Managing siloxanes in biogas-to-energy facilities: Economic comparison of pre- vs post-combustion practices.

Siloxanes present in small concentrations in biogas interfere with the operation of biogas-to-energy facilities. During biogas combustion, siloxanes form white deposits on engine components (engine heads, spark plugs, valves) in crystals or amorphous forms depending on the temperature. The purpose of this study was to evaluate the economic feasibility of biogas-to-energy systems for managing the operational challenges due to siloxanes in biogas.

Selectivity and limitations of carbon sorption tubes for capturing siloxanes in biogas during field sampling.

Siloxane levels in biogas can jeopardize the warranties of the engines used at the biogas to energy facilities. The chemical structure of siloxanes consists of silicon and oxygen atoms, alternating in position, with hydrocarbon groups attached to the silicon side chain. Siloxanes can be either in cyclic (D) or linear (L) configuration and referred with a letter corresponding to their structure followed by a number corresponding to the number of silicon atoms present.

Evaluation of a Full-Scale Water-Based Scrubber for Removing Siloxanes from Digester Gas: A Case Study.

Siloxanes are becoming more prominent in digester gas at water resource recovery facilities because of their wide use in personal care products. This study evaluates a full-scale water-based scrubber operating in a water resource recovery facility (Miami, FL). The digester gas is used for energy generation due to its high methane content.

Contribution of siloxanes to COD loading at wastewater treatment plants: phase transfer, removal, and fate at different treatment units.

Cyclic volatile methylsiloxanes (cVMSs) are entering to waste stream in increasing quantities due to their increasing use in personal care products (i.e., shampoos, creams).

Differences in volatile methyl siloxane (VMS) profiles in biogas from landfills and anaerobic digesters and energetics of VMS transformations.

The objectives of this study were to compare the types and levels of volatile methyl siloxanes (VMS) present in biogas generated in the anaerobic digesters and landfills, evaluate the energetics of siloxane transformations under anaerobic conditions, compare the conditions in anaerobic digesters and municipal solid waste (MSW) landfills which result in differences in siloxane compositions. Biogas samples were collected at the South District Wastewater Treatment Plant and South Dade Landfill in Miami, Florida. In the digester gas, D4 and D5 comprised the bulk of total siloxanes (62% and 27%, respectively) whereas in the landfill gas, the bulk of siloxanes were trimethylsilanol (TMSOH) (58%) followed by D4 (17%).

A multiphase analysis of partitioning and hazard index characteristics of siloxanes in biosolids.

Siloxanes are widely used in personal care and industrial products due to their soft texture, low surface tension, thermal stability, antimicrobial and hydrophobic properties, among other characteristics. As a result, they are released to gas phase during waste decompositions and found in biogas at landfills and digester gas at wastewater treatment facilities. The objectives of this study were to investigate the release of siloxanes in aqueous and gaseous phase as well as in biosolids in a local wastewater treatment facility.

Oxidation of siloxanes during biogas combustion and nanotoxicity of Si-based particles released to the atmosphere.

Siloxanes have been detected in the biogas produced at municipal solid waste landfills and wastewater treatment plants. When oxidized, siloxanes are converted to silicon oxides. The objectives of this study were to evaluate the transformation of siloxanes and potential nanotoxicity of Si-based particles released to the atmosphere from the gas engines which utilize biogas.

Emergence and fate of cyclic volatile polydimethylsiloxanes (D4, D5) in municipal waste streams: release mechanisms, partitioning and persistence in air, water, soil and sediments.

Siloxane use in consumer products (i.e., fabrics, paper, concrete, wood, adhesive surfaces) has significantly increased in recent years due to their excellent water repelling and antimicrobial characteristics.