some aspects of lca in the analysis of forestry operations

ELSEVIER

PII: SO959-6526(97)00040-I

.I. Cleaner Prod. Vol. 5, No. 3, pp. 21 I-217, 1997 0 1997 Elsevier Science Ltd. All rights reserved

Printed in Great Britain 0959-6526/97 $17.00 + 0.00

Some aspects of LCA in the analysis of forestry operations

Staffan Berg*

SkogForsk, The Forestry Research Institute of Sweden, Uppsala Science Park, S-751 83 Uppsala, Uppsala, Sweden

Accepted 27 May 1997

This study demonstrates how the LCA technique can be used to address issues concerning environmental stress caused by forestry. The stress caused by the use of fossil fuels is analysed for different forestry operations. Comparisons are made between:

0 clear cutting and shelterwood cutting in forest-management systems based on even-aged management; and

0 mechanized and motormanual operations for felling and bucking.

The analysis is based on data from northern and southern Sweden. Results show that motor-manual methods cause considerably lower emissions of CO, and NO, computed per cubic metre (solid o.b.) of harvested wood.

The use of shelterwood systems gives rise to emissions about 10% (felling) and 20% (forwarding) higher than those from clear cutting.

The results reflect the situation in Swedish forestry in the early 1990s. Since the use of the studied systems is influenced by the prevailing economic, climatic and biological conditions, the demonstrated effect is not caused by the difference in logging technique alone. 0 1997 Elsevier Science Ltd. All rights reserved

Keywords: LCA; emissions; forestry operations

Background

Life-cycle analysis or life-cycle assessment (LCA)’ is a tool for making a comprehensive assessment of the impact that a product has on the environment through- out the life span of the product, through extraction of the raw materials, conversion, manufacture, transport and use, to disposal of the product at the end of its useful life and management of the waste. Wood and wood fibre have many applications and are often in competition with alternative materials. In some modem product planning, LCA-based routines are used in the selection of raw materials. Relevant up-to-date environment data are needed to enable the environmental impact of wood to be compared with that of other materials. The need for such data has stimulated many LCA studies in forestry.

This report gives examples of how the LCA inventory process can be used to describe the environmental impact of some forest-technology systems. The basic

*Tel.: + 46 18 18 85 65; Fax: + 46 18 18 86 00. Paper presented at International Conference on Application of Life Cycle Assessment in Agriculture, Food and Non-Food Agro-Industry and Forestry: Achievements and Prospects 4-5 April 1996, Brus- sels, Belgium.

assumption is that a large proportion of the load imposed on the environment by forestry derives from the use of machinery that is powered by fossil fuels.

Study objective

The aim of this study is to present examples of the use of LCA techniques in assessing the environmental load imposed by some forest-technology systems. The report looks at the work input in felling and seeks to answer two questions:

1.

2.

Does the additional felling work involved in the shelterwood system give rise to higher fossil-fuel emissions than in clear cutting systems? Does the considerable work necessary for the transport of personnel in motor-manual logging methods (mo-ma) give rise to emission levels that are as high as those from the machinery used in mechanized methods (mech)?

Scope

The study is confined to emissions of carbon dioxide (CO,) and oxides of nitrogen (NO,) from diesel oil,

J. Cleaner Prod., 1997, Volume 5, Number 3 211

LCA aspects in forestry operations: S. Berg

engine oil and petrol (gasoline) and covers only the inventory phase. This is consequently not a complete LCA. The following activities are covered in the study;

??conveyance of people, machinery and materials to and from the site,

?? felling, and ?? forwarding to the forest landing.

The forest landing is the end boundary for this study. Logging operations, felling and forwarding, are defined as either motor-manual or mechanized The functional unit used is cubic metres (solid gross volume on bark) of felled timber.

The study does not take account of the resources needed to feed and clotbe the people involved in the specified work processes.

Study methods and basic data

Data for the period around 1990 were deemed to be most appropriate for the assessment, for a number of reasons. As a consequence of the combined pressure exerted by public opinion and the export markets, a change to forest policy in Sweden was both proposed and examined’. The primary aim of the policy prevailing at that time was to produce timber for the forest products industry. However, the new forestry legis- lation that took effect in 1994 places biodiversity issues on an equal footing with the production objectives. A number of studies were carried out before the new policy was formulated, including one in which projec- tions were made of sustainable annual cuts for ten consecutive lo-year periods, starting in 19883. This study (AVB 92), estimates the allowable annual cuts that would apply if the forest policy at that time were to continue. The study computes figures for four computation regions for timber supply and demand, known as ‘Wood-balance’ regions (Bo l-B0 4), show- ing the volumes of timber available for removal in final felling, thinning and other necessary silvicultural activities.

In the present study, we have used figures from the first period, i.e. 1988-1998, as a bench-mark for the annual volume of timber that Swedish forestry can produce, based on the situation just after 1990. The work input required to produce this volume was calculated from the production estimates presented by Hellstrom and Westerberg4 and Freij and Tosterud5. SkogForsk researchers have checked these figures and adapted them to take into account the technology in use in 1992 (Andersson et al., personal communication). The same researchers also investi- gated the amount of travelling to and from work sites, and the resources for moving machinery between sites that the specified level of production would necessitate. Unfortunately, as regards the travelling and the moving of machinery, there are less data available than in other aspects of the study.

Using these estimated figures, together with data collected by Landstr6m6, we calculated the consump-

Figure 1 Two regions (Bo 1 and Bo 4) for which allowable annual cuts were computed in AVB 92.

tion of fossil fuel. Landstrom’s figures are based on his own records and on data collected from companies and authorities.

In a study of felling methods, a comparison is made of the emission levels of fossil-fuel-derived CO2 and NO, from motor-manual and mechanized methods in final felling and thinning. The study also compares different types of felling, such as thinning, final felling in clear cutting and shelterwood systems. The shelterwood system is performed in order to promote natu- ral regeneration. In thinning and clear cutting, a given stand is treated once in each case. Each treatment involves the use of vehicles for conveying workers to and from the site, machinery and labour for felling, and machinery for extraction (forwarding). Shelterwood systems involve three operations in each stand: felling in order to create shelterwood, removal of windthrows and final cutting of the shelterwood.

A comparison is made for two regions, one in the north and one in the south of the country (see Figure 1). The northern region, Bo 1, contains close to 10 million hectares ha of forest land, more than half of which is owned by major enterprises pursuing large- scale forestry (Table I).

The region is an extensive one, and the variation around the average figures shown in the table is high. The same applies to the species composition of the standing timber: in the north of the region, Scats pine accounts for as much as 70% of the crop. The percent-

Table 1 Forest status in region Bo 1

Forest land area 9.7 million ha Standing crop 87 m3/ha Annual net increment 2.8 mYha Percentage of land owned by major enterprises 56%

212 J. Cleaner Prod., 1997, Volume 5, Number 3


Table2 Estimated annual volume of felled timber (million m’) in period 1, with breakdown by felling type and felling method in region Bo 1

Felling method First thinning

Mechanized 0.6 Motormanual 1.0 Total 1.6

Felling type

Subsequent thinnings Clear cutting

0.6 10.2 I .o 1.9 1.6 12.1

Shelterwood cutting

2.5 0.5 3.0

Total

13.9 4.4

18.3

age of Norway spruce increases the further south one goes, reaching a peak of nearly 60%. The region is sparsely populated, with just over one million people, the majority of whom live close to the coast. Several large pulpmills are also located on the coast, whereas the sawmills are more widely scattered. Roads are of a high standard, but forestry operations are characterized by long transport distances for timber, machinery and personnel alike. The major forest enterprises are the main players in forestry, and most machine systems are therefore of the type used in large-scale forestry systems (Table 2). Mechanized logging is performed by harvesters, and the timber is extracted by forwarders. Motor-manual felling is done by cutters with chain saws, and the timber is again extracted by the same type of forwarder as that serving the har- vesting machines. However, light-duty forwarders based on farm tractors are also used to an extent, particulary in thinnings.

Region Bo 4 comprises southern Sweden and has 4.5 million hectares of forest land, nearly all of which belong to small estates and small, private woodlot owners (Table 3). A large part of all the forestry here is therefore small scale, although it is also common for owners of forest holdings to use large-scale forestry system. Such operations are coordinated by woodlot owner associations and the purchasing functions of major enterprises.

Norway spruce comprises more than 50% of the standing crop, varying by f 10% across the region. This is a densely populated region, being home to 4 million people. The whole area is inhabited, although the most densely populated areas occur in the western and southern parts. Pulpmills are situated on the coast, whereas the many sawmills are close to the forests. The road network is also fairly dense and the roads are of a high standard. Forestry is characterized by good transport conditions for timber, machinery and people. However, one drawback is that general traffic conditions can create problems when machines are to be moved. Because of the large proportion of small enterprises, it is often difficult to establish suitable

Table 3 Forest status in region Bo 4

Forest land area 4.5 million ha Standing crop 148 m3/ha Annual net increment 6.2 mYha Percentage of land owned by small enterprises 85%

landings in the logging areas. The machine systems used are largely the same as those used in region Bo 1 (T&e 4). What differs is that the machines-both harvesters and forwarders-are smaller and that the use of farm tractors in extraction is more common.

Thus, the estimated volume of felled timber during the lo-year period, 1988-1998, is of the order of 200 million m3 or about 20 million m3 per year, in each region according to Tables 2 and 4. Even aged management is assumed to be totally dominant. Clear cutting is the most widespread form of final felling in both regions, although shelterwood cutting, leaving predomi- nantly Scats pine as the shelter-wood, followed by removal of windthrows and final cutting stages, is also common where it is technically and biologically viable. In region Bo 4, a substantially higher proportion of the cut comes from thinning than in region Bo 1.

Table 5 shows the conversion factors used in calcu- lating the emission levels of NO, and CO2 from fuel combustion. The consumption of fuels in logging related to the harvested quantity in all Sweden is published in EFI proceedings No. 87.

Results Thinning

Computation and collation of the emissions of CO, and NO, occurring during felling work in thinning show that CO* emissions in both first and subsequent thinnings vary between c. 4 and 5 kg per m3 of felled timber in mechanized felling (Figure 2). The figures are slightly higher for southern Sweden than for the north. Motor-manual felling gives rise to much lower emission levels than in mechanized felling, producing no more than 1 kg of CO, per m3 of felled timber.

As regards NO,, the findings are generally the same when we compare emissions between felling methods and regions. The levels vary between c. 80 and 110 g/m3 of felled timber in mechanized methods, as against motor-manual methods, where emission levels are below 10 g/m3.

It was not possible to define the forwarding work separately for motor-manual and mechanized felling. The average values for the two felling methods together are shown in Table 6.

Emission levels are higher in the south than in the north, and also in subsequent thinnings as opposed to first thinnings. The reasons for this are that productivity



Table4 Estimated annual volume of felled timber (million m”) in period 1, with breakdown by felling type and felling method in region Bo 4

Felling method First thinning

Mechanized 0.7 Motormanual 1.8 Total 2.5

Felling type

Other thinnings Clear cutting

1.6 7.2 3.7 2.9 5.3 IO.1

Shelterwood cutting

I.8 0.7 2.5

Total

Il.3 9.1

20.4

Table 5 Conversion factors used in calculations, tonne/m’ of fuel in logging’

NQ CO,

Diesel Petrol (gasoline)

0.054 0.019 2.610 2.646

was higher in the north and that smaller machines were used in first thinnings than in subsequent thinnings.

Final felling

Emissions of CO2 in mechanized final felling were estimated at 3 kg/m3 (Figure 3). The various operations involved in shelterwood cutting and subsequent removal result in 10% higher emissions than in tra-

First thinning First thinning

Bo 1 Bo4

4155

I 742

5143

Figure2 Emissions of CO* and NO, from mechanized and motormanual thinning in the north (Bo I) and south (Bo 4).

moma meoh mo ma mech

9 CQJ@ Subsequent thinnings Subsequent thinnings

4 6000

t

t

Bo 1 Bo4 5000

4000

3000

t 2000

1000

t

903

0 r 964

86

L 9

92

I moma mech moma mech moma mech mo ma mech

4175 4435

1oc

8C

60

40

20

0 I 7

Bo 1 Bo4

86

106

Bo 1 100

Bo4

80

60



3 000

2500

2 000

1500

1 000

500

0

Table 6 Estimated emissions of CO2 and NO,, per m’ during forwarding work in thinning in northern and southern Sweden (regions Bo I and Bo 4)

Thinning type

First thinning Subsequent thinnings

Emissions of CO* (kg/m’) Emissions of NO, (g/m’)

Bo 1 Bo 4 Bo 1 Bo 4

1.8 2.1 38 43 2.5 2.7 51 56

‘m3 g NO,/m”

238

769 L - momamech clearcuttings

Bo 1

850 r

g COdm3 g NOx/m3

Bo4

2 500

2

1

000 L

500

1 000

500 724

0 mon clearcuttings

shelterwood

793 r

3 122

meet shelterwood

-

Bo 1

‘74

67

moma mech momamech clearcuttings shelterwood

70 *-

60 *-

50,.

40,.

3@-

20..

l@-

0.

Bo4

mo ma mech momamech clearcuttings shelterwood

Figure 3 Estimated emissions of CO, and NO, in final felling (clear cutting and shelterwood cutting) using motormanual and mechanized methods in northern and southern Sweden (regions Bo I and Bo 4).

ditional clear cutting. The use of motor-manual felling leads to much lower emissions of COP, of between 0.7 and 0.9 kg/m3. Here, again, emissions are higher in the shelterwood system. Roughly the same pattern emerges in respect of NO, emissions. Estimated emission levels vary between 60 and 80 g/m3 in mechanized felling, as against less than 10 g/m’ in motor-manual felling. Emissions of both CO2 and NO, are lower in region

Bo 4 than in Bo 1, which is the converse of the situation in thinning.

Here, again, we were unable to define the forwarding work separately for motor-manual and mechanized felling. The combined figures are shown in Table 7.

Emissions from forwarding are estimated to be 20- 25% higher in shelterwood cutting. This is because the average productivity of the machines is usually lower,



Table7 Estimated emissions of CO* and NO, per m3 during forwarding work in final felling (clear cutting and shelterwood cutting) in northern and southern Sweden (regions Bo 1 and Bo 4)

Felling system

Emissions of CO* (kg/m’) Emissions of NO., (g/m’)

Bo I Bo 4 Bo 1 Bo 4

Clear cutting 2.2 1.6 45 34 Shelterwood cutting 2.6 2.0 54 41

given that the volume of timber extracted per site decreases on each subsequent forwarding operation. In addition, the forwarder operator needs to take care not to damage the shelterwood trees.

Combined jigures for felling and forwarding

There are two likely reasons for the variation in emission levels. The first is the significance of whether the method is motor-manual or mechanized; mechanized methods use considerably more diesel, whereas motor- manual methods use more petrol or gasoline. Combus- tion of a litre of petrol produces much lower emissions of NO, and somewhat lower levels of CO, than diesel (Table 5).

The other probable reason for the variations is the difficulty of the work and the type of machine used. Lower productivity means increased emissions per cubic metre of timber felled. Heavy-duty machines tend to carry larger payloads but also have a higher fuel consumption.

In the cases studied, the difficulty of thinning work was higher in the south than in the north, which resulted in higher productivity and lower emissions in the north. However, the converse applies to final felling. One decisive factor is that the trees are larger in the south, which means that the emissions per cubic metre of timber, compared to the north, are lower in final felling.

Emissions in forwarding are affected by the difficulty of the felling work, the size and capacity of the forwarder, the extraction distance and the concentration of felled timber. In the south, the difficulty of thinning and the greater use of small, less efficient machines result, compared to the north, in higher emissions in thinning. In final felling, much the same machines are used in both the north and south of the country. The greater extraction distances in the north, together with a smaller volume of standing timber per hectare, result in lower productivity and thus, in comparison to the south, higher emission levels in final felling.

Table 8 Estimated emissions of CO2 (kg/m3) from felling and forwarding in different systems for final felling

Felling system Bo 1 Bo 4

Clear cutting 5.0 3.9 Shelterwood cutting 5.7 4.4


If the CO, emission figures for felling and forwarding are combined (Table 8), we find that emissions from shelterwood cutting exceed clear cutting with 12-14%.

Travel to and from work and moving machines between sites

A summary of the significance to emissions of travel to and from work and the moving of machines between sites is shown in Figure 4.

The figure shows total emissions from felling work, travel to and from work and the moving of machines between sites. Forwarding is not taken into account, because collected data about emissions from forwarding do not differ in respect of the options included in the figure.

In southern Sweden (region Bo 4), emissions from moving between sites at motor-manual felling are nearly half those from mechanized felling. This can be partly explained by the greater extent of thinning work in the south-small cuts from small sites mean frequent moving of personnel and machines between sites. The small motor-manual work teams are easier to move than the machines.

In the north (region Bo l), greater distances between sites give rise to a high fuel consumption in the transport of machines and workers for motor-manual felling. Concerning mechanized methods, logging sites are larger, moving between sites is therefore less demanding, and emissions per cubic metre of harvested timber are lower compared to mechanized methods in the south or to motor manual methods in the north.

Conclusion

Our calculations show that final felling in the form of creation and removal of shelterwood give rise to somewhat higher emissions of CO* and NO, in both the north and south of the country as compared with clear cutting. The explanation for this is that the shelterwood system involves felling in several stages, with productivity in each stage being lower than in clear cutting. Another fact to be borne in mind is that the figures for clear cutting and shelterwood cutting apply to different types of stand and terrain. At present, the influence of -this factor on the results is beyond our control, which means that the figures presented here cannot be used for a straight comparison of felling

l.CA aspects in forestry operations: S. Berg

g C02/m3 g NOdm3

0

Bo 1

r-l 576

??moving of machines and personnel

0 felling

mo, ma mech mo me mech mo ma mech mo ma mech

100

90

80

70

60

50 40

30

20

10

0

cl ~n$%?z personnel

0 felling

Figure 4 Estimated emissions of COz and NO, from felling, travel to and from work and the moving of machines between sites. Combined figures for all types of felling with a breakdown by felling method and location.

systems. Similar considerations apply to the differences the levels constitute less than 1% of national CO, between north and south. emissions and only about 2% of NO, emissions.

The calculations on the study material show that motor-manual felling-give rise to lower emissions per cubic metre of harvested timber than mechanized felling. The magnitude of the difference between felling methods is so great that even the heavy deployment of resources for conveying personnel between home and work and between sites is not sufficient to balance this difference.

References

The work presented here demonstrates that the LCA technique can constitxrte one of many methods for assessing the environmental impact of logging. How- ever, the findings should be weighed against other aspects on the mat&agenrexrt s.ystem.

Anon., Product Life Cycle Assessment-Principles and Meth- odology, Nordic Council of Ministers 1992. Nord 1992:9, Copenhagen. Anon,, Skogspolitiken infor 2000-talet. Huvudbettikande 1990 ars skogspolitiska kommittt. Statens Offentliga utredningar 1992:76 Jordbruksdepartementet, Stockholm, 1992. Lundstrom, A., Nilsson, P. and Siiderberg, U., Avverknings- berlkningar 1992. Llnsvisa resultat. Swedish University of Agricultural Sciences, Department of Forest Survey. Report 56, 1993.

It also should be emphasized that emissions from the combustion of fossil fuels in forestry do not constitute a significant problem in Sweden. The estimated total emission 1eveLs of GO, and NO, in Sweden in 1993 were 59 million and 400 090 tonne$. Estimates of total emissions from the forestry sector7 show that

Hellstrom, C. and Westerbcrg, D., Prestationer och kostnader 1990 i det storskaliga skogsbruket. Forskningsstiftelsen Skogs- arbeten. Resultat nr 3, 1991. Freij, J. and Tosterud, A., Det storskaliga skogsbrukets system och metoder. Drivning, skogsvard och vlgar 1987-1992. For- skningsstiftelsen Skogsarbeten, Redogorelse nr 6, 1989. Landstrom, M., Skogsbrukets branslefijrbrukning och avga- semissioner i Sverige. SkogForsk. Stencil 1994-09-30. Berg, S., in Life Cycle Analysis--a Challenge for Forestry and Forest Industry, ed. A. Frtihwald and B. Solberg. EFI Proceedings no. 8. Anon., Statistical Yearbook of Sweden 1996. Official Statistics of Sweden, Stockholm, 1995.


some aspects of lca in the analysis of forestry operations

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