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

Journal Article · Sat Nov 15 00:00:00 EST 2014 · Waste Management

DOI:https://doi.org/10.1016/J.WASMAN.2014.07.025· OSTI ID:22436825

Tansel, Berrin; Surita, Sharon C.

Highlights: • In the digester gas, D4 and D5 comprised the 62% and 27% if siloxanes, respectively. • In landfill gas, the bulk of siloxanes were TMSOH (58%) followed by D4 (17%). • Methane utilization may be a possible mechanism for TMSOH formation in the landfills. • The geometric configurations of D4 and D5 molecules make them very stable. - Abstract: 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%). Presence of high levels of TMSOH in the landfill gas indicates that methane utilization may be a possible reaction mechanism for TMSOH formation. The free energy change for transformation of D5 and D4 to TMSOH either by hydrogen or methane utilization are thermodynamically favorable. Either hydrogen or methane should be present at relatively high concentrations for TMSOH formation which explains the high levels present in the landfill gas. The high bond energy and bond distance of the Si–O bond, in view of the atomic sizes of Si and O atoms, indicate that Si atoms can provide a barrier, making it difficult to break the Si–O bonds especially for molecules with specific geometric configurations such as D4 and D5 where oxygen atoms are positioned inside the frame formed by the large Si atoms which are surrounded by the methyl groups.

• OSTI ID: 22436825
• Journal Information: Waste Management, Vol. 34, Issue 11; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0956-053X
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ANAEROBIC CONDITIONS
BOND LENGTHS
CONCENTRATION RATIO
CONFIGURATION
FLORIDA
FREE ENERGY
HYDROGEN
LANDFILL GAS
METHANE
OXYGEN
REACTION KINETICS
SANITARY LANDFILLS
SILICON
SILOXANES
SOLID WASTES
TRANSFORMATIONS
VOLATILITY
WASTE WATER
WATER TREATMENT