Fast Pyrolysis Bio-oil

Partition coefficient

Link to relevant study record(s)

Reference

Endpoint:

partition coefficient

Remarks:

EPI Suite v.4.11

Type of information:

(Q)SAR

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Justification for type of information:

1. SOFTWARE: U.S. Environmental Protection Agency for EPI Suite™ v.4.11 and the individual programs included within the software.
http://www.epa.gov/oppt/exposure/pubs/episuite.htm

2. MODEL: KOWWIN estimates the log octanol-water partition coefficient, log KOW, of chemicals using an atom/fragment contribution method.

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL: The study is based on eight representative components of the test material.

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
The link: https://www.epa.gov/tsca-screening-tools/epi-suitetm-estimation-program-interface

EPI Suite (TM): Individual estimation programs and/or their underlying predictive methods and equations have been described in numerous journal articles in peer-reviewed technical journals. In addition, EPI Suite™ has undergone detailed review by a panel of EPA’s independent Science Advisory Board.

KOWWIN – which is part of EPI Suite – is one of the most commonly used programs. KOWWIN uses a "fragment constant" method to predict Kow. Fragment constant methods divide the chemical structure into smaller structural fragments (atoms or larger functional groups). Each fragment is associated with a preassigned coefficient value called fragment constants. The predicted log Kow value is obtained by summing all the fragment constants appearing in the chemical structure. (Ref. ECHA, Practical Guide - How to use and report (Q)SARs, v. 3.1, 2016 and ECHA Guidance on information requirements and chemical safety assessment, chapter R.6, 2008).

- Defined endpoint: partition coefficient

- Unambiguous algorithm: KOWWIN uses a "fragment constant" methodology to predict log P. In a "fragment constant" method, a structure is divided into fragments (atom or larger functional groups) and coefficient values of each fragment or group are summed together to yield the log P estimate. KOWWIN’s methodology is known as an Atom/Fragment Contribution (AFC) method. Coefficients for individual fragments and groups were derived by multiple regression of 2447 reliably measured log P values (Meylan and Howard (1995)). The method uses correction factors as described in Attachment KOWWIN methodology. Also regression results are presented in the Attachment.

5. APPLICABILITY DOMAIN
The modelled representative compounds are non-ionic organic substances covered by the applicability domain of KOWWIN.

Molecular weights of the representative components (test material) are within the Molecular Weight minimum and maximum values for Training Set (18.02 – 719.92) and Validation range (27.03 – 991.15).

KOWWIN has been tested on an external validation dataset of 10,946 compounds. Correlation is presented in the Attachment KOWWIN Accuracy and Domain.

Number of fragments is within the number maximum fragments in KOWWIN.


6. ADEQUACY OF THE RESULT
Accuracy of the calculated parameters versus experimental results of the representative compounds are as follows, respectively:

Acetaldehyde: -0.17; -0.34,
Acetic acid: 0.09; -0.17,
b-Sitosterol: 9.65; -,
Furfural: 0.41; 0.83,
Glucose; -2.98; -3.24,
Methanol; -0.77; -0.63,
Naphthalene; 3.17; 3.30,
Phenol; 1.51; 1.46
(Attachment: KOWWIN Results).

Due to the nature of bio-oils, which as UVCB substance consists of more than 500 different compounds, it is technically irrelevant to test partition coefficient for the substance. Therefore, the computational method gives a reasonably reliable estimate on the weighted average of the parameter.

Guideline:

other: REACH Guidance on QSARs R.6

Principles of method if other than guideline:

Meylan, W.M and P. H Howard 1995. Atom/fragment contribution method for estimating octanol-water partition coefficients. J. Pharm. Sci. 84:83-92

Other quality assurance:

other: EPI Suite (TM): Individual estimation programs and/or their underlying predictive methods and equations have been described in numerous journal articles in peer-reviewed technical journals.

Type of method:

other: EPI Suite v.4.11. The Model KOWWIN estimates the log octanol-water partition coefficient, log KOW, of chemicals using an atom/fragment contribution method.

Partition coefficient type:

octanol-water

Specific details on test material used for the study:

PHYSICAL-CHEMICAL PROPERTIES MODELLED WITH EPIWIN
v.4.11

Compound CAS number

Acetic acid CAS no 64-19-7;
Methanol CAS no 67-56-1;
Phenol CAS no 108-95-2;
Acetaldehyde CAS no 75-07-0;
Furfural CAS no 98-01-1;
Glucose CAS no 50-99-7;
Naphthalene CAS no 91-20-3;
Beta-sitosterol CAS no 83-46-5.


Test material, UVCB substance, consists of more than 500 different compounds such as long-chain fatty acids, PAHs, sesquiterpenes (Jenner et al., 2011), and phytosterols (Hewitt et al., 2000).
According to analytical data, such compounds may form ca. 4 % of FPBO in total.

REFERENCES
Hewitt, L.M., Parrot, J.L., Weells, K.L., Calp, M.K., Biddiscombe, S., McMaster, M.E., Munkittrick, K.R., van der Kraak, G., 2000. Characteristics of ligands for the Ah receptor and sex steroid receptors in hepatic tissues of fish exposed to bleached kraft mill effluent. Environ Sci Technol 34:4327-4334.

Type:

log Pow

Partition coefficient:

1.445

Remarks on result:

other: EPI Suite v.4.11, KOWWIN v.1.68, weighted average -0.30, average 1.445 (8 components)

Details on results:

See Table 1 (section_ "any other information on results incl. tables")

TABLE 1. Partition coefficient

PHYSICAL-CHEMICAL PROPERTIES MODELLED WITH EPIWIN
v.4.11
	Compound	FPBO, ww-%	MW (g/mol)	LogKow
	acetic acid	2.9	60.05	0.09
	methanol	0.41	32.04	-0.63
	phenol	0.42	94.11	1.51
	acetaldehyde	0.05	44.05	-0.17
	furfural	0.15	96.09	0.83
	glucose	0.96	180.16	-2.89
	naphthalene	0.00079	128.18	3.17
	beta sitosterol	0.057	414.72	9.65
Weighted average			88.95	-0.30
Average			131.175	1.445

---------------------------------------

Molecular weight, MW

Partition coefficient n-octanol/water, LogKow (KOWWIN v1.68 estimate)

Conclusions:

Octanol-water partition coefficients (LogKow) of individual eight compounds range from -2.89 to 9.65 with the weighted average being -0.30.

Executive summary:

Octanol-water coefficients (Log Kow) of the main components (contributing 5 % of the total wet weight) were determined using KOWWIN program developed by U.S. Environmental Protection Agency. LogKow values of the individual components range from -2.89 to 9.65 with the weighted average being -0.30.

Description of key information

Partition between octanol and water of FPBO has not been tested due to UVCB nature of the substance. Octanol-water coefficients (Log Kow) of the main components (contributing 5 % of the total wet weight) were determined using KOWWIN program developed by U.S. Environmental Protection Agency. LogKow values of the individual components range from -2.89 to 9.65 with the weighted average being -0.30.

Key value for chemical safety assessment

Log Kow (Log Pow):

-0.3

Additional information

Pyrolysis liquids can be considered as solutions of water and water-soluble organic compounds with water insoluble, mostly oligomeric, material. The ratio of these fractions depends on the feedstock, the pyrolysis process, production and storage conditions. The water insoluble fraction, mainly lignin-derived oligomers, usually accounts for about 20-25 wt% of the liquid (wet basis), while the water concentration typically ranges from 20 to 30 wt%. The water-soluble fraction consists mainly of water, "sugars" (sugartype compounds, ether-insolubles), acids, aldehydes, ketones, pyrans and furans (Oasmaa & Peacocke 2010). Consequently, the analysis of partition co-efficient for fast pyrolysis bio-oil was considered technically not feasible. Due to the nature of bio-oils, which consists of more than 500 different compounds, it is not possible to test partition coefficient for the substance.

Based on research of VTT Finland on bio-oils, general aspects are known concerning solubility of fast pyrolysis bio-oils. The solubility of pyrolysis liquids in organic solvents is affected by the degree of polarity. Good solvents for highly polar biomass pyrolysis liquids are low molecular weight alcohols, such as methanol, ethanol and iso-propanol. Polar biomass pyrolysis liquids do not dissolve in hydrocarbons such as hexane, diesel fuels or polyolefins. Neutral, mainly aliphatic, substances in forest residue and bark liquids (< 10 wt %) are soluble in n-hexane however. To dissolve forest residue liquids, a mixture of a polar (e.g., alcohol) and a neutral (e.g., dichloromethane) solvent is needed (Oasmaa & Peacocke 2010). 

A lot of research concerning bio oils has been done under IEA Bioenergy Task 34 Pyrolysis and under BIOTOX project funded by European Union. The project produced a final technical report called “An assessment of bio-oil toxicity for safe handling and transportation”. According to the report,testing of partition coefficient n-octanol/water require further chemical analysis to estimate the evolution of the test item concentrations in solution during the test. But due to the nature of bio-oils, which consist of more than 500 different compounds, it is not possible to assess the evolution of its concentration in solution and thus tests without chemical analyses to follow the evolution of tested substances were regarded as senseless (BIOTOX 2005).

 REFERENCES:

 BIOTOX. 2005. An assessment of bio-oil toxicity for safe handling and transportation. Final Technical Report. Part I: Publishable Final Report. Report drafted by Blin, J. Project N°: S07.16365. Project co-ordinator: Centre de Coopération Internationale de Recherche Agronomique pour le Développement (Cirad). Partners: Aston University,Bundesforschungsanstalt für Forst- und Holzwirtschaft (BFH).

Anja Oasmaa & Cordner Peacocke. Properties and fuel use of biomass-derived fast pyrolysis liquids. A guide. Espoo 2010. VTT Publications 731. 79 p. + app. 46 p.