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Espacios. Vol. 37 (Nº 26) Año 2016. Pág. 1

Economic Viability of Tree Stump Extraction X Tree Stump Reduction

Viabilidad económica para la extracción de tocones de árboles

Letícia Mantovani STEIN 1; Romano TIMOFEICZYK JUNIOR 2; David Alexandre BURATTO 3; Rodrigo Medeiros RIBEIRO 4

Recibido: 28/04/16 • Aprobado: 23/05/2016

Contents

1. Introduction

2. Material and Methods

3. Results and Discussions

4. Conclusions

References

1. Introdução

Brazil has about 7.2 million hectares of planted forests, of which 5.1 million are occupied by species of Eucalyptus (ABRAF, 2013) corresponding to 71% of the total area of planted forests. The fats growth, broad range of use and adaptability to different soil and weather conditions warrant such success. Despite being a native from Australia, has adapted very well to the soil and weather conditions in Brazil, which now has the most productive forests in the world (EMBRAPA, 2010).

The eucalyptus production cycle for paper and pulp ranges from 6 to 7 years. After forest harvesting can be carried out seedlings by replanting (reform of the area) or conduct of budding (coppice). Currently the forestry sector has been carrying out a large volume of stands of reforms in order to maximize production in a given area (BUSCARATO, 2007)

The reform areas the stumps reduction is the largest part of the operating costs. In addition, this directly conditioned activity to the type of equipment used (SEIXAS; MENDO, 1990). Some of the more traditional equipment to reduction or removal are chain saw blade KG, fillister BP and milling machines (crushers). The stumps left by forest harvesting in reform areas are responsible for operating income decline of silvicultural operations. These often difficult mechanization, preventing traffic and operation of machines and their implements. The stumps reduction operation, usually used in the north coast of Bahia as a solution to the problem, it is a very expensive activity for forestry. Still remembering that this operation does not remove the portion of the stump and the roots that are below ground level.

The reduction with chainsaw has some advantages such as not limiting declivity, it allows the residue selling and makes ease to find service providers. However, this high cost of operation, low operating income and presents ergonomic problems: requires a previous cleaning the stumps, does not cut close to the ground and has a high regrowth rate of the strains (LEMOS, 2006).

Crushers perform reduction to the ground height. They consist of metal cylinders with teeth or knives wear resistant, which are triggered by mechanical or hydraulic force being assembled in: tractors, hydraulic excavators or specific machines manufactured solely for this purpose. These have advantages over other methods because perform reduction at ground level, without removal and causing little damage, therefore, are currently the most used in the forestry sector (CASSELLI, 2013).

In the search for new alternatives, a new machine to extract stumps, able to reduce silvicultural costs, appeared on the market. This method includes the stumps reduction to make the areas of the third and fourth cycle mechanizable again, bringing benefits to the following operations involving the preparation of soil. However, it is necessary for companies to assess the operational and economic costs of stumps extraction activity for their areas.

The extraction of stumps activity can present economy following a forest planting, since the extraction promotes disturbance and disaggregation of the soil, leading to a possible reduction of level in the subsoiling activity.

Based on these assumptions, this study aimed to assess the cost of extracting (removal) stumps replacing stumps reduction in areas of forest reform in the coast of Bahia state.

2. Material and Methods

The study area comprised twenty-one cities of the region known as North Bahia Forest District, Brazil, a region situated between latitudes 11°16'10 '' and 12°36'17 '' S and longitude 38°59 '15' 'and 37°25'19' 'W. The cities included were:  Acajutiba, Água Fria, Alagoinhas, Aporá, Araçás, Aramari, Biritinga, Cardeal da Silva, Catu, Conde, Crisópolis, Entre Rios, Esplanada, Inhambupe, Itanagra, Jandaíra, Mata de São João, Olindina, Ouriçangas, Rio Real e Sátiro Dias.

The forest stands are deployed on podzolic soils, latosols and quartz sands. The wavy relief there is a predominance of red yellow podzolic and relief plans (trays) and soft wavy occur latosols and yellow podzolic, with or without a quartz sands. The gray podzolic occur on the lower slopes of the trays and basin areas with imperfect drainage. Near the coast occur marine quartz sands.

The stumps reduction , usually used in areas of forest reform on the north coast of Bahia, aims to lower stumps and grinding forest residues in the crop row in areas after harvest. The activity and waste grinding were divided into four different levels, taking into account the degree of difficulty of each, as follows:

Level 1 - All areas with a stump diameter less than 30 cm and average height of 30 cm with or without sprouting up to 1.5 m high, the presence of forest residues from the harvest with an average diameter of up to 10 cm, areas leveled ditches without any soil texture, plant spacing of at least 2 m in the reduction line. Reference to 1 h.machine.ha-1;

Level 2 - All areas with a stump diameter less than 40 cm and average height of 40 with or without sprouting up to 2 m high, It may have been conducted in the previous cycles budding, the presence of forest residues from the harvest with an average diameter of up to 10 cm, areas leveled ditches without any soil texture, plant spacing of at least 2 m in the reduction line. Reference to 1,25 h.machine.ha1;

Level 3 - - All areas with a stump diameter less than 50 cm and average height of 50 cm with or without sprouting up to 2 m high, It may have been conducted in the previous cycles budding, the presence of forest residues from the harvest with an average diameter of up to 10 cm, areas leveled ditches without any soil texture, areas affected by wood theft, fire and other accidents, minimum spacing between the plants 2 m na linha de in the reduction line. Reference to 1,5 h.machine.ha-1

Level 4 - Special areas conditions with average diameter of stumps up 50 cm and average height of 50 cm with or without sprouting up to 3 m high, the presence of forest residues from the harvest with an average diameter of up to 10 cm, areas leveled ditches without any soil texture , areas affected by wood theft, fire and other accidents, minimum spacing between the plants 3 m in the reduction line. Reference to 1,75 h.machine.ha-1;

For cost analysis, the software Excel 2010 were used , which compared the stump reduction and extraction activities considering three factors: operating costs, operating costs plus soil preparation costs and operational savings.

In the first analysis of costs were considered operating costs of extraction activities and reduction of stumps. Knowing that the first varies depending on the distance to the woodchip buyer and the second varies depending on the level of reduction, it was created a decision matrix, where it's possible to find which activity has lower operating costs in every situation. In the second analysis, were considered the operating costs of extraction activities and stumps reduction  added operating costs of soil preparation activities (subsoiling and phosphating). It was compared the stump reduction costs plus soil preparation with stump  extraction costs plus soil preparation , as well stump reduction plus soil preparation with a reduction of level plus soil preparation. From the information generated was created two matrix, which show what activity has the lowest operating costs in every situation. For both analyzes, the symbols were adopted "EX" for when the lowest cost for the extraction of stumps and "RB" for when the lowest cost for the stumps reduction.

In the third analysis was estimated the operational savings that extraction can bring compared to stump reduction. It was also estimated operational economy based on different levels. For both were considered the operating costs of extraction activities and stumps reduction added operating costs of soil preparation activities (subsoiling and phosphating). two matrices were generated for better visualization of the results

3. Results and Discussions

Operating income and operating unit cost of stumps reduction activity, practiced in areas of forest reform on the north coast of Bahia, are shown in Table 1, according to the operational levels to which the activity was divided.

Table 1. Operating income and operating unit cost of stumps reduction activity and stumps extraction.

The extraction activity showed a operational efficiency from 4 to 7 stumps / minute / machine and the operating unit cost, which varies with the distance from the extraction area to the woodchip purchaser. From the operating unit cost of both activities, was made a analysis of the data generated with the decision matrix presented in Picture 1.

Picture 1. Decision Matrix: lower cost activity
Where: EX: stumps extraction was the activity with the lower cost;
RB: stumps reduction was the activity with the lower cost.

For areas with distance up to 130 km from the woodchip buyer, the lower cost was the stump extraction, regardless of the degree of difficulty of the area (level of reduction). For distances 131-160 km, stumps reduction introduced lower cost for level 1 and the distances 161-190 km reduction presented lower costs for levels 1, 2 and 3.

For short distances to the woodchip buyer operating costs for extraction was significantly lower than the operating costs for stump reduction. While the extraction has cost R$ 400.00 / ha, for distances below 100 km, reduction can cost up to R$ 1231.00 / ha according to the level adopted for the area.

For economic analysis was considered, besides clean area method (extraction or demotion), the type of soil tillage (subsoiling and phosphating). Table 2 shows the operating unit cost of tillage, subsoiling and phosphating according to the depths and operational levels spacing of 3.5 meters between lines.

Table 2. Operating unit cost (US $ / ha) of soil preparation, subsoiling and phosphorus depending
on the depths and operational levels with 3.5 meters of space between lines

Where: DMB: machine developed for subsoiling and phosphate applications simultaneously; D6 and D8: bulldozers

Subsoiling was performed with DMB - developed machine for subsoiling and phosphate applications simultaneously. In order to standardize the calculation, the operating cost of subsoiling performed with D6 and D8 (both track-type tractors) was added to the operating cost of phosphating activity, R$ 224.82 / ha, which was held immediately following the subsoiling. The removal of stumps and root biomass, as weel the longer use of driving machines for this use, could potentially greater compression than in areas that have a more conventional process. (VESA E PALANDER, 2010)

On the basis of the operating cost of the activities of extraction and stumps reduction and considering that is possible a economy due to a reduction of level in soil preparation, was performed the economic analysis, generating the decision matrix, which show what activity was more feasible in each situation, taking into account the soil tillage type.

For the preparation of soil to 60 cm of depth the reduction was more feasible to larger distances and presents no cost difference when assumed the possible reduction level provided by the extraction, seen that we adopted the subsoiling with DMB as the minimum of soil preparation to be adopted in the areas.

On the basis of the operating cost of the activities of extraction and reduction and that there may be economy due to a possible reduction of level in soil preparation, was made to economic analysis, generating the decision matrix presented in Picture 2, which shows which activity had the best results in each situation, i.e. with lower operational cost, taking into account, in addition to the method of clean area (extraction or reduction), the type of soil preparation.

The soil tillage with 60 cm deep, reduction had lower costs over longer distances (Picture 2), and no difference in cost when assumed the possible reduction of the level due to the extraction, as the subsoiling was used with DMB as minimum tillage to be adopted in the fields.

Picture 2. Decision Matrix: Activity with the lower operating costs for tillage to 60 cm

Where: EX: stumps extraction was the activity with the lower cost; RB: stumps reduction was the activity with the lower cost.

The Picture 2 shows the economic viability of the extraction in level 4 areas, regardless of the distance of transport. As for the level 2 and 3, when the transport distance exceeded 160 kilometers, the operation with greater viability was stump's reduction. For level 1 areas the stumps extraction was viable at distances less than 130 km. For soil tillage with 90 cm, the generated decision matrix is presented in Picture 3.

Picture 3. Decision Matrix: Activity with the lower operating costs for tillage to 90 cm

Where: EX: stumps extraction was the activity with the lower cost; RB: stumps reduction was the activity with the lower cost.

The Picture 3 shows that the viability of the extraction is inversely proportional to increasing the transmission distances to the woodchip purchaser, that is, the greater the distance, the more onerous is the extraction operation. It was noted that the stumps extraction was made possible in 90% of cases when there was a reduction of soil preparation level due to extraction. For soil preparation to 110 cm, the generated decision matrix is presented in Picture 4.

Picture 4. Decision Matrix: Activity with the lower operating costs for tillage to 110 cm

Where: EX: stumps extraction was the activity with the lower cost; RB: stumps reduction was the activity with the lower cost.

Picture 4 shows, that the stumps extraction was possible in 72% of situations. When considered reducing tillage level extraction was viable in 88% of situations. It was observed that the cost of stumps reduction operation in critical areas (greater operational level) was so expressive, which makes possible the extraction and transport stumps even at greater distances.

It was noted that there is no reduction of level with tillage to 60 cm since it was adopted subsoiling with DMB as the minimum tillage. According to the analysis, the economy in the pre-plant operating costs can reach 831.00 R$ / ha depending on the distance of extraction and reduction level.

When the extraction provided the reduction of level in tillage situations that have potential for extraction increased from 73% to 89%. The economy in the pre-plant operating costs can reach 950.03 R$/ha for reduction vs. extraction and 1449.76 R$ / ha for redcution vs. extraction with a reduction of level in the subsoiling activity.

The economy in the pre-plant operating costs can reach 1237.88 R$ / ha for reduction vs. extraction and 1655.70 R$ / ha for reduction vs. extraction with a reduction of level in the subsoiling activity. In some cases the stumps reduction still presents itself as the best option, especially in cases where the reduction is in the lower levels and the extraction is greater distances woodchip buyer.

Smith and Wass (1991) says that the extraction of stumps and roots can result in initial productivity gains in the therms "above ground". However, these are reversed in the long therm because of the soil disturbance. These authors add that impacts of withdrawal operations may be related to each species. Thus, it is interesting the kind of variation that can occur in each case.

4. Conclusions

The extraction of stumps is shown as a viable alternative from an economic point of view, with lower cost than the reduction of stumps, for most situations, the feasibility tends to fall according to the distance required to woodchip buyer.

The reduction of level in soil preparation caused by stumps extraction makes extraction more attractive economically to stump reduction in most scenarios analyzed, with the economy in pre-plant operating costs that can reach up to R$ 1,655.70 / ha.

Operationally it is still necessary to test and verify possible limitations that may occur depending on the characteristics and soil conditions on the north coast of Bahia.

References

ANUÁRIO ESTATÍSTICO DA ASSOCIAÇÃO BRASILEIRA DE PRODUTORES DE FLORESTAS PLANTADAS (ABRAF), Ano base: 2012. Brasília: 2013. 148 p.

BUSCARATO, E. A. Medição de forças no corte de raízes de cepas de espécies de Eucalípto. 101 f. Dissertação (Mestrado em Engenharia Agrícola) - Universidade Estadudal de Campinas, Campinas, 2007.

CASSELLI, V. Remoção de tocos de eucalipto com sistema de serra tubular. Piracicaba. 2013. 111p. Dissertação (Mestrado em Recursos Florestais) - Escola Superior de Agricultura "Luiz de Queiroz", Universidade de São Paulo, Piracicaba, 2013.

EMBRAPA. Sistemas de produção. Eucalipto. 2010. Disponível em: http://sistemasdeproducao.cnptia.embrapa.br/FontesHTML/Eucalipto/CultivodoEucalipto_ 2ed/Aspectos_Eucaliptocultura.htm. Acesso em: 25/09/2014.

LEMOS, A.V.; SIMPÓSIO DE TÉCNICAS DE PLANTIO E MANEJO DE EUCALYPTUS PARA USO MÚLTIPLO, 1., 2006. Piracicaba, 2006. 60p.

SEIXAS, F.; MENDO, L.J.L.Teste de implemento para rebaixamento de tocos em raízes de reforma de povoamento de eucalipto. Circular Técnica, IPEF, Piracicaba, n.173, p. 1- 6, Jun.,1990.

SMITH, R.B., WASS, E.F., Impacts of two stumping operations on site productivity in interior British Columbia. Forestry Canada, Info. Rep BC-X-327.1991

VESA, L. AND PALANDER, T., (2010), Modeling stump biomass of stands using harvester measurements for adaptive energy wood procurement systems, Energy, 35, issue 9, p. 3717-3721, 

1. Specialization in Forest Management from the Universidade Federal do Paraná - UFPR Forest Engineer, Bahia Specialty Cellulose / Copener Florestal
2. Doctor in Forest Sciences, Professor, Department of Agricultural Economics and Extension of the Federal University of Paraná - UFPR, Curitiba / PR, Brazil.
3. PhD student in Forest Engineering from the Federal University of Paraná - UFPR, Curitiba / PR, Brazil. Email: davidburatto@yahoo.com.br

4. PhD student in Forest Engineering from the Federal University of Paraná - UFPR, Curitiba / PR, Brazil.