ABSTRACT
Paper industries are known for their large water demand and for producing polluted effluents, which, if not properly treated, can cause significant ecological damage in the streams into which the effluents are disposed. The pulp and paper industry in the USA withdraws approximately 5,500 billion litres of water annually from surface and groundwater sources (Figure 8.1), which is 2.5 per cent of the total industrial water withdrawal in the USA and a bit over 1 per cent of the total water withdrawal from ground-and surface-water bodies in the country (FAO, 2012b). A major part of the water used in the pulp and paper industry, however, returns to the catchments from where the water has been taken, so that consumptive water use is much less than the total abstraction: an estimated volume of 507 billion litres of water annually evaporates from pulp and paper mills in the USA, and 10 billion litres of water per year leave the mills (and the catchments) incorporated in products. Probably more important than the consumptive use of water in pulp and paper mills is the pollution that comes from those mills. Chemical pulps are made by cooking the raw materials and adding chemicals. The mixture of chemicals added depends on the process applied; we should distinguish between the kraft (sulfate) process, the sulfite process and the sodium process. Although mechanical pulping is applied as well, chemical pulping is the most commonly used pulping process, whereby the sulfate process is the most common technique applied. After pulping, the pulp is generally bleached to make it whiter. Different sorts of chemicals are used in this process, including for example chlorine, sodium hypochlorite and chlorine dioxide. Particularly the use of elemental chlorine or chlorine compounds result in high concentrations of undesired compounds in effluents. Water pollution from pulp and paper mills mostly stems from the organic matter contained in the effluents, which generally include a lot of chlorinated organic compounds like dioxins and other adsorbable organic halides (which go under the abbreviation
AOX). The organic matter content in effluents from pulp and paper mills is measured by the ‘biochemical oxygen demand’ (BOD) in the effluent; a large BOD in effluents can lead to oxygen depletion and fish kills in rivers. High concentrations of AOX can lead to toxicity and fish kills as well. In addition to the water consumption and pollution in the pulp and paper industry, there is a huge indirect demand for water to grow the trees that form the raw material for pulp. Most of the time, this is rainwater transpired by the trees or otherwise evaporated from the tree plantations. This evapotranspiration in itself is quite natural and most of the time not causing great changes in the hydrology of the catchments where the plantations are located. From a resource allocation point of view, however, it is relevant to quantify the amount of water resources allocated to forestry products like paper, timber and firewood, because land and water resources reserved for producing forestry products cannot be applied for producing crops or for sustaining natural forests and biodiversity. According to the latest Global Forest Resources Assessment (FAO, 2010), 30 per cent of the 4,000 million ha of forest in the world is production forest. The area of planted forest is estimated at 7 per cent of the total forest area and is increasing. Water resources associated with lands that are primarily used as production forest are designated to the production of forestry products and not available for other purposes. When considering the water demand for paper, it is interesting to look at the water use in pulp and paper mills, but relevant to consider the water claims related to wood production as well. As we will see in this chapter, we are talking about vast amounts of water that are allocated to wood production and indirectly for paper products. It is true that wood production primarily depends on rainwater (green water), while pulp and paper mills primarily consume ground and surface water (blue water) and that problems of water use are usually associated with blue and not green water use, but it is a misunderstanding that green water is not scarce. Indeed, discussions about freshwater scarcity are generally focused on the scarcity of blue water resources (rivers and groundwater), but there is as much reason to be concerned about the allocation of green water resources (rainwater). There is competition over green water resources as well as over blue water resources. Both green and blue water resources can be made productive for a large variety of purposes (food, feed, clothing fibres, biomass for biofuels, timber, firewood and paper) or left undisturbed (to sustain natural ecosystems). Forestry products put a large claim on the world’s green water resources, which cannot therefore be designated for other purposes. A complete picture of the water footprint of paper can only be obtained when we look at all sorts of water claims in all stages of production.
