Content uploaded by Joost Vogtlander
Author content
All content in this area was uploaded by Joost Vogtlander on Nov 06, 2014
Content may be subject to copyright.
CARBON FOOTPRINTING
Carbon sequestration in LCA, a proposal for a new
approach based on the global carbon cycle;
cases on wood and on bamboo
Joost G. Vogtländer &Natascha M. van der Velden &
Pablo van der Lugt
Received: 28 October 2012 /Accepted: 10 July 2013 / Published online: 6 August 2013
#Springer-Verlag Berlin Heidelberg 2013
Abstract
Purpose There are many recent proposals in life cycle as-
sessment (LCA) to calculate temporary storage of carbon in
bio-based products. However, there is still no consensus on
how to deal with the issue. The main questions are: how do
these proposals relate to each other, to what extent are they in
line with the classical LCA method (as defined in ISO
14044) and the global mass balances as proposed by the
IPCC, and is there really a need to introduce a discounting
system for delayed CO
2
emissions?
Methods This paper starts with an analysis of the widely
applied specification of PAS 2050 and the ILCD Handbook,
both specifying the credit for carbon sequestration as ‘optional’
in LCA. From this analysis, it is concluded that these optional
calculations give rather different results compared to the base-
line LCA method. Since these optional calculations are not
fully in line with the global carbon mass balances, a new
calculation method is proposed. To validate the new method,
two cases (one on wood and one bamboo products) are given.
These cases show the practical application and the conse-
quences of the new approach. Finally, the main issue is evalu-
ated and discussed: is it a realistic approach to allocate less
damage to the same emission, when it is released later in time?
Results and discussion This paper proposes a new approach
based on the global carbon cycle and land-use change, trans-
lated to the level of individual products in LCA. It is argued
that only a global growth of forest area and a global growth
of application of wood in the building industry contribute to
extra carbon sequestration, which might be allocated as a
credit to the total market of wood products in LCA. This
approach is different from approaches where temporary stor-
age of carbon in trees is directly allocated to a product itself.
Conclusions In the proposed approach, there seems to be no
need for a discounting system of delayed CO
2
emissions.
The advantage of wood and wood-based products can be
described in terms of land-use change on a global scale in
combination with a credit for heat recovery at the end-of-life
(if applicable).
Keywords Bamboo .Carbon sequestration .Carbon
storage .LCA .Wood
1 Introduction
In the period 2006–2009, after a long debate on how to
calculate biogenic CO
2
in life cycle assessment (LCA), it
was decided by the majority of scientists and practitioners
that the best approach in LCA is not to calculate biogenic
CO
2
. The basic idea was, and still is, that biogenic CO
2
, once
captured and stored by trees and other plants, will re-enter
the atmosphere sooner or later after the use phase of the
product. Hence, in computer programs like Simapro which
use the Ecoinvent database (Hischier et al. 2010), biogenic
CO
2
was removed from the lists of emissions of the
Intergovernmental Panel on Climate Change (IPCC) Global
Warming Potential (GWP) midpoint indicators, and conse-
quently from other leading indicator systems like CML-2
and ReCiPe (CO
2
emissions due to land transformation,
however, are still counted in these systems). The new ISO
14067 on carbon footprint calculations based on the same
logic (Section 6.3.9.2 of the standard, Note 1).
In the last few years, however, there is a feeling in the
wood industry and in the industry of other bio-based prod-
ucts, that a credit should be given to bio-based renewable
products, which is related to the temporary storage of carbon
Responsible editor: Matthias Finkbeiner
J. G. Vogtländer (*):N. M. van der Velden :P. van der Lugt
Department of Design for Sustainability, Technical University
Delft, Landbergstraat 15, 2628 CE Delft, The Netherlands
e-mail: joost@vogtlander.nl
Int J Life Cycle Assess (2014) 19:13–23
DOI 10.1007/s11367-013-0629-6
in these products (Brandao and Levasseur 2011; Brandao
et al. 2013).
Two important parties reacted on the political will to
incorporate carbon sequestration in LCA as an option: the
team of the International Reference Life Cycle Data System
(ILCD) Handbook (EC-JRC 2010) and the team of the
Publicly Available Specification (PAS) 2050:2011 (BSI
2011). In both systems, it is possible to give a credit to
temporary CO
2
storage by discounting delayed emissions.
Both systems define the credit as optional
1
by the following
statements:
&PAS 2050, Section 5.5.1: ‘Note 5.The use of a weighting
factor to assess delayed emissions is no longer a require-
ment of this PAS.However,for entities wishing to under-
take such assessment,provision is made in 6.4.9.3.2 and
Annex E’.
&ILCD Handbook, Section 7.4.3.7.3: ‘..i.e., per default,
temporary carbon storage and the equivalent delayed
emissions and delayed reuse/recycling/recovery within
the first 100 years from the time of the study shall not
be considered quantitatively’.
Both systems restrict the calculations on CO
2
sequestra-
tion to the 100-year period after the manufacturing of the
product (i.e., the 100-year assessment period). In the ILCD
Handbook, the 100-year limit is argued to be in line with the
decision of LCA scientists and practitioners to keep short-
and long-term emissions (from leaching) separate in the
LCA calculations (Hischier et al. 2010). The discussion on
short- and long-term emissions has many issues (Hischier
et al. 2010), but the main argument is summarised in (EC-
JRC 2010), regarding the delayed emissions from landfills:
‘…will the inventory of landfills—if the emissions are
modelled for e.g., 100,000 years—easily dominate the entire
LCA results.This is important to know,but needs a separate
interpretation.At the same time, does this issue illustrate one
weakness of LCA:LCIA methods usually do not account for
thresholds,but aggregate all emissions over time.Hence,
even if the concentrations in the waste deposit leachate after
1,000 years might be below any eco-toxic effect,the total
amount of these emissions over tenths of thousands of years
will be summed up and be considered the same way as the
same amount emitted at much higher concentrations over a
few years’.However, this argument for leaching does not
hold for CO
2
;CO
2
has no toxicity threshold, and the 100-
year assessment maximum for carbon sequestration is not
only applied to ‘slow’low level emissions but as well as to
pulse (peak) emissions.
Another argument to use the 100-year cut-off period is the
fact that the GWP midpoint weighting system of IPCC
applies a time horizon as well. The 100-year time horizon
is the most used in practice, since it was chosen as a basis for
the Kyoto protocol. It should be realised that this was a
political decision to balance the short term effect of CH
4
and the long-term effect of chlorofluorocarbons. The 100-
year time horizon is a rather arbitrary choice (Kendall 2012).
However, there is no scientific reason to confuse the two
sequential steps of the baseline LCA calculation, being the
life cycle inventory (LCI), and the system to arrive at a single
indicator in life cycle impact assessment (LCIA). The clas-
sical LCI is a relative straightforward calculation of mass and
energy flows: the timing of emissions is not considered, and
flows in the LCI are not discounted. Single indicator systems
in LCIA, however, are complex and per definition, subjec-
tive, and have many time-related issues, sometimes with a
long-time horizon, sometimes with a short one.
This paper will deal with the following issues:
&How do the optional calculations of PAS 2050 and the
ILCD handbook relate to each other, and how do they
relate to the global carbon mass balance as proposed by
IPCC? (Section 2)
&To what extent is carbon sequestration dealt with in the
baseline LCA method (as defined in ISO 14044)?
(Section 3)
&What is the relevance of the global carbon mass balances
from the IPCC for LCA? What is the new in the proposed
system of this paper? (Section 4)
The consequences of the proposed calculation method are
shown in a case on wood products (Section 5) and a case on
bamboo products (Section 6). The conclusions and discus-
sion can be found in Section 7and 8. In these two last
sections, the issue of the need for a discounting system for
delayed CO
2
emissions is dealt with.
2 The credit for carbon sequestration in relation
with the ‘delayed CO
2
pulse’
This section gives a summary of the background of the IPCC
calculations on global warming (‘radiative forcing’caused
by CO
2
), which is a rather complex issue, however, neces-
sary to understand the idea of the delayed CO
2
pulse. This
delayed CO
2
pulse is the basis for the ‘optional’calculation
on carbon sequestration as given in PAS 2050 and the ILCD
handbook. Readers who want more information on the issue
of radiative forcing are referred to the literature references
given in the text.
The 100-year cut-off (‘time horizon’), as mentioned in the
previous section, has a fundamental impact on the calcula-
tion of the credit for carbon sequestration. This is depicted in
1
The new ISO 14067 specifies that the calculation has to be done
‘without the effect of timing’; however, the effect of timing may be
included in a separate report (section 6.3.8)
14 Int J Life Cycle Assess (2014) 19:13–23
Fig. 1. In this figure the so called Lashof calculation
(Fearnside et al. 2000; Clift and Brandão 2008) is given for
the decay of a CO
2
pulse in the atmosphere, where the IPCC
2007 formula on the decay of CO
2
has been applied
(Solomon et al. 2007) as follows:
Decay ¼0:217 þ0:259 EXP −T.172:9
þ0:338
EXP−T.18:51
þ0:186
EXP −T.1:186
where T= time in years after the pulse
Figure 1shows the effect of applying a time horizon in the
calculation. When the CO
2
emission pulse is delayed with
the carbon storage time (in the example 50 years), the shaded
area will shift out of the time horizon of 100 years; this is the
calculation credit which results from the time shift of the
emission. The reality, however, is that the CO
2
is still there,
so ‘omission’would be a better word than ‘credit’.
The credit of a delayed-pulse emission as a function of
time is given in Fig. 2. It is the result of the Lashof calcula-
tion in combination with the 100-year time horizon. The
ILCD handbook and PAS 2050:2011 propose a linear ap-
proximation (where PAS follows the Lashof calculation for
the first 25 years).
The result for both systems (for delay periods more than
25 years) is the same as a linear discounting system would
have with a 1 % per year discount rate.
There is, however, no consensus at all on the credit system
of Fig. 2, so there is need for further development (Brandao
and Levasseur 2011; Brandao et al. 2013).
The Dynamic Life Cycle Assessment approach (Levasseur
et al. 2010; Levasseur et al. 2013) seems to be one of the
scientific answers on the aforementioned arbitrary credit prob-
lem: it has no specific time horizon. This system is based on an
integrated radiative forcing calculation of a series of emissions
over time. The disadvantage of this calculation system is,
however, that the result of the calculation depends heavily
on the sequence of pulse emissions in the given scenario. An
example on the LCA of a wooden chair shows that there is a
remarkable difference (300 %) between two scenarios:
(1) The tree for the wood is planted 70 years before the
chair is made
(2) A new tree is planted at the moment (after) a tree is cut
for the wood of the chair
The difference of the two scenarios is the period of carbon
sequestration by the tree: in year minus 70 until year 0, or in
year 1 until year 71.
The interesting aspect of the sequence issue of the
Dynamic Life Cycle Assessment approach is that the dilem-
ma of the sequence vanishes when the calculation is made for
a manufacturer of wooden chairs: when the manufacturer
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 20 40 60 80 100 120 140 160
decay of CO2 pulse in the atmosphere
years after pulse emission
pulse at year 0
pulse at year 50
50 years delay
Time horizon 100 years
“credit”
Fig. 1 Residence time of CO
2
in
the atmosphere and the resulting
credit of a delayed pulse as a
consequence of the 100-year
criterion, according to the Lashof
calculation
0
10
20
30
40
50
60
70
80
90
100
0 20 40 60 80 100
credit for pulse delay (percentage)
years of pulse delay (temporary carbon sequestration)
Lashof calculation
ILCD
PAS
ILCD + PAS
Fig. 2 The credit for a delayed CO
2
pulse in PAS 2050, the ILCD
manual, and according to the Lashof calculation of Fig. 1
Int J Life Cycle Assess (2014) 19:13–23 15
makes several chairs per year over several decades, the
problem can be modelled as a steady-state mass flow calcu-
lation. The forest is than regarded as steady state as well:
continuously, a small part of the trees is cut and replanted, the
major part consists of growing trees, and a small part is ready
to be cut. The same steady state applies then to the end-of-
life: the combustion of chairs (with or without heat recovery)
or the landfill of chairs is regarded as a continuous flow. With
this reasoning, we are back to the original way of calculation
in LCI. The remaining issue then is how to cope with the
aspect of land-use change (afforestation, reforestration, bet-
ter forest management and deforestation) when the steady-
state flow increases or decreases. This will be dealt with in
Sections 5and 6.
A remarkable issue in the approach of the ILCD
Handbook and PAS 2050:2011 is that the credit of delaying
emissions is to be applied to bio-based products as well as
fossil-based products like polymers (‘the atmosphere does
not differentiate between the two types of CO
2
’). Since many
polymers have a higher ratio of ‘kg carbon’/‘kg product’,
many polymers seem to benefit more from the credit for
delayed emissions. Neither the industry nor the politicians
seem to be aware of this issue (Brandao and Levasseur 2011;
Brandao et al. 2013).
The advantage of carbon sequestration in wood and other
bio-based products (over oil based polymers) in the baseline
LCA, however, is not related to the delayed emissions, but is
related to the end-of-life scenario, as explained in Section 3.
3 The relevance of carbon sequestration at product level
in LCI
Although the biogenic CO
2
is not counted in LCIA, it is
required to keep track of the biogenic CO
2
in LCI (EC-JRC
2010), see Fig. 3.
Biogenic CO
2
is first taken out of the air in the forest
(plantation), and then released back to the atmosphere at the
end-of-life. So, biogenic CO
2
is recycled, sooner or later in
time. When a wood product or a bamboo product, however,
is burnt with energy recovery at end-of life (e.g., in an
electrical power plant), the total system of Fig. 3generates
an output flow (e.g., electricity). This heat or electricity
replaces energy production from other sources, including
fossil fuels. In other words: the use of fossil fuels and the
related emissions is avoided, which results in a reduction of
the potential global warming effect. In LCI calculations, this
can be modelled as a system credit: the production of heat or
electricity from wood waste has a negative carbon footprint.
This is the so called substitution approach in consequential
modelling, see Section 14.5 of the ILCD Handbook (EC-
JRC 2010).
The conclusion of this section is that there is no system
credit for the biogenic CO
2
cycle, unless the wood (or any
other bio-product) is burnt for electricity and/or heat, and
unless the trees are replanted. A better efficiency of the
production of electricity results in a higher credit.
4 A general description of carbon sequestration at global
level
The effects of carbon sequestration can be understood when
studying it at a global system level (Vogtländer 2010). On a
global scale, CO
2
is stored in forests (and other vegetation),
in the ocean, and in products (e.g., buildings and furniture).
The details of carbon mass balances are very complex;
however, an understanding of the basics of the proposed
LCA method in this paper requires a system approach which
starts from the highest possible aggregation level (the so
called “Tier 1”and “Tier 2”approach of the IPCC). In this
approach, we look at vast forest areas (e.g., Scandinavia, the
Baltic countries, European Russia, Siberia, Canada, New
Zealand). At this aggregation level, there is a continuous
rotation of the forests. The local time-dependent carbon
sequestration effects caused by harvesting are levelled out
within the region since only a small proportion of the trees
are harvested each year. Figure 4is a simplified schematic
overview of the highest aggregation level of the global
carbon cycle.
The issue is that the anthropogenic CO
2
emissions on a
global scale can be characterised by three main flows:
&Carbon emissions per year caused by burning of fossil
fuels: 6.4 Gt/year (Solomon et al. 2007)
&Carbon emissions per year caused by deforestation in
tropical and sub-tropical areas (Africa, Central
America, South America, South and Southeast Asia):
1.93 Gt/year (FAO 2010)
Fig. 3 The life cycle of
biogenic CO
2
16 Int J Life Cycle Assess (2014) 19:13–23
&Carbon sequestration per year by re-growth of forests on
the Northern Hemisphere (Europe, North America,
China): 0.85 Gt/year (FAO 2010)
It can be concluded that the global carbon cycle can
significantly be improved in the short term by the following
changes (1) burn less fossil fuels, (2) stop deforestation, (3)
intensify the use of forest on the Northern Hemisphere by
better management and wood production in plantations, (4)
afforestation (plant trees on soils that have not supported
forests in the recent past), (5) increase application of wood
in durable (construction) products, such as buildings.
However, it is far too simple to claim that application of
wood in design and construction will lead to carbon seques-
tration and therefore it will counteract global warming. It
depends on the origin of wood and the growth of the wood
markets. One should realise that, if there is no change in the
area of forests and no change in the volume of wood in
buildings there is no change in sequestered carbon on a
global level and hence no effect on carbon emissions. This
means that only when more carbon is being stored in forests
(either by area expansion with an increase of net carbon
storage on that land, or by increased productivity in existing
forests by improved management), and when the total vol-
ume of wood in buildings is increasing, there will be extra
carbon sequestration.
In boreal and temperate regions such as in Europe and
North America, the forest area is increasing steadily for
several decades due to afforestation and reforestation (see
Fig. 5), which results to increased carbon storage over the
last decennia (see Fig. 6).
Figure 6shows that carbon storage in tropical areas is
decreasing. The demand for tropical hardwood is higher than
the supply from plantations (only 35–40% of Forest
Stewardship Council (FSC)-wood is from plantations).
This leads to deforestation, resulting in carbon emissions
caused by less carbon sequestration. This mechanism is
depicted in Fig. 7.
The conclusion in regard to the production side of wood
is:
&Extra demand of boreal and temperate softwood from
Europe and North America leads to a better forest man-
agement and an increase in forest area therefore more
sequestered carbon (Fig. 5)
&(Extra) demand of tropical hardwood leads to a decrease
in forest area, therefore less sequestered carbon (Fig. 7)
Extra demand of bamboo in China has an effect on carbon
sequestration which is similar to that of European and North
American wood: it leads to a better forest management and
an increase in bamboo forest area (Lou Y et al. 2010).
The carbon sequestration in wood in houses and offices is
slowly rising on a global scale (because of increasing popu-
lation), which is as such positive in terms of extra carbon
sequestration. This volume of carbon sequestration, howev-
er, is low in comparison with the volume of standing trees in
the forests: less than 30 % of the carbon above the ground (=
less than 24 % of the carbon above plus under the ground)
ends up in housing, which is explained in Section 5, steps 1
and 4.
The conclusion is that carbon sequestration is enhanced
when more boreal or temperate softwood from Europe and
North America and/or bamboo is applied in housing, since
more carbon is sequestered in the forests as well as in the
houses. On the contrary, the application of tropical hardwood
is damaging carbon sequestration, since the decrease of
carbon in the tropical forests is more than the increase of
carbon in the wood products.
Another key issue of the global mass balance is that
carbon sequestration is not increasing per house which is
built,but per extra house that is built above the number of
houses that are required to replace discarded,old,houses.
This is an important consequence of the global mass balance,
Fig. 4 Global anthropogenic
fluxes of CO
2
(Gt/year) over the
period 2000–2010
Fig. 5 Higher demand of boreal and temperate softwood from Europe
and North America leads to more carbon sequestration because of
afforestration (extra forests) and reforestration (converting naturally
regenerated forests to plantations and better forest management)
Int J Life Cycle Assess (2014) 19:13–23 17
which is often overlooked by LCA practitioners when they
study carbon sequestration at product level in the LCI phase
of the assessment.
In LCA, the aforementioned global aspect of carbon se-
questration in forests is defined in terms of land-use change.
The remaining question then is: how to allocate the positive
or negative effect of carbon sequestration in forests on global
scale to the wood or bamboo at product level?
In this paper, we propose an allocation of the extra global
carbon sequestration in forests to the total global production
of wood products. Such an allocation method is applied since
it is not realistic to assign the extra trees to specific wooden
products. This allocation method is different from the way
the optional calculations are specified in PAS 2050 and the
ILCD manual.
The way the proposed allocation method of this paper is
done in practice is explained in Step 3 of the examples in
Sections 5and 6.
5 Example 1: calculation of carbon sequestration caused
by land-use change for European softwood
The aim of the calculation in this section is to illustrate how
the proposed method is done in practice, and to validate the
method as such (by checking the impact on the output of
each calculation step).
The scope of the calculation is the carbon sequestration in
boreal softwood from cradle-to-grave, excluding emissions
from forest management equipment, product manufacturing,
transport, and end-of-life operations (a so called “stream-
lined”LCA approach). The geographical system boundary
is Europe, as defined in (FAO 2010)
The calculation of carbon sequestration caused by land-
use change for wood is done in five steps:
(1) The calculation of the relationship (ratio) of carbon
stored in forests and carbon stored in end-products
(planed timber); this first step is in compliance with
baseline LCA
(2) The calculation of a land-use change correction factor
(to cope with the fact that there was another type of
biomass before the area was changed to forests); this
step is in compliance with the IPCC standards
(3) The calculation of the extra stored carbon in forests (see
Fig. 5), because of growth of wood production, and its
allocation to the end-products (i.e., planed timber); this
step, and the way of allocation, is proposed in this paper
by the authors
(4) The calculation of the extra stored carbon in houses and
offices, because of growth of the volume; this step is in
compliance with PAS 2050 and the ILCD handbook
optional credit
(5) The final calculation of the total result of carbon se-
questration: the multiplication of the results of steps 1,
2, 3, plus the result of step 4.
Step 1 Calculation of the carbon ratio
It is important to realise that 1 kg of a wooden
end-product relates to many kilograms of wood in
the forests, which has been calculated according to
the baseline LCA procedure, applying Ecoinvent
data:
–1-kg biomass, dry matter (d.m.) in standing trees, is
equivalent to 0.65 kg of logs (Werner et al. 2007)
–0.65-kg d.m. of logs, is equivalent to
0.65×0.585=0.38 kg of sawn timber (Werner et al.
2007)
–0.38-kg d.m. sawn timber is equivalent to
0.38×0.87=0.33 kg of planed timber (Werner
et al. 2007)
–1-kg d.m. biomass in standing trees is equivalent to
1.25-kg d.m total biomass, since the root/shoot ratio
is 0.25 (Aalde 2006)
–1-kg d.m. of planed timber originates from
1.25/0.33=3.79-kg d.m. biomass in the forests
–The carbon content is 0.5-kg C per 1-kg wood
(Aalde et al. 2006; Verchot et al. 2006)
0
20
40
60
80
100
120
Africa Asia Europe North
and
Central
America
Oceania South
America
carbon stored in forests
(million tonnes)
1990
2000
2010
Fig. 6 Trends in carbon storage in forests from 1990–2010 (Source:
FAO 2010)
Time
Forest area
Plantations
(currently approx 35% - 40% of FSC wood)
loss of biodiversity
deforestation
natural
forests
Fig. 7 Higher demand of tropical hardwood leads to deforestation and
less carbon sequestration
18 Int J Life Cycle Assess (2014) 19:13–23
–Therefore, 1-kg d.m. planed timber, is equivalent to
the storage of 3.79×0.5=1.9-kg carbon in the forest
The result of step 1 is that 1-kg d.m. planed
timber is related to 1.9×3.67=6.97 kg CO
2
storage
in the forest.
Step 2 Calculation of the land-use change correction factor
The next step in the calculation is related with the
land-use change: before the afforestation, the land
had also stored biomass. So the ‘Tier 2 Gain–Loss
Method’(Verchot et al. 2006) of the IPCC has to be
applied (it must be mentioned that this method is not
described in the ILCD Handbook, Annex B (EC-
JRC 2010); however, it is fully in line with the
requirement of section 7.4.4.1 page 234). The es-
sence of this gain–loss method is a comparison of
the steady state before and after the of land-use
change. For European boreal softwood, we assume
that there was grass before the afforestation since
the boreal areas are hardly used for agriculture (ag-
riculture is concentrated in warmer areas).
The ‘total above-ground and below-ground non-
woody biomass’for grass is 7.5-t d.m./ha (it ranges
from 6.5 to 8.5), with a carbon content of 47 %
(Verchot et al.2006).
The biomass of softwood forests, is assumed at
120-t d.m./ha (Aalde et al. 2006) for the above-
ground biomass, with a root/shoot ratio of 0.25
and a carbon content of 50 %.
The land-use change correction factor for affor-
estation is therefore:
120 1:25 0:50ðÞ–7:50:47ðÞ
fg
.120 1:25 0:50ðÞ¼0:953
For reforestation, the situation is different when
the land-use change is from ‘naturally generated’
forests to plantations. Data on biomass in the
Global Forest Resources Assessment 2010 of the
Food and Agriculture Organisation of the United
Nations (FAO 2010) and Aalde et al. (2006) suggest
that the biomass in plantations might be about twice
the biomass in naturally generated forests. The land-
use change correction factor is 0.5 for such cases,
based on the total wood production, and 1.0 based
on the extra wood production.
Step 3 Calculation of extra stored carbon in forests and its
allocation
In Section 4, it was explained that only the extra
biomass in forests makes a differences in terms of
less CO
2
in the atmosphere. The total biomass in the
European forests was 88,516 million tonnes in 2005
and 90,602 million tonnes in 2010 (FAO 2010). So
there was a growth in biomass of 2,086 tonnes, or
2.36 % in 5 years. This is about 0.47 % per year.
For the calculation in step 5, the authors propose
to base the yearly growth of the total biomass in
forests on the expected average growth of European
timber production of 2.3 % (UNECE 2005). There
are two arguments to take the market growth of
European timber production: (1) The growth of
biomass may not always be in balance with the
timber production, since the stock of biomass is
very high (the turnover of stock is very low). (2)
The measurement of biomass in forests is quite
problematic, and therefore less accurate than the
market growth of timber production (FAO 2010).
The related growth of yearly extra carbon storage
in the forests is to be allocated to the total yearly
production of wooden products.
Step 4 Calculation of the extra stored carbon in houses and
offices
The extra carbon sequestration in houses and
offices is related to the planed timber minus ‘appli-
cation losses’, which we estimate at 10 %. This
results in 0.9×0.5×3.67 = 1.65 kg CO
2
storage in
the houses per 1-kg d.m. planed wood. The extra
storage is related to the market growth given in step
3. This extra carbon sequestration is:
1.65×0.023=0.038 kg CO
2
per kilogram dry
matter planed timber
Step 5 Calculation of the total result
The effect on carbon sequestration caused by
land-use change can be calculated now as follows:
carbon sequestration ¼6:97 0:953 0:023 þ0:038
¼0:19 kg CO2per kilogram diameter planed timber
6 Example 2: calculation of carbon sequestration caused
by land-use change for Chinese bamboo (Phyllostachys
pubescens)
The aim of the calculation in this section is to illustrate how
the proposed method is applied in practice in the case of
bamboo products, and to validate the method as such (by
checking the differences compared to European softwood in
each calculation step).
The scope of the calculation is the calculation on carbon
sequestration in Chinese bamboo from cradle-to-grave, ex-
cluding emissions from forest management, product
manufacturing, transport, and end-of-life operations (a so
called ‘streamlined’LCA approach). The geographical sys-
tem boundary is China, as defined in (FAO 2010)
Int J Life Cycle Assess (2014) 19:13–23 19
The calculation is made for Phyllostachys pubescens
(density 700 kg/m
3
, length up to 15 m, diameter on the
ground 10–12 cm, wall thickness 9 mm), also called Moso,
from the Anji region, the province of Zhejiang, China. It is
processed to planed bamboo products like plywood and
strand woven bamboo (SWB) in Huangzhou, the province
of Zhejiang. SWB is a relative new industrial bamboo prod-
uct with a high Janka hardness (12,500 N) and density
(1,080 kg/m
3
), made from compressed bamboo strips plus
resin. For LCI data of the production processes, see
(Vogtländer et al. 2010; Van der Lugt 2009).
The calculation for Chinese bamboo is done via the same
steps as given in Section 5.
Step 1 Calculation of the carbon ratio.
One kilogram of a bamboo end-product relates to
many kilograms of wood in the bamboo plantation:
–1-kg biomass, d.m. above the ground in the bamboo
plantation, is equivalent to 0.42 kg of bamboo in the
end-product (Van der Lugt et al. 2009)
–0.42-kg d.m. of bamboo, is used in 0.44-kg d.m.
plywood (the resin content is 5 % of the weight of
plywood) and in 0.546-kg d.m. SWB (the resin
content is 23 % of the weight of SWB) (Van der
Lugt et al. 2009)
–1-kg d.m. biomass above the ground in the bamboo
plantation is equivalent to 3.1-kg d.m. biomass
above + below the ground, since bamboo has a vast
root system
2
–1-kg d.m. of bamboo plywood originates from
3.1/0.44=7.05-kg d.m. biomass in the bamboo
plantation, and 1-kg d.m. of SWB originates from
3.1/0.546=5.7-kg d.m. biomass in the bamboo
plantation
–The carbon content is 0.5 kg C per 1-kg bamboo
(Aalde et al.2006; Verchot et al. 2006)
–Therefore, 1-kg d.m. bamboo plywood is equivalent
to the storage of 7.05×0.5=3.5 kg carbon in the
plantation, and 1-kg d.m. SWB is equivalent to the
storage of 5.7×0.50=2.85 kg carbon in the planta-
tion
The result of step 1:
–1-kg d.m. bamboo plywood is related to 3.5 ×
3.67=12.85 kg CO
2
storage in the plantation
–1-kg d.m. SWB is related to 2.85×3.67 = 10.5 kg
CO
2
storage in the plantation
Step 2 Calculation of the land-use change correction factor
It is assumed that the additional permanent planta-
tions are established on grassland and do not come at
the expense of natural tree forests. This is a plausible
assumption as a large portion of the Moso bamboo
resources comes from the industrialised provinces
around Shanghai (Zhejiang, Anhui, Jiangxi).
Furthermore, this assumption fits well in the current
policy for afforestation and natural forest protection of
the Chinese Government controlled by the Chinese
State Forestry. More information on this issue can be
found at (CSF 2013).
Similar to the calculation of this step in Section 5,the
Tier 2 Gain–Loss Method (Verchot et al. 2006)ofthe
IPCC has to be applied. The ‘Total above-ground and
below-ground non-woody biomass’is 7.5-t d.m./ha (it
rangesfrom6.5to8.5)withacarboncontentof47%
(Verchot et al. 2006).
The biomass of bamboo plantations is 35.8×
3.1=111 t d.m./ha for biomass above + below the
ground (Van der Lugt 2009;ZhouandJiang2004),
and a carbon content of 50 %.
The land-use change correction factor for afforesta-
tion is therefore:
111 0:50ðÞ–7:50:47ðÞ
fg
.111 0:50ðÞ¼0:936
Much of the extra Chinese bamboo production in the
past comes from better management (Lou Yet al. 2010)
of existing bamboo forests. In such a case the land-use
change correction factor is 1 for the extra bamboo
production.
Step 3 Calculation of extra stored carbon in forests and its
allocation
The Seventh Chinese National Forestry Inventory
provides data on the growth of bamboo plantations in
China. In the period 2004–2008, bamboo plantations
have grown from 4.84 to 5.38 million hectares, or
11.2 % in 5 years or 2.24 % per year. The growth of
tree forest area in China is at a similar level (11.7 %).
It does make sense, however, to base the future
yearly growth of the total biomass in bamboo forests
on the average growth of Chinese timber production,
3
which is expected to be as least 5 % for the coming
decades, given the high GDP of the Chinese economy.
The related growth of yearly extra carbon storage in the
2
Besides the trunks, branches, and shrub, there is CO
2
stored below
ground in the soil and roots of a plantation. Zhou and Jiang (2004)
found that, for a medium intensity managed Moso bamboo plantation in
Lin'an, Zhejiang province, the distribution of biomass above ground
versus below ground is 32.2 and 68.8 %, respectively.
3
Here is a similar argumentation as in footnote 2 for European wood. It
must be mentioned here that this growth does not require extra agricul-
tural land. Much of the bamboo production in the past comes from
better forest management (Lou et al. 2010). Moreover, bamboo is
planted in areas where farming is not feasible, e.g., at slopes for erosion
prevention, and for rehabilitating land (Kuehl Y et al. 2011)
20 Int J Life Cycle Assess (2014) 19:13–23
plantation is to be allocated to the total yearly produc-
tion of bamboo products.
Step 4 Calculation of the extra stored carbon in houses and
offices
The extra carbon sequestration in houses and
offices is related to the bamboo products minus
application losses, which we estimate at 10 %.
Taking into account the resin content in the end-
product (5 % for plywood and 23 % for SWB), this
results in:
–0.95×0.9×0.5× 3.67 = 1.57 kg biogenic CO
2
stor-
age in the houses per 1-kg d.m. bamboo plywood.
The extra storage, related to the market growth in
step 3, results in the extra carbon sequestration of
1.57×0.05=0.0785 kg CO
2
per kilogram dry matter
bamboo plywood.
–0.77×0.9×0.5× 3.67 = 1.27 kg biogenic CO
2
stor-
age in the houses per 1-kg d.m. SWB. The extra
storage, related to the market growth in step 3,
results in the extra carbon sequestration of
1.27×0.05=0.0635 kg CO
2
per kilogram dry matter
SWB.
Step 5 Calculation of the total result
The effect on carbon sequestration caused by
land-use change can be calculated now as follows:
–Carbon sequestration= 12.85 × 0.936 × 0.05 + 0.0785 =
0.68 kg CO
2
per kilogram dry matter bamboo plywood
–Carbon sequestration= 10.50 × 0.936 × 0.05 + 0.0635 =
0.55 kg CO
2
per kilogram dry matter SWB
7 Discussion
The discussion on how to deal with the carbon sequestration
in LCA reveals that some important issues in the LCA
methodology are still not resolved (Finkbeiner 2009). This
paper shows that methodological choices highly influence
the outcome of the LCA calculations.
Table 1shows the data on the baseline LCA method of
Section 3(the first four columns), compared to the land-use
change approach of Section 4(the last column). Ecoinvent
LCIs are used for softwood, and the Idemat 2012 LCI is used
for bamboo plywood (Vogtländer et al. 2010; Van der Lugt
et al. 2009). Idemat is a database which is used at the Delft
University of Technology, additional to Ecoinvent.
From Table 1, it can be concluded that the credit for the
carbon sequestration caused by the land-use change, as
presented in this paper, is relevant in comparison to the
emissions caused by the production. The calculation for
production is made for the default method of the ILCD
handbook: biogenic CO
2
has not been taken into account,
so the production data in the Table is for fossil CO
2
only. The
credit for combustion with heat recovery has been calculated
for two different levels of efficiency: an efficiency of a
modern coal fired electrical power plant of 45 % (IEA
2007), and an efficiency of a modern municipal waste incin-
erator of 24.75 %. The ‘avoided fossil fuels’are calculated
for the grid average energy mix of the Ecoinvent ‘electricity,
medium voltage, production Union for the Coordination of
the Transmission of Electricity (UCTE), at grid/UCTE S’
LCI.
Table 2provides some additional data with regard to the
issue of linear discounting of a delayed CO
2
pulse in
100 years (a 100-year time horizon). The issue here is
whether or not discounting brings additional information
which cannot be missed.
The discounting of a delayed CO
2
pulse results in a credit
in LCA (column 1 of Table 2), but reduces the credits for
combustion with heat recovery (column 2 and 3 of Table 2
compared to column 3 and 4 of Table 1), so the overall effect
of discounting is limited. Note also that the effect of
discounting in Table 2is an overestimation of the benefit in
reality since there is still a considerable amount of CO
2
in the
atmosphere after the 100-year cut-off criterion of in the
Lashof calculation (see Fig. 1, Section 2).
Given the fact that the result of the discounting is limited,
and that it gives an overestimation of the resulting credit, the
discounting system of the delayed CO
2
pulse does not make
sense in LCA, since it does not fulfil the precautionary
principle (which should be applied in LCA).
Furthermore, the traditional LCA accounting system has
the advantage that the approach on the level of one product is
Table 1 Traditional LCA data on European softwood and Chinese bamboo
All data in kg CO
2
equivalent, IPCC 2007 GWP 100a Combustion Municipal Land-use
change
Production Production Power plant Waste incin this paper
kg CO
2
e/m
3
kg CO
2
e/kg kg CO
2
e/kg kg CO
2
e/kg kg CO
2
e/kg
Sawn timber, softwood, planed, air dried, at plant/RER S (d.m. 80 %) 85 0.21 −1.08 −0.59 −0.15
Sawn timber, softwood, planed, kiln dried, at plant/RER S (d.m. 90 %) 104 0.26 −1.21 −0.67 −0.17
Idemat2012 Plywood Bamboo (including transport to Europe, d.m. 90 %) 811 1.16 −1.13 −0.62 −0.61
Int J Life Cycle Assess (2014) 19:13–23 21
in line with the approach of a continuous flow of products (of
the same type), which makes it robust for a wide range of
scenarios (from a local to a global level). The traditional
LCA is also less vulnerable for different assumptions on
the decay of wood in landfill: in wet regions the decay is
fast, in dry regions slow, which has a big impact in calcula-
tions with a time horizon.
An important issue is how to implement the proposed
method of this paper in practice. What are the implications
for LCA practitioners and to what level of detail land-use
change should be addressed?
A practical aspect is the availability of data. For the12
global regions in (FAO 2010) enough data are available to
make a Tier 2 calculation on the average forests in that
region. At the level of specific types of timber in the global
trade (e.g., spruce, scots pine, radiata pine, etc.), however,
data are not readily available. The most practical approach to
resolve that problem might be that FAO includes the required
information in their FAOSTAT database (at the level of the
233 countries), an initiative that should be done in close
cooperation with the developers of ILCD, USLCI and
Ecoinvent.
The accuracy of the Tier 2 calculations on specific types
of timber in the global trade cannot be high since wood is a
natural product with a rather high variation of the main
growth characteristics of the trees. It is important, however,
that data become available: data with low accuracy is better
than no data at all.
With regard to the accuracy of calculations on carbon
sequestration, it is important to realise that the carbon foot-
print is only one of the environmental indicators related to
land-use change. Two other important issues with regard to
land-use change are:
–The albedo effect of deforestation and reforestation in
boreal areas. The change in albedo (surface reflection) in
areas with snow has an effect on global warming which
is of the same magnitude as the effect of carbon seques-
tration in forests (Cherubini et al. 2012).
–The reduction of biodiversity caused by deforestation of
tropical rain forests. Reduction of biodiversity of natural
forests is one of the main issues in the debate on tropical
hardwood, making a difference between illegal logging,
reduced impact logging, FSC-certified logging and log-
ging from plantations. This is one of the main arguments
to use an indicator system that takes this important
aspect into account (as a midpoint), like the ReCiPe
system or the system of the eco-costs (Vogtländer et al.
2001; Vogtländer et al. 2004).
8 Conclusions
The conclusions with regard to the issue of carbon seques-
tration are as follows:
&The afforestation and reforestation related to a growing
application of boreal softwood, wood from temperate
regions, and bamboo products have a significant contri-
bution to carbon sequestration on a global level
&An even bigger contribution is the reduction of fossil
CO
2
emissions by combustion with heat recovery (pro-
duction of electricity) of the wood and bamboo products
at the end-of-life
The conclusions with regard to the LCA methodology are as
follows:
&Proper modelling of the end-of-life stage results in a
considerable credit for wooden products in the case of
combustion with heat recovery. There is no reason to
deviate from this ‘default’method in the ILCD
Handbook and PAS 2050:2011.
&The ‘optional’method in the ILCD manual and PAS
2050:2011 (i.e., discounting of the delayed CO
2
emis-
sions) results in an overestimation of the benefits of
temporary fixation of biogenic CO2. This optional meth-
od does not fulfil the precautionary principle, and should
therefore be avoided in LCA
&It is advised to reconsider the calculation procedure to
deal with carbon sequestration in wood (and other bio-
based products), as described in the ILCD Handbook
Section 7.4.3.7.3, 7.4.4.1, and Section 13, and bring it
in line with Section 4and the examples in Section 5of
this paper
Table 2 The effect of a discounted CO
2
pulse at the end-of-life (after 50 years, linear discounting 1 % per year) on LCA data of European softwood
and Chinese bamboo
All data in kg CO
2
equivalent, IPCC 2007 GWP 100a Optional Heat recovery Heat recovery
Carbon sequestration In power plant In munic waste incin
ILCD 50 years ILCD after 50 years ILCD after 50 years
kg CO
2
e/kg kgCO2
e
/kg kgCO
2
e/kg
Sawn timber, softwood, planed, air dried, at plant/RER S (d.m. 80 %) −0.734 −0.540 −0.295
Sawn timber, softwood, planed, kiln dried, at plant/RER S (d.m. 90 %) −0.826 −0.605 −0.335
Idemat2012 Plywood Bamboo (d.m. 90, 5 % resin) −0.785 −0.565 −0.310
22 Int J Life Cycle Assess (2014) 19:13–23
&Land transformation data of general LCI databases
should be applied with great care, since they cannot
simply be applied to single products (as explained in
Section 4).
The way that carbon sequestration in wood products is
dealt with in LCA, needs further refinement. In the proposed
approach there seems to be no need for a discounting system
of delayed CO
2
emissions. The advantage of wood and wood-
based products can be described in terms of land-use change
on a global scale in combination with a credit for heat recov-
ery at the end-of-life (if applicable). However, the availability
of data on transformation of land is limited (on the level of
specific types of timber), so systematic collection of reliable
data is required.
References
Aalde H, Gonzalez P, Gytarsky M, Krug T, Kurz WA, Ogle S, Raison J,
Schoene D, Ravindranath NH, Elhassan NG, Heath LS, Higuchi N,
Kainja S, Matsumoto M, Sánchez MJS, Somogyi Z (2006) IPCC
Guidelines for National Greenhouse Gas Inventories. Volume 4,
Chapter 4 Forest Land. Available at www.ipcc.ch. Accessed 6 Feb 2013
Brandao M, Levasseur A (2011) Assessing temporary carbon storage in
life cycle assessment and carbon foot printing: outcomes of an
expert workshop JRC 63225. Publications Office of the European
Union, Luxembourg
Brandao M, Levasseur A, Kirschbaum MUF, Weidema BP, Cowie AL,
Vedel Jørgensen S, Hauschild MZ, Pennington DW, Chomkhamsri
K (2013) Key issues and options in accounting for carbon seques-
tration and temporary storage in life cycle assessment and carbon
footprinting. Int J Life Cycle Assess 18(1):230–240
BSI, British Standards Institution (2011) PAS 2050: 2011 Specification
for the assessment of the life cycle greenhouse gas emissions of
goods and services. BSI, London
Cherubini F, Bright RM, Strømman AH (2012) Site-specific global
warming potentials of biogenic CO2 for bioenergy: contributions
from carbon fluxes and albedo dynamics. Environ Res Lett
7:045902. doi:10.1088/1748-9326/7/4/045902
Clift R, Brandão M (2008) Carbon storage and timing of emissions.
University of Surrey. Centre for Environmental Strategy Working.
Paper Number 02/08. ISSN: 1464–8083, Guildford
CSF (2013) website Chinese State Forestry, http://english.forestry.gov.
cn/web/index.do. Accessed 6 Feb 2013
European Commission–Joint Research Centre and Institute for Environment
and Sustainability (2010) International reference life cycle data system
(ILCD) handbook—general guide for life cycle assessment—detailed
guidance. Publications Office of the European Union, Luxembourg
FAO (2010) Global forests resources assessment, Forestry Paper 163.
Food and Agriculture Organisation of the United Nations, FAO.
Available at www.fao.org/forestry. Accessed 6 Feb 2013
Fearnside PM, Lashof DA, Moura-Costa P (2000) Accounting for time
in mitigating global warming through land-use change and forest-
ry. Mitig Adapt Strateg Glob Chang 5:239–270
Finkbeiner M (2009) Carbon footprinting—opportunities and threats.
Int J Life Cycle Assess 14(2):91–94
Hischier R, Weidema B, Althaus H-J, Bauer C, Doka G, Dones R,
Frischknecht R, Hellweg S, Humbert S, Jungbluth N, Köllner T,
Loerincik Y, Margni M, Nemecek T (2010) Implementation of life
cycle impact assessment methods. Ecoinvent report No. 3, v2.2.
Swiss Centre for Life Cycle Inventories, Dübendorf
IEA (2007) Biomass for Power Generation and CHP. Available at
https://www.iea.org/techno/essentials3.pdf. Accessed 6 Feb 2013
Kendall A (2012) Time-adjusted global warming potentials for LCA
and carbon footprints. Int J Life Cycle Assess 17:1042–1049
Kuehl Y, Henley G, Lou Y (2011) The climate change challenge and
bamboo: mitigation and adaptation. IMBAR, Beijing. Available at
http://www.inbar.int/publications/?category=1&sortby=
title&dlpage=4. Accessed 6 Feb 2013
Levasseur A, Lesage P, Margni M, Deschenes L, Samson R (2010)
Considering time in LCA: Dynamic LCA and its application to
global warming impact assessments. Environ Sci Technol
44(8):3169–3174
Levasseur A, Lesage P, Margni M, Samson R (2013) Biogenic carbon
and temporary storage addressed with dynamic life cycle assess-
ment. J Ind Ecol 17(1):117–128
Lou Y, Li Y, Buckingham K, Henley G, Zhou G (2010) Bamboo and
Climate Change Mitigation. IMBAR, Beijing. Available at http://
www.inbar.int/publications/?category=2. Accessed 6 Feb 2013
Solomon S, Qin D, Manning M, Chen Z, Marquis M, Averyt KB,
Tignor M, Miller HL (2007) IPCC Fourth Assessment Report:
Climate Change (AR4), The Physical Science Basis,
Contribution of Working Group I to the Fourth Assessment
Report of the Intergovernmental Panel on Climate Change,
Cambridge University Press, Cambridge. Available at www.ipcc.
ch. Accessed 6 Feb 2013
UNECE, United Nation Economic Commission for Europe (2005)
European Forest Sector Outlook Study 1960-2000-2020, Geneva
Timber and Forest Study Paper 20. Available at http://www.unece.
org/forests-welcome/publications.html. Accessed 6 Feb 2013
Van der Lugt P, Vogtländer J, Brezet J (2009) Bamboo a sustainable
solution for Western Europe. VSSD, Delft
Verchot L, Krug T, Lasco RD, Ogle S, Raison J, Yue Li, Martino DL,
McConkey BG, Smith P (2006) IPCC guidelines for national
greenhouse gas inventories. Volume 4, Chapter 6 Grass Land.
Available at www.ipcc.ch. Accessed 6 Feb 2013.
Vogtländer J, Brezet J, Hendriks CF (2001) The Virtual Eco-costs '99, a
single LCA-based indicator for sustainability and the Eco-costs/
Value Ratio (EVR) model for economic allocation. Int J Life Cycle
Assess 6(3):157–166
Vogtländer JG, Lindeijer E, Witte J-PM, Hendriks C (2004)
Chacterizing the change of land-use based on Flora: application
for EIA and LCA. J Clean Prod 12:47–57
Vogtländer J, Van der Lugt P, Brezet J (2010) The sustainability of
bamboo products for local and Western European applications
LCAs and land-use. J Clean Prod 18:1260–1269
Vogtländer J (2010) A practical guide to LCA for students, designers
and business managers, cradle-to-grave and cradle-to-cradle.
VSSD, Delft
Werner F, Althaus H-J, Künninger T, Richter K, Jungbluth N (2007)
Life cycle inventories of wood as fuel and construction material.
Ecoinvent Report No. 9. Swiss Centre for Life Cycle Inventories,
Dübendorf
Zhou GM, Jiang PK (2004) Density, storage and spatial distribution of
carbon in Phyllostachys pubescens forest. Sci Silvae Sin 6:20–24
(in Chinese with English summary)
Int J Life Cycle Assess (2014) 19:13–23 23
