ALS offers a wide variety of analytical methods for the characterization of landfill gas.
ALS services support our clients in complying with regulatory standards, as well as assist in effectively analyzing for trace level and potentially odorous compounds. The information we supply allows clients to establish baseline gas composition, perform routine monitoring, troubleshoot scrubber systems, evaluate energy content, and in the case of gas-to-energy operations, assist in preventing equipment/turbine damage.
FREQUENTLY ASKED QUESTIONS
What are the most common siloxanes found in LFG/biogas?
Our field research has consistently detected trimethylsilanol, octamethylcyclotetrasiloxane (D4), and decamethylcyclopentasiloxane (D5) in landfill gas. Similarly, D4 and D5 have been observed in biogas, while trimethylsilanol is not typically a significant factor.
Can the samples be collected and submitted in a Tedlar bag instead of sampling with a tube?
Yes, a Tedlar bag may be used to collect the samples for this analysis. Note, the standard hold time for a Tedlar bag sample is 72 hours from sample collection to analysis. Reporting limits for samples collected with a Tedlar bag will be higher than those for samples collected on a sorbent tube, due to a smaller sample size.
Will high humidity affect the sample results?
Some of the siloxane compounds are soluble in water (most notably Trimethylsilanol and D3). Therefore, high humidity (>90%) may hinder the overall siloxane recovery. Appreciable water build up inside the tubes may also reduce the performance of the sorbent, so in cases where there are visible water droplets it is recommended that a Tedlar Bag be used for collection.
What about inclement weather?
In cases of extreme cold, lower recoveries have been observed due to siloxane adherence to the sample tubing. Recommendations to improve recoveries in cold weather include making the sample train as short as possible to minimize losses, using insulated tubing, or sampling with a Tedlar bag.
Are there advantages in one collection method over the other?
Both methods yield comparable data, so the selection of sampling media can be a function of parameters such as sampling preference/familiarity, field time, reporting limits, shipping requirements, and hold time.
What is the sample hold time?
Sorbent tubes are stable for up to 14 days after sampling and may be stored at room temperature prior to analysis. Tedlar bags may be stored for 72 hours prior to analysis.
Can volatile organic compounds be determined from the siloxane sampling tube?
While this sampling and analytical approach is suitable for a limited list of VOCs, most of the VOCs typically reported by EPA TO-15 or TO-17 are not available with this analysis.