Eco-costs calculations on wood

Wood in the Idemat tables is “four sides sawn timber” (not planed), are based on 7 issues :

the effect of foresting on global carbon sequestration (Vogtlander et al, 2014)
the local effect on biodiversity for FSC wood (RIL with rotation), in contrast to illegal logging in tropical rainforests
the eco-burden of forest management
logging, four sides sawing and kiln drying (to 10 – 12% DM (dry matter), see Fig 6.1a.
the issue of allocation between timber and its byproducts (paper pulp, biofuel, the bark, chips, saw dust)
scenarios on transport (forest -> sawmill -> dispatch harbor -> Rotterdam)

Issue 1. The effect of foresting on global carbon sequestration

The effect of foresting on global carbon sequestration is rather complex, and not easy to understand. The first remark is that the carbon that is captured in wood (and products like paper, food and biodegradable plastics) is regarded to belong to the short-term carbon cycle (in contrast to the long-term carbon cycles of fossil fuels). Hence the contribution to carbon sequestration is set to zero by the IPCC since 2007 to avoid all kinds of miscalculations. The basic idea is that the carbon that is stored in logged trees will return in the atmosphere eventually. “Eventually” is defined in LCA by a maximum life time of 100 years for wooden products, since it is the most used time span in LCA for the calculation of the midpoint table for carbon footprint. For LCAs of products, the consequences of this approach of ‘carbon neutrality’ of ‘biogenic carbon’ for wood and bioplastics is given at (Biotechnology Industry org, 2010). For wood in buildings that last longer than 100 years, the carbon stored in the wood must be taken into account.
Under the condition of rotational forest management, the total boreal forest area is

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in “steady state” (overall, the total carbon sequestration in a forest area is kept constant), which holds not only for PEFC wood (basically nearly all European wood is PEFC) but also for FSC wood from tropical areas. So for this type of wood, there is neither carbon footprint credit, nor debit in LCA. This complex issue is dealt with in (Vogtlander et al, 2014).

The situation, however, is totally different for illegal logging in tropical areas: the harvested forest area will not re-grow, and will likely become agricultural area. The result will be a loss of carbon sequestration of 3.45 kg CO2 per kg four sides sawn timber.
The calculation is based on the following assumptions:

a big tropical tree has, above ground, a maximum yield of 61% ‘four sides sawn’ timber
the roots are 37% of the above ground tree, so the maximum yield is 45% ‘four sides sawn’ timber of the total wood of a big tropical tree (above and under ground)
The carbon content is 0.47 kg per kg dry wood, the carbon sequestration is 1.72 kg CO2 per kg dry wood
so the carbon content per kg dry wood in the forest is 1.72/.45 = 3.82 kg CO2
per kg wood MC 11% : 3.45 kgCO2

So there is approx. 3.45 kg CO2 debit for illegal logging in tropical rain forests.

Issue 2. The local effect on biodiversity

The local effect on biodiversity for FSC wood (RIL with rotation), in contrast to illegal logging in tropical rainforests, is of major importance. The assumptions for the calculation are:

rotational forest management with RIL has no effect on the “steady state” of biodiversity (the original biodiversity is fully back after a few years (Arbainsyah et al. 2014),
however clear cut logging for agricultural purposes reduces biodiversity to virtually zero (in comparison to the natural state)
so FCS has no degradation of the biodiversity factor (see webpage eco-costs of land-use) in the eco-costs system; Δ eco-costs of land-use change is zero.
however, illegal ‘clear cut’ logging has eco-costs of the full degradation of biodiversity
the yield of a tropical forest is estimated as 25 m3 wood logs per hectare (10000 m2), resulting in 14 m3 ‘four sides sawn’ timber (8% lost in the forest, 33% in the saw mill, 9% volume lost by drying)

Figure 6.1a The supply chain of wood (Druzhinina et al. 2012). The Idemat LCIs on wood have the red boundary limit with the gate in the Rotterdam harbor area.

This 14 m3 per 10000 m2, combined with the density of the wood species, and combined with the biodiversity factor of the specific region, results in the eco-costs of illegal logging.
Example of Teak: (1) density at MC 12% is 665 kg/m3 (2) yield 14m3 per 10000 m2 (3) resulting in 1.07 m2/kg (4) biodiversity factor of Thailand is 0.625, so the eco-costs of land-use change is 1.07 x 0.625 x 6 = 4.02 euro/kg. Note that 6 is the eco-costs of 1 m2 at Δ biodiversity factor = 1.

Issue 3. the eco-burden of forest management

It appears in practice that the eco-costs of forest management is negligible, compared to the eco-costs of the rest of the product chain (less than 2%).

Issue 4. logging, four sides sawing and drying

The main processes are logging, ‘four sides sawing’ and kiln drying to 10 – 12% DM (dry matter). See Fig. 6.1a.
All these activities are governed by energy consumption. For logging, the main energy source is diesel, but this diesel is negligible compared to the other sources of eco-burden.
Kiln drying requires by far the most energy, sawing much less (Druzhinina et al. 2012; Puettmann et al. 2013). The heat that is required for drying comes from wood waste that is available within the system (so is not counted as import). Therefore, the heat for drying is

not counted in LCAs for timber. Therefore only the electricity of the sawmill has to be taken into account: approx. 0.9 MJ/kg (Gopalakrishnan et al. 2012).

Issue 5, The issue of allocation

There are many byproducts (Fig. 6.1a): (1) byproducts of logging (wet wood waste that cannot be used for beams and planks) used for pulp and biomass (2) byproducts of sawing, such as sawdust, chips, and bark, that are applied in all sorts of wood products, like MDF and particle board.
In some literature on LCA, ‘system expansion‘ is recommended to deal with this specific case. A practical way to keep it simple is to apply the rule in ISO 14044, section 4.3.3.1 that “…outputs related to a combustible material can be transformed into energy…..by multiplying them by the relevant heat of combustion”, taking an MC of 50% (which is a fair average of practical rages between 30% and 70%), and a Lower Heating Value of 9 MJ/kg.

An alternative is to ‘cut-off” of the system at the stockpile of wood waste. In such an approach the wood waste is regarded as a final waste product of the production of timber, in line with EN15804. In such an approach the wood waste is free of eco-burden at the start of the production of byproducts like MDF and particle board: it does not make sense to carry over part of the eco-burden of timber to its byproducts. It is also in line with the way to deal with downcycling

as depicted in Fig. 5.6d of webpage EoL and recycling.

In Idemat, the following choices have been made:
(1) system expansion is only applied when combustion will takes place in reality. The efficiency of heat recovery and electricity production is taken as it is in reality (e.g. municipality waste incineration for end-consumer waste, or combustion in a pawer plant for industrial waste).
(2) system cut off at the the EoL is applied in case of recycling, and in case of use of byproducts (e.g. for MDF and particle board), where there is no carry over from the old product system to the new product system

In LCA, the real situation with regard to the (value) hierarchy of application of wood waste should be adhered to (Puettmann et al 2012): (1) particle board (2) MDF (3) pulp (4) combustion with heat recovery (5) composting with prevention of methane emissions.

Issue 6. scenarios on transport

The conclusion of the issues 3, 4, and 5 is that the eco-burden of wood is nearly fully determined by the electricity of the saw mill plus the transport chain: forest -> sawmill -> dispatch harbor -> Rotterdam. The transport scenarios of a great number of wood species are given in the Idemat excel file ecocosts calculations wood 2022.xsxl. LCA practitioners outside Europe might adapt the transport data by adapting the (sea) transport routes.

References:

Biotechnology Industry Organization, working group. Principles for the Accounting of Biogenic Carbon in Product Carbon Footprint (PCF) Standards. December 2010.

Vogtländer JG, Van der Velden NM, Van der Lugt P. 2014. Carbon sequestration in LCA, a proposal for a new approach based on the global carbon cycle; cases on wood and on bamboo. Int J Life Cycle Assess (2014) 19:13–23 DOI 10.1007/s11367-013-0629-6

Arbainsyah, De Iongh HH, Kustiawan W, de Snoo GR. 2014. Structure, composition and diversity of plant communities in FSC-certified, selectively logged forests of different ages compared to primary rain forest. Biodivers Conserv (2014) 23:2445–2472 DOI 10.1007/s10531-014-0732-4

Druzhinina E, Binder M, Deimling S, Merl AD. 2012. Life Cycle Assessment of Rough-sawn Kiln-dried Hardwood Lumber. AHEC – American Hardwood Export Council by PE International AG

Maureen Puettmann, Elaine Oneil, Jim Wilson. 2013. Cradle to Gate Life Cycle Assessment of U.S. Medium Density Fiberboard Production. WoodLife Environmental Consultants, CORRIM, Oregon State University

Gopalakrishnan, Mardikar, Gupta, Jalali, Chaudhari. Establishing Baseline Electrical Energy Consumption in Wood Processing Sawmills for Lean Energy Initiatives: A Model Based on Energy Analysis and Diagnostics. Energy Engineering. 2012