As described, burning black liquor in a recovery boiler is a process to get energy. At the same time, it reproduces the chemicals for pulp production. It’s necessary to use black liquor in a kraft pulp manufacturing plant. Therefore, all kraft pulp plants have a process to burn black liquor.

2.0 tones of black liquor are produced as a by-product from 1 tone of a hard wood pulp or 1.5 tones of a soft wood pulp. Generally, almost all amount of black liquor is used as biomass energy. The production of the kraft pulp in Japan is about 9,000,000 tones a year and

14.0. 000 tones of black liquor are produced during the process. And the amount of the liquor is equal to 4,710,000 kiloliters of crude oil in terms of energy.

In 1999, the production of chemical pulp in the world was 119,000,000 tones. In consequence, the production of black liquor was calculated to be about 200,000,000 tones. And it’s equal to

60.0.000 kiloliters of crude oil (Table 2.16.1).

Pulp and paper industry in Japan and Asian countries has been using planted woods as a material of pulp in these days and the production has been increasing. The industry is able to be developed by means of producing both material and energy from sustainable forest management which produces the resources for pulp. The utilization of black liquor is surely the foundation for the management.

Now that the utilization of black liquor is limited to the energy source in pulp and paper mills, however, various kinds of materials are produced such as lignosulfonic acids by dividing lignin from black liquor and nucleic acids by culturing of the yeast using sugars in the black liquor. It’s expected that biorefinery of black liquor utilization will be more and more developed in the future.

Further information

Keiichi Tsuchiya, Makoto Iwasaki, Tadanori Oihata, Yoshihiro Sakaguchi, Keiichi Tushiya, “Pulp and Paper Manufacturing Technology Complete Book, Vol. 2 Kraft Pulp”, 11-20, 185-223 (1996) JAPAN TAPPI (in Japanese)

JAICAF Edition, “World Forest White Paper 1997”, JAICAF (in Japanese)

JAPAN TAPPI Energy Committee, “Survey on Energy Consumption in the Pulp and Paper Mills in Japan Part 1”, 55, 573-591 (2001) JAPAN TAPPI (in Japanese)

JAPAN TAPPI Edition “Pulp and Paper technical handbook”, 105-136 (1971) JAPAN TAPPI (in Japanese)

Yuuichi Hayase, “Seishi-koujou kara-no Fukuseigenryou ”, 50, 1253-1259, Thermal and Nuclear Power Engineering Society (in Japanese)

Masahiro Kitazume, “Sekai no Kami Parupu”, 8-15, September (2000) Kami-Parupu (in Japanese) Keiichi Nakamata, “Kami to Shinrin no Kakawari”, Global Environmental Policy in Japan the 1st report, 1-9 (1999) Chuo University Press (in Japanese)