Mark J. Kirwan Paper and Paperboard Packaging Technology

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ENVIRONMENTAL AND WASTE MANAGEMENT ISSUES

This leaves an important group of chemicals which are used to enhance the

product, improve the efficiency of the manufacturing process and meet ecotoxico-

logical demands. This group would include coating ingredients, such as binders,

speciality sizing agents that impart specific properties, such as grease resistance,

optical bleaching agents also known as fluorescent whitening agents, fillers,

wet-strength additives, retention aids, defoamers, dyes and anti-fungal and anti-

microbial aids which keep the process system clean and efficient.

Waste chemical materials from the applications described are waterborne and

are subject to effluent regulations applying in the areas where mills are located.

Reference to Environmental Reports from paper mills indicates that process chemicals

are carefully chosen and that environmental impact, health and safety are key criteria.

From the standpoint of sustainability, it should be noted that some of these chemicals

are already derived from sustainable resources, for example starch, alum. Whilst

many of the synthetic polymers currently used are based on monomers derived

from oil, coal or natural gas, other renewable sources are technically possible.

A wide range of materials is used in printing, conversion and package use:

•

resins, vehicles and pigments used in inks

•

adhesives for both structural design and lamination – a wide range is used

including starch-based, PVA, crosslinking resins and hot melts based on resins

and waxes

•

plastic extrusion coatings (PE, PP, PET, PMP)

•

functional coatings for grease resistance, water repellency, non-slip, release, etc.

All these materials must be suitable for food packaging where they are required to

be in contact with, or close proximity to, food. Printers and converters should

check the status of all materials with their supplier with respect to the prevailing

regulations. In addition, the processes of making printing plates and cylinders also

involve the use of chemicals.

2.4.5 Transport

Packaging and packaged goods are, predominantly, transported by road. The

movement of logs, pulp, paper and paperboard is by road, rail and by sea. Reference

to the Environmental Reports issued by major forest-product companies indicates

that they are working on reducing the energy usage and the emission of volatile

organic compounds (VOCs) in transportation.

2.4.6 Manufacturing emissions to air, water and solid waste

So far we have discussed the resources necessary for the manufacture of paper and

paperboard packaging. Of equal concern from the point of view of environmental

impact and sustainability are the emissions and solid wastes which occur during manu-

facture and the disposal of packaging when its packaging function has been completed.

PAPER AND PAPERBOARD PACKAGING TECHNOLOGY

2.4.6.1 Emissions to air

We have already noted that the combustion of fossil fuel releases CO

into the

atmosphere and this is considered to be one of the main causes of the ‘green-

house effect’ which leads to global warming. Just over 50% of the fibre raw

material for the paper and paperboard industry is made from chemically sep-

arated fibre where the energy needs are provided by biomass and hence the main

emission to air is in the form of CO

. The balance, made up of recycled fibre and

fibre separated mechanically from wood, uses energy which is mainly derived

from fossil fuel.

Printers, converters and users of packaging all use electricity and, dependent on

the energy sources, can also be assessed for the amount of CO

which results from

their usage of electricity. Reference has been made to the work companies under-

take to reduce the environmental impact of transportation. Reductions in the use of

energy in this area are accompanied by reductions in the gaseous emissions associated

with the consumption of fossil fuels.

Producing energy from fossil fuels results in the emission of carbon dioxide (CO

sulphur dioxide (SO

) and nitrogen oxides (NO

). These gases can result in ‘acid

rain’ causing environmental damage to trees and lakes. The amounts which are released

of these three gases can be calculated in kg/tonne of product.

The use of natural gas as the preferred fossil fuel and the installation of CHP

plants for the production of electricity and steam result in lower emissions. In

some locations, mills have access to hydroelectric power which does not produce

gaseous emissions.

The separation of pulp by chemical means results in sulphur-based malodorous

gases which although present in very small amounts are noticeable in the areas

close to the mills because of the sensitivity of the human nose to the odours con-

cerned. Reference to pulp-mill environmental reports indicates that measures to

reduce these emissions are ongoing. These acidic and malodorous gases may be

burnt in the energy recovery boilers and the flue gases passed through an alkali

scrubber. Other possible emissions to air comprise soot (carbon particles) and

dust, which can be removed by electrostatic separators.

The printing industry has had to reduce organic discharges to the atmosphere

from the drying of solvent-based ink, varnishes and coatings. There is increased

usage of water-based inks. An Environmental Report cited the following example

from a folding carton–printing facility in that a reduction was made ‘in the use of

isopropyl alcohol by 40% in litho plate dampening water during litho printing.

This was achieved by installing osmosis equipment to treat fresh water and use

of safer chemicals to lower the surface tension of the plate dampening solution’

(M-real, 2002, p. 26).

2.4.6.2 Emissions to water

Water is collected after use in both pulp mills and paper mills. Some process water

is immediately recycled, for example whitewater containing fibre, fillers and dis-

solved chemicals, from the wet end of the paper machine.

ENVIRONMENTAL AND WASTE MANAGEMENT ISSUES

Wastewater is treated to render it suitable for reuse or discharge which is usually

directly back to nature or via an urban sewerage system. Mill discharges are

subject to external regulation. In Europe, the regulations are operated locally within

the guidelines of the EU Integrated Pollution Prevention and Control (IPPC)

Directive.

The contents of wastewater depend on the type of mill and the processes operated.

The processing could involve chemical or mechanical pulping, bleaching, recycling

of recovered fibre, de-inking, paper and paperboard manufacture, mineral-pigment

coating, etc. Wastewater can contain fibre, fines (fibrous particles), other solid

matters such as particles of bark, fillers and mineral pigments. It could contain

colloidal materials such as starch and soluble inorganic salts. Pulp-mill waste-

water can contain lignosulphonates, hemi-cellulose, organic high molecular weight

soluble fatty acids and degradation products from bleaching.

Wastewater is processed to achieve acceptable standards in respect of its:

•

total suspended solids (TSS) – this material would otherwise form deposits

in natural waterways

•

biological oxygen demand (BOD) – it is necessary to remove material which

would compete with other forms of aquatic life, such as fish, for oxygen

•

chemical oxygen demand (COD) – slowly decomposing organic material

would also compete with other forms of life

•

total phosphorus (P) – this is a nutrient and if the concentration (eutrophication)

builds up, algae and microscopic forms of life develop which, in turn,

prevent oxygen absorption and light penetration into water

•

total nitrogen (N) – eutrophication, as with phosphorus

•

temperature – the temperature of water emissions to nature must be regulated

•

adsorbable organic halogens (AOX) – this measures any organic chlorine

present as a result of the bleaching process, though some is naturally present

in wood itself.

Adsorbable organic halogens is not a measure of the toxicity of chlorine (halo-

gen) compounds present. This is an important point as the most common chlorine

chemical used today is chlorine dioxide where the by-products are simple com-

pounds which are not persistent in the environment and are similar to those which

occur in nature.

Particles in suspension are removed by settlement. This can be assisted by

coagulation and floatation aeration. BOD reduction can occur naturally in shallow

lagoons though this may take some time. If space is limited, aeration can be

employed to accelerate the process. The process of BOD reduction is also quicker

if ‘activated’ sludge is added (sludge containing bacteria which breaks down the

organic material). The treated effluent is subjected to settlement after which some of

the sludge is removed for reuse and the excess is removed as solid waste.

Recent developments of this process have occurred which offer improvements

and make the process more feasible for operating a closed water system in a pulp

mill or paper mill. This process combines biotechnology in a bioreactor aeration

PAPER AND PAPERBOARD PACKAGING TECHNOLOGY

tank with membrane filtration. The process is termed the thermophilic membrane

bioreactor process (PT, 2001).

Another recent development, in a mill making mechanical pulp, divides the

effluent water such that 20% is sent for biological treatment and the rest is evap-

orated and condensed in a plant which mainly uses waste heat from the chemi-

thermomechanical refining process. This recovers 93% of the incoming water, which

is returned to the process. Of the remainder, 4% is used in heat and chemical

recovery and the balance of 3% is sent to the biological wastewater treatment plant

(M-real, 2002, p. 27).

Significant improvements have been made in reducing the levels of the key

emissions. The reductions in Europe are shown in Table 2.2.

Regulations should not be based on arbitrary standards for BOD, TSS, etc. Local

conditions and environmental impact should be taken into account when setting

standards for non-toxic measurements of paper-mill emissions. The levels set must

take into account the environmental impact and long-term environmental sus-

tainability, especially in coastal waters and estuaries, due to the dynamic nature of

such environments.

A marine biologist who studied a specific estuary environment for 30 years

concluded that changes which occur in the disposition and dominance of

different species can be wrongly attributed to discharges from a paperboard

mill over that period. He found that, for example, a colony of one species

could move as the result of a storm disturbing its environment. Without such

knowledge, its demise could be associated with the discharge. In another

example, a successful colony of one species can attract the attention of a nat-

ural predator and disappear as a result. Again, the mill could be blamed for

the disappearance. A conclusion of this study was that observations had to be

made regularly over a long period – conclusions based on random observations

could be misleading (Perkins, 1993).

It is accepted, for example, that the environmental impact of cellulose residues

is less critical when discharged into open sea than when it is discharged into

with shallow lakes and rivers. In the former, it would not be an environmental

benefit to use energy, which in most cases would be derived from fossil fuel with its

associated emissions, to aerate using pumps, when the same effects of dilution, dis-

persion and aeration would be performed in nature through the action of the

wind and tides.

Table 2.2 Reductions in mill water emissions 1991–2000

Source: CEPI (2002, p. 30).

Feature Reduction 1991–2000 (%)

BOD 70

COD 66

AOX 90

ENVIRONMENTAL AND WASTE MANAGEMENT ISSUES

2.4.6.3 Solid waste residues in paper industry

Solid waste from pulp mills and paper mills comprises:

•

sludges from wastewater treatment

•

soda dregs from pulp-mill chemicals recovery

•

bark (biofuel or soil conditioner)

•

residues from washing and screening pulp in suspension

•

waste from mineral pigment coating

•

de-inking sludge

•

residues from the recycling of recovered paper which can be contaminated

with plastics, staples, etc.

CEPI (2002, p. 32) data shows that a reduction in mill waste disposal of around

15% has been achieved over the period 1990–2001. This has mainly been achieved

through an increase in the amounts composted and used in land spreading. The

main method for disposal of mill residues is by incineration with energy recovery.

Bark is used as either fuel or soil conditioner.

Mills also continue to seek other ways of diverting waste from landfill, for

example recovery of pigment-coating waste and its reuse as filler in papermaking

(M-real, 2002, p. 26; Stora Enso, 2002a).

2.5 Used packaging in the environment

2.5.1 Introduction

Natural resources provided by the environment are used in many ways but ultim-

ately everything is returned as waste to the environment. Some value has always

been extracted from waste by recovery, reuse and recycling but ultimately waste

has been disposed of to water, e.g. rivers and tidal estuaries, buried in landfill or

burnt (incineration). We are now more aware of the implication of using resources

and of the environmental impact of the various forms of waste disposal.

The main areas from which wastes arise are:

•

agriculture and horticulture

•

mining and quarrying

•

construction and demolition

•

sewage treatment and dredging

•

commerce and manufacturing, i.e. offices and factories

•

service sector, for example distribution, retail, hospitals, transport, education, etc.

•

municipal solid waste, mainly from households.

Cumulatively, total waste, measured as weight, in the UK is over 400 million

tonnes per annum (Mtpa). The used packaging component is around 8.5 Mtpa

(2% approx.), of which about 3.4Mtpa would be paper-based. Similar proportions

PAPER AND PAPERBOARD PACKAGING TECHNOLOGY

would be expected in other developed countries, yet the idea exists that waste is

synonymous with used packaging!

Whilst used packaging may not be a large proportion of total waste, it is highly

visible in places where people live and work. Many aspects of the ‘throw-away

society’ are accepted but society is concerned at the volume of used packaging

which accumulates.

In addition to comprising part of domestic waste, used packaging arises in

distribution, commerce, manufacturing and catering as well as the packaging

disposed of during travel, leisure, education, hospitals and all types of work. This

highlights one of the waste management problems associated with packaging –

packaging waste arises in relatively small amounts in a large number of locations.

2.5.2 Waste minimisation

The first principal of waste management is that waste should be minimised. This

can be applied to paper-based packaging in a number of ways:

•

Pack design changes can optimise the amount of material used whilst

maintaining strength. Combined plastics/paperboard tubs can optimise

protective properties of both materials, whilst at the same time minimising

the amounts used.

•

Reducing weight per unit area (g/m

) of material for the same pack design

and material ensuring that protection is not compromised. It may be possible

to make a net saving by reducing the material in the primary pack by increasing

strength in the distribution pack, or vice versa.

•

Changing the material specification – some paper and paperboard materials

offer the same strength with weight savings of at least 20% when compared with

alternatives, for example extensible kraft, corrugated board, use of virgin fibre.

A note of caution here is to make the point that ‘higher recovered paper utilisation

in a paper substrate is generally equal to greater weight’ (CEPI, 2002, p. 29).

2.5.3 Waste management options

2.5.3.1 Recovery

There are several disposal options once the weight of packaging has been minim-

ised, but they all require recovery once the primary function of protecting the

product throughout its distribution, point of sale and consumer use has been

completed.

Recovery can be achieved in several ways:

•

Segregation at the point of disposal, for example in the home, followed by

collection or by being taken to a central collecting point, after which the

material content of particular waste streams can be recycled.

ENVIRONMENTAL AND WASTE MANAGEMENT ISSUES

•

Collection in the form of mixed waste which is sent for segregation at a sorting

facility after which the material content can be recycled.

•

Collection in the form of mixed waste which is sent to a plant which can

use the waste in that form, for example an energy-from-waste incinerator

or composting plant.

Paper and paperboard packaging presents several disposal options since the

basic material is recyclable, combustible and biodegradable.

The reuse of paper and paperboard packaging as a bag, box or other container

in its original form is not widely practised. An example would be a rigid solid

board case which can be folded flat after the contents, such as folding cartons,

have been removed by the packer, so that the case can be returned to the converter

for reuse.

2.5.3.2 Recycling

Recycling is defined as reprocessing material in a production process for the

original purpose or for another purpose. Another purpose, here, could include

organic recycling (composting). Energy recovery is usually excluded in official

definitions of recycling.

In general there is a ‘feel-good’ factor about recycling. There is a consensus

that it is a good activity to promote. ‘Recycling is one of the most tangible symbols

of the commitment to do the right thing’ (Akerman, 1997). Unfortunately, society

often uses the word ‘recycling’ when it should use ‘recovery’ or ‘collection’; as

already noted, these actions must precede recycling. The recovered sorted material

is then sent to a reprocessing facility, which for paper and paperboard waste would

be a paper or paperboard mill.

Material recycling of paper and paperboard is a major business (Fig. 2.5).

Recovered fibre contributes 46% of the fibre used in the paper industry worldwide,

currently over 150Mtpa. It is a significant and essential resource and the proportion

is likely to increase, though its use, measured as a percentage of consumption, will

ultimately be limited by factors which will be discussed.

The proportions recovered from consumption and the proportions of recovered

fibre used in paper and paperboard manufacture in the US and Europe for 2001

are shown below.

A significant proportion of the recovered fibre in these markets is exported. In

2001, exports were 16 and 6% of the totals recovered for the US and Europe

respectively.

Market % Recovered % Recycled in production

US 48.3 (target by 2012 is 55) 37 (AF&PA website)

Europe (EU) 52.1 (target by 2005 is 56) 41.8 (CEPI, 2002, p. 24)

PAPER AND PAPERBOARD PACKAGING TECHNOLOGY

Waste management infrastructures have been operating during the last 100

years. Merchants collect recovered waste paper, which is then made available to

paper and paperboard mills.

There are three important facts about paper recycling which should be noted:

•

Some fibre by virtue of its use cannot be recovered – food contaminated

packaging and tissues used for hygienic purposes, cigarette paper, paper and

paperboard materials used in building and materials used in books, maps,

documents and archives. Some estimates put the proportion which cannot be

recycled, including those products, such as books, which cannot be recycled

within a relatively short time scale, as 15–20% and some as high as 30%.

•

Cellulose fibres cannot be recycled indefinitely. The fibre loses length and this

is a major cause for a relatively high fibre loss, as sludge, during reprocessing.

Interfibre bonding potential is also reduced each time it is recycled. The pro-

cessing of recovered fibre is an important subject for technical development.

Estimates of the number of cycles a fibre can survive and still be useful

suggest that 5–10 cycles are possible depending on the type of paper or paper-

board product and the life and usage of that product. The number of cycles is

somewhat theoretical because the logistics of the situation show that even at a

high recovery rate (50% approx.) from the market only 6% of original fibre

survives to the third reuse due to losses in production (20% approx.) and unre-

coverable waste (50% per cycle).

Cleaning

Hydrapulper fibre separation in water

Waste paper

bales at mill

Collection

Board machine

Water

Figure 2.5 Recovery and recycling of waste paper and paperboard. (Reproduced, with permission,

from Pro Carton.)

ENVIRONMENTAL AND WASTE MANAGEMENT ISSUES

•

Not all fibres are equal – fibres in waste comprise those which have been

chemically and mechanically separated and fibres which have already been

recycled through one or more cycles. There are also differences which relate

to the tree species from which any particular fibres have been derived, i.e.

long and short fibres, and other species-specific features.

For technical reasons all fibres cannot be satisfactorily used for all paper

products. The differences between fibres are taken into account in the way

waste paper and paperboard are classified and sold to the mills. In the European

(CEPI) classification, there are nine groups of waste which are subdivided into

67 specific types; other parts of the world use similar classifications. Each

classification has a price which reflects the quality of the fibre and hence its

value to the papermaker. Many people think of waste paper solely as ‘waste

paper’ and not as a whole range of products each with their own characteristics

and price/value.

The highest value waste paper is white, unprinted and woodfree – meaning

that it only comprises chemically separated bleached pulp, i.e. no mechanical

pulp or recycled pulp. Paperboard waste derived from industrial and commercial

premises is usually clean, i.e. no contraries or foreign matter, and easy to collect

regularly in reasonable quantities. Post-consumer waste is more difficult to

manage. It may be sorted at source, such as newspapers and white-printed waste

in the home, or brown corrugated cases at the supermarket. Waste which is mixed

has lower value and is more likely to contain contraries, inks, adhesives, other

materials laminated to the paper and, in the worst cases of unsorted mixed post-

consumer waste, broken glass and other solid contamination. It has been found

that as more waste is collected, i.e. recovered, it tends to contain higher propor-

tions of unsorted post-consumer waste. This can reduce the cost of recovery/

collection but lower the value of the waste for material specific recycling.

De-inking is a process whereby ink is removed from recovered printed papers.

First, the fibre is dispersed in water and then treated with surfactants which extract

the ink particles. The fibre is separated from the ink particles by a cascading, float-

ation process based on the difference in density between the two materials.

Finally, a mild bleaching treatment may be done to increase the brightness of the

pulp. This process is not widely used for packaging products though some may

contain a proportion of de-inked fibre.

Organic recycling may be described as ‘the aerobic (composting) or anaerobic

(biomethylisation) treatment under controlled conditions and using micro-organisms,

of the biodegradable parts of packaging waste, which produces stabilised organic

residues or methane’ (UK Packaging (Essential Requirements) Regulations 1998).

Waste paper and paperboard can be organically recycled because cellulose

fibre is biodegradable. It can be broken down into natural substances by organisms

in the environment and, in particular, by bacteria using microbial enzymes to

convert organic material into CO

, water and humus or compost. Compost is used

in agriculture and horticulture as a soil conditioner.

PAPER AND PAPERBOARD PACKAGING TECHNOLOGY

2.5.3.3 Energy recovery

In the past, burning or incineration was carried out as a hygienic way of reducing

the volume of waste. When emission regulations were brought into force municipal

incinerators were closed down and more waste was sent to landfill.

Although the technology to burn waste safely has become available in recent

years, the plants require large capital investments. There is also a deep public

mistrust of incineration due to lack of knowledge and information.

Paper and paperboard waste retains solar energy because the fibre is originated

from the wood. This energy can be recovered in an energy-from-waste (EFW)

incinerator. The minimum calorific value of paper and paperboard is 10 mJ/kg and

2 tonnes yield the energy equivalent of approximately 1 tonne oil or 1.5 tonne

coal. We cannot, however, discuss the incineration of waste paper and paperboard

in isolation from the disposal of mixed municipal waste. It makes no sense to

segregate paper and paperboard waste, which is unsuitable for recycling, from

mixed solid waste (MSW) and incinerate it in isolation. We must therefore examine

the issue of the disposal of MSW by incineration with energy recovery as part of

a holistic approach to MSW management.

The benefits of recycling with energy recovery are as follows:

•

The main benefit is the recovery of solar energy. A typical EFW facility can

recover 35MW from around 420 000 tonnes of MSW. South East London

Combined Heat and Power (SELCHP) collects waste from one million

people and provides electricity for 100000.

•

The energy recovered is non-fossil-based – fossil fuel, by contrast, is

non-renewable, contributes to the greenhouse effect and produces noxious

emissions.

•

In cities incineration greatly reduces lorry traffic to out-of-town landfill sites.

•

Incineration reduces landfill need by reducing the volume of waste by 90%.

•

Diversion of waste from landfill reduces methane production – methane

being a much more harmful greenhouse gas than CO

•

Recovery of other materials is possible, for example ferrous residues.

•

Hygienic benefit – organic waste is reduced to less biologically active

material.

•

Incineration is to be preferred for highly flammable, volatile, toxic and clinical

wastes which should not be landfilled.

When cartonboard and other types of paper-based packaging are incinerated

the cellulose component reverts to CO

and water vapour. The emission to air

should not contain carbon particles, or carbon monoxide, as this would indi-

cate incomplete combustion. The main community concern is, however, more

emissions which may arise from other components of mixed waste.

Incineration is now carried out under carefully controlled conditions to minim-

ise potentially harmful conditions and to meet the very tight regulations. This is

achieved using high temperatures of, approximately, at least 850°C and extensive

flue-gas cleaning. Processing comprises: