SUSTAINBLE SOLAR ENERGY KILN TO DRY EUCALYPTUS IN

PERU

MÓNICA ALVAREZ

WOOD 493

A Report Submitted in Partial Fulfillment of the Requirements for the Degree of

Bachelor of Science in Wood Products Processing

in

THE FACULTY OF FORESTRY

THE UNIVERSITY OF BRITISH COLUMBIA

April 2009

ii

Abstract

The purpose of this report is to evaluate the suitability of producing value added products

from eucalypts in Peru. Information from FAO and INRENA was used to analyse the

potential that Peru has to plant, grow and produce good quality eucalyptus wood. The

opportunities for eucalyptus wood in the market appear to be favourable especially for

furniture and other interior products. While searching for sustainable solutions to process

eucalypts to enhance the Peruvian wood industry, some problems were found during the

manufacturing of this genus. The main problems during the processing of eucalypts occur

during the drying process. Drying of eucalyptus requires care due to the tendency its wood

cells have to collapse, which causes excessive shrinkage and fibre separation or checks.

Eucalyptus wood needs to dry at low temperatures and in a high relative humidity

environment at least during the first stages of the process. The drying of eucalyptus has been

a challenge, and research has been done around the world to find the optimal method

according to the needs and resources of the individual countries. Countries such as Australia,

Argentina, and Brazil, have done studies to find the best trees, growing rates and drying

methods to minimize the defects on the wood at the desired final moisture content. Recently

there has been an increasing interest in using solar kilns to dry eucalyptus especially in

developing countries. The drying of eucalyptus using a solar energy kiln in Peru can be the

best alternative. The solar kiln for hardwoods designed by Dieter Steinmann in 2006 seems

to be a good fit for the Peruvian Industry. Not only are the initial investment for construction

prices low, but also the need for expertise and supervision during its performance is minimal.

Many locations in Peru satisfy the environmental requirements that this kiln needs to be able

to execute.

Key words: Eucalypts, drying, solar kiln, moisture content, value added wood products

iii

Table of contents

SUSTAINBLE SOLAR ENERGY KILN TO DRY EUCALYPTUS IN PERU ................ i

Abstract .................................................................................................................................... ii

Table of contents .................................................................................................................... iii

List of Tables .......................................................................................................................... iv

List of Figures .......................................................................................................................... v

Introduction ............................................................................................................................. 1

Peru and Eucalyptus ............................................................................................................... 1

Utilization of Eucalyptus ........................................................................................................ 5

Drying Eucalyptus wood ........................................................................................................ 7

Steinmann’s Solar Energy Kiln Design .............................................................................. 10

Steinmann Kiln ................................................................................................................... 11

Parts..................................................................................................................................... 13

Operation............................................................................................................................. 14

Advantages and Disadvantages ........................................................................................... 14

Conclusions ............................................................................................................................ 16

Literature Cited .................................................................................................................... 17

Appendices ............................................................................................................................. 19

iv

List of Tables

Table 1. Peruvian Forest and other wooded land .................................................................... 2

Table 2. Drying costs for spotted gum and blackbutt ............................................................. 7

v

List of Figures

Figure 1. Front view of Steinmann’s Solar Energy Kiln ...................................................... 11

1

Introduction

Value added products are the present and the future for obtaining the major economic value from

logs. The Peruvian forest land is an asset with the potential to increase the economic growth of

the country. The heterogeneity of the native forests and the low investment in technology

complicate harvesting and management plans limiting the traditional Peruvian wood industry to

small scale production companies (FAO, 2008). There is currently increasing interest in

establishing plantations for wood production. The majority of established plantations in Peru are

from exotic species such as pine and some eucalyptus species (FAO, 2008). Therefore, there is

also interest in utilizing eucalyptus wood for value added products. The drying of eucalyptus

species however, is difficult and is one of the major concerns when considering its use for

manufactured wood products such as furniture, flooring, and engineered products, amongst

others. Low temperatures need to be used when drying eucalyptus to avoid the collapse of wood

cells, and this can be achieved with solar drying. Other methods like air drying or conventional

kiln drying can be used to dry Eucalyptus wood; but using solar energy kilns, particularly the

design of Steinmann, can be a more economically feasible solution for Peru. In this essay I will

discuss the benefits of utilizing eucalyptus wood in Peru. I will also present and compare the

characteristics of using three different drying methods: air drying, conventional kiln drying and

solar energy kiln drying. I will argue that choosing Steinmann’s ―Homebuilt Solar Kiln for

Hardwoods‖ is the best and most sustainable option for drying eucalyptus in Peru during this

early stage.

Peru and Eucalyptus

Forest land covers about 53.5% of Peru. Peru has three natural regions: the coast, the highlands

and the jungle. Peru has more than 1 million hectares of potential forest land in it’s the coastal

2

region. The mountainous region has an even greater area ―suitable for forest use‖ (FAO, 2007),

that has already been planted with exotic pine and eucalyptus species (Eucalyptus globulus, E.

viminalis, E. bicostata, E. camaldulensis, and others) (FAO, 2007). Peru’s forest can be divided

into five main categories: primary, modified natural, semi-natural, productive plantation and

protective plantation (see table 1).

Table 1. Peruvian Forest and other wooded land. (FAO, 2006)

FRA 2005 categories Area (1000 hectares)

Forest Other wooded land

1990 2000 2005 1990 2000 2005

Primary 62, 910 62, 188 61, 065 - 1, 912 2, 213

Modified Natural 6, 983 6, 310 6, 923 - 20, 220 19, 919

Semi-natural 0 0 0 - - -

Productive

plantation

263 715 754 -

Protective plantation - - - - - -

Total 70, 156 69, 213 68, 742 - 22, 132 22, 132

Peru has one of the biggest and richest tropical rainforests in the world with vast biological

diversity and natural resources (WWF, 2009). Due to the heterogeneity and diversity of species

found in the Peruvian forest, the harvesting of wood for large scale industry is difficult.

Transport within the forest is mainly by water or by air. These ways of haulage add a constraint

when doing business, especially for the wood industry. The majority of the wood manufactured

products and the wood furniture produced in Peru are consumed by the national market. The

biggest international market for Peruvian sawnwood is the United States of America (USA),

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which consumes 74.12% of Peru’s, valued at $83,597,000 in 2006 (FAO, 2009). The USA is

currently mainly interested in wood for construction, but the use of wood for furniture maybe a

better use for Peru’s wood because highest value can be extracted from logs especially in the

case of custom designs. The opportunities for using eucalyptus wood to manufacture value

added products could be a profitable solution for the Peruvian wood industry. The comparably

higher growth rate of Eucalypts, together with the opportunity to harvest it from homogenous

plantation, can facilitate increased focus and efficiency for industry.

Eucalyptus species were introduced to Peru around 1860 (FAO, 2008). Eucalyptus trees and

resources are already a part of many Peruvian communities. The Eucalyptus genus in the

Myrtaceae family is native to Australia and consists of around 700 tree species (Grattapaglia,

2008). Eucalypts are sources of hardwood, pulp and paper, oils and floral beauty. Transforming

eucalyptus wood into value added products has greater economic potential compared to its use

for firewood and round timber. The quality of the fibre produced in the early stages of tree

growth is very suitable for the pulp and paper industry, but the pulp and paper industry requires a

big initial and continuous investment that is beyond the means of Peru. Hence the use of

Eucalyptus as sawlogs for value added products maybe a better option for Peru. It is now a

matter of choosing the best genetic material, management and utilization of technologies to get

the highest value from eucalyptus in Peru.

Eucalyptus globulus has been the most planted species in Peru (Luzar, 2007). According to

Waugh (1995), E. globulus is unsuitable for round timbers because of its propensity for end-

splitting and surface checking during drying. On the other hand, E .globulus is ―good‖ and

―acceptable‖ for the production of sawn engineering, and appearance products, engineering

veneer, fibre composites and pulp and paper products (Waugh, 1995). Nevertheless there is still

4

a need to develop appropriate technologies to process eucalyptus in developing countries and

utilize its sawnwood for value added products.

Eucalypts plantations can be used in short rotations because of their rapid growth, especially in

the first 10 to 15 years. One of the issues with growing Eucalyptus in Peru is that it does not

regenerate naturally; each tree needs to be individually planted (FAO, 1998). The physical and

mechanical wood properties of grown Eucalypt trees are controlled not only genetically, but also

through the specific management practices and the trees’ environment (Sánchez Acosta, 1999).

Research on wood processing and manufacturing techniques cannot be generalized for every

Eucalyptus species; experiments and specifications should be done separately to obtain better

and more accurate results.

The volumes of wood production by species collected in 2007 by the Instituto Nacional de

Recursos Naturales of Peru (INRENA), places eucalypt (Eucalyptus spp) in the first place in the

production of round wood with 333 170,36 m³(see Appendix A). The volume of round wood

produced is much greater than the volume of sawnwood, 54 334, 69 m³ (INRENA, 2008).

Eucalypt species are used in large quantities by small communities for firewood and also as

round timber for posts and power poles. The economic value that can be obtained from

sawmilled eucalyptus species and value added products could greatly exceed the current profits

from round timber if appropriate policies and technologies were applied. To be able to utilize

Eucalypt wood, the government and/or the wood industry needs to believe in the benefits of the

final products and invest in the necessary technology to produce good quality products in the

most efficient way.

5

Utilization of Eucalyptus

Conversion of eucalyptus to value added products can be difficult because of problems related to

grading, drying, and milling. One of the major concerns is the drying process (Oliver, 2000),

which is necessary when preparing wood for manufacture furniture, flooring and engineered

wood products.

Eucalyptus fibres from trees grown in plantations tend to have thin walls, which make the wood

very suitable for the pulp and paper industry, but this characteristic is not very helpful for the

manufacturing of wood products. The thin walls suffer collapse if specific requirements of

temperature and humidity during drying are not followed. The collapse of wood cells causes

excessive shrinkage while drying and fibre separation or checks also develop (Oliver, 2000).

Checking can be classified into internal checking (discovered during manufacturing), surface

checking and separation of rings (shakes). Defects during drying are more prone to occur in

wood from young eucalypts, especially if they come from plantations (Hillis and Brown, 1984).

This wood usually has lower density and wider growth rings. Eucalyptus wood from plantations

can also have many significantly different chemical and mechanical properties compared with

wood from native forests. Even within the same species, and grown under the same

environmental characteristics, there is a large within species variability in wood properties (Hillis

and Brown, 1984). Advantage could be taken from this variation, and together with the

advancements in process technologies there is opportunity to manufacture eucalypts for value

added products.

Many countries see the drying of eucalyptus as a challenge, and have focussed on developing

viable options to avoid the defects produced during drying. For more than 60 years, studies have

been taking place in Australia to reduce the excessive degrade during drying that appeared with

6

older and bigger diameter Eucalypts (Hillis and Brown, 1984). Now, that the majority of

Eucalyptus wood used comes from plantations and regrown forests. As mentioned earlier,

Eucalypts do not regenerate naturally in Peru; therefore the selection of trees to be planted

should always be done carefully.

Neighbouring countries to Peru, like Brazil and Argentina, have been trying to find the most cost

efficient techniques to dry Eucalyptus according to the end product. Numerous studies have

taken place in these countries to enhance the production and utilization Eucalyptus wood. In

Argentina, for example, the industry is not only producing, but also specializing in the

production of, parquet from Eucalyptus wood (Sanchez Acosta, 1999). This product has shown

enormous development as a result of managing the difficulties during the different processing

steps, including drying. In Brazil, aside from their huge development of their pulp and paper

industry, they have also been working on new alternative ways of processing the eucalypts wood.

The production of E. grandis lumber as a replacement for tropical woods such as Brazilian

cherry (Hymenaea courbaril), Muirapiranga (Brosimum rubescens), Tatajuba (Bagassa

guianensis); has been one of the greatest advances in Brazil in the last 20 years (Jankowsky and

Gonçalves Luiz, 2006).

Different Eucalypt species are suitable for different industries according to their origin and their

management. The transformations they undergo depend on their end use and their costs during

the processing. Some Eucalypt species are better for pulp and paper (E. globulus, E. regnans, E.

nitens, E.grandis), other for round timber (E. maculata, E. cladocalyx, E. camaldulensis, E.

sideroxylon), other for flooring or furniture (E. saligna, E. sideroxylon, E. maculate, E. nitens, E.

cladocalyx, E. botryoides, E. grandis) (Waugh, 1995). It is possible to obtain a good final

7

product quality from Eucalyptus, but the best methods for processing for individual species need

to be determined.

Drying Eucalyptus wood

Over time, the methods to dry wood have evolved and have been adapted to different situations

according to the needs and resources of the industry. Eucalyptus wood needs to be dried slowly

at low temperatures and high relative humidity especially during the first stages of drying (Hillis

and Brown, 1984). Wood in general shrinks when it loses moisture below the fibre saturation

point, but the amount of water and temperature are not homogeneous throughout the piece being

dried. The surface dries first and creates a gradient throughout the pieces that generates internal

stresses that can lead to defects such as surface checks, separation of fibres and collapse (Oliver,

2000). ―Tendency to collapse can be detected from measurements of shrinkage against moisture

content‖ (Oliver, 2000, (Innes, 1997)). Even though some of the defects can be removed during

reconditioning, the best option is to avoid them from the beginning. Methods that work better

and faster might not be profitable enough due to the time to recover the investment costs. The

drying methods that will be presented and discussed here: Air drying, conventional kiln drying

and solar energy kiln drying.

Air drying is the method that takes the longest to dry eucalyptus wood, requiring from 3 up to 10

months, to obtain final moisture content (MC) of 12% to 20%. The drying period and the final

moisture content depend on the species, wood thickness and the environment’s arrangement and

condition (Simpson, 1999). The required MC for high end quality products ranges from 5% to

15% according to the relative humidity of the environment where the wood is dried (DeWitt,

2002). Air drying can be a good and cheap starting point to pre - dry Eucalyptus wood, if the

8

cost of carrying inventory is not significant. It is quite a long process and the wood will most

likely need to pass through another more sophisticated drying method to get to the desired final

moisture content to machine it. Wood is usually transferred to a conventional kiln after air drying

when its moisture content is between 20% and 25% (Simpson, 1999). These two methods

might need to be scheduled together with reconditioning or moisturizing processes, like steaming

or spraying.

The most common wood drying method is conventional kiln drying. Conventional kilns are built

to work at temperatures between 40°C to 90°C, reached by a heating system that consists of

pipes which are channels that use steam as a heating fluid. Kilns have fans working on the

movement of air through the wood stacks, and they also have vents which act as regulators

exchanging the air from inside and outside the kiln. It is very important that the kiln has a

spraying system that moisturizes the air; this is a very important issue when drying Eucalyptus

(Jankowsky and Gonçalves Luiz, 2006). Wetting the surface of the wood is important to

maintain the moisture gradient throughout the piece as homogeneous as possible. Because of the

high temperatures at which conventional kilns work, this method is not the best choice for drying

Eucalyptus wood when the moisture content is still too high (Jankowsky and Gonçalves Luiz,

2006). Low temperatures could be set to dry Eucalyptus inside a conventional kiln, but the

process would take too long and it would also be a waste of energy and money. Some costs per

cubic meter of drying spotted gum (Corymbia macualata) and blackbutt are given below

(Eucalyptus pilularis) (see Table 2). This study was done by Davies and Palmer at the

Department of Primary Industries and Fisheries in Queensland. The input costs are: financial

variables, kiln design, process specification, energy consumption and prices, labour, land and

others (Davies and Palmer, 2005).

9

Table 2. Drying costs for spotted gum and blackbutt (Davies and Palmer, 2005)

Seasoning Method/Kiln Type Average cost

Single- stage drying

Conventional Kiln drying above 70ºC using LP gas fuel on a small scale $100.30/m³

Conventional Kiln drying above 70ºC using wood waste fuel on a large scale $149.50/m³

Conventional Kiln drying below 70ºC using LP gas fuel on a small scale $228.51/m³

Two- stage drying

Exposed pre-drying in the air and conventional kiln final drying $52.73/m³

Covered pre-drying in the air and conventional kiln final drying $61.39/m³

The advantage of using CK in the last stages of drying is that the system makes it possible to

obtain a low moisture content under the fibre saturation point. Regardless of the stage of drying

where CK operate, it should work hand in hand with a steaming process (see Appendix B) to

recondition or prepare the wood before, after or during drying. Even though the final product

quality reached with conventional kilns when drying eucalypts can be satisfactory, the costs

needed to build, adjust, supervise and combine it with other methods cannot be currently justified

by the profits of the Peruvian Industry.

A solar energy kiln uses a system that collects the energy from the sun to heat up the space

where wood is adequately stacked and ready to be dried. Because the energy of the sun has a

low intensity compared to the usual energy generators (electrical, gas, etc), its use is currently

effective only for some applications (Wengert and Oliveira, 1985). The highest temperature

achieved in a solar kiln is a round 60°C, which is fairly low compared to the temperatures that

can be attained using conventional drying (De Vore, Denny and Harper, 1999). Depending on

the design, the amounts of energy lost can also be comparably higher (Wengert and Oliveira,

10

1985). Solar kilns are usually less costly to build than conventional kilns. The energy

consumption costs can be almost zero if the fans run with solar energy. From previous research

done in countries like Brazil, an average saving on investment and electrical energy costs are

about 50% compared to kiln drying (Jankowsky and Gonçalves Luiz, 2006). For a country like

Peru where large investments, especially in the wood industry are unlikely, building a solar kiln

instead of a conventional kiln can reduce the costs for the industry.

It is not only the financial aspects that make solar kilns attractive. As mentioned earlier, the

drying rates and temperatures required to dry the majority of eucalyptus species need to be low

to decrease the development of drying defects. There are many solar kiln designs that work best

for specific latitudes, weather conditions and species. Steinmann’s homebuilt solar kiln for

hardwoods however, looks like it has many characteristics to make it suitable for the drying of

eucalypts in Peru.

Steinmann’s Solar Energy Kiln Design

Solar energy is the power that can be collected from the sun to perform a variety of functions.

Solar energy systems can be roughly divided into passive and active solar systems. Active solar

systems collect and transform the energy with the assistance of mechanical equipment; while the

passive systems utilize the intrinsic energy of the sun (orientation, movement, radiant energy)

(Kadulski, 2009). Solar kilns are categorized into three basic types: greenhouse, semi-

greenhouse and opaque walls. These three types of kilns are mainly designed using a passive

solar system, unless the profits justify investing in an active system (Wengert and Oliveira,

1985).

11

Usually, every solar kiln has a collecting system that needs to have a specific size and orientation

towards the sun. The collector needs to have a surface that receives the energy of the sun to be

later used as heat to dry the stacks of wood. The collecting surface is called glazing. The

collector can be the kiln chamber itself in the case of the greenhouse design, where the roof and

3 of the walls are made of the glazing material. The collector can also be outside the kiln with

the aid of an absorber, in the case of opaque kilns. The glazing needs to be of a clear or almost

transparent material such as glass, rigid sheets of fibreglass reinforced with polyester panels or

polymer plastic films (Mylar®, Tedlar®, Kalwall®, and others) (Wengert and Oliveira, 1985).

The glazing can be composed of one to three layers, depending on the drying expectations and

the budget to be spent on construction (Wengert and Oliveira, 1985). The solar kiln designed by

Steinmann is a greenhouse type and uses two layers of ultra-violet stabilized transparent plastic

sheet for the roof and sides. This kiln does not need to face any specific direction. Even though this

design uses two layers of glazing, the kiln is cheap and easy to build, and has been designed with the

drying of eucalyptus in mind.

Steinmann Kiln

Steinmann, now with the Nelson Mandela Metropolitan University in George, South Africa,

designed and built a solar kiln which is a good option for the drying of Eucalyptus in Peru. This

kiln is a good fit for Peru because: (1), it does not need a large initial cost investment; (2), it

gradually achieves higher temperatures according to the independent drying rate of the wood

species; (3), it does not need much extra technology and manpower to supervise and regulate its

temperature and humidity; (4), it has low energy costs and its size fits the present supply and

demand of the industry. A rough indicator of the performance of this design is that 38mm thick

12

ironwood (denser than Eucalypts, but lower initial MC), can dry to 12% in 4 months (Steinmann,

2006).

The Steinmann kiln is designed to work in a sunny location that has a difference between day

and night temperatures of approximately 10°C. The design prevents the kiln from reaching

extreme conditions. It has a self-regulating feature that ―automatically adjusts the settings‖ of

the kiln in response to the daily temperature and humidity differences between the wood pieces

and the chamber (Steinmann, 2006). The solar kiln is self regulated daily with the changes in

temperature of the environment that affect the relative humidity of the interior of the kiln while

drying the wood. As the kiln warms up, the relative humidity drops. The stacks of wood

properly stickered need to be covered on the top and side with a tarpaulin that creates a tunnel

where the air is forced to pass through back into the plenum chamber. The warm air is circulated

through the wood stacks at 1.5m/s with the aid of a 3kw fan that is located in the wall that

divides the plenum chamber from the rest of the kiln where the wood is dried. The temperature

of the wood rises and the water starts to evaporate from the surface. The hot air rises to the top

of the kiln and it is blown by the centrifugal fan located on the roof of the kiln into the space

between the glazing layers. During the night, the warm air between the glazing layers will

eventually undergo condensation when the temperature outside the kiln reaches the inside’s dew-

point. The condensed water is drained out of the kiln through small weeping holes that are

incised on the outer layer where the water accumulates (this would need to be done after

observing where the accumulation happens. The cooled air is then fed back into the kiln through

feedback valves. During the night, the temperature is lower and the relative humidity inside the

kiln is still high. The wood stops being heated and its moisture content gradient is reduced. The

high relative humidity affects the rate of evaporation from the wood surface (Steinmann, 2006).

The progressive mild changes in the kiln conditions depend on the rate of moisture content (MC)

13

evaporated from the wood. This self-adjusting rate does not allow steep gradients that cause

stresses and drying defects in Eucalyptus wood (Steinmann, 2006). This solar kiln is economical

and easy to build compared to conventional kilns and even compared to other solar kilns. The

design is very simple and requires a low initial investment, even though the principles behind the

operation of the kiln are quite sophisticated. Specifications for the construction and the

principles that explain the system are given in Appendix C.

Parts

The main parts of the Steinmann solar kiln (these can be found in Figure 1):

Figure 1. Front view of Steinmann’s Solar Energy Kiln

The structure that supports the shape of the kiln is made out of wood or pipe.

GLAZING

14

The approximate costs of parts of the kiln are as follows:

Tarpaulin: $73.00

Glazing layer of 40*50 ft: $64.87

Fan: $550

Centrifugal fan of 65 watt: $200.

Operation

It is possible that because of environmental conditions in some regions, the initial temperatures

in the kiln may be too high. It is important that while the moisture content of the wood is above

30%, the temperatures of the kiln are measured and kept below 35°C. The temperatures can be

kept below this level by covering the kiln with a shade cloth (preferably not directly on top of the

surface of the kiln, Steinmann, 2006). Attempts to vent the kiln to lower its temperature would

alter the drying cycle. This solar kiln design can dry wood to 10% moisture content. The drying

time depends on the thickness of the wood, the species being dried and desired final moisture

content. Regardless of the drying method, the green wood needs to be immediately and

properly stickered and stacked after cutting to avoid warping. It is recommended to put the

stacks under a shaded area while they are not being dried in the kiln. Once the kiln is empty, the

stacks of wood are loaded inside it with a small forklift. The position of the wood pieces should

be lengthwise perpendicular to the air circulation path.

Advantages and Disadvantages

The kiln consumes electric energy due to the utilization of the fan and the centrifugal fan. The

use of a solar panel to generate energy to run the fans is not justified at present because of the

15

high cost of solar panels. The small quantities of electric energy used can be justified

economically.

It has been determined that the solar kiln will take about 20% longer to dry eucalyptus than

conventional drying (Steinmann, 2006). This extra drying time is not a big disadvantage, and is more

than offset by the savings in the construction and operation of the kiln. The cost of building this

solar energy kiln is approximately $5 241.48. This amount is comparably lower than the cost of

building a modern conventional kiln, which costs around $131,037.00 (Steinmann, 2006).

This solar kiln does not need to work in combination with any other drying method to obtain the

desired final moisture content. It only needs to follow the construction and operation guidelines

(see Appendix C).

16

Conclusions

Eucalypt trees have rapid growth and can be exploited for multiple uses. In response to the local

conditions and international market demands, it appears that the most profitable opportunity for

eucalyptus wood in Peru is to convert it into high quality solid hardwood furniture, flooring, and

other interior products (Oliver, 2000). Peru already has high end hardwood products from native

species, but the availability of these specific species is declining and is inadequate to satisfy

market demands. From an environmental and economic point of view, the use of eucalyptus

wood as a substitute to native Peruvian hardwood species makes sense (instead of only using it

as for firewood, veneer, posts and sleepers). For this new option to occur, there is a need to

convince the industry that the wood from eucalypts can be processed, and that the technologies

for processing can be adapted by the Peruvian industry.

Peru has the potential to increase its production of wood products and their quality if adequate

processing and operating methods are adopted. If the country wants to become a better

competitor in the global market, it will require meeting basic economic, social and

environmental responsibilities. A good development would be the utilization of solar energy

kilns to dry eucalyptus.

The Steinmann kiln is suited to the economic and environment conditions of many locations in

Peru. The installation of this kilns to dry Eucalyptus instead conventional kilns, will save Peru a

lot of money in terms of initial investment and operating costs. Building such solar kilns is a

good and sustainable option for Peru. Its construction will result in the expansion of the wood

industry in Peru, increasing job opportunities in communities and companies, while it will also

save the industry energy and other expensive and non renewable resources.

17

Literature Cited

Baso López, C. (2002). Normalizar la madera de Eucalipto con destino estructural. Ponencia

Invitada al Forum IBEROEKA 2002 ―Innovación y Competitividad en la Comunidad

Iberoamericana‖ 13-15 Octubre de 2002, Montevideo, Uruguay

De Vore, J.B., Denny, G.S. and Harper, T.S. (1999). A Commercially Viable Solar Wood Drying

Kiln System, Drying Technology. Fayetteville, Arkansas, pp. 271-283

DeWitt, C. (2002). Wood Moisture Content. Retrieved March 30, 2009 from

http://www.rlcengineering.com/wmc.htm

FAO (2008). Forests and Forestry Sector. Forestry Country Profiles

FAO (1998). Especies Arbóreas y Arbustivas para las Zonas Áridas y Semiáridas de América

Latina. Red Latinoamericana de Cooperación Técnica en Sistemas Agroforestales

Grattapaglia, D. (2008). Genomics of Eucalyptus, a Global Tree for Energy, Paper, and Wood.

Plant Genetics and Genomics: Crops and Models. Volume 1, Brasilia, Brazil, pp. 259-298.

Hillis, W.E., and Brown, A.G. (1984). Eucalyptus for Wood Production. pp.259-356

Innes, T.C. (1997). Improved Seasoned Hardwood Timber Quality. Unpublished thesis,

University of Tasmania

INRENA. (2008). Perú forestal en Números Año 2007. Ministerio de Agricultura, Instituto

Nacional de Recursos Naturales, Intendencia Forestal y de Fauna Silvestre, Centro de

Información Forestal-CIF, Lima, Perú

Jankowsky, I.P., and Gonçalves Luiz, M. (2006). Review of Wood Drying Research in Brazil:

1984-2004. Department of Forest Sciences, ESALQ, University of Sao Paulo, Piracicaba, Sao

Paulo

Kadulski, R. Solar Energy. Retrieved March 15, 2009 from

http://www.thecanadianencyclopedia.com/index.cfm?PgNm=TCE&Params=A1ARTA0007549

Luzar J. (2007). The political ecology of a “forest transition”: eucalyptus forestry in the

southern Peruvian Andes. Ethnobotany Research & Applications 5, pp. 85-93.

Oliver, A.R. (2000). Advances in drying plantation-grown eucalypt timber: an overview of

Tasmanian research. A Regional Journal of Forestry Science and Forest Management,

Glenorchy, Tasmania, pp. 248-251

PRONFOR. (2007). Inversiones en Empresas de Bosques Tropicales Naturales. Confederación

Peruana de la Madera, Miraflores, Lima, Perú

Sánchez Acosta, M. (2005). Tecnología de la Madera de eucaliptos colorados: Propiedades –

usos – posibilidades. Jornadas Forestales de Santiago del Estero – Junio 2005

18

Sánchez Acosta, M. (1999). Experiencia Argentina en la producción y utilización de la madera

de eucalipto, panorama a 1999.

Simpson, W.T. (1999). Drying and Control of Moisture Content and Dimensional Changes. Forest Products Laboratory. Wood handbook—Wood as an engineering material.Gen. Retrieved March

26, 2009 from http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr113/ch12.pdf

Steinmann, D. (2006). Homebuilt Solar Kiln for Hardwoods. Stellenbosch University,

Stellenbosch, South Africa

Waugh, G. (1995). Plantation Eucalypts for Solid Wood Products. Environmental Management:

The Role of Eucalypts and other fast Growing Species. Proceedings of the Joint

Australian/Japanese Workshop held in Australia October 1995

Wengert, E.M., and Oliveira, L.C. (1985). Solar Heated, Lumber Dry Kiln Designs. Department

of Forest Products, Brooks Forest Products Center, Virginia Polytechnic Institute and State

University, Blacksburg, Virginia, U.S.A.

World Wildlife Fund. (2009). Progress and a Setback for Rain Forest Conservation in Peru.

Retrieved March 24, 2009 from

http://wwf.worldwildlife.org/site/PageServer?pagename=can_results_peruvian

19

Appendices

20

SPECIES

Round

Wood (m³)

Scientific Name Common Name

Sawnwood

(m³)

21

Appendix B

SPECIES

Common Name

Scientific Name

Round

Wood (m³)

Sawnwood

(m³)

22

Steaming process

Steaming can be done before drying, between two drying stages or at the end of the whole drying

process. When wood has already gone through a drying process, steaming is called

reconditioning. Reconditioning is preparing the wood for the next stage, being drying at higher

temperatures, or ready to cool down and be machined. ―Reconditioning to remove collapse

usually causes the surface checks to re-open during final drying. This can severely degrade

back-sawn timber. however, reconditioning tends to close internal checks‖ (Hillis and Brown,

1984). Steaming previous to air or kiln drying helps to even out the moisture gradient in the

wood pieces, and it can also accelerate the drying process (Hillis and Brown, 1984).

Appendix C

The construction of a Solar Kiln

• The kiln floor should be level, sturdy and dry even during the rainy season. Drain

water away from the kiln. Use a sheet of plastic as a moisture barrier against ground

moisture and use a layer of bricks to lift the floor 50 to 100 mm above ground level.

• Framework of wood or pipe is made to a suitable size to accommodate the stack of

wood you intend to dry and allow for air circulation.

• A tunnel shape is recommended for easy construction.

• Cover both ends of the tunnel with any material. Allow for a door to load the kiln.

• Cover top and sides with a double layer of ultra violet stabilized transparent plastic

sheet sealed all around its 4 edges

• Ensure that the kiln air can not leak out of the kiln!!

• Stack the wood in the kiln in such a way that an electric fan can blow the kiln air

through the stack. Baffle the stack to the fan to ensure that no air by-passes the stack.

An air speed through the stack of 1,5 m/sec is sufficient.

• Fit a small blower fan (50- 150 watt) to the inside of the kiln structure and use a

suitable air duct to blow the air between the two skins of the kiln at a point near the

top of the kiln and about halfway along its length.

• Cut vent holes through the inner skin of the kiln, about 200 mm above ground level

and at 2 metre spacing all along both sides of the kiln. These vent holes are required

to feed the air from the small blower back into the kiln.

• NB Make these holes small enough to allow a slight pressure build-up between the

two skins to keep them apart when the blower is running.

23

PRINCIPLES OF OPERATION

Wood is stacked in a double skinned solar kiln with transparent roof and walls

The wood is covered to protect it from direct sunshine

The sun heats the inside of the kiln and the air

The warm kiln air is circulated by a fan through the wood stack to heat it.

The wood releases its moisture into the kiln air

A small blower blows this moist air into the space between the two skins and back into

the kiln via vent holes in the inner skin.

When the temperature outside the kiln drops below the dew point of the kiln air, the

moisture condenses on the inside of the outer skin

This condensate collects between the skins and is drained through weep holes to the

outside of the kiln.

The above process removes the water from the wood and releases it outside the kiln

This process repeats itself in day/night cycles.

Principle #1

• During the day:

• Sun starts shining:

• Temperature inside kiln increases

• Relative humidity drops

• Wood starts drying from surface

• Normally no condensation on a sunny day

Principle #2

• Removal of water by condensation on inside of outer skin:

• Night time, outside temperature drops

• Air between skins cools below dew-point

• temperature (once a day)

• Water condenses (inside of outer skin) – beer can!

• Water runs down

• Water collects at bottom where skins meet

• Removed through weeping holes

• Cooled air fed back through feedback valves into kiln

Principle #3

• During the night:

• Lower absolute humidity

• Relative humidity still high!

• Wood is still hot from heating during day

• Water still moves by diffusion to surface

• Very little evaporation from wood surfaces because of high relative humidity of air

• Moisture content gradient in wood reduced during night

• Next morning : Principle # 1 repeated

24

Plan of Steinmann Solar Kiln (Steinmann, 2006)

25

Isometric view of Steinmann Solar Kiln (Steinmann, 2006)