Spent liquor from alkaline pulping and bleaching containing spent inorganic process chemicals and dissolved organic substances originating from the cellulosic raw material.

Ecotoxicological Summary

Additional information

Black liquor is registered as a transported isolated intermediate and is manufactured and consumed under strictly controlled conditions

during its whole life cycle. The derivation of PNECs is required for the chemical safety assessment (CSA) of substances manufactured/imported/used in quantities from 10 t/y onwards. CSA does not need to be performed for transported isolated intermediates.

The conclusion on classification is based on aquatic acute toxicity data according to Annex VII in the REACH regulation, applied for transported isolated intermediates, where no terrestrial or long-term aquatic toxicity information is required.

No data on sediment or terrestrial toxicity of Black liquor was available based on an extensive literature search. Black liquor recycles in the pulping process and no spillages occur in normal process conditions. Hence little ecotoxicological studies have been conducted on Black liquor.

Five supporting studies reported short-term toxicity to fish, aquatic invertebrates and aquatic algae and cyanobacteria. The tested sample as whole in wet weight (wwt) contained 47.3 % water/52.7% dry solids.

The EC50 (48 h) values for D. magna were 1300 mg/l (wwt.) and >1000 mg/l (wwt.) (n=2). The EC50 (72 h) values for P. subcapitata were 72.4 mg/l (wwt.) and 148.98 mg/l (wwt.) (growth rate) (n=2). The LL50 (96 h) value for P. promelas was >1000 mg/l (wwt.) (n=1).

NOEC (48 h) values for D. magna were 200 mg/l (wwt.) and 1000 mg/l (wwt.) (n=2). The NOEC (72 h) values for P. subcapitata were 12 mg/l (wwt.) and 5 mg/l (wwt) (growth rate) (n=2). The NOELr (96 h) value for P. promelas was 1000 mg/l (wwt.) (n=1).

Black liquor was the most toxic to algae (EC50 38 mg/l (dwt)/72 mg/l (wwt.), which drives the classification.

The EC50 value is higher than the limit value for the class Aq. Acute Cat.1 (< 1 mg/l), but is within the limits of Aq. Acute Cat.3 (10<EC50≤100 mg/l) according to the CLP rules. The criteria for Chronic Cat.3 hazard classification requires additionally information of (bio)degradability and/or bioaccumulation and/or chronic toxicity. The tested Black liquor sample was not readily biodegradable (see. 5.2.1).

Conclusion on classification

Black liquor is the spent cooking liquor from alkaline pulping and bleaching process. The source materials for Black liquor are softwood, hardwood, agricultural fibers and White liquor. Dry substance content of Black liquor varies from 3 to 80% consisting of ca. 30 -77% of inorganics and 23-70% organics. Black liquor is a UVCB substance with a variable composition. Therefore the ecotoxicological properties may be somewhat variable, depending on the ecomposition and the raw materials applied.

The ecotoxicological properties (Annex VII, REACH regulation) of a representative Black liquor sample were tested by a GLP laboratory during 2009-2010 (the Key studies). The tested sample contained 47.3 % water/52.7% dry solids. The endpoints for which additional supporting data was available in the literature were Short-term toxicity to fish, Short-term toxicity to aquatic invertebrates, Toxicity to aquatic algae and cyanobacteria and Toxicity to microorganisms.

No data was found for the other ecotoxicological endpoints, other than those referred in the endpoint records, through extensive literature searches. Black liquor is registered as a Transported Isolated Intermediate and no testing outside Annex VII in the REACH regulation is required.

 

According to the experimental results the ecotoxicological properties of Black liquor were:

- Hazardous to the aquatic environment (Acute toxicity to aquatic algae, 10 < EC50 <100 mg/l)

 

Black liquor was not toxic to:

- Aquatic invertebrate (Acute toxicity to Daphnia magna, EC50>100 mg/l (wwt.))

 

According to the supporting studies Black liquor was not toxic to:

- Aquatic algae (Acute toxicity to aquatic algae, EC50 >100 mg/l)

- Fish (Short-term toxicity to fish, LL50 > 100 mg/l)

Additionally, the need for classification according to the CLP rules was evaluated based on the expected maximum concentration of the only identified main ingredient, reported in the Black liquor typical composition (1.2), which holds a harmonized classification for aquatic hazard i.e.sodium sulfide (EC 215-211-5).

 

According to the main ingredients the ecotoxic properties of Black liquor were:

- Not toxic to aquatic life.

 

No Observed Effects Concentrations for aquatic organisms were:

- Daphnia magna, NOEC (48 h) 105 mg/l (dwt) (200 mg/l (wwt)) and 527 mg/l (dwt) (1000 mg/l (wwt.)) (n=2),

- Pseudokirchneriella subcapitata, NOEC (72 h) 6.3 mg/l (dwt) (12 mg/l (wwt)) and 2.6 mg/l (dwt) (5 mg/l (wwt)) (growth rate) (n=2),

- Pimephales promelas, NOELr (96 h) 527 mg/l (dwt) (1000 mg/l (wwt)) (n=1).

 

The classification derived from the experimental results of Black liquor is based on the acute aquatic toxicity and biodegradation (5.2.1):

Acute aquatic toxicity to algae (EC50)      38 mg/l (dwt) (72 mg/l (wwt))    Aq. Acute Cat. 3 (10<C≤100 mg/l)

Biodegradability (28 d)                             48%                         Not readily biodegradable

 

CLP:             Aquatic hazard: Chronic Category 3 (H412: Harmful to aquatic life with long lasting effects)