Biogas Monitoring

Analytical testing dots Biogas Monitoring

Biogas refers to gas produced by anaerobic digestion or fermentation of biodegradable materials such as biomass, manure, sewage, municipal waste, green waste, plant material and energy crops.

It is composed primarily of methane and carbon dioxide, with small amounts of other constituents.

ALS Environmental offers a wide range of tests to support biogas operations, from characterization of the gas itself to investigations of odors at biogas facilities.

Biogas production via anaerobic digestion can be applied as a treatment process in many agricultural animal operations to reduce odor, produce energy, and improve the storage and handling characteristics of manure.

Biogas can contain constituents that are less desirable for gas-to-energy applications, like siloxanes. Siloxanes are a product of the anaerobic decomposition of materials commonly found in soaps and detergents. Combustion of gas containing siloxanes can result in the formation of mineral deposits on the internal components of combustion engines. These deposits can greatly impede the performance efficiency of the power-generating turbines, thus it is desirable that the siloxanes be removed from the gas by either chemical or mechanical means.

The following is a list of common siloxanes, also referred to as volatile organic silicon compounds (VOSCs):

Name Formula Abbreviations
Hexamethylcyclotrisiloxane C12H18O3Si3 D3
Octamethylcyclotetrasiloxane C8H24O4Si4 D4
 Decamethylcyclopentasiloxane   C10H30O5Si5 D5
Dodecamethylcyclohexasiloxane C12H36O6Si6 D6
Hexamethyldisiloxane C6H18Si2O   L2, MM
Octamethyltrisiloxane C8H24Si3O2 L3, MDM  
Decamethyltetrasiloxane C10H30Si4O3 L4, MD2M  
Dodecamethylpentasiloxane C12H36Si5O4 L5, MD3M  
Trimethysilanol C3H10OSi TMS

D3, D4, D5, L2, L3 and TMS are the siloxanes most commonly detected in landfill gas.

ALS Environmental has developed a novel sampling and analytical approach for siloxanes. It involves collecting landfill gas with a sorbent tube, followed by extraction at the laboratory and analysis by gas chromatography/mass spectrometry.

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Benefits of this new approach:

  • Sampling is relatively simple. It does not require ice baths or complicated setups. Depending on the configuration of the sampling location, it can be as simple as connecting a length of tubing to a sampling port, connecting a rotameter to moderate the flow rate, and attaching the sample tube. After approximately 30 minutes, the sampling is completed, and the tubes may be disconnected and submitted to the lab for analysis.
  • Since the samples are collected on tubes, rather than with impingers of methanol solutions or in bags with flammable landfill gas, they do not represent a Dangerous Good or Hazardous Material. Therefore, they can be shipped more cost-effectively using normal shipping procedures. They do not require special boxes, containers, labels, documentation or additional procedures.
  • The data is reported in several units: µg/Tube, µg/m³, and as µg/m³ as Silicon, to accommodate a variety of uses or calculations by the end user.

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ALS Environmental offers the following methods often used to characterize biogas:

  • Methane by EPA Method 3C modified or EPA Method 25C modified
  • Carbon Dioxide by EPA 3C modified
  • Hydrogen, Oxygen, Nitrogen, Carbon Monoxide by EPA 3C modified
  • TNMOC by EPA 25C modified
  • BTU analysis by ASTM D3588
  • Hydrogen Sulfide and reduced sulfur compounds by ASTM D5504
  • VOCs by EPA TO-15
  • Siloxanes by ALS in-house method

Analytical testing dotsLearn more about Landfill Gas Monitoring...

Learn more about Fuel Testing...

Learn more about Micro-Elemental Testing...

Learn more about Waste-to-Energy...

Learn more about Siloxane Testing...

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