enthalpy of formation|standard enthalpies/heats of formation]] Δ''H''{{su|b=f|p=⦵}} of the products and reactants (though this approach is somewhat artificial since most heats of formation are typically calculated from measured heats of combustion).<ref>{{cite journal |title=Effect of structural conduction and heat loss on combustion in micro-channels |date=2006 |url=https://www.tandfonline.com/doi/abs/10.1080/13647830500277332 |publisher=Taylor & Francis Online|doi=10.1080/13647830500277332 |last1=Leach |first1=T. T. |last2=Cadou |first2=C. P. |last3=Jackson |first3=G. S. |journal=Combustion Theory and Modelling |volume=10 |issue=1 |pages=85–103 |bibcode=2006CTM....10...85L |url-access=subscription }}</ref>

By convention, the (higher) heat of combustion is defined to be the heat released for the complete combustion of a compound in its standard state to form stable products in their standard states: hydrogen is converted to water (in its liquid state), carbon is converted to carbon dioxide gas, and nitrogen is converted to nitrogen gas. That is, the heat of combustion, Δ''H''°comb, is the heat of reaction of the following process: : {{chem|C|''c''|H|''h''|N|''n''|O|''o''}} (std.) + (''c'' + {{frac|''h''|4}} - {{frac|''o''|2}}) {{chem|O|2}} (g) → ''c''{{chem|CO|2}} (g) + {{frac|''h''|2}}{{chem|H|2|O}} (''l'') + {{frac|''n''|2}}{{chem|N|2}} (g)

Chlorine and sulfur are not quite standardized; they are usually assumed to convert to hydrogen chloride gas and {{chem|SO|2}} or {{chem|SO|3}} gas, respectively, or to dilute aqueous hydrochloric and [[sulfuric acid]]s, respectively, when the combustion is conducted in a bomb calorimeter containing some quantity of water.<ref>{{cite journal |last1=Kharasch |first1=M.S. |title=Heats of combustion of organic compounds |journal=Bureau of Standards Journal of Research |date=February 1929 |volume=2 |issue=2 |pages=359 |doi=10.6028/jres.002.007 |doi-access=free }}</ref><ref>{{cite journal |title=Theoretical Analysis of Waste Heat Recovery from an Internal Combustion Engine in a Hybrid Vehicle |url=https://www.jstor.org/stable/44687347 |publisher=Jstor|jstor=44687347 |last1=Arias |first1=Diego A. |last2=Shedd |first2=Timothy A. |last3=Jester |first3=Ryan K. |journal=SAE Transactions |date=2006 |volume=115 |pages=777–784 }}</ref>

== Definitions ==

=== Higher heating value === The higher heating value (HHV; ''gross energy'', ''upper heating value'', ''gross calorific value'' ''GCV'', or ''higher calorific value''; ''HCV'') indicates the upper limit of the available thermal energy produced by a complete combustion of fuel. It is measured as a unit of energy per unit mass or volume of substance. The HHV is determined by bringing all the products of combustion back to the original pre-combustion temperature, including condensing any vapor produced. Such measurements often use a standard temperature of {{convert|25|C|F K|abbr=on}}.<ref name="tdb14"/> This is the same as the thermodynamic heat of combustion since the [[enthalpy]] change for the reaction assumes a common temperature of the compounds before and after combustion, in which case the water produced by combustion is condensed to a liquid. The higher heating value takes into account the [[enthalpy of vaporization|latent heat of vaporization]] of [[water]] in the combustion products, and is useful in calculating heating values for fuels where [[condensation]] of the reaction products is practical (e.g., in a gas-fired [[boiler]] used for space heat).

The [[American Petroleum Institute]] (API) refers to the HHV at 25 °C as the ''standard heat of combustion'', and the HHV at 60 °F as the ''gross heat of combustion''. The two values are approximately equal.<ref name="tdb14"/>

When used as a "heating value", HHV assumes all the water component is in liquid state at the end of combustion (in product of combustion) and that all heat delivered at temperatures below {{convert|150|C}} can be put to use.

=== Lower heating value === The lower heating value (LHV; ''net calorific value''; ''NCV'', or ''lower calorific value''; ''LCV'') is another measure of available thermal energy produced by a combustion of fuel, measured as a unit of energy per unit mass or volume of substance. In contrast to the HHV, the LHV considers energy losses such as the energy used to vaporize water{{dash}}although its exact definition is not uniformly agreed upon.

; Water-only LHV : One definition is simply to subtract the [[enthalpy of vaporization|heat of vaporization]] of the produced water from the higher heating value. This treats any H2O formed as a vapor that is released as a waste. The energy required to vaporize the water is therefore lost. It assume that the water component of a combustion process is in vapor state at the end of combustion, as opposed to the [[#Higher heating value|higher heating value]] (HHV) (a.k.a. ''gross calorific value'' or ''gross CV'') which assumes that all of the water in a combustion process is in a liquid state after a combustion process. ; GPSA LHV : This definition, used by Gas Processors Suppliers Association (GPSA), is the [[enthalpy]] of all combustion products minus the enthalpy of the fuel at the reference temperature (GPSA currently uses {{convert|60|F|C|frac=9}}), minus the enthalpy of the [[stoichiometry|stoichiometric]] oxygen (O2) at the reference temperature, minus the heat of vaporization of the vapor content of the combustion products. : It can be alternatively restated as the HHV at reference temperature minus the heat of vaporization of the vapor content of the combustion products. By specifying a ''reference temperature'', all products can be taken into account. : This work is based on [[American Petroleum Institute]] (API) research project 44, which used {{convert|25|C|F}} as the reference. ; API LHV : The API defines a ''net heat of combustion'' to correspond to LHV. It uses the reference temperature of {{convert|60|F|C|frac=9}}, but with gaseous water. It is calculated as the ''gross heat of combustion'' (HHV at reference temperature) subtracted by the heat of vaporization of water at reference temperature (and at the [[vapor pressure]] corresponding to reference temperature).<ref name="tdb14">{{cite web |title=Technical Data Book: Chapter 14 – Combustion [API TECHNICAL REPORT TDB-14 1ST EDITION, XXXX 202X] |url=https://eballotprodstorage.blob.core.windows.net/eballotscontainer/TDB-14_e1%20ballot%20draft.pdf}}</ref> ; 150 °C LHV : This LHV is the amount of heat released when the products are cooled to {{convert|150|C}}. This means that the latent heat of vaporization of [[water]] (and many other potential products) is not recovered. It is useful in comparing fuels where condensation of the combustion products is impractical, or heat at a temperature below {{convert|150|C}} cannot be put to use.

The definition in which the combustion products are all returned to the reference temperature is more easily calculated from the higher heating value than when using other definitions. It will in fact give a slightly different answer.

=== Accounting for moisture === Both HHV and LHV can be expressed in terms of AR (all moisture counted), MF and MAF (only water from combustion of hydrogen). AR, MF, and MAF are commonly used for indicating the heating values of coal:

* {{anchor|AR}}'''AR''' (as received) indicates that the fuel heating value has been measured with all moisture- and ash-forming minerals present. * '''MF''' (moisture-free) or '''dry''' indicates that the fuel heating value has been measured after the fuel has been dried of all inherent moisture but still retaining its ash-forming minerals. * '''MAF''' (moisture- and ash-free) or '''DAF''' (dry and ash-free) indicates that the fuel heating value has been measured in the absence of inherent moisture- and ash-forming minerals.

==== Gross heating value ==== '''Gross heating value''' accounts for water in the exhaust leaving as vapor, as does LHV, but gross heating value also includes liquid water in the fuel prior to combustion. This value is important for fuels like [[wood]] or [[coal]], which will usually contain some amount of water prior to burning.

===End products for different elements=== Zwolinski and Wilhoit defined, in 1972, "gross" and "net" values for heats of combustion. In the gross definition the products are the most stable compounds, e.g. {{chem|H|2|O}}(l), {{chem|Br|2}}(l), {{chem|I|2}}(s) and {{chem|H|2|SO|4}}(l). In the net definition the products are the gases produced when the compound is burned in an open flame, e.g. {{chem|H|2|O}}(g), {{chem|Br|2}}(g), {{chem|I|2}}(g) and {{chem|SO|2}}(g). In both definitions the products for C, F, Cl and N are {{chem|CO|2}}(g), {{chem|HF}}(g), {{chem|Cl|2}}(g) and {{chem|N|2}}(g), respectively.<ref>{{cite book |last1=Zwolinski |first1=Bruno J |last2=Wilhoit |first2=Randolf C. |chapter=Heats of formation and Heats of Combustion |pages=316–342 |chapter-url=https://web.mit.edu/8.13/8.13c/references-fall/aip/aip-handbook-section4l.pdf |editor1-last=Dwight E. |editor1-first=Gray |editor2-first=Bruce H. |editor2-last=Billings |title=American Institute of Physics Handbook |date=1972 |publisher=McGraw-Hill |isbn=978-0-07-001485-5 |access-date=2021-08-06 |archive-date=2021-08-06 |archive-url=https://web.archive.org/web/20210806144519/https://web.mit.edu/8.13/8.13c/references-fall/aip/aip-handbook-section4l.pdf |url-status=dead }}</ref>

There are many other definitions of "gross" and "net".

== Estimating heating values ==

=== By elemental composition === The heating value of a fuel can be estimated with the results of ultimate analysis of fuel, which provides for the percentages of each element by mass.

==== By oxygen consumption ==== For an [[Organic compound|organic]] fuel of composition C''c''H''h''O''o''N''n'', the (higher) heat of combustion is {{nowrap|418 kJ/mol × (''c'' + 0.3 ''h'' − 0.5 ''o'')}} usually to a good approximation (±3% for more than 500 organic compounds). This corresponds to 418 kJ/mol for each mole of {{O2}} consumed.<ref name="Schmidt-Rohr 15">{{cite journal |last1=Schmidt-Rohr |first1=Klaus |title=Why Combustions Are Always Exothermic, Yielding About 418 kJ per Mole of O 2 |journal=Journal of Chemical Education |date=8 December 2015 |volume=92 |issue=12 |pages=2094–2099 |doi=10.1021/acs.jchemed.5b00333 |bibcode=2015JChEd..92.2094S |doi-access=free }}</ref><ref name="Dlugogorski1994"> Dlugogorski, B. Z.; Mawhinney, J. R.; Duc, V. H. (1994). "The Measurement of Heat Release Rates by Oxygen Consumption Calorimetry in Fires Under Suppression". ''Fire Safety Science'' '''1007''': 877.</ref> The accuracy of such a simplistic formula is due to the very high [[bond enthalpy]] of {{O2}}, which renders other bond enthalpies largely irrelevant.<ref name="Schmidt-Rohr 15"/>

This estimate does not work well for inorganic fuels such as [[carbon monoxide]].{{efn|The oxygen-consumption formula estimates 209 kJ/mol for CO, compared to the actual ΔcH of −283.0 kJ/mol.}} It also works poorly for [[explosives]] such as [[nitroglycerin]]{{efn|The oxygen-consumption formula estimates a nonsensical 0 kJ/mol for nitroglycerin, though it does not really combust.}} and other substances containing high-energy functional groups such as nitro and azide groups.

==== Dulong's Formula==== The heating value can be calculated using Dulong's Formula, which treats [[carbon]], [[hydrogen]], [[sulfur]] as combustible elements:

: HHV [kJ/g] = 33.87 mC + 122.3 (mH − mO/8) + 9.4 mS

where mC, mH, mO and mS are the mass fractions of carbon, hydrogen, oxygen, and sulfur on any (wet, dry or ash free) basis, respectively.

There are many modifications of the formula using different weighing terms. Some estimate the LHV instead of the HHV. A comparison of these formulas is available in Hokosai ''et al.'' (2016).<ref>{{cite journal |last1=Hosokai |first1=Sou |last2=Matsuoka |first2=Koichi |last3=Kuramoto |first3=Koji |last4=Suzuki |first4=Yoshizo |title=Modification of Dulong's formula to estimate heating value of gas, liquid and solid fuels |journal=Fuel Processing Technology |date=1 November 2016 |volume=152 |pages=399–405 |doi=10.1016/j.fuproc.2016.06.040 |bibcode=2016FuPrT.152..399H }}</ref>

The API publishes its own Dulong-style formulas for petroleum liquids and synthetic fuels.<ref name="tdb14"/>

== Measuring heating values == The higher heating value is experimentally determined in a [[Calorimeter#Bomb calorimeters|bomb calorimeter]]. The combustion of a stoichiometric mixture of fuel and oxidizer (e.g. two moles of hydrogen and one mole of oxygen) in a steel container at {{convert|25|C}} is initiated by an ignition device and the reactions allowed to complete. When hydrogen and oxygen react during combustion, water vapor is produced. The vessel and its contents are then cooled to the original 25 °C and the higher heating value is determined as the heat released between identical initial and final temperatures.

When the [[#Lower heating value|lower heating value]] (LHV) is determined, cooling is stopped at 150 °C and the reaction heat is only partially recovered. The limit of 150 °C is based on [[acid gas]] dew-point.

Note: Higher heating value (HHV) is calculated with the product of water being in liquid form while lower heating value (LHV) is calculated with the product of water being in vapor form.

== Relation between heating values == {{cleanup section|reason=LHV is derived from HHV by definition, so any relation should be merged into the definition section.|date=March 2026}} The difference between the two heating values depends on the chemical composition of the fuel. In the case of pure carbon or carbon monoxide, the two heating values are almost identical, the difference being the sensible heat content of carbon dioxide between 150 °C and 25 °C ([[sensible heat]] exchange causes a change of temperature, while [[latent heat]] is added or subtracted for [[phase transition]]s at constant temperature. Examples: heat of vaporization or [[enthalpy of fusion|heat of fusion]]). For hydrogen, the difference is much more significant as it includes the sensible heat of water vapor between 150 °C and 100 °C, the latent heat of condensation at 100 °C, and the sensible heat of the condensed water between 100 °C and 25 °C. In all, the higher heating value of hydrogen is 18.2% above its lower heating value (142{{nbsp}}MJ/kg vs. 120{{nbsp}}MJ/kg). For hydrocarbons, the difference depends on the hydrogen content of the fuel. For [[gasoline]] and [[diesel fuel|diesel]] the higher heating value exceeds the lower heating value by about 10% and 7%, respectively, and for natural gas about 11%.

A common method of relating HHV to LHV is: : <math>\mathrm{HHV} = \mathrm{LHV} + H_\mathrm{v}\left(\frac{n_\mathrm{H_2O,out}}{n_\mathrm{fuel,in}}\right)</math> where ''H''v is the heat of vaporization of water at the datum temperature (typically 25 °C), ''n''{{chem|H|2|O}},out is the number of moles of water vaporized and ''n''fuel,in is the number of moles of fuel combusted.<ref>Air Quality Engineering, CE 218A, W. Nazaroff and R. Harley, University of California Berkeley, 2007</ref>

* Most applications that burn fuel produce water vapor, which is unused and thus wastes its heat content. In such applications, the lower heating value must be used to give a 'benchmark' for the process. * However, for true energy calculations in some specific cases, the higher heating value is correct. This is particularly relevant for [[natural gas]], whose high hydrogen content produces much water, when it is burned in [[condensing boiler]]s and [[power station|power plants]] with [[flue-gas condensation]] that condense the water vapor produced by combustion, recovering heat which would otherwise be wasted.

== Usage of terms == Engine manufacturers typically rate their engines fuel consumption by the lower heating values since the exhaust is never condensed in the engine, and doing this allows them to publish more attractive numbers than are used in conventional power plant terms. The conventional power industry had used HHV (high heat value) exclusively for decades, even though virtually all of these plants did not condense exhaust either. American consumers should be aware that the corresponding fuel-consumption figure based on the higher heating value will be somewhat higher.

The difference between HHV and LHV definitions causes endless confusion when quoters do not bother to state the convention being used.<ref>{{cite web|url=http://www.claverton-energy.com/the-difference-between-lcv-and-hcv-or-lower-and-higher-heating-value-or-net-and-gross-is-clearly-understood-by-all-energy-engineers-there-is-no-right-or-wrong-definition.html|title=The difference between LCV and HCV (or Lower and Higher Heating Value, or Net and Gross) is clearly understood by all energy engineers. There is no 'right' or 'wrong' definition.{{dash}}Claverton Group|website=www.claverton-energy.com}}</ref> since there is typically a 10% difference between the two methods for a power plant burning natural gas. For simply benchmarking part of a reaction the LHV may be appropriate, but HHV should be used for overall [[Energy efficiency (physics)|energy efficiency]] calculations if only to avoid confusion, and in any case, the value or convention should be clearly stated.

== Heat of combustion tables == {| class="wikitable sortable" style="text-align: right;" align="left" |+ Higher (HHV) and lower (LHV) heating values of some common fuels<ref name=NIST>{{cite book |title=NIST Chemistry WebBook |date=2021 |publisher=NIST Office of Data and Informatics |series=NIST Standard Reference Database Number 69 |doi=10.18434/T4D303 |editor-last1=Linstrom |editor-first1=Peter }}</ref> at 25 °C ! rowspan=2 | Fuel ! colspan=3 | HHV ! LHV |- ! [[megajoule|MJ]]/kg{{efn|name=mol2kg}} ! [[BTU]]/lb{{efn|name=mj2btu}} ! [[kilojoule|kJ]]/[[mole (unit)|mol]] ! MJ/kg |- |align=left| [[Hydrogen]]<ref>{{cite web |url=https://webbook.nist.gov/cgi/inchi/InChI%3D1S/H2/h1H |title=Hydrogen |website=NIST Chemistry WebBook |publisher=NIST Office of Data and Informatics |series=NIST Standard Reference Database Number 69}}</ref> || 141.79 || 60969 || 285.83{{efn|name=water}}<ref>{{cite web |url=https://webbook.nist.gov/cgi/inchi/InChI%3D1S/H2O/h1H2 |title=Water |website=NIST Chemistry WebBook |publisher=NIST Office of Data and Informatics |series=NIST Standard Reference Database Number 69}}</ref> || 119.96 |- |align=left| [[Methane]] || 55.52 || 23874 || 890.7<ref>{{cite web |url=https://webbook.nist.gov/cgi/inchi/InChI%3D1S/CH4/h1H4 |title=Methane |website=NIST Chemistry WebBook |publisher=NIST Office of Data and Informatics |series=NIST Standard Reference Database Number 69}}</ref> || 50.00 |- |align=left| [[Ethane]] || 51.90 || 22319 || 1560.7<ref>{{cite web |url=https://webbook.nist.gov/cgi/inchi?ID=C74840&Units=SI&Mask=1#Thermo-Gas |title=Ethane |website=NIST Chemistry WebBook |publisher=NIST Office of Data and Informatics |series=NIST Standard Reference Database Number 69}}</ref> || 47.62 |- |align=left| [[Propane]] || 50.33 || 21641 || 2219.2<ref>{{cite web |url=https://webbook.nist.gov/cgi/inchi/InChI%3D1S/C3H8/c1-3-2/h3H2%2C1-2H3 |title=Propane |website=NIST Chemistry WebBook |publisher=NIST Office of Data and Informatics |series=NIST Standard Reference Database Number 69}}</ref> || 46.35 |- |align=left| [[Butane]] || 49.51 || 21288 || 2877.5<ref>{{cite web |url=https://webbook.nist.gov/cgi/inchi/InChI%3D1S/C4H10/c1-3-4-2/h3-4H2%2C1-2H3 |title=Butane |website=NIST Chemistry WebBook |publisher=NIST Office of Data and Informatics |series=NIST Standard Reference Database Number 69}}</ref> || 45.75 |- |align=left| [[Pentane]] || 48.64 || 20913 || 3509{{efn|name=pentane}}<ref>{{cite web |url=https://webbook.nist.gov/cgi/inchi/InChI%3D1S/C5H12/c1-3-5-4-2/h3-5H2%2C1-2H3 |title=Pentane |website=NIST Chemistry WebBook |publisher=NIST Office of Data and Informatics |series=NIST Standard Reference Database Number 69}}</ref> || 45.35 |- |align=left| [[Jet kerosene]]<ref>{{cite web|url=https://cdn.cdp.net/cdp-production/cms/guidance_docs/pdfs/000/000/477/original/CDP-Conversion-of-fuel-data-to-MWh.pdf|title=CDP Technical Note: Conversion of fuel data to MWh}}</ref> || 46.42 || 19960 || || 44.1 |- |align=left| [[Kerosene]] || 46.20 || 19866 || || 43.00 |- |align=left| [[Paraffin wax]] || 46.00 || 19780 || || 41.50 |- |align=left| [[Diesel fuel|Diesel]] || 44.80 || 19264 || || 43.4 |- |align=left| [[Coal]] ([[anthracite]]) || 32.50 || 13975 || || |- |align=left|[[Wood]] ([[Heat of combustion#Accounting for moisture|MAF]])|| 21.70 || 9331 || || |- |align=left|[[Wood fuel]] || 16.0 || 6880 || || 17.0 |- |align=left|[[Coal]] ([[lignite]]{{dash}}[[United States|USA]])|| 15.00 || 6450 || || |- |align=left|[[Peat]] (dry)|| 15.00 || 6450 || || |- |align=left|[[Peat]] (damp)|| 6.00 || 2580 || || |} {{clear}} {{notelist|refs= {{efn|name=mol2kg|MJ/kg values are calculated from kJ/mol (ΔcH°/(molecular weight * Mu), Mu {{=}} 1.00000000105)}} {{efn|name=mj2btu|BTU/lb values are calculated from MJ/kg (1 MJ/kg {{=}} 430 BTU/lb)}} {{efn|name=water|ΔfH°, liquid phase)}} {{efn|name=pentane|liquid phase}} }} {{clear}}

{| class="wikitable sortable" style="text-align: right;" align="left" |+Higher heating value of some less common fuels<ref name=NIST/> ! Fuel !! [[megajoule|MJ]]/kg !! [[BTU]]/lb !! [[kilojoule|kJ]]/[[mole (unit)|mol]] |- |align=left| [[Methanol]] || 22.7 || 9,800 || 726 |- |align=left| [[Ethanol]] || 29.7 || 12,800 || 1,367 |- |align=left| [[1-Propanol]]|| 33.6 || 14,500 || 2,020 |- |align=left| [[Acetylene]]|| 49.9 || 21,500 || 1,300 |- |align=left| [[Benzene]] || 41.8 || 18,000 || 3,268 |- |align=left| [[Ammonia]] || 22.5 || 9,690 || 382.6 |- |align=left| [[Hydrazine]] || 19.4 || 8,370 || 622.0 |- |align=left| [[Hexamine]]|| 30.0 || 12,900 || 4,200.0 |- |align=left| [[Carbon]] || 32.8 || 14,100 || 393.5 |}

{| class="wikitable sortable" style="text-align: right;" align="left" |+Lower heating value for some organic compounds (at {{convert|25|C|disp=sqbr}}){{Citation needed|date=May 2011}} ! Fuel ! [[megajoule|MJ]]/kg ! [[megajoule|MJ]]/[[liter|L]] ! [[BTU]]/lb ! [[Joule|kJ]]/[[mole (unit)|mol]] |- ! colspan="5" | Alkanes |- | [[Methane]] | 50.009 | 6.9 | 21,504 | 802.34 |- | [[Ethane]] | 47.794 | — | 20,551 | 1,437.2 |- | [[Propane]] | 46.357 | 25.3 | 19,934 | 2,044.2 |- | [[Butane]] | 45.752 | — | 19,673 | 2,659.3 |- | [[Pentane]] | 45.357 | 28.39 | 21,706 | 3,272.6 |- | [[Hexane]] | 44.752 | 29.30 | 19,504 | 3,856.7 |- | [[Heptane]] | 44.566 | 30.48 | 19,163 | 4,465.8 |- | [[Octane]] | 44.427 | — | 19,104 | 5,074.9 |- | [[Nonane]] | 44.311 | 31.82 | 19,054 | 5,683.3 |- | [[Decane]] | 44.240 | 33.29 | 19,023 | 6,294.5 |- | [[Undecane]] | 44.194 | 32.70 | 19,003 | 6,908.0 |- | [[Dodecane]] | 44.147 | 33.11 | 18,983 | 7,519.6 |- |- ! colspan="5" | Isoparaffins |- | [[Isobutane]] | 45.613 | — | 19,614 | 2,651.0 |- |- | [[Isopentane]] | 45.241 | 27.87 | 19,454 | 3,264.1 |- | [[2-Methylpentane]] | 44.682 | 29.18 | 19,213 | 3,850.7 |- | [[2,3-Dimethylbutane]] | 44.659 | 29.56 | 19,203 | 3,848.7 |- | [[2,3-Dimethylpentane]] | 44.496 | 30.92 | 19,133 | 4,458.5 |- | [[2,2,4-Trimethylpentane]] | 44.310 | 30.49 | 19,053 | 5,061.5 |- ! colspan="5" | Naphthenes |- | [[Cyclopentane]] | 44.636 | 33.52 | 19,193 | 3,129.0 |- | [[Methylcyclopentane]] | 44.636? | 33.43? | 19,193? | 3,756.6? |- | [[Cyclohexane]] | 43.450 | 33.85 | 18,684 | 3,656.8 |- | [[Methylcyclohexane]] | 43.380 | 33.40 | 18,653 | 4,259.5 |- ! colspan="5" | Monoolefins |- | [[Ethylene]] | 47.195 | — | — | — |- | [[Propylene]] | 45.799 | — | — | — |- | [[1-Butene]] | 45.334 | — | — | — |- | [[cis-2-Butene|''cis''-2-Butene]] | 45.194 | — | — | — |- | [[trans-2-Butene|''trans''-2-Butene]] | 45.124 | — | — | — |- | [[Isobutene]] | 45.055 | — | — | — |- | [[1-Pentene]] | 45.031 | — | — | — |- | [[2-Methyl-1-pentene]] | 44.799 | — | — | — |- | [[1-Hexene]] | 44.426 | — | — | — |- ! colspan="5" | Diolefins |- | [[1,3-Butadiene]] | 44.613 | — | — | — |- | [[Isoprene]] | 44.078 | - | — | — |- ! colspan="5" | Nitrous derived |- | [[Nitromethane]] | 10.513 | — | — | — |- | [[Nitropropane]] | 20.693 | — | — | — |- ! colspan="5" | Acetylenes |- | [[Acetylene]] | 48.241 | — | — | — |- | [[Methylacetylene]] | 46.194 | — | — | — |- | [[1-Butyne]] | 45.590 | — | — | — |- | [[1-Pentyne]] | 45.217 | — | — | — |- ! colspan="5" | Aromatics |- | [[Benzene]] | 40.170 | — | — | — |- | [[Toluene]] | 40.589 | — | — | — |- | [[o-Xylene|''o''-Xylene]] | 40.961 | — | — | — |- | [[m-Xylene|''m''-Xylene]] | 40.961 | — | — | — |- | [[p-Xylene|''p''-Xylene]] | 40.798 | — | — | — |- | [[Ethylbenzene]] | 40.938 | — | — | — |- | [[1,2,4-Trimethylbenzene]] | 40.984 | — | — | — |- | [[N-Propylbenzene|''n''-Propylbenzene]] | 41.193 | — | — | — |- | [[Cumene]] | 41.217 | — | — | — |- ! colspan="5" | Alcohols |- | [[Methanol]] | 19.930 | 15.78 | 8,570 | 638.6 |- | [[Ethanol]] | 26.70 | 22.77 | 12,412 | 1,230.1 |- | [[1-Propanol]] | 30.680 | 24.65 | 13,192 | 1,843.9 |- | [[Isopropanol]] | 30.447 | 23.93 | 13,092 | 1,829.9 |- | [[n-Butanol|''n''-Butanol]] | 33.075 | 26.79 | 14,222 | 2,501.6 |- | [[Isobutanol]] | 32.959 | 26.43 | 14,172 | 2,442.9 |- | [[Tert-butanol|''tert''-Butanol]] | 32.587 | 25.45 | 14,012 | 2,415.3 |- | [[1-Pentanol|''n''-Pentanol]] | 34.727 | 28.28 | 14,933 | 3,061.2 |- | [[Isoamyl alcohol]] | 31.416? | 35.64? | 13,509? | 2,769.3? |- ! colspan="5" | Ethers |- | [[Methoxymethane]] | 28.703 | — | 12,342 | 1,322.3 |- | [[Ethoxyethane]] | 33.867 | 24.16 | 14,563 | 2,510.2 |- | [[Propoxypropane]] | 36.355 | 26.76 | 15,633 | 3,568.0 |- | [[Butoxybutane]] | 37.798 | 28.88 | 16,253 | 4,922.4 |- ! colspan="5" | Aldehydes and ketones |- | [[Formaldehyde]] | 17.259 | — | — |570.78 <ref>{{cite web|url=http://webbook.nist.gov/cgi/cbook.cgi?ID=C50000&Mask=1|title=Methanal|website=webbook.nist.gov}}</ref> |- | [[Acetaldehyde]] | 24.156 | — | — | — |- | [[Propionaldehyde]] | 28.889 | — | — | — |- | [[Butyraldehyde]] | 31.610 | — | — | — |- | [[Acetone]] | 28.548 | 22.62 | — | — |- ! colspan="5" | Other species |- | [[Graphite|Carbon (graphite)]] | 32.808 | — | — | — |- | [[Hydrogen]] | 120.971 | 1.8 | 52,017 | 244 |- | [[Carbon monoxide]] | 10.112 | — | 4,348 | 283.24 |- | [[Ammonia]] | 18.646 | — | 8,018 | 317.56 |- | [[Sulfur]] (solid) | 9.163 | — | 3,940 | 293.82 |- |}

; Note * There is no difference between the lower and higher heating values for the combustion of carbon, carbon monoxide and sulfur since no water is formed during the combustion of those substances. * BTU/lb values are calculated from MJ/kg (1 MJ/kg = 430 BTU/lb).

=== Higher heating values of natural gases from various sources === The [[International Energy Agency]] reports the following typical higher heating values per Standard cubic metre of gas:<ref name=KWES>{{cite web|url=https://www.ourenergypolicy.org/wp-content/uploads/2016/09/KeyWorld2016.pdf|title=Key World Energy Statistics (2016)|website=iea.org}}</ref>

{{div col|colwidth=22em}} * [[Algeria]]: 39.57{{nbsp}}MJ/Sm3 * [[Bangladesh]]: 36.00{{nbsp}}MJ/Sm3 * [[Canada]]: 39.00{{nbsp}}MJ/Sm3 * [[China]]: 38.93{{nbsp}}MJ/Sm3 * [[Indonesia]]: 40.60{{nbsp}}MJ/Sm3 * [[Iran]]: 39.36{{nbsp}}MJ/Sm3 * [[Netherlands]]: 33.32{{nbsp}}MJ/Sm3 * [[Norway]]: 39.24{{nbsp}}MJ/Sm3 * [[Pakistan]]: 34.90{{nbsp}}MJ/Sm3 * [[Qatar]]: 41.40{{nbsp}}MJ/Sm3 * [[Russia]]: 38.23{{nbsp}}MJ/Sm3 * [[Saudi Arabia]]: 38.00{{nbsp}}MJ/Sm3 * [[Turkmenistan]]: 37.89{{nbsp}}MJ/Sm3 * [[United Kingdom]]: 39.71{{nbsp}}MJ/Sm3 * [[United States]]: 38.42{{nbsp}}MJ/Sm3 * [[Uzbekistan]]: 37.89{{nbsp}}MJ/Sm3 {{div col end}}

The lower heating value of natural gas is normally about 90% of its higher heating value. This table is in Standard cubic metres (1{{nbsp}}[[standard atmosphere (unit)|atm]], 15{{nbsp}}°C), to convert to values per Normal cubic metre (1{{nbsp}}atm, 0{{nbsp}}°C), multiply above table by 1.0549.

== See also == {{Portal|Chemistry|Energy}} {{div col|colwidth=20em|small=yes}} * [[Adiabatic flame temperature]] * [[Cost of electricity by source]] * [[Electrical efficiency]] * [[Fuel efficiency#Energy content of fuel|Energy content of fuel]] * [[Energy conversion efficiency]] * [[Energy density]] * [[Energy value of coal]] * [[Exothermic reaction]] * [[Figure of merit]] * [[Fire]] * [[Food energy]] * [[Internal energy]] * [[ISO 15971]] * [[Mechanical efficiency]] * [[Thermal efficiency]] * [[Wobbe index]]: heat density {{div col end}}

== References == {{notelist}} {{reflist|30em}}

==Further reading== * {{Cite book |title=Carburants et moteurs |first=J.-C. |last=Guibet |publisher=Publication de l'Institut Français du Pétrole |isbn=978-2-7108-0704-9|year=1997 }}

== External links == * [http://webbook.nist.gov/chemistry/ NIST Chemistry WebBook] * {{cite web |url= http://cta.ornl.gov/bedb/appendix_a/Lower_and_Higher_Heating_Values_of_Gas_Liquid_and_Solid_Fuels.pdf |title= Lower and Higher Heating Values of Gas, Liquid and Solid Fuels |work= Biomass Energy Data Book |publisher= U.S. Department of Energy |date= 2011}}

[[Category:Engineering thermodynamics]] [[Category:Combustion]] [[Category:Fuels]] [[Category:Thermodynamic properties]] [[Category:Nuclear physics]] [[Category:Thermochemistry]]