Paper mills produce large amounts of paper mill sludge in the treatment of process water. According to overburden studies, the hydraulic conductivity of the paper mill sludge originating from a paper mill in Northern Finland at a pressure of 30 kPa was 4.4610 À 10 m s À 1 , and 1.7610 À 10 m s À 1 at a pressure of 100 kPa. These values well meet the generally required values of between 1.0610 À 7 m s À 1 and 1.0610 À 9 m s À 1 for a geological barrier in landfill base and sides at landfills in the European Union. Paper mill sludge can also be used in the artificially constructed geological barrier layer of landfill cover structures. The angle of internal friction of the paper mill sludge was 34.8 and the cohesion of interparticle adhesion 23 kPa, which are important measures for assessing the shear strength of paper mill sludge and thus the stability of the landfill layer in which it is used. During a 28-day period, the biodegradability of the paper mill sludge in soil was ca 0.4% and in ground water under 1%, whereas according to the OECD 301F standard concentrations (BOD 28 ), it was ca 8%. For the determination of total element concentrations in the paper mill sludge, the dried sample was digested using USEPA method 3052. A five-stage sequential leaching procedure was also used to fractionate trace elements in the paper mill sludge between the water-soluble (H 2 O), exchangeable (CH 3 COOH), easily reduced (HONH 3 Cl), oxidizable (H 2 O 2 þ CH 3 COONH 4 ), and (5) the residual (HF þ HNO 3 þ HCl) fractions. This paper covers also examples of case studies how paper mill sludge is utilized in Finland.

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The biodegradability of certain biofuels was studied in the case of forest soils using the manometric respirometric technique, which was proved to be very suitable for untreated, fertilized as well as pH adjusted soils. Experiments carried out in infertile sandy forest soil gave a BOD/ThOD value of 45.1% for a typical model substance, that is, sodium benzoate after a period of 30 days and mineral addition improved the BOD/ThOD value to a value of 76.2%. Rapeseed oil-based chain oil almost did not biodegrade at all in 30 days in nonprocessed soil, and when pH was adjusted to 8.0, the BOD/ThOD value increased slightly to a value of 7.4%. Mineral addition improved the BOD/ThOD value on average to 43.2% after 30 days. The combined mineral addition and pH adjustment together increased the BOD/ThOD value to 75.8% in 30 days. The observations were similar with a rapeseed oil-based lubricating oil: after 30 days, the BOD/ThOD value increased from 5.9% to an average value of 51.9%, when the pH and mineral concentrations of the soil were optimized. The mineral addition and pH adjustment also improved the precision of the measurements significantly.

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Municipal solid waste management is a basic service that, in Finland, consists of collection, transportation and treatment systems provided by municipalities, waste management companies and producer responsibility organizations. The amount of municipal solid waste in Finland has risen quite steadily for many decades. In 2012, the recovery rate of municipal solid waste as material or energy was 67%. The Finnish Waste Act has been updated in 2012, with the key goal to further reduce waste amounts and progress recycling. The paper describes the best practices in strategic waste management planning and describes the organization of municipal solid waste in city of Oulu, Finland.