‘Locally Produced Wood Seasoning Kilns Will Mitigate Deforestation’

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Prof. Hussaini Ibrahim.
Prof. Hussaini Ibrahim.

The director-general of the Raw Materials Research and Development Council (RMRDC), Prof. Hussaini Ibrahim, talks to NKECHI ISAAC about tree-felling and preservation, the concept of ‘seasoning’ and its direct relationship with deforestation.

What is the status of the wood products’ sector in Nigeria?

Wood is a versatile raw material; the only renewable construction material. The global timber sector currently faces the dual challenges of meeting the growing demand of quality timber products and minimizing possible adverse impacts on the environment and on forest degradation and deforestation.  In Nigeria, more than 92 per cent of wood processors – especially those in the sawmill and furniture industries – are cottage and small-scale enterprises which utilise sub-optimal processing methods.  Locally, timber consumption may reach 15,500,340 m3 by 2025, besides those that will be exported illegally.

Also, the World Bank has forecasted that global timber demand will quadruple by 2050. The concern now is how this increasing demand for timber products will be met without a proportionate increase in the depletion of forest resources.

Given the connection you are trying to make, how can this be addressed?

Wood processing affects the environment and promotes deforestation. As awareness of climate and environment issues increase and consumption habits change, new opportunities open up for the forest industry to develop functional, green solutions to meet consumers’ needs. Triggers of environmental impacts exist within the global wood supply chain, from sawmills to final product.  As a result, the rate of deforestation and consumption of industrial timber products are increasing. In view of the high rate of urbanisation, housing construction and poor wood processing practices, the rate of deforestation is expected to increase by 35 per cent over the next 5 years.

This can be addressed by promoting best practices in the industry. A good example is the increased efficiency in the timber production process. This will mitigate forest degradation and deforestation, as well as other environmental challenges which accompany.

 Can you expatiate on these?

Timber products are products produced from renewable and sustainable environmental resources. However, as with other processing industries, timber production may impact the environmental in different ways, at different stages of production; from harvesting to disposal. Production of timber products also involves emission of carbon.  As a result, deforestation contributes as much as 17 per cent to the emission of greenhouse gases (GHGs) into the atmosphere.

In Nigeria, the present method of wood processing by cottage, small and medium enterprises subject the final products to short shelf lives. They end costing the users more, as they have replaced them constantly.  For instance, most SME operators use the air-drying method because, as you can guess, they have a very short time and the need for immediate profit is high. For the user, frequent replacements mean recourse to virgin lumber, leading to forest degradation and deforestation.  

In processing timber into high-value finished products, drying is one key step. This is why research is being conducted into optimal drying technology fitting for the different climes.  One of the objectives is to reduce deforestation as the world continues to lose some 15 million hectares of forests annually. Deforestation and forest degradation directly threaten as many as 400 million people, including 50 million forest indigenous people who depend on the forests for subsistence in sub-Saharan Africa.

Deforestation estimates for Nigeria is about 6 per cent per year.  The regional breakdown of deforestation from 1979 to 1995 shows that Nigeria’s total forest declined by 48 per cent in the north-central, 7 per cent in the northeast, 60 per cent in the northwest, 53 per cent in the southeast, 13 per cent in the south-south and 12 per cent in the southwest. In 2000, the forest cover was estimated at 13.5 million hectares, compared to 17.5 million hectares in 1990. This indicates that forest cover loss of close to 400,000 ha per annum, or a decline of about 2.6 per cent was recorded. Forest/woodlands now stand at only 13 per cent of the total land area. With global outcry on the consequences of continuous unsustainable forest destruction topping major intellectual discourses, the need to optimise wood-processing patterns among small and medium-scale enterprises has become critical.

What is wood seasoning?

Wood seasoning, in other words wood drying is one the major operations wood must undergo during processing to increase its life in service.  This ‘seasoning’ reduces the moisture content of wood before its use. When ‘green’ wood dries, free water from the cell lumina, held by the capillary forces only, is the first to go. The fibre saturation point (FSP) is the point at which free water is completely gone, while the cell walls are saturated with bound water. In most types of woods, the fibre saturation point is at 25 to 30 per cent moisture content, while wood expected to be used for most products should be dried to between 10 and 12 per cent moisture content before deployment.  

Many properties of wood show considerable change as the wood is dried below the fibre saturation point.  Among these are the volume of wood, its strength (strengths generally increase consistently as the wood is dried below the FSP, except for impact-bending strength and, in some cases, toughness), electrical resistivity, all of which increases very rapidly with the loss of bound water when the wood dries below the FSP.  However, wood has the ability to take in or give off moisture in the form of vapour.  As a result, wood must be dried to the stage where the vapour pressure within the wood will be equal to vapour pressure in the ambient space.  The amount of moisture that remains in the wood at this stage should be in equilibrium with water vapour pressure in the ambient space and is termed the ‘equilibrium moisture content’ (EMC). At this stage, the wood is stable and it stops absorbing moisture from or releasing moisture into the surrounding air.  Wood products produced at this level have optimal shelf life.  This stage can only be got to through optimal seasoning.   

What are the major ways of ‘seasoning’ wood?

There are two major methods. These are natural (air) or traditional method and the artificial (kiln) drying methods. The traditional method of seasoning timber is to stack it in air and let natural air and atmospheric heat move around them and remove the moisture.  This allows air to circulate around each piece. Nevertheless, it is a slow process, particularly for hardwoods.  It takes about 6 to 9 months for the wood to be dried by this method, to reach about 2 to 25 per cent moisture content.  This method is mostly adopted by the cottage, small and medium-scale wood processors in Nigeria.  In view of the period, it takes to dry and the fact that most processors cannot wait for 9 months, most wood used by these processors are not properly dried.  This leads to various problems when wood is deployed for use.

Which method of ‘seasoning’ is best deployed, then?

Kiln-drying of lumber is the most effective and economical method available. Although there are different variants of the kiln-drying process, the principles are generally the same. Drying rates in a kiln can be carefully controlled and defect losses reduced to a minimum. Length of drying time is also greatly reduced and is predictable.  Where staining is a problem, kiln drying is often the only reasonable method that can be used, unless chemical dips are employed.  A kiln can dry wood quickly, so close to the average EMC conditions to which it should be exposed to, ideally. This, according to global best practices, is between10 and 12 per cent.  Also, at this level, shrinkage and further dimensional changes can be minimised.

How will these profit wood processors?

Kiln-drying significantly adds value to sawn products. The value of wood that is kiln-dried can increase as much as 700 per cent per cubic metre or more.

Also, kiln-drying, if carried out promptly after felling of trees, protects timber against primary decay, fungal stain and attack by certain kinds of insects. Most organisms which cause decay and stain cannot thrive in timber with moisture content below 20 per cent. In addition, kiln-dried timber is lighter and the transportation and handling costs are reduced in that state.  It is also stronger than green timber and boasts better properties; paints and finishes last longer on dry timber, while the electrical and thermal insulation properties are generally improved.

What has the RMRDC done to create awareness in the sector to solve these issues and ensure local timber is optimally dried?

In order to address the challenges and ensure that best global practices are enthroned locally, the council, in collaboration with Nova Palcon Nig. Ltd. Enugu, designed and developed two variants of wood-seasoning kilns with a capacity of 25m3 each. The primary objective was to domesticate the kiln-seasoning technology to reduce the current rate of deforestation occasioned by the short life-span of wood in service and increase the income generated by SMEs.  This will also promote the export of wood products from Nigeria. 

To this effect, two types of seasoning kilns have been designed, fabricated and test-run. ‘Variant A’ adopts the condensation method and has a capacity of 20m3. It uses electricity for its operations. ‘Variant B’ uses wood waste to fire-boil, with fan-induced hot air. Both are insulated with 100m polystyrene inserts.

Both kilns can also dry off-cuts successfully, for use in the artifacts industry.  The council is assiduously working on the commercialisation of both kilns.  For them to be very effective and achieve the major objectives of their production in the country, there is the need for mass production for use in wood clusters in various states within the country.  As a result, the council has discussed with a number of investors and state governments. Some of them have shown interest in the technology.  It is our hope that, in the course of the next few years, both kilns would have been established in some of the wood clusters in the country.  This will increase quality/standard of wood processing, lead to economic growth, job creation and rapid industrialisation.

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