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Evaluation of forest operations in Spanish eucalypt plantations under a lifecycle assessment perspectiveSara González-García a; Staffan Berg b; María Teresa Moreira a; Gumersindo Feijoo a

a Department of Chemical Engineering, School of Engineering, University of Santiago de Compostela, Spain b

The Forestry Research Institute of Sweden (Skogforsk), Uppsala, Sweden

Online Publication Date: 01 April 2009

To cite this Article González-García, Sara, Berg, Staffan, Moreira, María Teresa and Feijoo, Gumersindo(2009)'Evaluation of forestoperations in Spanish eucalypt plantations under a life cycle assessment perspective',Scandinavian Journal of ForestResearch,24:2,160 — 172

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ORIGINAL ARTICLE

Evaluation of forest operations in Spanish eucalypt plantationsunder a life cycle assessment perspective

SARA GONZALEZ-GARCIA1, STAFFAN BERG2, MARIA TERESA MOREIRA1 &

GUMERSINDO FEIJOO1

1Department of Chemical Engineering, School of Engineering, University of Santiago de Compostela, 15782-Santiago de

Compostela, Spain, 2The Forestry Research Institute of Sweden (Skogforsk), Uppsala Science Park, SE-751 83 Uppsala,

Sweden

AbstractThe forest is an essential natural resource providing multiple benefits to people. However, forests face several environmentalproblems created by modern industrial society such as acidification, eutrophication and global warming. This studyinvestigated the environmental loads associated with the Spanish forest sector, where this activity plays an important role insocioeconomic development. A Eucalyptus globulus plantation located in north-western Spain was considered as a case study.Forest operations were divided into three subsystems: silvicultural operations, logging operations and secondary hauling.The results showed that logging operations consume more energy than any other part of the wood supply chain, with aremarkable contribution in the potential impact categories of global warming, acidification and photochemical oxidantformation. Transportation of timber from forest landing to industrial sites (secondary hauling) is the second most importantenergy user. Silvicultural operations made an important contribution to eutrophication, mainly due to phosphorus-basedfertilizer application. This study will enable improved Iberian life cycle assessment studies of wood products in the absenceof detailed studies for this region.

Keywords: Energy use, environmental impact, Eucalyptus globulus, forest operations, pulpwood, Spain.

Introduction

Forests are sources of economically important

sustainable raw materials and there is a growing

recognition of forestry’s function as a provider of

indirect services supplied by forests (Bjørnstad &

Skonhoft, 2001). Through forest management, for-

ests supply industry with stem wood for forest

products. However, these forests also contain avail-

able wood of a quality that does not match the

requirements of the forest industry, such as

branches, resins and bark. In addition, forests

provide environmental benefits such as soil and

water protection, have the potential to reduce net

carbon dioxide (CO2) emissions, and favour prolif-

eration of non-wood products such as medical

plants, mushrooms and berries. Forestry and forest

industries concern a large part of the European

Community and it is therefore not surprising that

some of the aforementioned environmental services

are in conflict with the services offered to industry

(Eriksson & Berg, 2007).

The European Union (EU) forest sector is char-

acterized by a great diversity of forest types, extent of

forest cover, ownership structures and socioeco-

nomic conditions. The forest sector (forestry, for-

est-based and related industries) comprises the

following industrial sectors: woodworking, cork and

other forest-based materials, pulp, paper and paper-

board manufacture, and paper and paper-board

converting and printing industries. The annual

production value of this sector was about t356

billion in 2001 and it employed about 3.4 million

people (European Commission, 2007).

Spain is a major forest country. Its forests supply

roughly 46% of the total wood required in the

Spanish forest-based industry, which is of growing

Correspondence: Sara Gonzalez-Garcıa, Department of Chemical Engineering, School of Engineering, University of Santiago de Compostela, 15782-Santiago

de Compostela, Spain. E-mail: sara.gonzalez@usc.es

Scandinavian Journal of Forest Research, 2009; 24: 160�172

(Received 16 July 2008; accepted 22 January 2009)

ISSN 0282-7581 print/ISSN 1651-1891 online # 2009 Taylor & Francis

DOI: 10.1080/02827580902773462

Downloaded By: [González-García, Sara] At: 16:56 13 May 2009

importance (MMA, 2005). At present in Spain there

are approximately 28.2 million ha of forest and other

woodlands (56% of the country’s total land area).

The growing conditions are favourable in the north

and consequently forestry activities there, and the

raw material from forests, are important to dynamic

industrial operations. The most productive forests

are found along the Atlantic coastal zone and consist

mainly of pines and eucalypts, although some mixed

natural forests of oak and beech can still be found

(FAO, 2005; Skogsstatistisk Arsbok, 2007). Even

most of the southern part of Spain has small forest

cover, but generally this land is treeless former arable

land, often covered with extensive Mediterranean-

type scrub. It holds potential for the future, but is of

minor importance to the influx of raw material to

industry (FAO, 2005).

The EU has established a policy to reduce its

contribution to global warming (European Commis-

sion, 2008). Forest operations in Spain as well as

other European countries are highly mechanized and

generate CO2 emissions through the use of fossil

fuels, lubricants and chemicals (fertilizers and pes-

ticides). The use of fossil fuels will depend on the

intensity of the processes. In recent decades fuel use

(in relation to cubic metres of timber harvested) has

been reported to have been reduced in some

European countries by 32% by using improved

machines and logging systems (Lindholm & Berg,

2005a).

Under sustainable forestry conditions, the combus-

tion of renewable fuels such as forest fuels is con-

sidered to be CO2 neutral, although fossil fuels are

often required for their production and distribution.

Hence, there is a need for better knowledge of fossil

fuel consumption in forest activities. A distinct feature

of the EU pulp, paper and board industry today is its

prominent use of energy from renewable energy

sources. In 2000, biomass energy corresponded to

half of the thermal energy and electricity use in these

countries (European Commission, 2006).

Life cycle assessment (LCA), a methodology that

aims to analyse products, processes and/or services

from an environmental point of view, has been shown

to be a useful and valuable tool for the environmental

evaluation of forest systems (Aldentun, 2002; Berg &

Karjalainen, 2003; Berg & Lindholm, 2005; White

et al., 2005).

LCAs have been carried out not only to compare

different products, but also to obtain information

about material and energy flows linked to products

and systems. The main products considered in forest

sector LCAs are wood, pulp, paper and board, and

the common functional units are either cubic metres

(in the case of wood) or tonnes. Other resources or

materials considered are use of energy, water and

chemicals. In addition, transportation distances of

products, emissions, and sometimes land use are

included. It is important to take into account that in

the particular case of forestry, LCA implementation

can be problematic owing to the different time scales

relating to tree growth (which takes years) and other

forest operations (such as logging or secondary

hauling) (Lindholm, 2006).

With the aid of LCA some authors have evaluated

the material consumption associated with some

forest operations (specifically logging) due to the

use of spare parts by harvesters and forwarders

(Athanassiadis, 2000; Athanassiadis et al., 2000) as

well as Swedish road transport (Eriksson et al., 1996).

Eucalypt wood is used extensively for paper pulp

manufacture in several countries, including Spain,

Portugal and Brazil. Among the different eucalypt

species, the wood of Eucalyptus globulus Labill. is the

most economically important raw material for paper-

pulp production in south-west Europe and specifi-

cally in Spain. In Galicia (north-west Spain), mono-

cultures of E. globulus are a basic resource in areas

where agriculture is not profitable and there is

growing concern about the ecological effects of

E. globulus plantations, associated with biodiversity

loss and the absence of insects (Cordero Rivera &

Santolamazza Carbone, 2000; Humara et al., 2000;

Gutierrez et al., 2001).

So far no detailed LCA study for both eucalypt

and Spanish forest operations has been performed.

The aim of this study is to identify the hot spots in

Spanish forest operations for pulpwood production,

in order to propose improvement opportunities.

Eucalypt, the most important forest tree species

used today in pulpmills in Spain, was selected for

the study.

The main objectives of this study were: (1)

identification of the forest operations that take place

in a forest scenario, with the corresponding energy

and/or chemical requirements; (2) identification of

the most intensive processes in terms of energy use

and with the highest contributions to impact cate-

gories analysed, from soil management to delivery of

timber to the pulpmills; and (3) proposal of

improvements and alternatives to the most proble-

matic areas (hot spots).

Materials and methods

Life cycle assessment methodology

LCA is a methodology for making a holistic assess-

ment of the impact that a product has on the

environment throughout its lifespan. This lifespan

follows the product from the extraction of raw

materials to the disposal of the product at the end of

Environmental impact of forest operations in Spain 161

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its use. LCA may give insights into areas in the forest

wood chain that need improvement, and also demon-

strates environmental applications of wood for

industry and consumer markets (Karjalainen et al.,

2001; Werner & Nebel, 2007). The forest sector has

environmental relevance not only because of its

potential low fossil fuel use and related low emissions

to air, water and soil, but also because of its potential

for carbon storage.

This paper studies the scenario of pulpwood

supply from a Spanish forest to a Spanish pulpmill.

The basic assumption was that a large proportion of

the environmental loads in forestry activities derive

from the use of machinery that is powered by fossil

fuels (diesel, petrol and lubricants).

This paper is not a complete LCA study according

to the standard (ISO 14040, 2006), since it does not

fulfil the requirements of section 7.3 (the critical

review processes). Its boundaries are constituted by

the study of the following activities: transportation of

workers, machinery and materials to and from the

forest site; silvicultural operations; logging opera-

tions; and transport of roundwood from forest

landing to the pulpmill (secondary haulage).

The function of the forest system under study is to

produce pulpwood, which is the main fibre raw

material used in a pulpmill. Therefore, the functional

unit was defined as 1 m3 (40% humidity) of industrial

round pulpwood under bark (m3 s.u.b.) delivered to

the pulpmill. The selection of the functional unit

seems to be in agreement with other forest-related

LCA studies (Berg & Karjalainen, 2003; Berg &

Lindholm, 2005; Scheinwle, 2007), where a

volume-based functional unit was considered.

The impact assessment phase was carried out

according to the Swedish Environmental Manage-

ment Council’s criteria (SEMC, 2000), and in

particular the potential impact categories considered

in forest and agricultural LCAs were analysed: global

warming, eutrophication, acidification and photo-

chemical oxidant formation. The LCA software

SimaPro 7.10 developed by PRe Consultants

(2008) was used to perform the impact assessment

stage. Only the classification and characterization

stages were considered in the impact assessment

stage. Normalization and evaluation were excluded

since they are optional elements and, according to

the goal and scope defined, were deemed not to

provide any extra information.

Global warming

The rapid increase in atmospheric CO2 and other

greenhouse gas concentrations is anticipated to cause

a variety of environmental, social and economic

problems, and is considered to be one of the most

pressing environmental issues facing society today

(IPCC-NGGIP, 2003). Emissions of gases with

specific radiative forcing characteristics, such as

CO2, nitrous oxide (N2O), methane (CH4) and

different forms of chlorofluorocarbons (CFCs), lead

to an unnatural warming of the earth’s surface. This

impact is commonly known as global warming.

Global warming is calculated in this study as CO2

equivalents.

Eutrophication

Eutrophication covers all potential impacts of having

a high environmental level of macronutrients, speci-

fically nitrogen (N) and phosphorus (P) emissions

into the air, water and soil. Organic matter and

mineral fertilizers in water (measured as biological

oxygen demand or chemical oxygen demand) in-

crease eutrophication (Bernes, 2001). This situation

may cause serious damage in both aquatic and

terrestrial ecosystems since when the amount of

nutrients increases, growth of certain populations

in the water system, such as algae, is boosted. When

these populations decompose, a large amount of

oxygen (O2) is needed, causing oxygen depletion at

the sea or lake bottoms. Eutrophication is calculated

in this study as O2 equivalents.

Acidification

Acidification is an impact category mainly owing to

the emission of acidifying substances, which causes

important effects in the soil, groundwater, ecosys-

tems and materials. Sulphur dioxide (SO2) and

nitrogen oxides (NOx) emitted into the air are spread

in the atmosphere which, combined with other

substances in the atmosphere, turn into acids. These

compounds reach the earth’s surface as rain or fog.

These acid rains lower the pH of soils and water,

which can lead to fish being wiped out, forests being

drained of nutrients and groundwater being con-

taminated with metals. Acidification is calculated in

this study as mol H� equivalents.

Photochemical oxidant formation

Ozone is formed in the presence of sunlight in the

atmosphere. The amount of ozone formed depends

mainly on the amount of nitrogen oxides and organic

compounds in the atmosphere. Increased levels of

ozone may affect human health and ecosystems, and

damage crops. Photochemical oxidant formation is

calculated in this study as ethene equivalents.

162 S. Gonzalez-Garcıa et al.

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Forest operations

The development of a wood plantation starts with a

cutover clearing and site preparation, e.g. soil

scarification (Figure 1). Site preparation operations

will improve planting and seedling establishment by

altering soil physical properties (Nohrstedt, 2000;

Bergquist et al., 2001; Mattson & Bergsten, 2003;

Lhotka et al., 2004; Thiffault et al., 2005; Johansson

et al., 2007). Soil treatments such as scarification

involving exposure of the mineral soil and/or ele-

vated planting spots may improve the microclimate

and soil temperature, and rearrange water supply

and nutrients for seedling establishment (Johansson

et al., 2007). Cutover clearing means the elimination

of unwanted vegetation to facilitate further regen-

eration treatment, such as soil scarification. The

latter breaks up the forest ground as preparation for

regeneration. Both processes are completely me-

chanized and disc trenchers and rippers connected

to tractors as well as brush saws are commonly used.

Soil scarification is done before regeneration

(planting). Planting is performed manually by a

worker equipped with a planting pipe (manual hoe

or drill). The worker carries plants or seedlings in a

box. Immediately after planting, agrochemicals such

as N, P and potassium (K)-based fertilizers are

applied. Pesticide application is mechanized. During

the management of the stand, some silvicultural

operations (Figure 1) have to be carried out, such as

cleaning, fertilization and/or pesticide application.

Undesirable vegetation is removed from a young

stand to regulate tree species composition, growth

and quality. Fertilizer and pesticide applications are

necessary to reduce the mortality of desired tree

species, improve forest production and favour spe-

cies that are desired for felling. Nowadays, cleaning

is performed by motor�manual and/or mechanized

methods. In this study, only mechanical cleaning was

considered.

Logging means that trees are felled and timber is

transported to the roadside. The management of

eucalypt forests includes only final fellings; no

thinnings are performed. The final felling operation

is done in two stages. First, some trees are felled with

power saws to make room for a harvester. Secondly,

a wheel-harvester completes the felling. The extrac-

tion of wood to the roadside is carried out by

forwarders.

Timber is transported from forest landing to the

pulpmill gate by 40 t timber lorries. Each lorry can

carry 25 t. The average load factor (the ratio of the

average load to the total vehicle freight capacity) is

50% in this case, including a full load to the pulpmill

and empty backhaulage. This is the dominant kind

of vehicle used in Spain (ECMT, 2007). No lorries

used in this study are equipped with cranes and they

are therefore served by independent loaders. The

average distance from forest landing to the pulpmill

gate in this case study scenario is 90 km.

System boundaries

Forest operations carried out over one whole year

(season 2006�2007) in a Spanish eucalypt (E.

globulus Labill.) plantation considered representative

of the state of the art were used in this study. This

paper focuses on eucalypt wood production since

this is the main raw material for the manufacture of

paper pulp in Spain. High-quality kraft pulps are

obtained from eucalypt wood (Gutierrez et al.,

2001). Eucalypt is a fast growing species, is highly

productive and is easily adaptable to low-fertility

soils.

The Spanish plantations are located in Galicia

(north-west Spain). Climatic conditions in this

region are mainly temperate subtropical with humid

winters (Rodrıguez & Macıas, 2006) and the annual

mean precipitation is approximately 1200 mm

(Xunta de Galicia, 2006). Galician forest soils are

mainly shallow or of moderate depth. The soil

texture varies from sandy (when developed on

granitic rocks) to loamy (developed on schist and

slates). Galician forest soils feature a high content

(from an Iberian perspective) of organic matter and

the pH is around 4.4. In fact, 69% of Galicia’s total

surface area is covered by forest systems, some ofFigure 1. Subsystems included in the process chain.

Environmental impact of forest operations in Spain 163

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them natural forests. The most frequent species are

maritime pine (Pinus pinaster Ait.) and eucalypt,

followed by oak (Quercus robur L.) (Xunta de

Galicia, 2001). The timber growth depends on the

species, climatic and soil characteristics, and applied

forest management procedures. This study reflects

the use of eucalypt forest plantations. Maximum

values have been observed in eucalypt stands near

the littoral zone. Much lower productivity has been

found in continental areas in the interior (Rodrıguez

& Macıas, 2006). The dry density of eucalypt

roundwood is 549 kg m�3 and the bark content is

16% (by volume). Annual production is 11.4

m3 ha�1.

Forestry, like other land management, affects the

soil storage of organic carbon in topsoils. The

Iberian peninsula, like many other areas in southern

Mediterranean Europe, has a low organic carbon

content (the major component of soil organic

matter) in comparison to areas in northern Europe

(Jones et al., 2004). Natural factors such as the

climate, soil material and a long history of land use

contribute to this situation. Repeated cultivation

with mechanical treatment of soils or intensive

grazing may enhance carbon mineralization if no

other measures to add organic materials are taken.

The land cleared for eucalypt plantations is marginal

land for agriculture that has a long history of carbon-

depleting measures such as repeated ploughing,

harrowing or grazing. Planting with eucalypt also

involves soil treatment but the interval between

treatments is longer than with agricultural use. It is

debatable whether plantation forestry on such soils

will increase or decrease the mineralization of soil

carbon. There is a lack of relevant data that fits

within the framework of this study; the technical

system for eucalypt plantations. Therefore, this

paper does not include the effects of land clearing

and carbon emissions due to soil processes during

the management of the forest plantations.

A detailed description of the system evaluated is

presented in Figure 1. The production of capital

goods (machinery, buildings and roads), and trans-

port of energy carriers and ancillary materials from

the industry production to the forest management

region were not included within system boundaries.

Neither the assimilation of CO2 during tree growth

nor biodiversity depletion was considered.

Field data were supplied by a leading Spanish

eucalypt woodland company with sustainable forest

management certifications (Programme for the En-

dorsement of Forest Certification Schemes*PEFC

and UNE:EN:ISO:14001:2004) (ENCE, 2008a,

2008b). Interviews, company visits and informal

conversations were carried out to gather inventory

data. These data were rounded off with company

reports and bibliographic resources.

Variations in fuel use depend greatly on the degree

of mechanization and the type of machinery used. It

is important to point out that major differences have

been reported not only between logging in conifer-

ous and non-coniferous forests, but also between

tree species (Schwaiger & Zimmer, 2001; Dias et al.,

2007). For example, the primary energy demands

for harvesting spruce are double those of oak, beech

and pine, and hardwood harvesting is more energy

intensive than pine owing to higher resistance

because of branches.

Life cycle inventory data for fuels (petrol and diesel)

used in the study come from Frischknecht et al.

(1996) and lubricants were assumed to have the same

inventory data as petrol, according to Uppenberg

et al. (2001).

Energy requirements related to energy use in each

forest operation, as well as fertilizer and pesticide

production and transport (from an energy point of

view), were taken into account. In addition, the

system includes not only field operations but also

impacts related to the extraction of raw materials

(energy carriers, minerals, etc.), as well as the

production and transportation of system inputs

(inorganic fertilizers and synthetic pesticides). Pro-

duction (including extraction) of all energy sources

was also considered.

System outputs were the following: round hard-

wood solid under bark (s.u.b.), waste and emissions

to air, water (groundwater and water surface) and

soil. As the functional unit was 1 m3 s.u.b. delivered

to the pulpmill, all the inputs and outputs were

allocated to that value.

Inventory data relating to the production of ferti-

lizer used in the system (N, P and K-based fertilizers)

were taken from the Ecoinvent database (Nemecek

et al., 2004) and Davis and Haglund (1999).

The use of fertilizers is an important source of

nutrient-related emissions in the field, with a major

contribution to global warming, acidification and

eutrophication (Charles et al., 2006). Nutrient flows

are not often considered in detail in forest LCA

studies. However, it is important to identify nutrient

flows because of their impact on the environment.

The nutrients of interest from an environmental

point of view are macronutrients (N, P, K) and

micronutrients (iron, copper, etc.). The nutrients

are both stored and cycled in the forest�wood

product system, but nutrient flows within trees

have no impact.

There are limitations in evaluating nutrients flows

since directly measuring the nutrient flows from

forests is complicated. Some studies (Lethonen

et al., 2004; Rodrıguez & Macıas, 2006; Fang et al.,

164 S. Gonzalez-Garcıa et al.

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2008) have studied soil and vegetation nutrient

contents and nutrient flows by vegetation uptake

and litterfall.

It is necessary to develop a full mineral balance for

each particular scenario to determine emissions from

fertilizers, since emission rates are variable owing to

the influence of the soil type, and climatic and

agricultural conditions. However, lack of data

made that impossible. Consequently, nutrient-

related emissions (ammonia, nitrate, nitrogen, ni-

trous and nitrogen oxides, and methane) were

calculated using emission factors proposed by sev-

eral authors (Audsley et al., 1997; Brentrup et al.,

2000; Arrouays et al., 2002; EMEP/CORINAIR,

2006). Data for atmospheric deposition in Galician

soils were taken from Rodrıguez and Macıas (2006).

In addition, it was necessary to determine the total

biomass (stem, bark, living branches, dead branches,

needles, stump, roots) generated to calculate the

total N retained and complete the N balance. This

value was calculated according to Lehtonen et al.

(2004). Under Spanish fertilizing conditions, there is

no nitrate leakage. The model shows that forest

ecosystems act as filters, removing most N atmo-

spheric deposition (Lehtonen et al., 2004).

P losses from the field are very difficult to

estimate. The extent of losses depends strongly on

local conditions (composition, pH, wind erosion,

drainage and surface water) as well as the type of

farming system. Some authors have estimated P

losses between 0.01 and 1.8 kg ha�1 (Audsley et al.,

1997; Valimaa & Stadig, 1998; Djodjic et al., 2004).

Phosphorus losses from agricultural and forestry

fields contribute to enhanced eutrophication and

must be reduced to improve or maintain surface

water quality. In this study, an emission factor to

surface water of 0.024 kg P kg P�1 was used

(Audsley et al., 1997).

Plant protection substances are applied to control

organisms to improve the productivity of forest

systems. One of the main current goals in agricul-

tural research is to reduce the total amount of these

chemicals and therefore their toxic effects (Mourad

et al., 2007). Emissions of synthetic pesticides into

the air, water and soil take place via wind drift,

evaporation, leaching or surface run-off (Brentrup

et al., 2004) and they were estimated according to

the method proposed by Hauschild (2000).

Roundup† (glyphosate 36%) is one of the most

commonly used herbicides worldwide because of its

effective weed control and negligible persistence in

the environment (Amoros et al., 2007). Therefore, it

was used in practical operations and was conse-

quently considered in this LCA of the forest system.

Previous studies have been published regarding this

pesticide’s toxicity and the fate and persistence of

herbicide residues in the forest floor (Giesy et al.,

2000; Haney et al., 2000; Thompson et al., 2000;

Amoros et al., 2007). Inventory data for pesticide

production (organic P compound) were taken from

different published reports (Audsley et al., 1997;

Ahlgren, 2003; Nemecek et al., 2004). A short

description of diffuse emissions related to fertilizer

and pesticide application is shown in Table I.

Representative emission factors for the Spanish

forest machines (carbon monoxide, NOX, hydrocar-

bons) were approximated to Swedish forest and

agricultural machines and came from Hansson et al.

(1998). Other emission factors for the machines were

taken from Uppenberg et al. (2001). In the case of

motor�manual machinery, emissions were considered

according to Holmgren (2000) and Naturvardsverket

(2002). The emission factors associated with heavy

lorries (used in secondary hauling) were taken from

Frees and Weidema (1998). The maximum legal

sulphur content in Spanish fuel is 2000 ppm (BOE,

2006) and this value was taken into account in all of

the forest processes.

Results

Table II shows the simplified energy use per func-

tional unit for each subsystem and corresponding

processes in the forest system under study.

The total energy use per harvested cubic metre

(under bark) is calculated as being about 395 MJ, of

which logging (155 MJ) dominates, with silviculture

and secondary transport on a similar level (around

Table I. Diffuse emissions from fertilizers and pesticide application per m3 of industrial round pulpwood solid under bark (s.u.b.).

Emissions to air Quantity estimated Emissions to water Quantity estimated

N-N2 46.00 g Phosphate (PO43�) 14.98 g

N-NH3 21.95 g Glyphosate 11.90 mg

N-N2O 6.39 g

CH4 3.55 g Emissions to soil Quantity estimated

N-NOX 0.639 g Glyphosate 45.11 mg

Glyphosate 19.74 mg

Environmental impact of forest operations in Spain 165

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120 MJ). This energy use results in emissions that

have an environmental impact.

Global warming

In this forest scenario, logging operations and

secondary hauling were identified as the main

subsystems responsible for emissions that contribute

to global warming, followed by silvicultural opera-

tions (Figure 2). CO2 emissions dominate the

contributions to global warming (91%), followed

by N2O (6%) and CH4 (3%).

The harvesting and forwarding of pulpwood con-

tribute 44% of total non-biogenic CO2 emissions

and represent 39% of total energy use. Timber

transport by road accounts for 31% of CO2 emis-

sions and approximately 29% of the total energy use.

Nearly 89% of total N2O emissions are derived from

silvicultural operations. These emissions are related

to the amount of mineral fertilizer applied and the

combustion of fossil fuels in its production and

application.

Eutrophication

Silvicultural operations contribute to most of the

emission of eutrophicating substances (approxi-

mately 71%) owing to the emissions associated

with the application of fertilizers in the soil: nitrogen

oxides, ammonia (into the air) and phosphate (into

the water), which constitute 64% of total eutrophi-

cating emissions.

Secondary transport and logging have lower con-

tributions (Figure 2). Their impact is due to emis-

sions associated with fossil fuel combustion in both

forwarding and harvesting stages and delivering

roundwood to the pulpmill. Forty-eight per cent of

total NOx emissions are associated with logging

operations.

Acidification

Secondary hauling and logging are the main con-

tributors to this impact category, adding up to 66%.

Silvicultural operations make up the remaining 34%

(Figure 2).

Energy-related emissions dominate: NOX and

SOX (about 86%). Both compounds originate from

fuel combustion, although NOX is produced in

combustion in engines and SOX is released from

fossil fuels containing sulphur, constituting 68% and

18%, respectively. Ammonia emissions associated

with N-based fertilizer application comprise 11% of

total acidifying emissions.

Photochemical oxidant formation

In this impact category, the logging operations

subsystem is the most important contributor and

its contribution adds to 42% of the total, followed by

secondary hauling and silvicultural operations (Fig-

ure 2). Hydrocarbon emissions, specifically non-

methane volatile organic compounds (NMVOCs)

and volatile organic compounds (VOCs), formed in

Table II. Energy use (MJ) per m3 of industrial round pulpwood solid under bark (s.u.b.).

Subsystem Processes Quantity Subsystem Processes Quantity

Silvicultural operations Cutover clearing 9.31 Logging operations Felling Chainsaw 13.97

Soil scarification 20.96 Harvester 69.86

Pesticide application 2.79 Extraction 69.86

Total cleaning 27.94 Workers’ transport 1.41

Fertilization 11.18 Total 155.10

Pesticide application Secondary hauling Loading 5.92

Fertilizer production 41.40 Transport 113.22

Pesticide production 0.11 Deloading 4.61

Workers’ transport 2.52 Total 123.75

Total 116.22

Figure 2. Analysis of contributions per subsystem in impact

categories under study. GW�global warming; E�eutrophica-

tion; AC�acidification; PO�photochemical oxidant formation.

166 S. Gonzalez-Garcıa et al.

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the incomplete combustion of fossil fuels are re-

sponsible for 100% of contributions to this environ-

mental category, with NMVOC emissions

constituting 92% of total emissions.

Hot spots

To summarize the results, Table III presents the

processes (as well as the main substances within

them) that are responsible for the highest contribu-

tions to impact categories. Those elements are

generally called ‘‘hot spots’’ and their identification

helps to improve the environmental performance of

the system under study. Results are presented as a

percentage of the total value for each impact

category.

Table III shows that harvesting and forwarding

stages (logging operations) make a great contribu-

tion to global warming (more than 36%), acidifica-

tion (more than 40%) and photochemical oxidant

formation (more than 32%). Secondary hauling is

the second largest contributor to global warming,

acidification and photochemical oxidant formation.

Eutrophication is due to P-based fertilizer applica-

tion.

Sensitivity analysis: load factor

Energy use in the secondary transport subsystem is

the second most energy-intensive stage. Higher pay-

loads (e.g. 40 t, which is similar to other European

countries) would considerably reduce energy require-

ments compared to Spanish conditions. However,

Spanish transport regulations allow only 25 t. One

option could be to reduce the total transport distance

(choosing better routes) and adjust the load factors.

Sensitivity analysis of the load factors demonstrates

that the energy requirement could be reduced in

timber transport (Figure 3). Two reasonably realistic

load factors, achievable with better logistics manage-

ment (Frisk & Ronnqvist, 2005), were taken into

account, i.e. 60% and 70%, and reductions of 7% and

13%, respectively, were achieved.

Discussion

The results obtained in this study indicate that

energy requirements in the Spanish scenario are

higher than in other European scenarios reported in

almost all the subsystems into which the forest

operations were divided (excluding secondary haul-

ing) (Schwaiger & Zimmer, 2001).

The management and owner structure of forests,

data availability, level of technology and region

considerably influence the quality of the data. The

availability and quality of inventory data in an LCA

study in the forestry sector will depend on the

management and landowner structure, as well as

on the country under study. For example, in the

Scandinavian countries, useful data of good quality

are available for different forest operations. No such

availability of data was found for other countries,

such as in southern Europe. This shortage of data

makes assessments more difficult.

Industrial wood processed in forest industries in

Spain is around 60% from coniferous and 40% from

non-coniferous species although, from the point of

view of wood pulp production, more than 70% of

wood processed is eucalypt (non-coniferous species)

(Gutierrez et al., 2001; Skogsstatistisk Arsbok,

2007).

The productivity of forests and the degree of

mechanization of forest operations seem to account

for the main influences on environmental burdens.

Table III. Processes that contribute more than 10% to impact categories in the Spanish forest scenario under study and main responsible

emission.

Main processes Impact category % Main pollutant emission %

Fertilizing and pesticide application E 63.3 P-total 55.3

Secondary hauling from landing to pulpmill GW 18.4 CO2 17.7

AC 13.7 NOX 9.8

PO 20.1 NMVOC 19.8

Secondary hauling from pulpmill to landing GW 10.6 CO2 10.3

PO 11.6 NMVOC 11.5

Stand treatment: cleaning AC 10.5 NOX 8.5

Felling (harvester) GW 18.5 CO2 17.8

AC 20.1 NOX 16.2

PO 15.8 NMVOC 15.6

Timber extraction (forwarder) GW 18.5 CO2 17.8

AC 19.7 NOX 16.0

PO 15.8 NMVOC 15.6

Note: E�eutrophication; GW�global warming; AC�acidification; PO�photochemical oxidant formation; P�phosphorus;

CO2�carbon dioxide; NOx�nitrogen oxides; NMVOC�non-methane volatile organic compound.

Environmental impact of forest operations in Spain 167

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The results of this environmental study indicate that

more than 39% of the energy use in the Spanish

process occurs in logging operations (harvesting and

forwarding), followed by timber transport between

forest landing and the pulpmill gate (secondary

hauling subsystem), and silvicultural operations.

This result differs from other similar studies carried

out mainly in Scandinavian countries (Schwaiger &

Zimmer, 2001; Berg & Karjalainen, 2003; Lindholm

& Berg, 2005a, 2005b; Berg & Lindholm, 2005),

where energy use associated with timber hauling is

50�65%.

Research on timber haulage (Forsberg, 2002)

suggests that there are many ways of decreasing the

energy demands in secondary road transport, such as

reducing the transport distance, adjusting the load

factors, designing better route-planning systems,

improving the standards of roads (curve geometry

and surfaces), adopting more fuel-efficient driving

techniques and using the best available transport

carriers. It has also been reported that well-educated

timber drivers could enable a 10% decrease in

energy consumption (Forsberg & Lofroth, 2002).

Pulpwood haulage can be considered to constitute

one of the main hot spots owing to its major

contribution to almost all the impact categories

under study, not only in the present study (Table

III), but also in other forest-related studies (Schwai-

ger & Zimmer, 2001; Berg & Lindholm, 2005;

Lindholm & Berg, 2005b).

Fuel use and the corresponding greenhouse gas

emissions in this subsystem depend on the engine

efficiency, weight and payload of lorries, quality of

roads, average transport distance, load factor, max-

imum gross weight permitted on public roads, and

transport system (train, lorry or boat). Machinery

manufacturers are trying to design more efficient

engines to reduce both fuel consumption and

exhaust gasses.

It is important to note that this study is focused on

the supply of timber to a Spanish pulpmill and

pulpmills generally have a wide radius of transport

(up to 300 km) because they need large amounts of

pulpwood. However, in this case the hauling radius

is considerably smaller than for other European

countries (Eforwood, 2007).

Weight and payload are regulated in European

countries and there are wide variations. In Spain,

timber lorries are allowed a total gross weight of 40 t,

which corresponds to 25 t of payload. In other

European countries the maximum load for a timber

rig is up to 60 t (a little more than 40 t of timber

weight). These differences have an influence on fuel

use per kilometre and per tonne loaded. The

introduction of heavier lorries could reduce the

energy use in this subsystem further.

Regarding the quality of country roads, it has been

reported that fuel consumption could be 25�40%

higher on the worst paved roads compared to the

best. In addition, good-quality roads increase pro-

ductivity and fuel savings for industrial pulpwood

haulage (Forsberg & Lofroth, 2003). If all these

variables are taken into account, load factor is one of

the most important measurements for improving the

Spanish scenario (in this study, the load factor was

50%). An analysis of the variation in load factor

shows that if it were increased by up to 70%, fuel use

could be decreased by up to 13%, with a corre-

sponding reduction in the environmental impact.

With regard to the logging stage (which is the most

energy-intensive stage), productivity depends on the

volume of wood processed being higher in mechan-

ized processes. Furthermore, larger harvesters and

forwarders use more energy. Improvement alterna-

tives in this stage could be to increase the load

capacity or increase the final size of the logs.

Fuel use (l h�1) and the machinery used in the

Spanish process (harvesters and chain saws) concur

with other related studies (Schwaiger & Zimmer,

2001; Markewitz (2006). However, the productivity

of the Spanish process (m3 h�1) is slightly lower and

fossil fuel use (kg m�3) is higher, which could be

due to ground conditions, operator skill, stand

density, worksite conditions and/or the nature of

the wood.

In addition, a single machine is being developed to

carry out harvesting and forwarding works (known as

a harwarder), to reduce fuel consumption per cubic

metre of timber harvested (Berg, 2003; Bergkvist

et al., 2006) as well as to introduce new technologies

in this forest stage, such as electric motors (electric

hybrid forwarders) or fuel cells. In the latter, no

emissions would be generated in the forest, although

they should be taken into account, e.g. in the power

plant. Lofroth et al. (2007) report a 20�50% reduc-

tion in fuel consumption per cubic metre of harvested

Figure 3. Energy use in the secondary hauling subsystem with

different load factors.

168 S. Gonzalez-Garcıa et al.

Downloaded By: [González-García, Sara] At: 16:56 13 May 2009

timber in comparative studies between conventional

forwarders and hybrid forwarders.

The energy use in silvicultural operations is almost

as much as for secondary hauling. The energy use for

machine operations is dominant, but the production

and application of fertilizers constitutes an impor-

tant part. Emissions allocated to impact categories

demonstrate that, despite this, silvicultural opera-

tions make a small contribution to almost all impact

categories except in eutrophication due to P-based

fertilizer application. Total P leaching takes place

and contributes to eutrophication of freshwater

systems. A general indicator for P leaching losses

for all soil types was taken into account in this study

and it would be interesting to acquire site-specific

factors that may serve as local indicators.

The silvicultural stage is highly mechanized and

uses larger engines in cleaning and soil scarification

steps. Usually up to three cleaning steps are carried

out during the stand treatment by a crane-tip

connected to a tractor or forwarder, and the entire

stand is scarified. Furrowing and ridging could be

implemented instead of ripping in soil scarification,

and mowing instead of disking in cleaning, to reduce

the associated environmental impact (Dias et al.,

2007).

The environmental impact evaluated in this study

by the analysis of four impact categories shows that

the use of fossil fuels in all the forest operations is the

largest contributory factor. For this reason, there is

interest in using biomass-derived fuels in forest

operations instead of fossil fuels, and some studies

are being carried out on this topic (Lofroth &

Radstrom, 2006). Black liquor from pulpmills,

wood chips and wood waste are some of the possible

alternative fuels.

Considering the levels of carbon reported in forest

soils in Europe (Jones et al, 2004), mineralization of

carbon can cause emissions that may be very relevant

compared to what is reported from the technical

system in this paper. However, good data regarding

these emissions are not available, and no alternative

land use to forest plantations is defined in this case.

This issue is an important area for further research

and it is anticipated that the process of land

treatment in conjunction with forest establishment

may be a source of carbon emissions from soils.

The main conclusions drawn from this study are

as follows. First, the results provide valuable infor-

mation that can help Spanish forest-based industries

(not only the pulp industry) to improve their

environmental performance and increase sustain-

ability. Secondly, Spanish forest operations present

higher energy requirements than in other countries

mainly because of machinery with low efficiency

levels. Thirdly, the leakage of nutrients from the

application of fertilizers is a significant environmen-

tal aspect (specifically in eutrophication) and atten-

tion should be paid to the optimum dosage of

fertilizer to apply or the best moment of application

to reduce nutrient loss. Finally, CO2 emissions may

be reduced by the introduction of biofuels in forest

operations.

Acknowledgements

This research study was developed within the frame-

work of the BIORENEW Integrated Project (project

reference NMP2-CT-2006-026456). S. Gonzalez-

Garcıa would like to express her gratitude to the

Spanish Ministry of Education for financial support

(grant reference AP2005-359 2374). The authors

would also like to thank the ENCE pulpmill for the

inventory data provided, as well as Skogforsk staff for

all the information supplied. The paper has also

benefited from co-operation with work under project

number 518128 EFORWOOD within Thematic

Priority 6.3 Global Change and Ecosystems.

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