In 2011, the Swedish coastline suffered a major oil spill of about 800 tonnes of CTO (crude tall oil) from a land based tank farm on the east coast, into the Söderhamn archipelago in the brackish Baltic Sea. The impacted area exhibit a high ecological value and is frequently used for outdoor recreation and a large number of private properties.
There are very few incidents reported on CTO spills. CTO is a viscous yellow-black odorous liquid obtained as a by-product in the kraft pulping process. Sometimes the general notion is that it is harmless to the environment since it origins from coniferous trees. The name originated as an anglicization of the Swedish “tallolja” (“pine oil”).Tall oil is the third largest chemical by-product in a Kraft mill after lignin and hemicellulose.
Although CTO is less harmful compared to mineral oil, release of CTO, especially large quantities, may also cause severe environmental damage to aquatic systems and to impacted shores. CTO may also cause allergic reactions to humans and mammals.
The shores of the Söderhamn Bay consist mainly of rocky beaches, large rocks as well as very small pebble stones. Since the oil also got into jetties, the entire clean-up process has been difficult and time consuming, also due to the cold weather conditions in the north. Remediation of the shores and stone coffins, inside the jetties, has been made through manual labor.
The impacts to the bird population were minimal since most birds had migrated for the winter. The incident happened during late fall, when the biological activity in marine organisms is low; hence low impact on the marine organism's active reproductive periods.
In Söderhamn, fatty acids, recin acids and sterols have been sampled in sediments, fish muscle, and mussels. Limited impact could be noted, however, established test methods are missing for CTO. Degradation time of the CTO was longer than expected.
Extensive and hardcore cleanup usually causes more damage to nature; removal of important microorganisms, increased soil erosion and diminishes the possibilities for the vegetation recovery. It is crucial to start the communication process with public and property owners as early as possible to set expectations on “how clean is clean”.
The clean-up process in Söderhamn has been very successful and is coming to an end in the spring of 2016. The status and conclusions after five years of remedial actions will be presented.