Introduction

Since the production of pulp uses the renewable resource wood, the environmental

impact starts with the selection of the tree species and their planting. All forestry

operations have an environmental impact. Forestry certification, for example

by the Forest Stewardship Council (FSC), is used to describe “best” conditions.

Logging processes and the transport of wood similarly have an impact, as can

wood storage and debarking. Bark can be described as the natural protection of

trees against biological activity. Fungi and bacteria use wood as nutrition source,

and therefore trees naturally produce compounds (e.g., resin acids) that have a

certain toxicity and a very high concentration of poorly biodegradable organic matter

to hinder rapid decay. The leaching of bark with water can result in a rather

high level of toxicity in such an effluent, and dry debarking is therefore preferred.

Bark is burned and used as energy source. Because bark is generally richer in

minerals than the corresponding wood [1], the ash content is usually more than

10% – which is ten times higher than that in wood. The resulting ashes contain

high levels of elements such as calcium, magnesium, potassium, sodium, iron,

manganese, zinc, and phosphorus. These trace elements are important to the

nutrition of trees, and should be returned into the forest, though this is not always

permitted.

This chapter will focus briefly on the impact of the pulping process. The dominant

process for chemical pulp production is the kraft or sulfate process. Apart

from some specific differences, other processes such as sulfite pulping or soda

pulping have a rather comparable environmental impact. Although the operation

of a pulping process requires energy. modern mills do not require fossil fuel as

the source for all energy is combustion of the compounds dissolved during the

pulping process. The resultant emissions are the release of volatile compounds

during the high-temperature pulping process and during brown stock washing.

Evaporation and combustion of the recovered liquor causes additional emissions.

In alkaline pulping the operation of the lime kiln represents an emission source.

Handbook of Pulp. Edited by Herbert Sixta

Copyright © 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Isbn: 3-527-30999-3

©2006 WILEY-VCHVerlag GmbH&Co .

Handbook of Pulp

Edited by Herbert Sixta

The standard measures to reduce the impact of volatile and odorous compounds

Is by the sophisticated management of these sources. This comprises their collection,

combustion and scrubbing of the remaining noncondensable gases. These

methods are applied similarly for the on-site generation of bleaching chemicals

such as chlorine dioxide and ozone. The build-up of nonprocess elements (chloride

Ions, potassium, or transition metals) in the process requires the introduction

of cleaning steps that cause additional liquid or solid emissions. Washing of the

fibers in the bleach plant removes organic matter, these dissolved compounds

require a biological treatment of the effluent.

The impact of pulping, and the measures to control and limit the emissions,

have been described in a variety of publications, with the European Commission

publishing standards in 2000 [2]. Integrated Pollution and Prevention Control

(IPPC) is used to describe the “best available techniques in the pulp and paper