A further NOK 36 million were invested in 1990 and 1991, reducing water consumption, fiber emissions, and smoke emissions. A precipitation process was introduced in the sedimentary process. NOK 202 million was invested in a four-stage biological treatment plant completed in 1992. This produces biogas and sludge, which were burned and used for heating. The most important factor was the closing of the sulfate mill in 1991, which cut most of the pollution to water. By 1995 emissions had been reduced sufficient to reestablish ordinary biological activities in the fjord. NOK 180 million was invested in a bio boiler in 1996.