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Environmental fate & pathways

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The results from an OECD 301B CO2 evolution test (Clarke, 2008) showed that NExBTL renewable diesel was readily biodegradable with 82 % degradation within 28 days. Degradation of alkanes is a widespread phenomenon in nature, and numerous microorganisms, both prokaryotic and eukaryotic, capable of utilizing these substrates as a carbon and energy source have been isolated and characterized (Prince et al, 2002 and 2003, Wentzel et al, 2007).

In mesocosm studies in the marine environment, the half-life n-pentadecane was found to be 4.3 d at 3-7 °C and 0.8 d at 20-22 °C in surface water (Mackay et al, 2006). In the same experiment, the half-life of n-heptadecane was 5 d at 3-7°C and 0.9 d at 20-22°C. The half-life of n-octadecane was 1.5 d in the Rhine surface water, and 23 d in marine surface water. Data on half-lives of alkanes in sediments or soils is lacking, however numerous studies have shown that alkanes are readily biodegradable in soils and sediments (Hoeppel RE et al, 1991, Hawle-Ambrosch E et al, 2007, Miethe D et al, 1994, Salanitro J, 2001, Sugiura K et al, 1996). Degradation in soils would be expected to be faster due to higher temperatures and higher oxygen status compared to sediments. This is supported by calculations with EUSES model, according to which degradation of NExBTL renewable diesel in water is

2x103times faster than in soil and 2x105times faster than in sediment (Table2.3.).

Table2.3.Degradation rates and half-lives of NExBTL renewable diesel in different environmental compartments estimated using EUSES.

Environmental compartment

Degradation rate (12 °C) d-1

t1/2(12 °C)

d

t1/2(20 °C)

d

Water

0.0462

15

7.9

Sediment

2.31x10-7

3000000

1580000

Soil

2.31x10-5

30000

15800

REFERENCES

CONCAWE, 1998, Heavy fuel oils. Product dossier no. 98/109. CONCAWE, Brussels, May 1998.

Hawle-Ambrosch E, Ripe W, Dornmayr-Pfaffenhuemer M, Radax C, Holzinger A and Stan-Lotter H, 2007, Biodegradation of fuel oil hydrocarbons by a mixed bacterial consortium in sandy and loamy soils, Biotechnology Journal 2(12), 1564-1568.

Hoeppel RE, Hichee RE and Arthur MF, 1991, Bioventing soils contaminated with petroleum hydrocarbons.J. Indust. Microbiol. 8, 141-146.

Mackay D, Shiu WY, Ma K-C, Lee CS, 2006, Handbook of Physical-chemical Properties and Environmental Fate for Organic, Volume I, Introduction and Hydrocarbons, 2nd edition, CRC Press.

Miethe D, Riis V and Babel W, 1994, The relationship between the microbial activity of the autochthonous microorganisms of pristine and contaminated soils and their potential for the degradation of mineral oil hydrocarbons. Acta Biotechnol. 14,131-140.

Prince RC, Owens EH and Sergy GA, 2002, Weathering of an Arctic oil spill over 20 years: the BIOS experiment revisited. Marine Pollution Bulletin 44, 1236–1242.

Prince RC, Garrett RM, Bare RE, Grossman MJ, Townsend T, Suflita JM, Lee K, Owens EH, Sergy GA, Braddock JF, Lindstrom JE, Lessard RR, 2003, The Roles of photooxidation and biodegradation in long-term weathering of crude and heavy fuel oils, Spill Science & Technology Bulletin 8(2) 145-156.

Sugiura K, Ishihara M, Shimauchi T and Harayama S, 1997, Physicochemical properties and biodegradability of crude oil Environmental Science and Technology 31(1), 45-51.

Wentzel A, Ellingsen TE, Kotlar H-K, Zotchev SB and Throne-Holst M, 2007, Bacterial metabolism of long-chainn–alkanes, Applied Microbiology and Biotechnology 76(6) 1209-1221.