siloxanes in biogas: formation and effect on biogas ...biogas produced at landfills and anaerobic...

Siloxanes in Biogas: Formation and Effect on

Biogas Quality and Energy Costs

Sharon Surita, PhD Candidate

Department of C iv i l &Environmental Engineering

January 22, 2015

OBJECTIVES Compare levels and types of siloxanes present in biogas produced at landfills and anaerobic digesters,

Evaluate conditions which cause differences in siloxane profiles between landfills and anaerobic digesters;

Evaluate potential effects of siloxanes on the operation of biogas to energy facilities, and

Evaluate potential effects of siloxanes on energy costs due to increased maintenance activities and/or installation of pretreatment units.

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Project Website

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https://siloxane.fiu.edu/

https://siloxane.fiu.edu/

Research papers Surita SC, Tansel B. Sci Total Environ. 2014 Jan 15;468-469:46-52. doi: 10.1016/j.scitotenv.2013.08. 006. Epub 2013 Sep 4. Emergence and fate of cyclic volatile polydimethylsiloxanes (D4, D5) in municipal waste streams: release mechanisms, partitioning and persistence in air, water, soil and sediments.

Tansel, B., Surita, S. Environ Toxicol Pharmacol. 2014 Jan;37(1):166-73. doi: 10.1016/j.etap.2013.11.020. Epub 2013 Dec 1. Oxidation of siloxanes during biogas combustion and nanotoxicity of Si-based particles released to the atmosphere.

Tansel, B., Surita, S., Waste management (New York, N.Y.) 08/2014; DOI: 10.1016/j.wasman.2014.07.025 Differences in volatile methyl siloxane (VMS) profiles in biogas from landfills and anaerobic digesters and energetics of VMS transformations.

Surita, SC., Tansel, B., Ecotoxicol Environ Saf 2014 Apr 1;102:79-83. Epub 2014 Feb 1. A multiphase analysis of partitioning and hazard index characteristics of siloxanes in biosolids.

Surita, SC., Tansel, B., Sci. Total Environ. Sci Total Environ 2014 Oct 18. Epub 2014 Oct 18. Response to "Comment on Emergence and fate of siloxanes (D4, D5) in municipal waste streams: Release mechanisms, partitioning and persistence in air, water, soil and sediments"

Surita, S., Tansel, B. Water Environment Research 2014 (accepted) Evaluation of a full-scale water-based scrubber for removing siloxanes from digester gas: A Case study.

Surita, SC., Tansel, B., Chemosphere. 2014 (accepted) Contribution of siloxanes to COD loading at wastewater treatment plants: Phase transfer, removal and fate at different treatment units.

Surita, SC., Tansel, B., Renewable Energy. 2014 (under review) Preliminary investigation to characterize deposits forming during combustion of biogas from anaerobic digesters and landfills.

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http://www.ncbi.nlm.nih.gov/pubmed/24355797

http://www.pubfacts.com/author/Sharon+C+Surita


http://www.pubfacts.com/detail/24580825/A-multiphase-analysis-of-partitioning-and-hazard-index-characteristics-of-siloxanes-in-biosolids.

http://www.pubfacts.com/detail/24580825/A-multiphase-analysis-of-partitioning-and-hazard-index-characteristics-of-siloxanes-in-biosolids.



http://www.pubfacts.com/detail/25457195/Response-to-







Conferences 1. World Environmental & Water Resources Congress 2014 (EWRI 2014) -

Emerging siloxanes and Environmental Implications in Wastewater Treatment Systems

2. Global Waste Management Symposium (GWMS 2014) - Concentration and comparison of siloxanes found in urban landfill

3. Odors and Air Pollutants 2014 Conference (WEF 2014) - Release and Partitioning of Siloxanes during Biosolids Decomposition in Anaerobic Digesters

4. Solid Waste Association of North America Florida Sunshine Chapter (SWANA 2014) - Contribution of siloxanes from WWTP to codisposal landfills

5. 8th Intercontinental Landfill Research Symposium (ICLRS 2014) - Emergence and Fate of Siloxanes in Landfills

6. World Environmental & Water Resources Congress 2015 (EWRI 2015) - Loading, persistence, and fate of siloxanes in wastewater treatment plants: Levels in influent, effluent, biosolids, and digester gas

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Where are siloxanes used? (different industries)

Siloxane Use Concerns Life Cycle Projections Current Research

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Personal care products

Cyclopentasiloxane

Cyclohexasiloxane

Dimethicone


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Still not convinced???


Cyclopentasiloxane

Dimethicone

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Compound characteristics


Property D4 D5 D6

Chemical formula C8H24O4Si4 C10H30O5Si5 C12H36O6Si6

Molecular weight (g/mol) 296.6 370.8 444.9

Density (g/cm3 at 25°C)a 0.95 0.954 0.963

Henry's constant (Pa-m3/mol at 25°C)a 1,214,000 3,342,000 14,667

Water solubility (μg/L at 25°C)b 56.2 17 5

Atmospheric half-lives (days) 10c -15.8d 6.9e -60f 2.6–12.8d

Air-water partition coefficient (KAW) 2.69g - 2.72h 3.13g - 3.16h 0.80h - 3.01g

Soil-water partition coefficient (KSW)i 3.38 3.71 3.25

Octanol-water partition coefficient (KOW)j 6.98 8.07 8.87

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Fate and transport of siloxanes in waste


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Historical Silicone-based patents

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Potential concerns

Credit: Frédéric Back

and Québec Amérique

• Deposition on engine components (SiO2),

• Potential bioaccumulation,

• No federal, state mandates


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Combustion effects


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Fate in living systems via inhalation


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Global mean siloxanes in LFG


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Predicted growth curve


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Waste Composition


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Patent

Use in paper products

Useful life

Disposal

Recycling(28.2%)

Decomposition

Landfill disposal(71.8 %)

Volatilization to landfill gas

Solubilizationin leachate

0.5 - 5 years 0 - 0.5 year 1 - 30 years

Siloxane release: 0.5 - 10 years

Fate of siloxanes used in paper products


FATE OF SILOXANES USED IN PAPER PRODUCTS

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PSWs = SPF · PSS · P

PSWs: projected silicone waste per sector in a given year (tons) SPF : total annual silicone production factor (1,394 tons/patent; Oxford Economics) PSS : percent of silicone present per sector (i.e., paper, C&D) (Brandt et al., 2012) P : number of patents filed (estimated by regression analysis)

Projected silicone waste per sector


Construction 30.9%

Electronics 57.1%

Industrial 2.8%

Personal & Lifestyle 2.0%

Transportation 7.2%

100.0% 19

Disposal and recycling • 29% increase within 10

years

•78% increase within 25

years


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Emissions for 5% siloxane release

Emissions for 15 % siloxane release

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Cost Estimation of fixed – bed carbon adsorption

Primary paramaters

◦ Landfill or biogas flow Q (acfm)

◦ Surface area/pore space of carbon


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Estimated fixed-bed Adsorption system costs


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Facility LFG utilized

(scfm)

LFG

utilized

(acfm)

Correction

percentage

from scfm to

acfm (%)

Rc S Nt Rounded

CA

1 12 12 0 5.02 400 1 $ 446,000

2 550 557 1.27 3.01 667 1 $ 399,000

3 700 709 1.29 2.92 667 1 $ 386,000

4 1100 1103 0.27 2.75 667 1 $ 364,000

5 1200 1192 -0.67 2.72 667 1 $ 359,000

6 1300 1303 0.23 2.69 667 1 $ 356,000

7 3000 3028 0.93 2.40 1000 1 $ 436,000

8 3200 3222 0.69 2.38 1000 1 $ 432,000

9 14700 14910 1.43 1.94 2000 3 $ 1,211,000

Estimated fixed-bed Adsorption system costs


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Installation cost estimates


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Facility LFG utilized

(scfm)

Rounded

CA Rounded DEC Rounded TIC

1 12 $ 446,000 $ 530,000 $ 920,000

2 550 $ 399,000 $ 470,000 $ 823,000

3 700 $ 386,000 $ 460,000 $ 800,000

4 1100 $ 364,000 $ 130,000 $ 750,000

5 1200 $ 359,000 $ 420,000 $ 740,000

6 1300 $ 356,000 $ 510,000 $ 730,000

7 3000 $ 436,000 $ 510,000 $ 900,000

8 3200 $ 432,000 $ 510,000 $ 890,000

9 14700 $ 1,211,000 $ 1,430,000 $ 2,500,000

Cost comparison •Capacity factor – percent of equilibrium adsorption capacity

•Regeneration rates

•Maintenance schedule (annual) ◦ Technician/operator rank

($72K to 108K) ◦ Man hours (8,000 – 11,000)

($277K – 571K)


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Cost comparison Installation vs. maintenance


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Siloxane Use Concerns Life Cycle Projections Future Research

TREATMENT VIA CARBON ADSORPTION

t (min) = 30, 60, 90, 120

Total mass of

carbon =

2.286 grams

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Closing Comments & Ongoing research

◦ Siloxane concentrations in landfills (in conjunction with 5% emissions) will increase by

• 29% within the next 10 years

• 78% within the next 25 years

◦ Patent trend assumptions (T or F)

◦ Lag times for common products

• Paper <1 year

• C&D <30 years

• Carbon Adsorption capacity

Siloxane Use Concerns Life Cycle Projections Future Research

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Questions?

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siloxanes in biogas: formation and effect on biogas ...biogas produced at landfills and anaerobic...

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