Water in cartonboard production
Water is an essential element for paper and board production. Water acts as a bond between the fibres and in the production process, is needed for transporting, cleaning, as a solvent, carrying energy in the form of steam and is used in cooling process units.
Use of Water:
- to process chemicals – cartonboard mills use water to prepare and dilute chemicals
- as a cooling medium – used in various parts of the mill
- as a transport medium – fibres are carried through the production process in water. When the pulp reaches the cartonboard machine it is 99% water and most of this water is then re-used.
- to produce steam – steam is used to heat the process equipment, including the drying cylinders on the cartonboard machine
- cleaning and sealing – much of the fresh water required is used for this
The methods of treating water before it is discharged from the mill vary from site to site depending on local conditions and are regulated by environmental permits.
- Mechanical Treatment Discharged water is channelled into ponds where particles, mainly fibres, sink to the bottom and are removed
- Biological treatment Organic substances in the discharged water are broken down with the aid of micro-organisms, similar to the natural process
- Chemical Treatment Effluent is treated with chemicals that cause contaminants to precipitate after which they are removed mechanically
Water is usually taken from a nearby surface source such as a lake or river. 95% of the water used in the industry is cleaned and reused on site. All waste water is purified at the mill in accordance with European regulations and standards, before being returned to the environment. Mills are working to reduce process water use as this makes good economic as well as environmental sense. The trend over the past two decades has been to reduce fresh water withdrawal by 20% in total volume.
The idea of providing a footprint for the use of water is becoming increasingly important and as well as carbon, water is the next resource that the paper and board industry will have to account for. Evaluating water use will be even more challenging than measuring carbon footprints. To prepare for this, the Confederation of Paper Industries (CEPI) is a member of the Water Footprint Network and other related associations, to contribute to the development of methodology and to share experience gained through involvement in forest certification. In 2008, CEPI developed new definitions for water use with a local perspective and created a profile of the water used for manufacturing pulp and paper products in its member countries. In 2012, CEPI updated this profile and found that member companies withdrew approximately 3.71 million cubic metres of water from surface and ground water sources, compared to 4,000 million cubic metres in 2008. In 2015, 93% was returned to surface water supplies, cleaner than before.
Water Footprint methodology
Assessment methodologies are under development, including an ISO standard to ensure harmonised global rules. As part of the debate, the Water Footprint Network defines a water footprint as “the total volume of freshwater that is used to produce the goods and services consumed by the individual or community or produced by the business”. Water accounts distinguish between:
- withdrawals of water from rivers, lakes and aquifers (surface and ground water) that are used in industry (blue water)
- water from rainfall that is used to grow crops (green water)
- water which is an effluent from an industrial process (grey water)
Calculations of the “green water” footprint is of particular importance to paper based products as it relates to the interaction between the raw material from the forests and rainfall. The debate is ongoing about the scope of a “green” water footprint, but the view of CEPI (Confederation of European Paper Industries) is that a clear distinction should be made between the water balance of forests and the forest component of a water footprint of a paper based product. A green water footprint component for a paper based product should reflect:
- the difference in water impact between an unmanaged forest (or a forest managed for other purposes) and a forest from which paper based products are sourced
- the share of the wood that is actually harvested and within that, the share of the harvested wood that is used for making paper based products. (The industry uses only small diameter trees and thinnings. Other users of the forest include the timber and biomass industries)
- the relevance of recycling of paper based products including cartonboard packaging. Fibres from cartons can be recycled 5 or 6 times without any bearing on the water in the forest
It is recognised that a water footprint is not like a carbon footprint. A water footprint is specific in time and place to the industrial process which is being measured. Indicators that only measure the volumes of water used are potentially misleading, as they may not accurately reflect impacts on the local environment. Thus a paper water footprint should clearly specify:
- the “blue” and “grey” components at mill level
- the net water impact of forests (“green” water)
Water Footprint of Cartons
The main parameters affecting the water footprint of a carton is the grade of cartonboard used and the type of ink selected.