National Physical Laboratory

Biogas

Biogas

Biogas and biomethane are becoming an increasingly important means to delivering a sustainable, low carbon energy future. Renewable energy targets have driven significant growth in the biogas economy, as biomethane can be blended with natural gas in existing transmission networks and used to power vehicles.

NPL provides traceable high accuracy gas mixtures for biogas analysis. Mixtures containing additional components not listed on this page may also be available on request.

Biogas composition

Multi-component standards are available, including, but not limited to, the components and ranges in the table below. UKAS accreditation is also available for the majority of components.

Component Amount fraction range
(cmol/mol)
Uncertainty
(k=2) (% rel.)
Methane 40 – 99.9 ≤ 0.2
Carbon dioxide 0.04 – 55 ≤ 0.2
Nitrogen 0.02 – 25 ≤ 0.2
Hydrogen 0.05 – 2 ≤ 1.0
Oxygen 0.05 – 2 ≤ 1.0


Biogas impurities

Raw biogas contains a diverse range of impurities, which vary in amount fraction depending on the source material used. A European specification is being developed that will impose maximum limit values on the impurities found within upgraded biogas and biomethane. NPL's gas reference standards are being used to directly support the development of the biogas economy.

Siloxanes

Siloxane impurities within biogas cause damage to processing equipment when combusted, even at trace-levels. NPL offers traceable gas standards containing the most common siloxanes found in biogas. The table provides typical values for amount fraction ranges and uncertainties, based on over six years of research and development.

Molecular structure of L2, L3, D4 and D5 siloxanes (C: black, H: white, O: red, Si: teal)
Molecular structure of L2, L3, D4 and D5 siloxanes
(C: black, H: white, O: red, Si: teal)

 

Component Amount fraction range (µmol/mol) Relative Uncertainty (%) Matrix
L2 (Hexamethyldisiloxane) 0.025 – 200 1 – 3

Biogas,
Methane or
Nitrogen

L3 (Octamethyltrisiloxane) 0.004 – 100 1 – 10
D4 (Octamethylcyclotetrasiloxane) 0.085 – 55 1 – 7
D5 (Decamethylcyclopentasiloxane) 0.006 – 10 2 – 10


Sulphur species

Depending on the nature of the substrate, the anaerobic digestion process produces sulphur-containing compounds ranging from ppb levels to several thousands of ppm. NPL offers traceable reference standards of binary and multi-component sulphur compounds within biogas. UKAS accreditation is available for matrices of methane and nitrogen.

Component

Amount fraction range (µmol/mol)

Relative Uncertainty (%)

Matrix

Hydrogen sulphide

0.4 to 5000

2 - 5

Biogas

Carbonyl sulphide

0.4 to 5000

2 - 5

Carbon disulphide

0.4 to 200

2 - 5

Dimethyl sulphide

0.4 to 200

2 - 5

Ethyl methyl sulphide

0.4 to 200

2 - 5

Diethyl sulphide

0.4 to 200

2 - 5

Methanethiol

0.4 to 200

2 - 5

Ethanethiol

0.4 to 200

2 - 5

2-propanethiol

0.4 to 200

2 - 5

1-propanethiol

0.4 to 200

2 - 5

2-methyl-2-propanethiol

0.4 to 200

2 - 5

Tetrahydrothiophene

0.4 to 200

2 - 5


Terpenes

Terpenes are a common impurity found within biogas due to the nature of the biological source material. The presence of trace level terpenes within biomethane cause the scent of typical sulphur odorant additives to be masked, posing a health and safety risk. In addition they are capable of causing degradation of polymeric seal materials used within transmission grid pipelines. NPL provides reference standards containing terpenes within biogas, methane and nitrogen matrices.

Component

Amount fraction range (µmol/mol)

Relative Uncertainty (%)

Matrix

(+/-)-α-pinene

0.01-10

2 - 5

Biogas or
Methane

(+/-)-β-pinene

0.01-10

2 - 5

(+)-3-carene

0.01-10

2 - 5

1,8-cineole (eucalyptol)

0.01-10

2 - 5

Limonene

0.01-10

2 - 5

Isoprene

0.01-10

2 - 5


BTEX

Benzene, toluene, ethylbenzene and xylenes are volatile mono-aromatic hydrocarbons found within biogas. NPL provides reference standards containing terpenes within biogas, methane and nitrogen matrices.

Component

Amount fraction range (nmol/mol)

Relative Uncertainty (%)

Matrix

Benzene

500 - 2000

2 - 5

Biogas or
Methane

Toluene

500 - 2000

2 - 5

Ethylbenzene

500 - 2000

2 - 5

m+p-xylene

500 - 2000

2 - 5

o-xylene

500 - 2000

2 - 5


Ammonia

Ammonia is produced during the anaerobic digestion process and is found within biogas. NPL provides reference standards containing ammonia within biogas, methane and nitrogen matrices.

Component

Amount fraction range (µmol/mol)

Relative Uncertainty (%)

Matrix

Ammonia

10 - 1000

5 - 10

Biogas or
Methane


Proficiency testing

NPL offers 'on-demand' proficiency testing schemes for biogas composition and impurities. Please contact us for more information using the details below.

Contact

To enquire about any of our measurement service offerings and receive a quotation, please email gases@npl.co.uk or telephone Customer Services on +44 20 8943 8715.

Last Updated: 26 Sep 2016
Created: 19 Sep 2013

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