And tell the real story of print and paper

 
line decor
  
line decor
 
   
       
   
 

 
 
DRAFTING A STANDARD FOR CALCULATING THE CARBON FOOTPRINT OF PAPER

FOPAP believe that many of the assumptions used in current carbon lifecycle analysis models are flawed or inadequate. Perhaps the biggest of the potential errors is the commonly assumed rate of decay of carbon content when paper is sent to landfill. If paper breaks down quickly, as is assumed in these models, then the carbon it has sequestered from the atmosphere will be quickly returned to it. This would make landfill a short term carbon sink – and a possibly undesirable one, as paper is also known to produce methane and other greenhouse gases as it decays.

But what if paper does not decay in landfill to the extent thought? And what if any methane produced could be collected and used for energy?

In fact, paper does not decay as readily and to the extent that the figures used by governments, policymakers and the IPCC itself, would suggest. This has been proved quite recently by a team of Australian scientists, led by Dr. Fabiano Ximenes, who have spent the last 10 years digging up landfill in various sites across Australia and documenting their findings. You can find out more about their discoveries here.

The other generally held misconception is that landfill methane emissions cannot be prevented and, when they do occur, cannot be captured. This is simply not true. Methane is produced when organic and carbon-based waste, such as paper, decays. However, in modern landfill the decay of these organics is sometimes accelerated purposely to harvest the methane for fuel and complete the inevitable chemical reaction. More commonly, each layer of waste is covered and made airtight. Under these conditions, known as ‘anaerobic’, the decay reaction does not take place as readily and less methane is produced. The methane that is produced can be collected.

The Australian team who conducted the research claim a 95% collection rate. This is much greater than the 71% currently assumed by the UK’s government.

These facts would seem to suggest we ought to be reducing the amount of paper we recycle in order to take advantage of landfill as a long-term carbon sink. Moreover, when FOPAP's logic is applied even to the currently accepted figures for decay and emissions, surprisingly there are still circumstances where it is better to send paper to landfill, rather than recycle.

We present the full details of these circumstances and our recommendations for the methodology that should be adopted for the calculation of a carbon footprint for paper, below. These represent a worse-case scenario as, if the decay of carbon factors and methane emissions collected are revised, as we believe they should be, it would be better to manufacture practically every grade of paper from virgin pulp and abandon paper recycling in its entirety.

The main point of drafting a standard for calculating the carbon dioxide emissions associated with any category of products or services is the proposed link between the recent rise in atmospheric carbon dioxide levels and climate changes; and the perception that most or all of these changes are and/or will become undesirable.

Whether or not the aforementioned link is true and its consequences undesirable, once any standard for carbon footprinting is published and organizations start to report carbon footprints that conform with it, current attitudes mean that regulatory, marketing and other pressures are likely to encourage such organizations to minimize their standard-compliant carbon footprints.

In so far as the aforementioned link is true and its consequences undesirable, it is in the interests of the world and its population that the carbon dioxide emissions associated with human activity are minimized irrespective of how they are measured by standards. It is therefore important that carbon footprints, as measured by a standard such as 16759, should faithfully reflect actual carbon dioxide equivalent emissions.

Printing is an element in a process chain in which a material (paper) produced from a renewable resource (trees) that absorbs atmospheric carbon dioxide plays a major role and which has the potential – unlike many other process chains – to actually reduce atmospheric carbon dioxide levels rather than simply increasing them less rather than more rapidly.

For it to do so carbon dioxide absorption and emissions need to be considered and minimized over the entire cycle from tree growth to paper disposal in order to ensure that minimizing the carbon footprint of one stage in the cycle – printing for example – truly reflects the fact that carbon dioxide emissions have actually been minimized rather than simply shifted up- or downstream. A standard that does not do this or that is not linked to other up-or downstream standards to show the overall picture would be failing the world and, sooner rather than later, would be criticized for doing so.

On the other hand, a standard aimed at one specific community and stage in the cycle – in this case printers – that requires a knowledge of the subsequent history of upstream processes (for example, the subsequent use of the land after the tree was felled) and a knowledge of downstream fates (for example, how the printed product is disposed of after use) runs the risk of being complex and unwieldy to calculate accurately and may therefore suffer from a poor uptake.

How can the standard be both simple to use and an accurate reflection of reality?

Some Principles
Trees use energy from the sun to fix carbon dioxide from the atmosphere. The basic chemical reaction for this process can be summarized as:

                6 CO2 + 6 H20 + energy -> C6H12O6 + 6O2 [photosynthesis]

This is followed by various processing stages to produce the complex organic macromolecules (cellulose, hemicellulose and lignin) that are the chemical components of the structures that form paper.

All the organic carbon present in a tree felled to make paper and subsequently in the paper (excluding any carbon that may be present in any coatings applied to certain grades of paper) was present relatively recently (decades or centuries ago) in the atmosphere, with every kilogram of carbon in wood or paper being the equivalent of 44 (the molecular weight of carbon dioxide)  / 12 (the atomic weight of carbon) = 3.67 kilograms of carbon dioxide (CO2).

Once paper has been used and is discarded, its component macromolecules may potentially be degraded in a reaction that can be summarized as:

C6H12O6 + 6O2 -> 6CO2 + 6 H20 + energy [respiration]

The exact opposite of the first.

If paper IS completely degraded after use then the amount of carbon dioxide released back to the atmosphere is exactly the same as the amount originally fixed by the tree, there is no net absorption or emission of atmospheric carbon dioxide. In addition to the carbon dioxide that is absorbed by trees or released by decaying paper, energy is required to convert trees into paper and this energy may – but is not necessarily – generated from sources such as fossil fuels that release non-biogenic, long-cycle carbon dioxide. In terms of impact on atmospheric carbon dioxide levels, it is only the release of non-biogenic, long-cycle carbon dioxide that has been locked up over geological timescales that matters.

If paper is NOT completely degraded after use then the carbon in the undegraded portion represents carbon dioxide that is not returned to the atmosphere and the manufacture of paper followed by its incomplete degradation is a mechanism that could, potentially, remove carbon dioxide from the atmosphere.

Paper can degrade by various pathways but in modern landfills, the sites where most paper that is not recycled or incinerated is disposed of, anaerobic conditions will develop very quickly. [Historically, this was not the case, organic waste was not immediately covered and more aerobic decay would have taken place. This may still be case in certain countries]. However, under anaerobic conditions, any lignin the paper contains will not decay at all. The other organic components – essentially cellulose and hemicellulose will decay partially and, under anaerobic conditions will release carbon dioxide and methane in roughly equal amounts by volume. Ultimately, there will be a portion of the organic carbon that never decays, representing carbon dioxide in the ratio of 1 kilogram of carbon to 3.67 kilograms of carbon dioxide (as explained above) and a portion of organic carbon that degrades to give roughly equal weights of carbon dioxide (this is effectively neutral in terms of atmospheric carbon dioxide, since it was fixed in the recent past) and methane, which is a cloud with a silver lining.

Why?

Methane (CH4) can be captured and burnt to yield energy (which can be harnessed), producing carbon dioxide (which is neutral for the above reasons) and water. Methane, however, is a much stronger absorber of infrared than carbon dioxide. Once released into the atmosphere, methane has a relatively short lifespan of 10 to 12 years; being oxidized to produce carbon dioxide (neutral) and water. In order to quantify the impact of gases such as methane that have a greenhouse effect but limited lifespans, a calculation is performed to determine the amount of infrared a unit mass of a specified gas and its decay products will absorb over a chosen time period in relation to the amount absorbed by the same mass of carbon dioxide over the same time period.

This is known as the Global Warming Potential (GWP) of a gas.

Over a period of 100 years (the time period conventionally but for no good reason chosen for much current climate discussion), the GWP of methane is currently deemed to be 25. Over a period of 20 years its GWP is 72, over 500 years it is 7.6. These figures have been and may in future be revised. The US EPA, for example, is still using a 100-year GWP of 21.

Any methane that paper degrading in landfill gives off can – with the right equipment and by acting at the right time – be captured and burnt to yield useful energy. The useful energy obtained in this way may be used to reduce the need to obtain energy from the combustion of fossil fuels and the resulting release of non-biogenic or long cycle carbon dioxide. Exactly how much of such carbon dioxide emissions are or could be avoided depends upon the fuel mix any individual country uses for power generation.

Under what combination of circumstances therefore, might waste paper act as a carbon store or sink?

Assuming paper is made from trees grown in plantations that are replanted after felling, the level of carbon dioxide equivalents in the atmosphere will fall if the amount of carbon dioxide equivalent that remains locked in undecayed fibre in landfill (A) plus the carbon dioxide that is not emitted from fossil fuels because of the combustion of the methane captured from the decaying paper (B), less the non-biogenic carbon dioxide emissions produced during is manufacture (C), less the amount of methane (D) emitted from the landfill adjusted by the GWP for the chosen time frame is greater than zero:

                Av+Bv-Cv-Dv > 0

If paper is made from recycled paper, the level of carbon dioxide equivalents in the atmosphere will fall if the amount of carbon dioxide equivalent that remains locked in undecayed fibre in landfill (A) [assuming the fibre when no longer fit for recycling is sent to some form of landfill – other fates are conceivable] plus the carbon dioxide that is not emitted from fossil fuels because of the combustion of the methane captured from the decaying paper (B), less the non-biogenic carbon dioxide emissions produced during is manufacture (C) multiplied by the number of cycles (x) the fibre can be recycled for [recycled fibre may be used for different, typically lower quality, types of paper each time round and so the non-biogenic emissions may be different for each cycle], less the amount of methane (D) emitted from the landfill adjusted by the GWP for the chosen time frame is greater than zero:

               Ar+Br-Crx-Dr > 0

For the same quantity of paper, virgin fibre will result in lower atmospheric carbon dioxide levels if: Av+Bv-Cv-Dv) x > Ar+Br-Crx-Dr
               
As a further refinement, which will be touched on later, one might also make some allowance for additional accumulation of carbon in the forest as a result of not felling trees to make paper. It is possible to conceive of certain realistic scenarios in which any of the above conditions might be true or false, of which more later.

The Quandary
It is often claimed – but is far from always being the case – that the non-biogenic carbon dioxide emissions involved in making paper from virgin fibre are greater than making it from recycled fibre. For the time being let us assume that this is the case. Let us also assume the standard does not take into account the carbon dioxide equivalent of the paper when it reaches the printer or its downstream fate, merely the non-biogenic carbon dioxide emissions involved in its manufacture. In such a scenario, the carbon footprint of a printed product produced with recycled paper would, all other things being equal, be lower than one produced on virgin fibre paper.

If the paper in question was one that decayed slowly and only to a limited degree in landfill then it might be found that had the fate of the paper and the carbon dioxide emissions associated with its disposal been considered then the overall carbon dioxide equivalent emissions would have been lower for the product produced from virgin fibre even though the standard suggested that recycled paper was preferable.

How can a printer take into account events that are beyond his or her control and occur after his or her work is finished? 

Paper Decay Models
A number of countries and international bodies such as the IPCC have developed models for predicting emissions from their landfills or to advise countries on how to do so. The following pages summarize the models developed by the IPCC itself, the UK and the USA. The original documents that the current pages summarize run to hundreds of pages. Inevitably, matters have been simplified – but I hope not distorted – and only certain aspects considered. I would be happy to discuss any point in greater detail with anybody who is interested.

Many other countries have models that are similar in principle but differ in their details. Should it become necessary in order to develop emissions factors for paper disposal, the models and values adopted by other countries could be looked at in greater detail. For the time being, the three approaches discussed here should provide an adequate impression of what is involved.

IPCC – Intergovernmental Panel on Climate Change
The IPCC itself does not undertake research but it does draw up guidelines based on other people’s research. These guidelines may – but are not necessarily – adopted by individual countries in calculating their greenhouse emissions. In modelling the decay of organic matter, the IPCC adopts the practice of dividing the total of amount of waste into fractions, namely:

DOC –Degradable Organic Content – the mass of organic carbon waste accessible to biochemical decomposition expressed as a decimal fraction of total waste
DOCf – This is the decimal fraction of the DOC that actually decomposes. Under anaerobic conditions and assuming the DOC to contain lignin, the IPCC recommends a default value of 0.5 for the DOCf – FOPAP's view is that this is a ‘fudge’.

In Chapter 2 of its 2006 Guidelines for National Greenhouse Inventories it recommends the following values for the DOC of paper:

 

Dry matter as  % wet weight

DOC as % of wet weight

DOC as % dry weight

Total C content as % dry weight

Fossil C as % dry weight

 

Default

Default

Range

Default

Range

Default

Range

Default

Range

Paper/board

90

40

36-45

44

40-50

46

42-50

1

0-5

Wood

85

43

39-46

50

46-54

50

46-54

 

 

 

In the case of paper, Chapter 3 of its 2006 Guidelines for National Greenhouse Inventories recommends the following :

The use of a first order decay model for calculating the amount of organic carbon remaining and the emissions of gases from the decaying carbon. In such a model the rate of decay at any given time is proportional to the amount of decaying material. As this material decays and its amount declines, so too does the rate of decay. Consequently, the half-life (t1/2 or h) – the time for the level of decay to decline to a half of the initial value  is a constant for any given substance undergoing decay.

Such a decay curve can be described by the equation:

Remaining mass mr at time t = mi x 1/2 (t/h)

And the rate of decay d is:

d = k m, where k (the decay constant) = ln(2)/h

It then provides the following table of values for the decay constants and half-lives of paper (expressed in years), which it categorizes as ‘slowly degrading’:

 

Boreal and Temperate
(MAT < 20 °C)

Tropical
(MAT > 20 °C)

 

Dry
(MAP/PET <1)

Wet
(MAP/PET >1)

Dry
(MAP < 1000 mm)

Wet
(MAP > 1000 mm)

 

Default

Range

Default

Range

Default

Range

Default

Range

Paper/textiles

17

14-23

12

10-14

15

12-17

10

8-12

Wood/straw

35

23-69

23

17-35

28

17-35

20

14-23

MAT = Mean Annual Temperature
MAP = Mean Annual Precipitation
PET = Potential Evapotranspiration

To put things in a topical context, Berlin’s
MAT is 9.6 °C
MAP is 571 mm
PET is 650 mm
Berlin is therefore dry temperate, with a default half –life for paper of 17 and a range of 14 – 23 years, according to the IPCC

To go to the other extreme Rio de Janeiro’s
MAT is 24
MAP is 1175 mm
Rio de Janeiro is therefore wet tropical, with a default half-life for paper of 10 and a range of 8 – 12 years.

Wood has been included in the above table because paper is sourced from wood. In wood, the original fibre structure has not been disrupted and all wood contains lignin (the precise proportion varies slightly depending on wood type), whereas some papers contain lignin, some do not. This may be significant for the decay of paper – see later.

Worked example
As an exercise, using the IPCC’s default values, what will be left of the organic carbon in a kilogram of paper left to degrade under anaerobic conditions in the vicinity of Berlin after 100 years (the conventional period adopted for deciding whether carbon has or has not been ‘locked up’)?

Default DOC 0.4 (wet weight). Therefore the kilogram of paper contains 400 gm of organic carbon.
Default DOCf 0.5. Therefore 200 gm of organic carbon will potentially degrade over 100 years, 200 grams will not degrade.
Default half-life 17 years. Therefore after 100 years, the organic carbon remaining is 200 x 1/2(100/17) = 1.7 gm

200 grams of carbon didn’t degrade at all, therefore the amount of undegraded organic carbon left at 100 years from the original kilogram of paper is 201.7 gm.

As previously explained, every gram of fixed organic carbon represents 3.67 grams of carbon dioxide that has been removed from the atmosphere and not returned to it. Therefore, in this example, the carbon dioxide equivalent of the undegraded organic carbon in the kilogram of paper after 100 years is 201.7 x 3.67 or 740.24 gm CO2

When organic waste decays under anaerobic conditions, roughly half the landfill gas by volume (and therefore moles) is methane and half carbon dioxide. The carbon dioxide that is given off is irrelevant, since it was recently fixed from the atmosphere (as discussed previously), the methane is important because of its higher GWP.

The precise ratio of methane to carbon dioxide depends on site conditions, since some methane may be oxidized to carbon dioxide as it ascends the waste column and before it reaches the atmosphere and some carbon dioxide may dissolve in water descending the landfill column and be carried away in the leachate. For the sake of this exercise we will assume a 50/50 ratio.

400 – 201.7 = 198.3 gm of organic carbon degrades, with 198.3 /2 = 99.15 g as methane. The methane that comes off will therefore weigh 99.15 x 16/12 (ratio of mw CH4 to aw C) = 132.2 g CH4. Weight for weight, over 100 years (remember, it’s different over different time frames), the GWP of methane is 25. This 132.2 g of CH4 is therefore the equivalent of 25 x 132.2 = 3,305 gm of CO2.

This means the net release of carbon dioxide equivalents to the atmosphere from this kilogram of paper over 100 years is 3,305 – 740.24 = 2,564.76 gm.

It is possible to install equipment at landfill sites to collect methane. There are differences from site to site and country to country as to whether such equipment is installed, the design of the equipment and its associated efficiency of collection, and the stage in a landfill’s life history when such equipment is brought into operation. There is therefore a very broad range of collection efficiencies of anything from 10% to 90%. The IPCC suggests adopting a default efficiency of 20% because of the many uncertainties.

Using the IPCC default, the amount of methane that is not recovered would be 3,305 x 0.8 = 2,644 gm and the net increase in atmospheric carbon dioxide equivalent levels over 100 years would be 2644 – 740.24 = 1,903.76 gm.

Using the IPCC spread (10% to 90% collection), the carbon dioxide equivalents not recovered would range from 3,305 x 0.9 = 2,974.5 gm to 3,305 x 0.1 = 330.5 gm. In the former case there would be a net increase in atmospheric carbon dioxide equivalent levels of 2,234.26 gm and in the latter case of a net decrease of 409.74 gm.

From the above, given the GWP of methane, the crucial factor in determining atmospheric carbon dioxide emission levels is the extent to which the methane emissions are recovered.

The IPCC guidelines allow for individual countries to adopt different parameters in drawing up their inventories, where there are good grounds for doing so. The methane that is collected may be flared, i.e. burned, converted to carbon dioxide (neutral because of recent biogenic origin) but without useful energy being extracted or it may be used as a fuel for some power generating system. In so far as useful power is generated from it, it can be used to avoid emissions from fossil fuels used by a country’s power generation system.

As to exactly which alternative fuel source it may be a substitute for will vary from country to country. The amount of CO2 emissions from fossil fuels that can be avoided as a result of the power sourced from methane allows will depend upon the specific characteristics of that country’s power generating system. The IPCC makes no default recommendation. This point will be looked at in relation to specific countries, based on their power generation infrastructure.

To sum up:
Using the IPCC’s default values, 1,000 gm of the same paper decaying under the same conditions can cause anything from an increase in atmospheric carbon dioxide levels of 2,234.26 gm to a decrease of 409.74 gm, without taking into account avoided power generation emissions, using the methane recovery efficiency spread quoted by the IPCC.

UK
The UK has recently reviewed its methodology for calculating its greenhouse gas emissions in a report entitledInventory Improvement Project – UK Landfill Methane Emissions Model (Dominic Hogg, Ann Ballinger, Hans Oonk) Final report to Defra [a UK ministry] January 2011

The UK government accepted some of the recommendations of this report, rejected others. The current values used by the UK in calculating its methane emissions are outlined below. This report is a review of the model used by the UK to calculate methane emissions, it is not primarily about the degradation of paper. However, in the course of reviewing the UK model it does specify the values used by the UK and the reasons for their adoption. The UK would be classed as Wet Temperate according to the IPCC’s table, although parts of the south east corner are close to being dry, whereas parts of the north and west as well as being somewhat cooler are very much wetter.

Rather than adopt a default DOCf for all organic waste, the UK model (MELMod) divides the organic carbon into that present as lignin (which does not degrade or to only a very limited degree) and that present as cellulose and hemicellulose (which degrades more extensively).

The current UK position, so far as paper is concerned, is to assume that 65% of the non-lignin fraction is degradable and that 5% of the lignin fraction is degradable – remember, different papers have different percentages of lignin. It should also be remembered that the ‘carbon content’ of lignin is higher than that of cellulose/hemicellulose.

The UK assigns rate constants to the biochemical fractions, rather than the type of waste, with that fraction of the lignin that degrades being classed as slow, and cellulose and hemicellulose being classed as medium. The half-lives adopted are:

Slow: 15.2 years
Medium: 9.2 years

In the UK therefore, on the basis of the values, used for the national emissions model, different papers will decay to differing degrees and at differing speeds, depending on their lignin content.

Given that the UK model is based on chemical composition, in order to calculate decay rates it would be necessary to know the lignin/cellulose/hemicellulose content; something that is not immediately apparent from looking at the paper. However, in the current UK GHG model paper is only divided into two categories – paper and card – which appear to differ only in their moisture content. For the purpose of the UK model therefore it is not necessary to know lignin content, since all paper is deemed to have the composition lignin 15%, cellulose 61%, hemicellulose 9%.

In real life, however, papers do differ in composition, so if the UK approach of calculating decay on the basis of chemical composition were adopted and one wanted to model decay for different types of paper there would need to be some easily usable method by which those monitoring waste would be able to assign paper to the right category.

Worked examples
For the sake of simplicity let us take one paper containing lignin and the rest cellulose and another with no lignin and simply consisting of cellulose/hemicellulose, ignoring all other components – since all we are really interested in is the degradation of organic carbon. These are notional rather than real papers, but the same principles apply to real papers with appropriate adjustments for other components and moisture.

1 kg of lignin containing paper
20% lignin, typically the proportion of carbon in lignin is 0.72 (108/150), so the lignin contains 144 grams of carbon.
80% cellulose/hemicellulose, typically the proportion of carbon in cellulose is: 0.44 (72/162) so the cellulose/hemicellulose contains 355 grams.
Overall carbon content: 499 grams

After 100 years the lignin has decayed as follows: 95%, i.e. 136.8 grams, is intact. The remaining 7.2 grams has decayed with a half-life of 15.2 years, therefore 0.075 gm remain.  In total 136.875 gm of carbon remain in the lignin.

The cellulose/hemicellulose has decayed as follows: 35% is intact, i.e 124.25 gm. The remaining 230.75 gm have decayed with a half-life of 9.2 years, therefore 0.12 gm remain. In total 124.37 gm remain.

At 100 years a total of 261.245 gm of carbon remains undegraded, i.e. 52.35%. The 261.245 gm of fixed carbon is the equivalent of 958.77 gm of carbon dioxide. 237.76 gm of carbon will degrade as landfill gas (50/50 CH4/CO2).

1 kg of non-lignin containing paper
100% cellulose/hemicellulose, typically the proportion of carbon in cellulose is: 0.44 (72/162) so the cellulose/hemicellulose contains 440 grams.
Overall carbon content: 440 grams

After 100 years the cellulose/hemicellulose has decayed as follows: 35% is intact, i.e 154 gm. The remaining 286 gm have decayed with a half-life of 9.2 years, therefore 0.153 gm remain. In total 154.153 gm remain.

At 100 years a total of 154.153 gm of carbon remains undegraded, i.e. c. 35%. The 154.153 gm of fixed carbon is the equivalent of 565.74 gm of carbon dioxide. 285.847 gm of carbon will degrade as landfill gas (50/50 CH4/CO2).

In 2008, the UK assumed that 71% of methane was recovered at landfills and reports on that basis.

Therefore, in the case of the lignin paper
237.76/2 x 16/12 = 158.50 gm of methane will be emitted
In the UK model 71% of this is captured, i.e. 112.54 gm and 45.96 gm emitted
The GWP of these 45.96 gm is 1,149 gm
There is 958.77 gm of carbon dioxide equivalent retained in the landfill so the atmospheric level of carbon dioxide equivalents is increased by 1,149 – 958.77 = 190.23 gm

Therefore, in the case of the non-lignin paper
285.847/2 x 16/12 = 190.56 gm of methane will be emitted
In the UK model 71% of this is captured, i.e. 135.30 gm and 55.26 gm emitted
The GWP of these 25.37 gm is 1,381.50 gm
There is 565.74 gm of carbon dioxide equivalent retained in the landfill so the atmospheric level of carbon dioxide equivalents is increased by 1,381.50 – 565.74 = 815.76 gm

Under the same conditions, the two papers differ considerably in their net carbon dioxide emissions at 100 years.

However, there is much more for us to consider for this calculation.

Methane has a high heat of combustion. The methane that is recovered can simply be flared (i.e. burned to produce carbon dioxide – neutral for our purposes since it is biogenic) or it may be used as a fuel in a power generation plant.

The heat of combustion of methane is 55 MJ kg-1. Therefore the methane collected from the lignin paper has an energy value of 55 x 0.11254 = 6.19 MJ. 1 kilowatt hour = 3.6 MJ. The recovered methane therefore has an energy value of 6.19/3.6= 1.72 kWh

Assuming, for the sake of argument, 30% efficiency in the conversion of the methane to electricity, the recovered methane would generate 0.516 kWh. The UK government currently (2011) proposes a savings emissions factor for electricity generation of 533 gm CO2/kWh
The 0.516 kWh generated from the recovered methane would therefore allow 0.516 x 533 = 275 gm of CO2 emissions from fossil fuels to be avoided.

This means that the lignin paper would result in a net reduction in atmospheric carbon dioxide equivalent levels of 275 – 190.23 = 84.77 gm

The methane collected from the non-lignin paper has an energy value of 55 x 0.1353 = 7.44 MJ. 1 kilowatt hour = 3.6 MJ. The recovered methane therefore has an energy value of 7.44/3.6= 2.07 kWh

Assuming, as above, a 30% efficiency in the conversion of the methane to electricity, the recovered methane would generate 0.62 kWh

The UK government currently proposes a savings emissions factor for electricity generation of 533 gm CO2/kWh. The 0.62 kWh generated from the recovered methane would therefore allow 0.62 x 533 = 330.46 gm of CO2 emissions from fossil fuels to be avoided. This means that the non-lignin paper would result in a net increase in atmospheric carbon dioxide equivalent levels of 815.76 – 330.46 = 485.30 gm.

To sum up:
Using the UK’s GHG inventory values, a notional power generation efficiency of 30% and the UK’s saved emission factor, 1,000 gm of a notional lignin paper result in a reduction in atmospheric carbon dioxide levels of 84.77 gm after 100 years whereas 1,000 gm of a notional non-lignin paper, under the same conditions, result in an increase in atmospheric carbon dioxide equivalent levels of 485.30 gm.

USA
The United States Environmental Protection Agency has published a series of reports entitled Solid Waste Management and Greenhouse Gases The most recent of edition of this dates from 2010 and is available on the EPA’s web site as a series of online chapters that together describe the EPA’s WARM model. For the purposes of the current discussion, the most relevant chapter is the one entitled Landfilling.

Most of the values adopted by the EPA are based on work done by Barlaz over a number of years in the laboratory, with subsequent verification in the field. So far as paper and related products are concerned, Barlaz has carried out studies on several different categories of product by placing samples in containers under moist, anaerobic conditions and then allowing the reaction to run to completion. The results may be summed up in the following table:

 

Initial C as % dry weight

Final C as % of initial C

CH4 emissions (50% of landfill gas) as % of initial C

Corrugated containers

47

55

22

Magazines/3rd class mail

34

75

12

Newspaper

49

85

8

Phone books

49

85

8

Office paper

40

12

44

Textbooks

40

12

44

Coated paper

34

75

12

A different series of studies were then carried out to determine the rates at which these various fractions decayed under different conditions. In the case of the EPA model the categories are Dry (less than 25 inches [635 mm] precipitation per annum); Average (more than 25 inches [635 mm] per annum; Wet (landfills wetter than normal or operated using leachate recirculation) and Bioreactors (a particular kind of landfill encouraging rapid decay and complete methane collection). Whatever the rate of decay, the end point of the decay is that shown in the above table, so, under wet conditions a particular type of paper will decay faster than under dry conditions but it will decay no further.

The rates at which the above categories decay under the 4 different conditions are as follows
k = the decay rate; Half-life expressed in years.

 

Dry

Average

Wet

Bioreactor

 

k

Half-life

k

Half-life

k

Half-life

k

Half-life

Corrugated containers

0.01

70

0.02

35

0.04

17.5

0.06

11.7

Magazines/3rd class mail

0.02

35

0.03

23.3

0.06

11.7

0.09

7.8

Newspaper

0.02

35

0.03

23.3

0.07

10

0.10

7

Phone books

0.02

35

0.03

23.3

0.07

10

0.10

7

Office paper

0.02

35

0.03

23.3

0.06

11.7

0.09

7.8

Textbooks

0.02

35

0.03

23.3

0.06

11.7

0.09

7.8

Worked examples
In the US model, a certain proportion of the organic carbon decays at a faster or slower rate depending upon conditions and paper type. However, the proportion that decays is fixed for the type of paper, whatever the conditions. Therefore, for the sake of simplicity, let us assume that the entire fraction that will decay has decayed within the 100 year time frame conventionally adopted – this is not actually true but it is near to being true and by making this assumption it will actually exaggerate the release of carbon dioxide equivalents to the atmosphere and underestimate the amount of carbon stored.

Newspapers
Newsprint is, typically, a high lignin paper. It is the category in the US studies that decays least. With a carbon content of 49%, 1 kg of newsprint represents 1,798 gm CO2e. 85% of this carbon does not decay, therefore, at 100 years, 416.5 gm of the initial 490 gm of carbon present in a kilogram of newsprint remain undegraded and these represent 1,529 gm CO2e. 8% of this carbon has decayed into CH4, i.e. 490 x 0.08 x 16/12 = 52.27 gm.

The US EPA is still using a GWP for methane of 21, but for the sake of consistency we will use 25, as elsewhere. These 52.27 gm of CH4 are equivalent to 1,307 gm. If no methane is recovered this means that at 100 years the 1 kg of newsprint has decreased atmospheric carbon dioxide equivalent levels by 1798 – 1307 = 491 gm.

At the other end of the scale:

Office paper
A low lignin, uncoated grade. It is the category in the US studies that decays most. With a carbon content of 40%, 1 kg of newsprint represents 1,468 gm CO2e. 12% of this carbon does not decay, therefore, at 100 years, 48 gm of the initial 400 gm of carbon present in a kilogram of office paper remain undegraded and these represent 176.2 gm CO2e. 44% of this carbon has decayed into CH4, i.e. 400 x 0.44 x 16/12 = 234.67 gm.

These 234.67 gm of CH4 are equivalent to 5,867 gm of CO2. If no methane is recovered this means that at 100 years the 1 kg of newsprint has increased atmospheric carbon dioxide equivalent levels by 234.67 – 5867 = 5,632 gm.

As in the UK, the US recovers methane at landfill sites. Unlike the UK, which adopts a single collection efficiency (71%) for all methane emissions, the US – in the 2010 version being referred to here, considers four different landfill collection scenarios (three of which are modelled in WARM) for the four different moisture levels, making a total of 16 (12 modelled in WARM) different methane collection efficiencies for different types of landfill operating under different conditions. So for each of the six different types of paper modelled, which release differing overall amounts of methane in the course of their decay, up to twelve different levels of methane may be collected, making a total of 72 different combinations of methane generation and collection.

Suffice it to say that the principle is the same as for the UK worked examples. The US recovery values range between 59% and 91%, with most in the 80% band. In the UK report referred to previously, the US is quoted as reporting a recovery efficiency of 49% in 2008. Its not clear why the US is reporting 49% recovery when most of the efficiencies in its model are higher, possibly because the 49% it reports relates to all waste and for some categories the recovery levels are lower than for paper.

For the sake of simplicity, if one took 75% as the mid point for the US recovery spread for methane from decaying paper (but remember 72 different combinations are actually modelled) the position would be as follows:

Newspapers
25% of the methane or 13.07 gm are not recovered, this has a GWP of 326.69 gm, meaning that at 100 years the 1 kg of newsprint has resulted in a 1,529 – 326.69 = 1,202.31 gm reduction in atmospheric carbon dioxide equivalent levels.

Office paper
25% of the methane or 58.67 gm are not recovered, these have a GWP of 1,466.69 gm, meaning that at 100 years the 1 kg of office has resulted in a 176.2 – 1,466.69 = 1,290.49 gm increase in atmospheric carbon dioxide equivalent levels.

The US model then proceeds to consider the CO2 emissions that can be avoided by extracting useful energy from the methane, using the same principle as in the UK worked examples. However, the energy mix differs for different regions of the US and so seven different regional values for CO2 avoided per unit of recovered CH4 are considered, as well as a national average. Potentially, in the US, the six different categories of paper that are modelled can result in 72 different combinations of methane generated and collected and 504 different combinations of methane emissions and avoided carbon dioxide emissions.

The national average for the US power generation mix (but remember it is actually modelled against seven regional values) is 0.21 kg C/kWh or 0.77 kg CO2 /kWh. At this point the US model uses a mix of imperial and metric units and a GWP of 21. For ease of comparison with the figures for the UK, let us assume an energy conversion efficiency of 30% [the US model seems to be assuming 85% but let’s be consistent not greedy] when the methane is burned and a GWP of 25.

Newspapers
75% of the methane or 39.20 gm are recovered and at 55 MJ kg-1 these have a calorific value of 2.156 MJ or 2.156/3.6 = 0.599 kWh.
The emissions avoided are therefore 0.599 x 0.3 x 770 = 138.34 gm of CO2. Therefore at 100 years the 1 kg of newsprint has resulted in a decrease of 1202.31 + 138.34  = 1,340.65 gm in the atmospheric carbon dioxide equivalent levels.

Office paper
75% of the methane or 176.00 gm are recovered and at 55 MJ kg-1 these have a calorific value of 9.68 MJ or 9.68/3.6 = 2.69 kWh.
The emissions avoided are therefore 2.69 x 0.3 x 770 = 621.39 gm of CO2. Therefore at 100 years the 1 kg of office paper has resulted in an increase of 1290.49 - 621.39  = 669.10 gm in the atmospheric carbon dioxide equivalent levels.

To sum up:
Using the US EPA’s values, a notional power generation efficiency of 30% and a methane GWP of 25 [as opposed to the 21 assumed by the EPA], 1,000 gm of newsprint result in a reduction in atmospheric carbon dioxide levels of 1,340.65 gm after 100 years whereas 1,000 gm of office paper, under the same conditions, result in an increase in atmospheric carbon dioxide equivalent levels of 669.10 gm.

Note that the EPA actually models a very large number of scenarios, the above figures are simply presented as examples.

Recycling
When paper is not disposed of to landfill but recycled, there is no accumulation of stored organic carbon and no release of methane, the organic carbon is retained in the fibre used for the next batch of paper. However, paper fibres cannot be recycled ad infinitum. Eventually they have to be disposed off, either to a form of landfill – although the conditions under which fibre rejected during the recycling process may be disposed of by burial may not be exactly the same as modern landfill – or they may be used as a fuel for the paper making process, in this instance no carbon is stored but the incineration of a biogenic fuel source reduces the non biogenic emissions involved in the manufacture of the paper and so is reflected in the lower non-biogenic carbon dioxide emissions associated with the manufacture of a paper.

Essentially, if, when no longer suitable for recycling, the organic carbon in the discarded fibres is sent to landfill then the mass of carbon in that fibre needs to be divided by the number of times it can be recycled and this mass of carbon – less the fraction that will degrade, methane generated etc, all as calculated previously, can be offset against the non-biogenic carbon dioxide emissions involved in the manufacture of each batch of paper.

Incineration
Waste paper can also be incinerated and the energy released used to avoid carbon emissions from fossil fuels – in the same way as methane from decaying paper can be captured and burnt. Again, as for methane, the exact amount of emissions that can be avoided depends on the energy mix of the region or country in question – what fuels does it use to drive its power stations, which ones could be made less use of if there was a secure source of fuel in the form of paper.

The calorific value of paper differs from paper to paper. This is because papers differ the proportion of inorganic to organic [combustible sources of biogenic fuel] and the organic components each differ in their calorific value. Ideally the calorific value of a paper should be measured and stated by the manufacturer. Alternatively an approach to working it out might be made if the manufacturer provides details of the composition of a paper, i.e. what percentage is lignin (which has a higher calorific value than cellulose), percentage cellulose, percentage coating and so on. Knowing the calorific value of the paper being used for a job would allow the avoided downstream emissions to be calculated on the basis of the energy mix of the country – as outlined in the earlier worked examples. It is also necessary to know the efficiency with which the plants incinerating paper operate..

Process emissions
Each of the proposed fates for paper – landfill, incineration, recycling – involves the collection of waste paper and its processing in some way or other. The equipment used for this may have involved carbon dioxide emissions in its manufacture and to power its operation. These need to be taken into account in drawing up a complete carbon footprint for paper. They have not been highlighted here because the focus of this article is on the carbon storage potential of paper but it would need to be considered in any standard aimed at drawing up an accurate footprint.

The forest
If you examine most/all life cycle analyses in detail that allegedly show that recycling paper is more environmentally friendly than making paper from virgin fibre, the reason for this conclusion is to be found in the forest. It is not what happens in the paper mill or the landfill site that matters it is whether the felled area is replanted or how much additional carbon a stand of trees felled to make paper would have accumulated before reaching senescence.

An answer to this requires a knowledge of land use post felling – or at least some scheme that certifies how its adherents will behave once they have cut the trees – and access to forest growth models or at least their results. Much of this may well be deemed too complex for a printer to have to consider in his or her daily work and to be out of scope for this standard – it is, however, absolutely crucial if the true carbon footprint of paper (and therefore print) is to be determined.

Key Factors

Lignin
The scientific literature and the UK and US models (which are based on some of this research) all suggest that under anaerobic conditions papers with a high lignin content decay to a lesser degree and more slowly than ones with a low lignin content. Even the IPCC, although it does not build it into its default values, agrees in its discussions that lignin does not decay.  Lignin appears to have a two-fold effect.  It does not decay (or does so to only a very limited degree) and because it appears to shield the other components from decay. Lignin also has a higher calorific value than cellulose, i.e., you get more joules / kg when you burn it. Incinerating a high lignin paper will enable you to avoid more carbon dioxide emissions than incinerating a low lignin paper. Lignin has a higher carbon content than cellulose. Lignin does not have one formula, rather it is a class of compounds with slightly different formulae for the monomers and the ‘monomers’ are combined to form ‘polymers’ in a more complex way then cellulose.

A ‘typical’ lignin might have the formula C9H10O2. Which means it has a molecular weight of 150 and a carbon content of 108. Carbon therefore represents 108/150 = 0.72 of lignin. Cellulose has the formula (C6H10O5)n. Its molecular weight is therefore 162 and its carbon content 72. Carbon therefore represents 72 / 162 = 0.44 of cellulose.

On the other hand, the lignin can be exploited for its energy value in the manufacture of low lignin papers, allowing lower non-biogenic carbon dioxide emissions from their manufacture than would otherwise be the case.

If, given the complexity of the questions considered here, it is felt to be too difficult to calculate the carbon footprint of paper in a way that easy and certain enough for a printer to use, then, all other things being equal, perhaps printers should be told to go for a high lignin paper. They may not be able to quantify the footprint in accordance with the standard but the chances are it will be lower than if they use a low lignin paper.

High lignin papers tend to be ‘low quality’ papers that do not keep well – they become yellow and brittle. For ephemeral products that have a short life span before being disposed off this doesn't matter, and these are precisely the papers where the decay or calorific qualities matter. Products that are going to be retained over long periods as paper – a book for example – might use papers that keep better; but, since they are not being disposed off but (the author hopes) kept on the shelf, their decay or incineration qualities are not so vital.

The conventional view is that one is being environmentally friendly by choosing a recycled paper. Perhaps the message should be that you are being environmentally friendly if you choose a high-lignin paper.

In short, paper is not paper but a class of products that differ in their energy content and decay. Papers should be clearly assigned to the relevant category at the start of the process chain so that those further down the chain can assign the appropriate emission factor to them.
Ideally key parameters such as calorific value, lignin content and/or carbon content should be specified for every paper to enable those downstream to calculate how the paper will behave for themselves.

Disposal infrastructure
Besides the extent to which the paper decays, the high GWP of methane means that it is important to know how efficiently methane emissions from landfill will be collected. This again is downstream of the print stage, it is downstream of the printer’s customer, it may even be in a different country. So far as the printer is concerned, the emissions generated or avoided depend upon the details of a downstream disposal infrastructure that is beyond its control at an unknown time and in unknown place. However, given the GWP of methane, this stage (see the worked example of office paper in the US) has the potential to far outweigh not only all other emissions associated with the manufacture of paper but with the printing as well.

POSSIBLE SOLUTIONS

Sweep it all under the carpet
Assessing the true carbon footprint of paper involves so many factors that are up- and downstream of the printing process that the obvious approach is simply to include the non-biogenic emissions associated with the production of paper and to ignore the carbon capital account (i.e. carbon accumulating or being depleted in the forest, in landfill, downstream methane emissions and avoided non-biogenic emissions), leaving this to be covered by some other standard.

The advantage of this is ease of use, the disadvantage is that by forgoing the potential for paper to be classed as a carbon store, print and/or paper is giving up items in its carbon account that, under certain circumstances  -- such as, for examples, large amounts of carbon accumulated in discarded newspaper and energy generated from efficiently recovered methane -- would allow it to present a much more favourable carbon footprint in relation to other media. Conversely, under other conditions – office paper discarded to landfill, accumulating little carbon, emitting large amounts of methane from landfills not equipped to recover it – paper has the potential to significantly worsen atmospheric carbon dioxide equivalent levels. By ignoring this aspect the standard could be attacked (and almost certainly would be by those who do not wish print well) for painting a distorted, unrealistically positive picture of the carbon footprint of print.

If not under the carpet, how?
If, however, the accumulation or depletion of organic carbon and the reciprocal changes in carbon dioxide equivalent levels in the atmosphere are to be taken into account by the standard how is this to be done since far and away the most significant stages in terms or fixation and release occur before or after printing takes place, are outside the control of printers and in many cases they have no way of knowing what is happening and lack the expertise to analyse it.

Upstream
In the case of upstream events, it is possible to divide them into process emissions, i.e those associated with the production of the paper, which can be transferred down the supply chain and changes that occur in the carbon stock in the forest after the tree that is the raw material for the paper has been felled.

Essentially, when a tree is felled to make paper the carbon it contains leaves the forest, it moves down the production line, inevitably some of it is wasted and returns to the atmosphere as carbon dioxide, some is turned into paper and if, after use, it is disposed of to landfill after a period – conventionally set at 100 years – some portion of that organic carbon will still be fixed and from that point on will no longer need to be considered for [conventional] carbon footprinting purposes. If the land from which that tree was felled, is not replanted, all the carbon locked in the tree has been released back to the atmosphere apart from that portion locked in the remaining fraction in the landfill. If the land from which the tree was felled is replanted and the new tree allowed to grow to the same age/size as the previous one than all the carbon lost from the forest when the first tree was felled has been replaced and any carbon remaining in the landfill is in addition to the carbon locked in the tree.  In short, if the forest is replanted, one more tree’s worth of organic carbon is fixed than if the tree is not replanted. However, this is a choice made after the paper starts to be made. The downstream stages have to be informed about what is happening in the forest in order to build this into their carbon accounts.

When a tree is felled to make paper it is often/usually felled before it reaches full size. Were it not felled to make paper, more carbon would be laid down in the forest. Recycling, by reducing the amount of felling for the same quantity of paper, allows more carbon to be accumulated in the forest (as opposed to landfill) because it allows more trees to grow to maturity (assuming they are not felled for some other non-paper use).

However, no tree or forest grows infinitely, sooner or later it reaches a steady state where as much carbon is being released through breakdown as is being accumulated through photosynthesis. The amount of additional carbon that can be accumulated in the forest is therefore the difference between the amount at felling and the amount when the steady state is reached. Without increasing the area given over to forest, the switch from virgin fibre to recycled allows a one-off increase of carbon in the forest but once the unfelled areas have reached their steady state there is no further accumulation.

Here is probably not the place to discuss the details of how this one-off increase in the carbon stock might be credited to paper being produced downstream from recycled fibre. Suffice it to say, most of the models we have seen ‘work’ because they are only run forward for relatively short periods of time, ending before accumulation tails off. This is politically expedient, provides a quick fix but could be very misleading for the longer term future. However, on the assumption that the forest industry has or develops a sufficiently robust monitoring system for ensuring that the carbon accumulation/depletion consequences of replanting and/or reduced felling are reflected in the carbon footprint figures for paper delivered to printers; then, in principle, these upstream uncertainties that are beyond a printer’s ken can be resolved.

Downstream
As the various worked examples from the UK and US show, there are very wide differences in net carbon dioxide equivalent emissions between different kinds of paper and between different ways of handling those emissions. The printer knows what kind of paper a job has been printed on but the way paper is disposed of post-use is usually beyond both the knowledge and control of the printer. How it is disposed of is essentially controlled by the regional or national government at the point of disposal: does that government’s waste disposal policy favour recycling, landfill or incineration and does it – perhaps in conjunction with various sectors of industry - provide the associated infrastructure?

This may be beyond the control of a printer but it is not necessarily beyond the knowledge. Leaving aside the fact that some printed products are exported and that a printer does not necessarily know in which country his or her products will be disposed of, provided the waste disposal authorities of the country in which a printer is based carry out an analysis of how its paper waste is disposed of, a printer or some kind of expert body working on his or her behalf can work out figures for downstream emissions based on paper disposal statistics.

Essentially, printer X in country Y does not know how or when any item of printed matter will be disposed of but the bean counters of the Ministry of Waste may be able to tell him or her that a% is recycled, b% is landfilled and c% incinerated. The regional or national authorities can also provide figures for methane recovery, power generation emissions avoided etc. when energy is extracted from methane or incinerated paper and so on. The printer or some expert can then combine this statistical breakdown with the known (as currently understood) properties of the various types of paper and provide the printer with emission factors that can be used to calculate the carbon footprint of his or her product. The devil, however, is in the detail.

Global or specific
As is clear from the previous examples, there are wide differences between the emissions associated with different papers, different countries use values to calculate emissions that differ from each other, that differ in the categories that they apply to and that differ from the IPCC default values. By applying national models, the same paper will generate different emissions depending upon whether it is disposed of under the same conditions in the UK or the US. This is a purely ‘mathematical’ difference that results from the different models used to calculate emissions. The ‘real’ emissions should be the same. The UK and the US also differ in the methane recovery efficiencies that they build in to their models. To some extent, these differences may be real, there may be real differences in the methane recovery infrastructure and processes between the countries but, as is clear if you read the details of how the two countries calculate methane recovery, some of the differences are due to different approximations being adopted. Moving on, the emissions associated with power generation that may be avoided are different in the two countries and, in the case of the US, they are different between regions of the country (the US quotes different avoided emission values for seven regions).

The UK is a relatively small country and its model assumes conditions are sufficiently uniform for the same decay rate across the country. However, even in the UK parts of the country (and the most populous ones at that, with, presumably, the highest volumes of paper disposal) are, contrary to popular perception, close to being dry temperate under the IPCC definition rather than wet temperate. Berlin, for its part, is dry temperate. So, using the IPCC default model, parts of Western Europe would be classed as wet and parts as dry temperate and, using the IPCC model let alone national ones, paper would decay at different rates in different parts of Europe. The US model has three different climate categories for use in one country (as well as the 7 different power generation regions). The conditions across other ‘large’ countries are also likely to be so different that more than one decay condition prevails. Under the IPCC system Rio de Janeiro would be tropical, São Paulo temperate. How would Harbin and Canton be classed?

In short, not only do the conditions that govern decay vary between regions of the world and countries, they vary within countries, there are differences between countries in how waste is dealt with, in the efficiency of methane recovery and in the emissions that can be avoided, when combined with the differences between different types of papers (which almost certainly exist but which are only taken into account by certain models), there is a very wide range of possible emission scenarios for a print job depending upon the paper it is printed on and where it is disposed of. How can this variety be shoe-horned into a system that is simple and straightforward enough for practical use?

At one extreme, could one develop one single, universal emission factor based on weighted averages that could be applied to any printed product in any country? The calculation of such a factor would involve a considerable amount of work in gathering the data needed to calculate the figure but in principle it could be done and once done printers would have just one figure to apply and all printers, the world over, would use the same one.

This would be simple for the printer and allow comparisons to be made. The problem is that it would also be very inaccurate and misleading. Although, if calculated correctly, the average might be valid, any single job might potentially differ from this average by a significant amount. The stated footprint for a job would be very different from its real one. By using a broad average, real differences are masked.

If, for example, country A has invested heavily and developed a state of the art system for recovering methane and exploiting it for power generation and country B has not, why should country A (and its printers) not reap the benefit of its investment by being able to quote lower footprints and, conversely, why should country B be able to hitch a free ride on the coat tails of country A. If paper type A decays to a lesser extent in landfill than paper type B, shouldn’t this be made clear in the emission factor so that printers and customers can choose a paper with a lower emission factor, if this is important to them? The more specific the emission factors to narrowly defined paper types and disposal conditions the more accurate the results – although the resulting emission factor is still an average, it is an average with a narrower spread – but the greater the number of variables the printer or other interested party will need to take into account in calculating the footprint and the more difficult and time consuming the task will be.

Is there a happy medium that offers both accuracy and ease of use?

FOPAP suggest the following:

Categorize paper by decay properties. This could be, as in the US, using broad categories printers are familiar with. It could be based on lignin/cellulose content, as in the UK, with the paper supplier providing this information. In either case, paper would be assigned to one of these categories at the top end of the stream and the category to which it had been assigned passed on with the paper from one stage to the next.

For each individual country or regions of a country, where there are significant differences within a country, or groups of neighbouring countries when they are similar, the waste disposal statistics, where available, are analysed to determine what percentage of paper is recycled, sent to landfill or incinerated. Ideally, if the statistics are available, this should be done separately for each of the decay categories of paper, since it is possible that the disposal patterns may be different for different types of paper and the papers differ in the extent and rate to which they decay or the energy they yield when burned. 

Generally speaking the printer has no control over the downstream fate of what he or she prints but the end user has some control, within the framework of the disposal options offered by the country where he or she resides. The publisher of the newspaper does not know and cannot control how we dispose of it but we can decide whether to throw it in the waste bin, the recycling bin or to use it as a fire lighter.

If one of the uses to which the standard might be put is to encourage users to dispose of paper products in a ‘responsible’ way then at this point different carbon footprints might be calculated for each of the three main options (recycling, landfill, incineration) for the paper category in question, the prevailing climate conditions, the country’s waste disposal and power generation infrastructure, as illustrated by the worked examples. The factors in question would be worked out by some appropriate national or international body and all the printer would have to do would be to apply them – possibly with the aid of some simple program or automated spreadsheet that could be made available.

The end user would then be informed in some appropriate way that the carbon emissions are 'a' if the product is recycled in country 'x', 'b' if disposed of to landfill in country 'x', 'c' if incinerated in country 'x' and if disposed of in another country the emissions would depend upon the conditions prevailing in that country.

On the other hand, it might be felt that it was no part of the standard to encourage end users to dispose of products one way or the other, simply to inform them of the footprint. In that case it might be decided that there was no need to calculate carbon footprints for different disposal scenarios.  From an analysis of the waste figures for a country it may be possible to determine the proportion of paper disposed of by recycling, landfill and incineration. Knowing the emissions associated with each of the disposal pathways – as illustrated in the earlier worked examples, and knowing the percentage being disposed off by each channel it is possible to calculate a weighted average emission factor. This may not be true for any individual piece of printed matter but it is true for print or the category as a whole and since the printer has no control over the disposal route there is nothing to be gained by going beyond the average.

Ideally, such a breakdown should be available for each of the categories paper is divided into, since these differ in their decay properties. If, for example, the disposal mix for paper products overall is 45-35-20 but the mix for newsprint is 30-60-10 then it is this latter mix – if available – that should be used for calculating the weighted emission factor for newsprint, since applying the overall mix to a fraction whose decay properties differ from the average would give a distorted result.  It is of course possible that not all the required waste disposal data will be available in all countries. If that is the case, one would need to work with what data are available or proxy values from ‘similar’ countries until such time as the missing data became available. 

Once these downstream emission factors for disposal have been calculated, printers upstream can use them in the calculation of the carbon footprints of their products.

In FOPAP's view, the more specific these factors, the better, since they provide the most accurate possible picture for any given product and by highlighting differences between materials or processes that would be obscured by broad averages they can serve as a tool for improving performance. In order to make them as easy as possible for individual printers to use, national printing federations or equivalent bodies could calculate emission factors for the various disposal channels in their own countries using the values adopted by the country in question for its greenhouse gas inventories. In that way, printers in any one country are basing their footprints on the same values as their national authorities use for their greenhouse gas inventories.

    Recommendations
  1. Forest growth models and management schemes should be examined to determine to what extent it is possible to construct a robust and accurate mechanism for quantifying the impact on forest carbon levels of felling trees to make paper.
  2. If, and in so far as, these allow a figure to be calculated for the carbon accumulated or depleted as a consequence of a specific management regime, if, and in so far as, it is possible to determine what portion of this management regime relates to paper and if, and in so far as, it is possible to express this figure as an amount per unit quantity of paper produced, then such a figure should be calculated and passed down the process chain together with the figure for the non-biogenic emissions from the manufacture of the paper in question.
  3. Since papers differ in their decay and calorific properties, papers should be classed by their decay properties, besides other attributes, and the category that any specific paper belongs to should be clearly stated as it moves down the process chain. These classes might be based on usage categories (i.e. newsprint, office paper etc. as in the US) or chemical composition (lignin/cellulose content, as in the UK). In the latter case, in particular, the information would need to be provided by the original manufacturer. The manufacturer of the paper should also calculate the calorific value of the paper and its carbon content and this information should also be passed down the process chain.
  4. An analysis, ideally on a country by country basis or, in the case of large countries, region by region, of the waste disposal mix should be carried out to determine the proportion of waste paper recycled, sent to landfill or incineration.  Ideally, if the statistics are available, this waste analysis should be carried out separately for each decay category. In some cases these figures may not be available or the paper categories recorded by the waste authorities may not be the same as the paper decay categories. Where the data is inadequate the aim should be to come as close to the ideal as possible and to revise the analysis as and when it becomes possible to make improvements.
  5. The scientific literature and a range of national GHG inventory models should be examined to identify the decay values and methods of calculation that yield results most closely in line with the best current understanding of the processes – bearing in mind that there are still many unknowns in this area and the adopted values may need to be revised in the light of new knowledge. The values adopted should reflect local conditions and local infrastructure and, if a particular country or region has a sophisticated model for these calculations, the default position should be that unless there are strong grounds for not doing so, printers should use the value and model of their home country, since this is most likely to best reflect local conditions and printers will be reporting GHG inventories on the same basis as their national authorities.
  6. In the case of recycled paper, assuming it has been possible to quantify its impact on forest carbon, as outlined above, and assuming reject fibre is disposed of in ways that are comparable with the incineration or landfilling of paper made from virgin fibre, then a batch of recycled paper should be credited or debited with the same value as an equivalent virgin fibre divided by the average number of times that that paper can be recycled.
  7. On the basis of the above, emission factors can be calculated for different papers, disposed of in different ways, in different countries. How these might be worked out is shown in greater detail in the main part of this document. Printers should be provided with the data to work these out for themselves if they so wish; but, in many cases, national trade bodies, consultants, etc. might do this on behalf of individual printers, providing them with the up- and downstream emission factors they need to combine with their process emissions to calculate an overall footprint.



 
 
(C) 2011 fopap.org