*2.2. Lignin Extraction*

Lignin was extracted from Norway spruce by soda process using a MK circulation reactor. In this method, 400 g dried chips were cooked with cooking liquor which comprised 30% NaOH (30 g NaOH/100 g dried chips). The liquid wood ratio was 7.5:1. The temperature was increased slowly in order to ge<sup>t</sup> a good impregnation of the chips with the cooking liquor. Once the reactor reached the operating temperature of 180 ◦C, it was maintained for 100 min. After cooling, the cooking liquor was removed from the bottom of the reactor.
