BY JAMES OWINO
In case we are good enough in providing the right furnishes to the paper manufacturer, he is able to add runnability to his machine and to go sleeping at home without any nightmare. However, according to the grades of paper he is manufacturing, he is demanded to have differentiated properties in the final
product. Eucalyptus pulps are special products to the manufacture of bulky and/or opaque papers.
Today, eucalyptus pulps are preferred raw materials in the manufacture of tissue, printing and writing, carton boards, industrial filters, base-papers for impregnation or coating, cigarette and many other papers. Eucalyptus fibers may be the sole fiber in the pulp furnish or to be part of a blend with other short and/or long fibers.
Tissue and high bulk papers
Tissue (and other highly porous papers) demand the following quality requirements in relation to paper specifications and machine runnability:
•Loosened paper structure
•Liquid absorption ( fast absorption and capacity to retain water)
•Hydrophilic paper surface
•Porosity (pore sizes and distribution)
•Structural softness (the feeling of a soft and fluff paper)
•Superficial softness (tactile softness, the feeling when touching paper surface in the act of crumpling or wrinkling the tissue paper sheet)
•Drawings caused by dry creping and embossing (these drawings improve the feeling of softness and provide better absorption and beauty to the paper sheet)
•Exact paper strength (wet and dry) to allow not to fall apart when customer is utilizing the paper
•Minimum tensile strength ( it is said to be maximum 20 Nm/g in the furnish), to prevent fiber lumen collapse, excessive bonding and high paper density
•Minimum elasticity modulus, a mechanical property negatively correlated with paper softness
•Capacity in the paper to retain pulp anatomical components (fines and vessels) to avoid excessive dust generation in papermaking and converting operations
•Exact wet web and dry strength to provide machine runnability
•Very fast drainage in the wet end 31
•Low fines to prevent fines build up in the white water and low consistency after wet presses (more steam is consumed in these cases)
The tissue papers and other porous-alike papers demand for loosen fibers in the paper structure. For this reason, fiber bonding is a poison, up to a certain extent. The fibers cannot collapse because this effect will flat the fibers and the paper surface; the paper becomes stronger in tensile, but all the tactile properties will be lost due to sheet compactability.
Pulp fines are also undesirable for two reasons:
Fiber bonding and building up in the paper-machine white water system, reflecting in losses of drainability. The most indicated eucalyptus pulps for tissue and highly porous paper manufacturing are those showing: low fiber population and consequently high coarseness (for eucalyptus, do not forget), low fines
and vessel elements contents, low bonding ability, low fiber collapsibility, low wet fiber flexibility, low hemicellulose content, low extractives and pitch content, low water retention value, thick cell walls, high cell wall fraction, rigid and cylindrical fibers, low unbeaten pulp Schopper Riegler, pulps resistant to the refining (slow beating development).
Fiber deformations are also important, since these deformations improve the bulk, porosity, softness and absorption of these papers. An important issue to remember is that fiber deformations may be artificially created in the pulp mills.
The manufacture of industrial filter papers, and impregnation-based papers are demanding the same properties, but in a higher level.
This means, to go to these specialty paper markets, the pulp differentiation must be even more pronounced. The simplest way to work in differentiated pulps to these very specialty markets is to work towards very high coarseness (low fiber population, what means high wood basic density in the wood supply), low hemicellulose content, low fine content (by fractioning fines or removing fines from one paper line and using them in another one, where more desirable) and to intensify fiber deformations (by high consistency presses, fiber shredding, or
pulp flash drying).
Another possibility that has feasibility to improve the pulp properties for tissue and highly porous papers is to take advantage of hysteresis. Drying of pulp has very good impact in the WRV, WFF, fiber bonding and fiber collapsibility. Integrated tissue mills have more difficulties to reach the desired furnish and paper properties. A solution is to add some DIP (market deinked pulp) or some percentage of dried market pulp in the furnish,in a percentage that may solve the
eventual bottlenecks the mill is facing.
Printing & writing papers
For printing and writing papers, the desirable paper properties are:
•Dry paper strengths (tensile, tear, fold)
•Paper internal strength (delaminating in the Z direction)
•Paper surface smoothness
•Paper surface strength (Scott bonding test or wax pick test)
•Good porous structure (porosity or air resistance)
•Liquid (ink) absorption properties
•Light scattering coefficient
At the same time, the papermaker wants to keep the machine runnability. We should never forget about the papermaking physiology. A higher fiber population is welcome for improved formation and opacity, associated to lower fiber coarseness. Also, fiber bonding is important to improve strengths. Hemicellulose and pulp fines contents do help in this task. However, there are limits to all this and the limits depend on each paper-machine system and operation.
A very high fiber population may be wonderful to improve opacity and formation, but drainage in the wet end and consistency after wet presses may become deteriorated, and machine speed reduced. The papermaker is to refuse this pulp. He wants quality and runnability both aligned, remember this. Fiber deformation here may not be so important, but they may help to balance the pulp properties, since machines may create it. Higher contents of hemicelluloses are welcome because they favor refining, bonding, consolidation of the paper web, and strength properties (tensile, burst, tear, folding).
An ideal pulp should have high strengths at the low levels of refining (fast beating response). This is possible for pulps with high zero span test, a demonstration of strong individual fibers. This situation allows the possibility to have strengths and bulk / porosity / drainage at the same time in the papermaking. The P&W papermaker loves to have a good combination of strengths, bulk, porosity and opacity. The papermaker don’t like to refine a pulp very hardly: he is raising energy costs, reducing the life of refiner discs, and deteriorating machine drainage, machine speed, steam consumption and a very important paper property that is dimensional stability.
Definitively, the best pulps are those showing good strengths at low levels of refining. For this reason, an interesting beating test for pulps is the measurement of strengths properties (tensile, tear, stretch) at a given bulk (for example:
1.6 or 1.8 cm³/g), or at a given sheet density (for example: 0.5 or 0.55
g/cm³), or at a given freeness level (25, 30 or 35ºSR, depending on the paper grade being produced) P&W papermaker is very sensitive to all these pulp and paper properties.
In addition, there is another wood anatomical characteristic very important to the printing grade papers: vessel elements content and vessel dimensions (specially the vessel diameter). Large, wide and numerous vessels are undesirable for P&W papers. They are responsible for a printing defect known as vessel picking. The papermaker needs to have special conditions to combat the vessel-picking tendency in the paper. For these reasons, a wood with smaller vessels and not so abundant is preferred. The same for the corresponding pulps
There are many other grades of papers manufactured with eucalyptus pulps: self-copying, cigarette, thermo-facsimile paper, glassine, filters, labels, etc. In most of the cases, the eucalyptus fibers are used to improve paper formation, opacity, smoothness, dimensional stability, bulk and porosity. The eucalyptus fiber population in the pulps, and their rigid and difficult to be collapsed fibers are important properties loved by the papermakers.
Eucalyptus pulps are not oriented to be highly refined, unless the papermaker is willing to discard the best properties the eucalyptus pulps have: bulk, porosity, formation, dimensional stability, opacity, softness, and water absorbency. In case of very low coarseness eucalyptus fibers (around 4.5 to 5 mg/100m), the fiber collapsing may become valuable for the manufacture of glassine, bible paper, and other high density papers. This is a clear indication that eucalyptus pulps may offer a variety of fiber qualities, what may make these pulps able for a wide range of utilization’s.
There is another key driver to papermakers for using eucalyptus fibers: the market pulp prices of this pulp fiber. Thanks to the low production costs, high pulping yield and lower chemical and wood consumption, these pulps are in general less expensive than softwood pulps. No doubt that production costs are also key issues for papermakers. The same to the entire eucalyptus pulp and paper production chain
BY JAMES OWINO
Paper mills have targets for productivity, quality, costs and efficiency. Eucalyptus
pulps are raw materials for the manufacture of several grades of papers. For each paper grade and for each paper mill design, different may become the pulp
quality requirements. This means that there is no universal pulp, a pulp that may perform well everywhere.
Productivity means fast speed in the paper machine, fast drainage in the wet end, high consistency after wet presses, excellent consolidation in the paper web, and minimum number of paper sheet breaks along the machine. Quality implies in maximum percentage of paper in the specification ranges and minimum generation of broke. Machine operation efficiency is the dream of any paper manufacturer. He wants his machine working smoothly, at the maximum speed as possible, no breaks, no maintenance problems, and achieving the required quality in the manufactured products. The consequence of all this is that the specific unit cost is also here optimized. No doubts that a good pulp is the one able to provide good paper-machine runnability and appropriate quality in
the end product, no matter this paper product is a commodity (toilet
tissue, cut size paper, etc) or a specialty grade (industrial filters, cigarette
Some of the pulp properties are very much related to these performances. For this reason, the papermaker should keep an eye on them. Some of these properties are result of the wood quality, other depends on the conversion of wood to pulp (chipping, cooking, bleaching, pumping, blending, etc), and many are a combination of these two factors influencing the pulp quality. For example, some properties that are related to pulping and bleaching are: viscosity and degradation of cellulose chains, fiber deformations, cell wall integrity, individual fiber strengths, surface charges in fibers, adsorbed ions on pulp surfaces, etc. Some other important pulp properties are related to wood quality and pulp conversion, as the hemicellulose content in the pulp and the microfibril organization in cell wall.
The hemicellulose content depends on how high is the presence of hemicelluloses in the wood and in the ability of the pulping and bleaching processes to preserve them in the pulp fibers. The organization and integrity of the microfibrils in the cell wall depend on how aggressive the pulping process has been to the original fiber wall, and also the type of original wall in the wood (reaction wood, juvenile wood, etc).
There are other properties that are 100% dependent on the wood supply, the pulping and papermaking processes cannot modify them: fiber length, fiber wall thickness, vessel dimensions, etc. There are many pulp properties that are dependent both on wood quality and on pulping/bleaching processes. There are also many cases where many exigencies are placed on the wood quality, when the wood is not the main factor to determine these pulp qualities for paper. It is the case of properties as: WRV – water retention value, WWS – wet web strength, WFF - wet fiber flexibility, fiber bonding and individual fiber strength.
There are many other proper ties related not only to the wood quality.
For example, the fine content of the pulp. Fines in the wood are mainly parenchyma cells, but in the pulp they are also fiber and vessel fragments that are generated in operations such as wood chipping, pulp pumping, pulp dynamic mixing, pulp pressing for dewatering, etc.
THE MOST IMPORTANT EUCALYPTUS PULP AND FIBER PROPERTIES
Today, the pulp and paper laboratories are squeezed by thousands of different types of analyses. Some mills are spending so much time on measuring everything, that the speed to take decisions and actions is completely affected. The laboratory manager has fewer people, due to the constant downsizing obliged by the company’s high administration. He feels lost, but he wants to keep his area working as much as possible to satisfy his customers (paper production manager and commercial manager). Since the number and the type of analyses grow due to the Information Technology support, the time to reflect over the results decreases. The danger is that the quality of the data may also be affected. The following pulp quality parameters are key drivers to distinguish
the different eucalyptus fibrous raw materials and to allow pulp furnish optimizations:
Fiber population or the number of fibers per gram of pulp (associated to fiber coarseness)
The fiber population is related to the weight of each individual fiber, and by extension to the fiber coarseness and to the percentage of fiber wall in the fiber volume. Fiber population is a compound property derived from fiber length, and fiber coarseness. Since fiber length in eucalyptus pulps is a morphological property relatively stable (the weighted average ranges from 0.6 to 0.85 mm maximum), there is a strong correlation between fiber population (Number of fibers/gram) and fiber coarseness.
There is a number of fiber properties associated to fiber population and fiber coarseness: fiber length, cell wall thickness, cell wall cross sectional area, fiber wall fraction (ratio between cell wall thickness and fiber ray), Runkel index, fiber flexibility index (ratio between the lumen diameter and fiber diameter), fiber collapsibility, ratio fiber wall thickness and fiber perimeter, cell wall packing density, wood basic density, wet fiber flexibility, and fines content. Since fiber population and fiber coarseness are definitively some of the most important eucalyptus pulp properties, it is very important to know the type of effects they may impart to papers.
First, it is important to understand the fiber morphological characteristics related to fiber population:
Cell wall thickness (-)
Fiber length (-)
Cell wall fraction (-)
Cell wall cross sectional area (-)
It is clear, that the relationships of these above mentioned morphological characteristics with fiber coarseness are in the opposite way. It is relative simple to understand that higher coarseness in eucalyptus fibers are associated with thicker walled fibers. These fibers produce a more open and loosen paper structure. Fibers are rigid and difficult to be collapsed. Fiber bonding and fiber consolidation are not that favored with such stiff cylindrical fibers. The corresponding papers are more porous, bulkier, and more absorbent. A better consolidation of the paper web is expected with more fibers per gram in the paper structure. As a result, higher the fiber population better is the inter-linkage among fibers, and better are the properties depending on bonding (tensile, folding, surface strength, surface smooth). Paper formation also pleases high fiber population in the furnish.
The number of fiber to fiber crossings in the web at a constant paper grammage and sheet area is expected to be proportional to the fiber population. Because bonding is favored, the paper properties that do not like fiber bonding are affected negatively (bulk, porosity, water absorbency,tactile sensibility or softness, surface roughness). Coarseness in eucalyptus fibers varies from 4.5 to 11 mg/100m. Fiber population, in opposition, varies from 12 to 30 million of fibers per gram of pulp. Both properties have wide ranges of variability, and allow good selections of pulps in the market, depending on the desired end-use.
Fiber population and fiber coarseness are associated to a great number of paper properties. To simplify things, let’s inform the correlation of fiber population with some of the most important paper properties, no matter the type of paper. Obviously, the correlations for fiber coarseness will happen in the opposite way.
Fiber population correlates positively with: formation, surface smoothness, opacity, light scattering coefficient, fiber bonding, surface strength, tensile strength, burst strength, folding, air resistance, water retention value, wet fiber flexibility,wet web strength, wet web stretch, unbeaten Schopper Riegler.
Fiber population correlates negatively with: porosity, stiffness, drainage, bulk, tear strength, dimensional stability, water absorbency, paper softness.
It may be also shortly said that pulps with lower fiber population show better drainage in the wet end, and the paper sheets are more porous, bulkier, more permeable and absorbent. They are very much appreciated by papermakers because they allow faster machine speeds, as far as the furnish may impart enough strengths to the wet paper sheet.
Individual fiber strength
This fiber characteristic is very difficult to be measured in short fibers as those from eucalyptus. There are tests correlated to this strength, as the zero span, very useful for predicting pulp quality and behavior previously to send the furnish to the pulp-machines. Fiber deformations (curl and kinks), micro-fractures in the cell wall, and other fiber defects may contribute to reduction on the individual fiber strength. The consequence of reduced individual fiber strength may be reduced WWS (wet web strength) and dry paper strength properties. Zero span tests provide good indications on the fiber wall resistance.
There are different parameters that the zero span test may evaluate: wet zero span, dry zero span, wet short span, dry short span, B value. These tests provide sound and valuable correlation with fiber specific strength and also with fiber bonding ability (B value). Zero span most valuable tests related to individual fiber strength are the wet and dry zero span. These results are affected by: fiber wall integrity (+), cell wall packing density (+), fiber length (+), pulp viscosity (+) or cellulose chain degradation (-), micellar angle (-), hysteresis (+), fiber wall fraction (+), and fiber chemical composition. Although many times referred as an excellent indicator to individual fiber strength in softwood pulps, the micellar angle does apparently not play so important role for eucalyptus pulps. Most of the eucalyptus fibers have small angles, relatively close to the fiber axis.
In the S2 layer, this angle has been found ranging from 8 to 15º. The intrinsic strength of the fiber may be given either by the dry zero span and/or the wet zero span. For eucalyptus pulps, in unbeaten level, the ranges of results are the following: Wet Zero Span (from 70 to 140Nm/g) ; Dry Zero Span (from 90 to160 Nm/g). B Value is related to increase fiber bonding in the fibrous test pad. Higher the value, better the bonding (results for eucalyptus pulps varies from 1.5 to 3)
Fiber collapsibility is associated to the wet paper sheet compactability. Wet sheet compactability is referred to the readiness the fiber surfaces are adapted and conformed to each other when the wet sheet is pressed. A well conformed wet sheet has more ability to keep fibers and fillers together and conformed after paper drying. The sheet compactability makes the paper sheet denser and places the fiber walls closer to each other during paper manufacturing. As a consequence, fiber bonding is sharply improved, and the strength properties depending on bonding (tensile, burst, folding, surface strength) have their results
On the other hand, some very welcome eucalyptus pulp properties are lost: bulk, porosity, opacity, water absorption, softness, dimensional stability. Fiber collapsibility and wet sheet compactability are result of the fiber resistance to collapse. There are other chances for collapsing fibers in a paper mill, as the operations of paper drying and paper calendaring. However, the wet paper compactability has more effect on collapsing the fiber wall. Collapses convert cylindrical fibers into flat ribbon-like fibers, with better link and contact surface. The lumen collapses because the fiber structure (cell wall and fiber architecture) is unable to support or to absorb the energy applied by the papermaking pressures and forces. In most of the cases, the thick-walled fibers, with higher fiber wall fraction, are stiff, rigid, and more resistant to collapse.
Eucalyptus fiber collapsibility is also negatively related to fiber coarseness. Higher the fiber coarseness, lower is the ability of the eucalyptus fibers for collapsing. The fibers with greater potential for collapsing are usually more difficult to drain the water in the wet end of the paper-machine. Another morphological property very much related to fiber lumen collapse is the cell wall cross section area (area of cell wall in the fiber cross section or diameter). A derived morphological characteristic is the cell wall density or packing density. Itis calculated based on the fiber coarseness and the cell wall cross sectional area. The formula for this calculation is:
Cell wall density (g/cm³)= ( 10 x coarseness) / (wall cross sectional area)
Coarseness in mg/100m
Cell wall cross sectional area in micrometers
One indirect measure of fiber collapsibility is the dry paper sheet bulk (or sheet density) at a given Schopper Riegler or freeness level, or at a given tensile strength. Higher the bulk in a certain level of drainability or tensile, more resistant are the fibers to be collapsed. Higher the densities of the sheet, more collapsed are the fibers, and more compacted the paper sheet. Bulk or sheet density at a given drainability (for example 25 or 30ºSR) or tensile ( for example 50 to 70 Nm/g) and fiber coarseness, are able to give good indications of pulp behavior in relation to fiber collapsibility.
Another interesting property to be measured at a given freeness (or at a given bulk, or at a given tensile) and strongly related to fiber collapsibility and paper compactability is the dry paper porosity (or the opposite property, the air resistance).
Fiber bonding ability and paper network properties
Better the fiber bonding, better is the paper sheet cohesiveness. Cohesiveness and bonding are developed by beating (fibrillation and fiber collapsibility) and by the presence of fines and fiber debris. Bonding may be measured by the dry/wet short span (B value) technique or by other equipment for dry paper bonding tests, as the Scott bond tester or wax picking of paper surface.
Bonding is also related to a number of dry paper strengths, as tensile, burst, folding, and also to sheet apparent density. It is also related to the hemicellulose content of fibers, fiber population, fiber drainability (CSF or ºSR), fines content and fiber collapsibility.
Bonding is very much related to pulp fines content and web consolidation by pressing and collapsing fibrous materials. Higher is the sheet density, the more bonded are the fibers and other anatomical and chemical elements present in the paper structure. Low hemicellulose content and high
coarseness fibers reflect in low cohesiveness and low bonding. Instead of being “glued or linked” to each others, these types of fibers are rigid and stiff: “they tend to touch and to stick one to another, but they are not glued”. Finer fibers with lower coarseness values and higher fiber population make closer-formed and better printing oriented sheets of paper.
Wet fiber flexibility
Wet fiber flexibility (WFF) is one of the most important pulp properties. It is highly related with inter-fiber bonding (+), fiber lumen collapsing (+), water retention value (+), and bulk (-). It has been proved for several researchers that wet fiber flexibility is easily measured and gives a very good indication of paper strengths and paper optical properties. The wet fiber flexibility correlates very well with the paper conformability, paper consolidation, and fiber collapsibility. However, WFF is affected by fiber deformations and cell wall damages. WFF is the opposite property when compared to fiber stiffness.
As a measure of flexibility, the condition is that a force be applied to bend the fiber in its length. What is really very important to papermaking is that WFFcorrelates very well with Wet Web Strength and Wet Web Stretch, two very important properties for predicting machine runnability.
Wet fiber flexibility shows very good correlation with several fiber characteristics, as follows: fiber coarseness (-), cell wall thickness or cell wall fraction (-), paper tensile strength (+), paper sheet density (+), Water Retention Value (+), fiber stiffness (-), paper sheet bulk (-).
Fiber swelling and hydration
This property is very affected by the pulping and bleaching operations during pulp manufacture, and by the pulp hemicellulose content. Several properties are associated to the swelling of fibers: freeness or Schopper Riegler level, WRV - Water Retention Value, fiber charges, carboxyl groups, fines, fiber wall micro-porosity, fiber wall micro-fractures, wet fiber flexibility. Hydration of fibers has to be understood under different approaches. First, we have the cell wall water, the water that is absorbed to the fiber wall due to fiber charges and polarity (carboxylic groups, carbonyl groups, etc) and micro-porosity. Second, we have the water retained by capillarity inside the lumens.
More lumen volume a pulp has, more water will be retained in such way. Third, we have the inter-fiber water, the water that stays held between the fibers in the pulp mat. Water Retention Value is a measure of the affinity of the pulp for water. Depending on the fiber network, and on the number of fibers/gram, more or less water will be retained by the pulp. When Water Retention Value is measured utilizing a pulp pad and a centrifuge to perform the test, the resulting WRV gives a number comprising all these three types of water. It is easy to understand that pulps with fibers containing more lumen total volume, and more fibers have higher WRV results. Small pores (lumens) are able to hold water more strongly than large pores due to the greater surface tension forces associated with the small pores. As a consequence, WRV is strongly related to fiber population (+),
fiber coarseness (), cell wall fraction (-), wet fiber flexibility (+) and fiber saturation point (+). WRV is also influenced by the chemical composition of the fibers.
The hemicelluloses retains more water, thus, fibers with more hemicelluloses are able to retain more water in the fiber walls. On the other hand, most of the pulp extractives are hydrophobic. Pulps with high extractive content have poorer ability to retain water in the fiber wall. It should be well understood that WRV is a combined effect of chemistry (hemicellulose content) and physics (fiber population, total pore volume and pore size distribution). This combined effect will be responsible for the WRV result. You may eventually have a pulp with low
hemicellulose content, but with high WRV due to a huge fiber population.
The high hemicellulose content associated with high fiber population and degraded fibers (low viscosity) will lead to pulps very hard to drain in the paper machine.
These unbeaten pulps have high initial Schopper Riegler degree, proving that drainability is difficult even in the measurement of this property. Paper machine runnability is negatively affected in these conditions. There are eucalyptus pulps with high hemicellulose contents, as example the Eucalyptus globulusmarket pulps.
However, a typical feature of E.globulusis the high fiber coarseness, and low fiber population Under these circumstances, the WRV in
Eucalyptus globulus pulps does not represent problem in normal conditions.
To the papermaker, mainly the one manufacturing porous and absorbent papers, the porosity and capillarity he is concerned are those in the paper sheet. High WRV pulps may have a huge small pore volume (lumens) in the pulp pad used for testing WRV, but these pulps are not recommended to the manufacture of tissue and filter paper. The reason is understandable. These pulps have high WFF, high population of fibers, thin cell walls, high ability to have the lumens collapsed. The paper structure will be dense and compacted, unless the papermaker may have some magic procedure in the manufacture.
Excessive fiber swelling and hydration may be a problem in integrated mills, when the pulp has never been dried prior to its use in paper manufacturing. When a pulp is dried, the hysteresis phenomenon provides a substantial reduction in the WRV of the pulp. Dried pulps, with lower WRV, have a much better drainage in the wet end. However, they are somewhat more difficult to be refined, but the desired strengths are reached in a drainability level that is still convenient to the machine operation. For this reason, in many occasions in an integrated paper mill, the mill manager loves to add some broke (already dried fibers) to the furnish. He believes that some broke is required to improve the performance of the furnish. It is a completely inappropriate thinking, since broke recycling is a loop in his process: he is wasting all the value has being added to the manufacture of this paper. Even worse, he is reducing the paper-machine net production.
The machine has part of its capacity filled by a recycled material, in a loop that consumes resources, reduces capacity and raises costs and inefficiency. In case an integrated mill may eventually have problems due to excessive furnish swelling caused by any reason, the most simple method to improve machine runnability is to buy or to add some dried market pulp in the furnish recipe. The pulp drying operation causes substantial reductions in the WRV and WFF, favoring wet end drainage. However, dried pulps are more difficult to be refined and to develop pulp strengths. Today, there is a trend among pulp buyers to request higher market pulp pH in the pulp sheets. This trend is happening due to alkaline sizing in printing and writing paper manufacture. The papermaker wants to save some money in chemicals for controlling pulp furnish pH and pulp refining. Higher pulp pH means more swelling in the pulp, and more difficulties to drain the pulp sheet in the wet end of the pulp drying machine. The usual market pulp pH has been 5.0 to 5.5 for years. Today, to many customers, the trend has been raising it to 7.0 – 7.5.
Hemicellulose content of the pulp
Hemicellulose content is vital for papermaking. Pulp makers also love to preserve hemicelluloses in the digesting and bleaching operations.
They are improving the pulp yield, and consequently, reducing costs and raising economic margins. Pulps with low hemicellulose content, as the dissolving pulps, are hardly beaten, and fiber bonds are weaker and fewer. Since the great percentage of the eucalyptus pulp hemicelluloses are xylans, the significance of the pentosan content to predict pulp quality is very important. Those pulps containing more hemicelluloses are able to produce paper with better fiber bonding, better strengths properties, better surface smoothness, and lower bulk and porosity. No other fiber chemical component in eucalyptus bleached kraft pulps has so much influence on paper properties than the hemicelluloses, provided these pulps have not been damaged or degraded too much in their manufacture.
The hemicellulose content in pulps can be affected by the today’s operation of the modern digesters. The type and operation of the bleaching sequence is also responsible for removing more or less hemicelluloses. These two factors combined may represent significant improvements or losses in the pulp manufacturing stage. Consequently, the pulp manufacturer must understand very well its role in this process.
The wood raw material, the pulping and bleaching operations, and the pulp mill daily performance may represent opportunities to save or to reduce the hemicellulose content in the pulp.
Hemicelluloses are very hydrophilic organic compounds. The presence of high hemicellulose content in the pulp helps to increase the ability of the fibers to attract and to retain water in the fiber wall. This phenomenon improves the fiber swelling, brings weakening in the microfibril linkages in the cell wall, and favors the pulp refining. Higher the hemicellulose content, better is the wet fiber flexibility, and improved becomes the fiber bonding. Fiber walls may become more plastic and flexible.
As a consequence, for the same level of fiber coarseness and pulp refining, the pulps containing more hemicelluloses give origin to denser paper sheets, and sheets more resistant to the flow of air in the paper Z direction (reduced porosity). Sheet softness is also negatively affected.
Although the hemicelluloses are hydrophilic compounds (“friends of the water”), when they cooperate to reduce paper sheet bulk due to collapsed fibers and better bonding, the paper sheet become less porous. The reduced porosity of the paper structure has lower ability to absorb and to retain water. Curious behavior, intriguing performance: chemically speaking is favorable, but physically may not. Because the characteristics the hemicelluloses impart to the pulps, there are a number of other papermaking performance items being affected.
Drainage in the pulp machine may be negatively affected, but there are cases of opposite behavior. This happens when the pulp refining may be driven to lower Schopper Riegler levels to achieve the same required strengths. In these cases,the machine runnability does not suffer. When the refining is performed to a lower level of ºSR, there are very good improvements in the machine runnability and paper properties: drainage, steam saving, paper dimensional stability, softness, porosity, etc.
For some grades of papers, the effects of hemicelluloses are not completely welcome: tissue, decor, impregnating-base papers, etc. The removal of hemicelluloses may become a solution. This “removal” may be achieved in several ways: utilization of low hemicellulose content wood raw material; more intense cooking to lower kappa number and with more alkalinity in the end of cooking to prevent xylan re-precipitation; removal of hemicellulose by drastic alkaline bleaching stage. When hemicelluloses are partly removed, the weight of each individual fiber is reduced in some extent: this means that the number of fibers per gram of pulp is increased, and coarseness reduced.
The reduction on hemicelluloses in the digester is painful to the pulp maker. The pulp yield drops considerably in this operation. Drastic pulping of wood helps to reduce hemicelluloses to more acceptable levels for tissue manufacturing, but pulp yield may drop about 1.5 to 2.5% based on wood. This means more wood cost in the pulp cost; or reduction on pulp production in case the digester, the causticising or the recovery boiler is bottlenecked in the pulp mill. As an indication of effects: a reduction of 2.5% on the bleached kraft pulp hemicellulose content allows reductions of 10% in tensile strength, and improvements in bulk, porosity and absorption.
In recent days, new opportunities to remove hemicelluloses from wood, and associated to pulp making, are been investigated. The concept of bio-refinery is exactly proposing the utilization of part of the wood hemicelluloses to the manufacture of ethanol, a valuable biofuel. The consequence will be interesting: the possibility to differentiate eucalyptus pulps reducing hemicellulose content without bringing damage to the pulping process or to the environment (more COD in the bleaching filtrates, when hemicelluloses are removed in the bleaching line).
Fiber deformations and cell wall integrity/damages
Eucalyptus pulp fibers are submitted to very hard mechanical forces and stresses. Fiber life is not really easy, believe me. During cooking and bleaching, the alkaline conditions along these processes favor the structural disorganization of the microfibril chains in the cell wall. The removal of wood constituents during pulping and bleaching creates macro-pores in the cell wall. The wall becomes more fragile and damaged in relation to its original organization in the wood. This cell wall fragility enables the fibers to suffer more and to deform when mechanical forces are applied to them.
Deformations and lumen collapse become more frequent. More the fiber is damaged during pulping and bleaching, more sensitive is the fiber wall to be deformed and collapsed. The alkalinity favors fiber hydration and wall swelling; it helps to loose the microfibrils in the wall structure. The fibril network becomes loosen and more porous. This helps pulp refining and improves fiber bonding and wet fiber flexibility. However, the individual fiber strength is reduced. Severe cooking conditions to reduce kappa numbers or to delignify denser woods in general are very harmful to cell walls. At the same time, more hemicelluloses are removed from the fibers. The fibers become weak and sensitive to the mechanical forces, such as those created in presses, pumps, valves, agitators, etc. For these reasons, sometimes we have pulps with the same wall fraction and obtained from the same eucalyptus wood raw material, but with distinct fiber strength and paper performance. This may be explained by an excessive cooking or bleaching in one of them.
Degraded fibers have increased Water Retention Value and Fiber Saturation Point. They absorb water more easily because the microfibrils are more open, loosen and the fibril network more porous. Wet fiber flexibility is also increased, and together, the ability for lumen collapsing. These pulps have fast beating response, the Schopper Riegler degree raises fast. However, this is not followed by an increase in pulp strength (tensile and tear). Fibers are weak, they are more easily broken and form more fiber debris and fines. Wet Web Strength and Zero Span are also harmed. This is a terrible world, but it is a real world in many pulp mills.
Degraded fibers like these do not behave as normal fibers. They are not able to resist the forces of the refining, wet pressing, etc. The papermaker faces a dilemma: “fast refining, high swelling, but no strengths, no bulk, no porosity”.
When fibers are submitted to mechanical forces, they are sensitive to changes in their form, no matter they are low or high viscosity. Deformations in good quality fibers are interesting for a number of reasons.
The deformations in the fibers are measured as curl index, fiber kinks, fiber latency, and fiber micro-fractures in the cell wall. They affect the individual fiber strengths, but they provide substantial improvements in the paper sheet porosity, bulk, softness and water absorption. Fiber deformations are possible to be developed by artificial means at the pulp or the paper mills (shredders, washing presses, etc). Although not completely implemented as a source of pulp and paper differentiation, the utilization of fiber deformations for this particular subject may become more significant in the years to come. Mainly considering that pulp strengths are not the most demanded properties in the eucalyptus pulps. They are important, but not vital.
Fines content in the pulp
Fines are perhaps one of the most important kraft pulp properties, and most of the times, they are seen as a problem, never as a solution. This fundamental property is being neglected by pulp and paper makers; perhaps because fines are no fibers, they are debris or “weak parenchyma cells”. Fines are seen as a filler in the pulp supply. They are created in great extent when the pulp is refined, what means that fines dramatically affect drainability in the wet end section. What I would like to propose to papermakers is really to pay attention to fines in the furnish
The best methodology to measure fines in a pulp stock is the dynamic jar test. It is based on the percentage of the dry weight of a pulp that passes through a 200 mesh wire (openings of 70 micrometers), under constant conditions of time, temperature and consistency. The “management of fines” in the furnish may provide to paper operators one the most simple and convenient methods to control the great majority of the end-product properties.
When a paper mill has two or more machines, the management of fines, via the white waters, may be even more effective, by distributing fines in right dosages in one or another paper machine, according to the paper grade being manufactured. A low fines content eucalyptus pulp is able to better perform in the paper machine. Formation, softness, bulk, porosity, absorption, dimensional stability, and permeability are improved in the paper sheet. Strengths are reduced in opposition to these other gains. In terms of machine performance, the reduction on furnish fine content improves the drainage in the wet end,
the consistency after wet presses, and the consumption of steam in the drying section.
For this reason, fractioning of fines may become an operation to be considered according to the paper end-product being manufactured. In cases of machines bottlenecks, fractioning of fines may also become a solution.
BY JAMES OWINO
The paper sector has as fundamental issues like the high productivity, high operational efficiency (no losses, no problems, no breaks, no stops, no nightmares), the low production costs and the uniform quality in the process and products. It is important to mention that all papermakers have these basic physiological needs, no matter the paper is being made, or the paper-machine being used. For achieving these targets, the raw material must be as uniform as possible, with characteristics in a narrow range of variation in order not to cause strong impacts in the papermaking process and paper qualities.
To tame this variability, the paper mill engineers are used to control a number of pulp quality parameters. However, many times, the selected portfolio of pulp quality specifications does not give a previous idea or a predicted behavior and performance in the pulp utilization, neither in the operation nor in final paper product quality. When the paper maker asks for uniform pulp, he is not making a request only for brightness, brightness reversion, viscosity and cleanliness. He includes here a number of pulp quality parameters that are very important to his conversion process. His objective is to have a papermaking operation with the minimum variability, without undesirable surprises. The final paper quality must be uniform and within the specification limits, and the losses along the process should be as minimum as possible. When standardization in the pulp intake is demanded by the paper mill manager, he is first trying to guarantee a raw material that may perform well in the paper-machine operation (machine runnability and efficiency).
The second important objective is to guarantee in the manufactured paper the quality specifications his customers are demanding. Since fibrous raw material performance behavior is difficult to be measured or predicted, the paper mill manager requests the help from the laboratory chief to perform what is called the “management of peripherical pulp quality specifications”. He needs a number of selected data to help him to justify the problems he may eventually have when the machine run ability is poor, or the paper quality specifications are not being reached. When a uniform pulp intake is guaranteed; refining, chemical additions, sheet drainability, energy and steam consumption, web consolidation, and paper strength/physical properties do not sharply change and the paper process runs smoothly. The process and product qualities are more easily achieved. In an attempt to control some of these pulp quality parameters, the laboratory evaluates pulp brightness reversion, pulp cleanliness, pulp viscosity, pulp conductivity, pitches content, and performs some beating runs. The first and important goal is not to have sharp variations in the general pulp properties.
Brightness, brightness reversion, viscosity, cleanliness, ash and mineral contents, and beating performance are the key issues in these “peripherical quality specifications. The complementary pulp quality parameter is the moisture content. The papermaker does not want to pay more to the pulp he is buying than what he considers to be fair and right.
The second type of management that the mill manager wishes is the variability control. The “management of pulp variability” tries to guarantee a narrow variability in the pulp and its consequences. The variability is also measured indirectly, by watching the paper-machine behavior and performance. When machine works smoothly, without breaks, at pre-settled speeds, and the quality specifications in the final product are met, the process is said to be controlled, and variability has been tamed. When problems start to happen, the usually first accused is the pulp quality.
Management of peripherical quality and management of pulp variability are really basic physiological requirements in any paper mill.
The mill manager needs to have these exigencies fulfilled to go further in the next type of management: the “management for product differentiation”, or “tailor making orientation in the manufacture of products”. This type of management requires substantial changes and offers important challenges to the paper mill personnel. The changes may happen in pulp quality (for example: long fibers and short fibers blends), pulping process conditions (for example: ECF or ECF-Light bleaching sequences reflectingon AOX and/or OX pulp contents), or even others
recently added qualities (certified or non-certified wood in the pulp).
Differentiation of paper products is more easily achieved in mills with more than one paper-machine. This means that the mill may run each machine with a differentiated product, without experiencing the usual troubles with transitions from one product to another using a single paper-machine. Anyhow, the tailor making concept will only be winner when the paper maker has guaranteed the two first mentioned types of management: peripherical pulp quality
specifications and variability plus machine performance.
It is very simple to say, but very difficult to understand and to implement. For this reason, many conflicts and misunderstandings are frequent among the commercial, production and product innovation areas in a paper mill. Each of these areas has its own needs and dreams about product uniformity, product uniqueness, and product differentiation. In most of the cases, each area has difficulties to understand the other side’s position. As a result, few paper mills have products that may be said completely differentiated in their products portfolio.
Most of the paper manufacturers aim to have a single product, as uniform as possible, with the minimum cost and maximum in productivity and in operational efficiency. Having in mind that the behaviors, needs, commitments and purposes are different, what is really important to promote a culture for tailor making in paper manufacturing?
What is important to be managed? How to do this? What properties in the pulpwood may be successfully controlled to offer differentiation in paper products? What are the most important pulp parameters that the mill manager, commercial director and the R&D manager care about?
In integrated paper mills, the paper product differentiation may be built at the forest, at the pulping process and/or at the paper machine. At the forest, it means to segregate the different wood and to cook the different types separately (for example: high and low wood basic density).
At the pulp mill, the differentiation may be achieved taking advantage of the different opportunities the company may have (different bleaching lines, different digesters). Finally, at the paper mill, the different products may be also obtained by different pulp furnishes, involving blends of different pulps (produced onsite or purchased).
In integrated paper mills, it is very common the need to purchase some dried pulp in the market, to facilitate drainage in the wet end. Dried pulps have much better drainage than never dried pulps, because they have substantially lower Water Retention Values. This offers a good opportunity for fiber blends and to improve the product portfolio. In case the company may eventually have difficulties to handle different types of woods coming from forest areas that are not very close, one recommended solution is to work with a single, flexible and uniform wood supply, and to differentiate pulps and/or papers in the mill, not in the forest.
The objective is to select and to develop trees with a broad wood and fiber characteristics and relative concentration on wood components (lignin and hemicelluloses). These trees should be able to provide optimum combination of pulp and paper properties (beyond pulp yield) according to different market segment demands. The wood is improved to provide better pulping attributes. The uniformity and flexibility on wood supply is reached by controlling genetics, species, age, silvicultural practices and forest environments. At the pulp mills, utilizing the different fiber lines the company has, differentiation is defined to supply targeted markets and customers.
It is relatively difficult to say what is the single most important pulp characteristic for a given paper mill.
The reason is that there is no universal pulp property to be managed. Depending on the paper mill bottleneck, the pulp quality is defined to guarantee the maximum performance to this mill. The most common bottlenecks are: refining capacity, drainage and retention in the wire section, paper-machine speed, steam availability, wet web consolidation and strengths, final product uniformity. As a conclusion, it may be said that the type of mill bottlenecks will define the most desirable pulp quality, up to a certain extent.
This is the case for existing mills. For new greenfiend mills, the quality may be previously built and designed, before the construction of the paper-machine and auxiliary equipment’s. However, soon the mill starts up; the bottlenecks will appear to define the new pulp quality standards. This is the reality, no doubt about. This is also the cause for domestic conflicts within the company.
BY JAMES OWINO
Eucalyptus bleached kraft pulps are rich in fibers, but fibers are not the sole anatomical elements in their contents. Fibers, fiber debris, fines and vessel elements are combined in a rich blend, in a very low pulp consistency. This complex blend is usually referred to as eucalyptus pulp. On the other hand, there is a relative trend among papermakers to consider eucalyptus pulps as a commodity product; one product that independently from the origin, the performance would be required to be similar. This is an enormous technological mistake. The purpose of this manual is to show the potential differences we may find in distinct eucalyptus pulp furnishes for papermaking. Eucalyptus bleached kraft pulps may have very distinct papermaking properties, depending on the wood raw material and on the conditions applied in the manufacture of the pulp (chipping, digesting, washing, screening, bleaching, drying, etc).
The papermaking behavior of the pulp depends very much on the anatomical and chemical properties of this mixture, but also in the different pulping and papermaking processes applied to these elements. Fiber morphology and chemical constituents are both very important to allow predictions about pulp behavior in papermaking operations. Fibers consist in the most abundant pulp component. Although their dimensions in lengths and widths are rather similar for different eucalyptus pulps, the cell wall thickness plays important difference. Based on the variations of the fiber morphology and dimensions, there are important characteristics being affected in the paper-machine operation and runnability. Fiber population and coarseness may, up to certain extent, reflect this potential behavior. However, there are other issues to be considered. Fines and
fiber deformations are some of them.
Fines are important for bonding. A pulp with no fines has poor bonding ability and low strengths. However, excess of fines brings problems in drainage in the wet end section, in dewatering in the press section, and higher density in the paper sheet. Fiber deformations are not natural on fibers, the pulp and paper manufacturing processes create them. Fiber deformations may reduce individual fiber strengths, but they are important to promote bulk and absorbency properties in paper dry sheet. Cell wall integrity and microfibril organization is another issue frequently forgotten.
The pulp maker is used to change the pulping and bleaching conditions and he has no indications about the disastrous effects he may eventually be bringing to the fiber wall. The only figure he has is the measurement of the pulp viscosity, very little to really show the damages being happening in the fiber wall. Chemical characteristics of the pulps have also been proved to be important.
The hemicellulose content plays important role. In addition to hemicelluloses, fines, fiber population, fiber coarseness and bonding, there are some other important pulp characteristics, such as water retention value, fiber collapsibility, wet fiber flexibility and wet web strength. Moreover, the ability of the fiber to hold water is becoming a critical issue. Fiber charges and hysteresis-associated properties are now being part of a pulp evaluation, due to their potential influence in the paper-machine performance (drainage and dewatering) and final product quality. Pulp quality is, for all these reasons, a group of attributes that 5 may vary according to the eucalyptus wood, the pulping process and with the particular papermaking operations the pulp user has on his hands to utilize this pulp. Pulp quality is so far very dependent on the production chain: it is built along this complete chain.
Eucalyptus pulps are recommended for papermaking due to specific properties they impart to paper: bulk, opacity, formation, softness, porosity, smoothness, absorbency, dimensional stability. Faster and more sophisticated machines are being developed to run with these pulps, but the aim is not to lose these paper properties. All the considerations about pulp quality for papermaking presented in this book chapter are solely related and valid for eucalyptus bleached kraft pulps. We are not making comparisons about different fibrous raw materials or different pulping processes. When comparisons are presented, they are comparing one type of bleached kraft eucalyptus fibers to another one. When high coarseness fibers are suggested for a specific utilization (tissue and filter papers), we are referring to high coarseness eucalyptus fibers (around 9 - 11 mg/100m). Low coarseness eucalyptus fibers are in the range 4.5 - 6 mg/100m.
The same to other properties, It has to be understood that other pulp grades, as the high yield eucalyptus pulps have also their distinct advantages and own destination for paper manufacture.
BY WANJIRU MURAGE
Mushrooms are a type of fungi and, like many plants, can be grown as food in greenhouses. Unlike most plants, however, mushrooms do not require sunlight to grow. In fact, mushrooms grow best in cool, dark areas. If you have a space like this in your greenhouse, or if you are able to make a few modifications to create such an environment, you may be able to grow mushrooms yourself
Though a small amount of light will not hurt your mushrooms, they are best grown in darkness. To grow mushrooms in a greenhouse, you may need to make a few modifications to a portion of the greenhouse to block out light. You may also need to take steps to ensure that the temperature stays fairly stable, somewhere between 55 and 60 degrees Fahrenheit. Keep the air in the greenhouse moist, and take precautions against strong drafts which can be fatal to developing mushrooms.
Trays vs. Logs
Two of the most common ways to grow mushrooms are in trays or logs. Mushroom trays are typically at least 2 feet long and 10 to 12 inches deep, and they can be purchased prefabricated or built from scrap wood. Fill the trays with growing medium, then treat with mushroom spawn. If you plan to grow a relatively small quantity of mushrooms, you may choose to use a log instead. The log should be 4 to 6 inches in diameter, at least 40 inches long and cut from an oak or some other hardwood tree during the late winter or early spring. To use the log, drill several holes into the log and plug the holes with mushroom spawn.
Mushroom Growing Medium
While many edible plants and vegetables can grow in soil, mushrooms require a different kind of growing medium. Mushrooms grow best in organic materials that are rich in natural sugars as well as nitrogen. Horse manure mixed with straw makes an excellent growing medium for mushrooms because it is moist and nutrient-rich. It is also possible to make your own mushroom compost using corn fodder, straw, peat moss and water. Unless you plan to grow a large quantity of mushrooms, however, making your own growing medium may not be practical. Many people who grow mushrooms at home choose to purchase mushroom kits that include the growing medium and mushroom spawn.
Mushroom spawn comes in several forms, and the type you need may depend on the growing method you select. Two of the most common forms of mushroom spawn are bricks and flakes. When using flake spawn, mix it directly into the growing medium at a rate of 1 quart per 15 feet of growing space. Break brick spawn into golf ball-sized pieces and plant them 1 to 2 inches deep in the growing medium, spacing the pieces 6 inches apart. During the weeks after being planted, the spawn will begin to grow mycelium, the web-like root system used by mushrooms to retrieve nutrients from the growing medium.
Caring for Mushrooms
Several weeks after planting the mushroom spawn, the growing area should become covered in a white web of mycelium. To encourage growth during these weeks, raise the temperature in the greenhouse to between 65 and 70 degrees Fahrenheit. Watering is also important during this stage to keep the spawn moist - mist the trays or logs with water twice a day for the best results. Once the mycelium forms, drop the temperature back down to 60 degrees Fahrenheit and cover the trays or logs with a thin layer of garden soil or damp newspaper. After another few weeks, tiny mushroom heads should begin to appear.
You can pick mushrooms when they are still small, in the "button" stage, or when they grow to maturity. To harvest mushrooms, use a sharp knife to cut the stem at the base. You may also harvest the mushrooms by hand, pressing down the soil around the stem with one hand and gently twisting the mushroom to separate it from the compost. Once your first batch of mushrooms appears, new growths should appear every 10 to 12 days until the compost becomes exhausted of nutrients. After harvesting your mushrooms, mist the compost twice a day until new growths appear. Do not spray developing mushrooms with water because they will most likely turn brown and die.
BY JANE MULI
Sylvi culture or Agro forestry as it is commonly known is a new farming method which is gaining momentum and being practiced widely in Kenya and the rest of the African countries. In kenya most people know it as "Shamba system" as well. This method of farming encompasses planting trees and crops at the same time, its profitable venture that ensures there is food security and at the same time generating income after a few years, thus providing the balance in food production and income at the same time.
Generally this type of farming involves planting legumes or maize in a tree plantation for few years before the canopies of the trees hoovers the crops thus avoiding them the sunlight thus maximum yields production.
It will depend on the type of trees being planted as some trees grow faster than the others and other slower.
For example planting crops together with eucalyptus trees this will call for 2 years only in planting the crops. For cypress which is a bit slower growing tree it might take 3- 4 years.
COMBINED INCOME: PLANTING OF TREES AND BEANS IN A 2 ACRE PIECE OF LAND
Labor / Material Cost
Ploughing 1 acre is Ksh. 3000 Ksh 6,000
Harrowing 1 acre is Ksh. 2000 Ksh 4,000
Irrigation 1 acre Ksh 3200 per month for 3 months Ksh 9,600
Weeding 1 acre (twice) Ksh. 2000 x 2 Ksh 4,000
Seeds 1 acre 15kgs x2 Ksh 4,000
Fertilizers 25kgs DAP 25kgs @ Ksh 1,500x2 Ksh 3,000
Harvesting 1 acre Ksh 2,000 Ksh 4,000
Miscellaneous expenses 1000 per acre Ksh 2,000
Total Expenses for one planting season Ksh 36,000
There are 8 planting seasons of beans in 2 years before the trees hoovers beans.
Cumulative Labor for this planting seasons with exception of harrowing will be Ksh 256,000
Selling one bag of bean averagely goes for 5,500 per bag.
1 acre produces 12 bags of beans normally. In this case production might reduce up to 8 bags per acre due to the space occupied by trees.
First planting season 8 bags x Ksh 5,500 = Ksh 44,000
For 2 acres 44,000 x 2 = Ksh 88,000
For 8 planting seasons is 88,000 x 8 = Ksh 704,000
Less Expenses 704,000 - 256,000 = Ksh 448,000 - harrowing 1st planting season Ksh 4,000
Profits for 2 years = Ksh444,000
In this segment the following labor costs wont be incurred as they have already been incurred above;
Digging holes and planting 2,600 x 9 Ksh 23,400
Pruning 2,600 x 8 Ksh 20,800
Fertilizers C.A.N / N.P.K 100kgs @ Ksh 3,600 Ksh 3,600
Manures 1 acre Ksh 12,000 Ksh 24,000
Tree seedlings 1,300 trees Per acre @ Ksh 12 Ksh 31,200
Miscellaneous Expenses Ksh 5000 per acre Ksh 10,000
Total Expenses Ksh 113,000
2500 trees x 4,000 = 10,000,000
Less Expenses 113,000
Profits for 5 years 9,887,000
Combined profits of Beans farming and Timber investment = 9,887,000 + 444,000
To have an in depth knowledge on Agro Forestry Click here
If we combine the profits of the above investments you will find that this type of farming is very profitable which we all should embark on.
BY PETER WANGAI
Am not against maize farming in Kenya and neither am i advocating for farmers to do away with maize farming. Reasons known well, maize is the staple food in Kenya and we all depend on it. Today we are going to have a look at timber and commercial maize farming investments.
Here is the break down.
1. COMMERCIAL MAIZE FARMING IN 20 ACRES OF LAND
Ploughing 1 acre is Ksh. 3000 .....................................................................................Ksh. 60,000
Harrowing 1 acre is Ksh. 2000 .......................................................................................Ksh. 40,000
Planting 1 acre Ksh 1600........................................................................................Ksh. 32,000
Weeding 1 acre (twice) Ksh. 2000 by 2.........................................................................Ksh. 80,000
Irrigation 1 acre Ksh 3200 per month, maturity period 7 months.................................Ksh. 448,000
Harvesting 1 acre Ksh 2000............................................................................................Ksh. 40,000
Seeds 5 bags per acre, 2kgs @ Ksh 520................................................................Ksh. 52,000
Fertilizers DAP 50kgs Ksh2800 C.A.N/UREA 50kgs Ksh1800...................................Ksh 56,000
Other expenses 1 acre Ksh 5,000...................................................................................Ksh 100,000
TOTAL EXPENSES........................................................................................Ksh 944,000
YIELDS.. 1 acre 50 bags @ Ksh 3000 by 20 acres = 3,000,000M - 944,000= 2,056,000
Profits Per Year 2,056,000 Million
Total expenses for 5 years =................................... Ksh 4,720,000
Income for 5 years =................................................Ksh 10,280,000
Income for 5 years we subtract expenses as shown below.
10,280,000-4,720,000 = 5, 560,000
TOTAL PROFITS FOR 5 YEARS...............................5,560,000
*All other factors held constant
2.TIMBER INVESTMENT PLANTING IN 20 ACRES OF LAND
Ploughing 1 acre 3,000 ..........................................................................................Ksh. 60,000
Harrowing 1 acre 2,000 ...........................................................................................Ksh. 40,000
Digging holes and planting 20 acres 8 by 26,000......................................................Ksh. 234,000
Controlling Weeds 20 acres.......................................................................................Ksh. 60,000
Pruning 20 acres (3 times, 1 time free, 2 times Ksh 4 each) 8 by 26,000................Ksh. 208,000
Irrigation 1 acre Ksh 3200 P/m (Piped water) (15 months).........................................Ksh 960,000
Tree seedlings 1 acre 1300 trees @ Ksh12 by 20 acres.........................................Ksh, 312,000
Fertilizers (NPK, CAN) 1 acre 50kgs @1800 by 20.................................................Ksh. 36,000
Manures 1 acre Ksh 12,000 .................................................................................Ksh.240,000
Other expenses 1 acre Ksh 5,000............................................................................Ksh. 100,000
TOTAL EXPENSES ............................................................Ksh 2,250,000
Income 23,000 trees by Ksh 4,000 = 92,000,0000 -2,250,000 = 89,750,000
Profits Per Year 17,950,000
*All other factors held constant
By comparing the two investment we can clearly see that timber investment is much more profitable.
PRO'S OF TIMBER INVESTMENT OVER COMMERCIAL MAIZE INVESTMENT.
Timber investment requires a lot of patience since the profits will be realized after a number of years unlike maize where the profits will be realized annually.
If we can compare the profits of 20 acres maize investment, it is almost equal to 1 acre timber investment which is Ksh 4,722,230
Everybody has already heard much about South Africa - its history, culture, political leaderships, extremely beautiful natural parks and their wild animals, privileged geographical location, gold and diamond mining and extremely good wines - a country which is now also famous for the football/soccer. However, South Africa also distinguishes itself by the excellence in planted forests and is worldwide acknowledged for the advanced technological levels developed for the forests and industrialized products obtained from Pinus, Eucalyptus, and Acacia mearnsii. For the country’s total territorial area of about 119 million hectares, there is an area of approximately 1.5 million hectares of forest plantations, which corresponds to 1.2% of the country’s total area. Due to the low pluviometric index in many of its provinces, it can be practically said that the forest plantation area has reached its maximum and should not grow further. The reason is that the planted forests require at least 800 mm of rain per year. These areas, not so abundant in the country, are also viewed by agriculture for the production of food, in order to meet the requirements of the 49 million inhabitants the country has, as well as for other important economic export-oriented agricultural crops, such as sugar cane, corn, and wheat. There is in the country so great a concern about the water resources, that there is a Ministry of Waters and Forests, with its Department of Water Affairs, Forestry and Environmental Conservation (http://www.dwaf.gov.za). This public organization establishes orientations, guidelines and promotes studies about the forest plantations, focussing much on their hydrology.
The country has a very interesting and privileged geography, as it occupies the southernmost point of the African continent. For this reason it has a vast coastal region bathed by the Atlantic, as well as by the Indian Ocean. In general, the lands are not rich in fertility, the soils are sandy and the areas have low rain precipitation in the more central region, where the mineral extractions and the biodiversity conservation parks are dominant. The richest and more populated areas are located on the coasts of the provinces of KwaZulu-Natal and Eastern Cape. The topography of these regions is flat, favoring agriculture and plantation forests. The poorest and most degraded soils are destined for Pinus and Eucalyptus plantations. The highlands of the region of the ancient Transvaal, with altitudes between 900 and 1,600 meters (at present the provinces of Mpumalanga, Limpopo and Gautang) are also very appreciated for forest tree plantations.
The forest-based business represents about 1.5% of the GDP (Gross Domestic Product), approximately 9% of the agribusiness and 4% of the exports. 55% of the woods produced by the planted forestry areas are destined for pulp and paper production, 38% for sawmills, 3.5% for underground mine props and supports, and the rest for firewood and other minor uses. The pulp production amounts to 2.4 million tons/year and that of paper and board to 2.6 million tons (45% of packaging papers; 33% of printing and writing papers; 6.5% of tissue papers). Among the specialties produced by the pulp industry are the approximately 600 thousand tons per year of dissolving market pulp manufactured by SAPPI, the most important manufacturer of this kind of pulp from Eucalyptus wood (Sappi – Saiccor pulp). The main - highly internationalized - pulp and paper manufacturing companies are two: Mondi and SAPPI. They have strong presence in important markets, such as the European and the Asian ones. The export of pulp, paper and solid wood products is very important for the country’s economy. Besides pulp and paper, other forest products distinguish themselves, such as: sawn wood, veneers, wood panels, particle boards, export-oriented chips, plywood, resins, tannin, etc.
Eucalyptus was introduced into South Africa as an exotic tree in the second half of the nineteenth century. The first experiments took place in arboreta, where Pinus and Acacia species were also tested. The commercial Eucalyptus plantations were intensified from 1930 onwards, to meet the demand for wood destined for underground mining. Very much developed for this purpose was the species Eucalyptus grandis, known by the local population as "saligna gum", because it was originally introduced as E.saligna, due to the similarity in the morphology of the trees of these two species. At present, E.saligna is much less popular than E.grandis due to its lower growth rate, similarly to the situation occurring in Brazil. E.grandis and its hybrids continue to be the most important genetic materials for the South-African silviculture and are oriented to the regions where the altitude is lower than 1,400 meters. Above that, species more tolerant of cold or frost (E.nitens, E.viminalis, E.macarthurii, E.dunnii) are planted.
In 1950, there was a forest base of 170,000 hectares of planted Eucalyptus forests, amounting at present to approximately 580 thousand hectares. From 1970 to 1990, the role of South-African research and development for the genetic forest and classic Eucalyptus breeding was fundamental, even influencing this type of research in Brazil with its technological achievements. At present, the emphasis of researching on forest improvements has been the forest biotechnology, by means of centers of investigations like FABI, CSIR, etc. (See Euca-Links).
Practically the whole forest plantation base is distributed over the coastal region in the provinces of KwaZulu-Natal and Eastern Cape, as well as in the mountains of Mpumalanga and Limpopo. The majority of the planted forests is certified (approximately 1.1 million hectares), the FSC being the dominant certification scheme.
The main planted genera in terms of area extension are: Pinus (52% or roughly 760 thousand hectares ), Eucalyptus (39% or about 580 thousand hectares) and Acacia mearnsii (8%). There are still remnants of native forests in those regions. According to the statistics (relatively uncertain), about 9% of the country is still covered by forests; what is difficult is to clearly define how and what are those forests. This is a common problem in statistics; even those from FAO - Food and Agriculture Organization – present this difficulty.
The main species in commercial Pinus plantations are: Pinus taeda, P.patula, P.elliottii, P.caribaea, P.greggii. The main Eucalyptus species are: Eucalyptus grandis, E.dunnii, E.saligna, E.macarthurii, E.nitens, E.fastigata, E.viminalis, E.smithii, E.microcorys. Furthermore, there are hybrids produced among these species and E.urophylla, E.tereticornis, and E.camaldulensis. For pole production, the preferred species are: E.paniculata, E.cloeziana, Corymbia maculata. In very arid regions, the preferred species are E.camaldulensis and E.cladocalyx, but this only occurs in small areas, to supply local demands. As the Eucalyptus introduction into the country did not occur for so large a number of species as in Brazil, the natural hybridization did not occur in so serious a way. The black wattle (Acacia mearnsii), oriented to tannin extraction from its bark, occupies about 130,000 hectares and completes the list of the main forest species planted in South Africa.
The average annual growth rate of the Eucalyptus plantations ranges from 25 to 45 m³/ha.year, but in the cold and semiarid regions the growth rates are lower, ranging from 15 to 25 m³/ha.year. Very common is the sprout coppicing for new and successive forest rotations, between 2 and 8, the number of which is higher among the rural farmers. There is a very good stump sprouting and almost total absence of more severe pests, as ants, which favors this type of management.
E.grandis, E.saligna, E.tereticornis, and E.dunnii species are very much used by the pulp and paper industry. Practically all mills consume a wood mix, in spite of the advanced forest technology largely present in the country. The first Eucalyptus pulping tests were performed in a lab in 1943 and the industrial production has already begun at the SAPPI mill of Enstra at that same time period. Since then, the Eucalyptus pulp production (paper and dissolving grades) has had a substantial growth for both export as market pulp and printing and sanitary paper manufacturing.
Considering the unavailability of areas to expand the planted commercial forest area, the emphasis in research has been placed on increasing the forest productivity. The purpose is to produce more wood from the same forest base. For this reason, silviculture and forest tree breeding are rather advanced in terms of technologies and search for new alternatives. Several universities and research centers (see Euca-Links) are dedicated to try to find new silvicultural and genetic routes, in order to guarantee the sustainability of the forest-based business in the country. The main technological forest research lines in South Africa are as follows:
• genetic forest improvement and breeding;
• forest biotechnology and genetic mapping;
• irrigated silviculture and forest hydrology;
• soil and natural resource conservation;
• Eucalyptus stump sprouting and coppicing;
• plantation reestablishment of less productive forest stands;
• hybridization and cloning;
• precision silviculture, mechanization and operations automation;
• Eucalyptus species more tolerant to cold, frost, fire, and hydric deficit;
• mechanical strength, basic density, lumber stability, and quality of the Eucalyptus wood logs;
• woods of higher aggregated value: saw-timber, furniture, mining wood, housing construction wood, etc.
Some of the South-African researchers and technical people who helped or are cooperating to build the Eucalyptus silviculture and wood-based industry histories in the country have been or were: A.P.G. Schonau, F.S. Malan, M.P.A. Coetzee, G. Malan, K. von Gadow, P.W. Varkotsch, G. van Wyk, J.G. Myburgh, J. Fox, M.J. Wingfield, B.D. Wingfield, Z. Myburg, C. Clarke, R. Baxendale, M.J.P. Shaw, P. Clegg, W.K. Darrow, R.C. Bigalke, N.O. Wessels, C. Young, D. Ramsay, E.J. Smith, G. Gerischer, L. Christov, M.J.P. Shaw, M. Plessis, J. Wright, T. Coutinho, M. Rouget, P. Crous and N. Denison. Certainly many other names would deserve to be nominated by what they are doing for the technological forest and industrial development in the country. Unfortunately, my knowledge and my network are not so great in South Africa.
Considering all this, it can be definitively stated that South Africa is one of the world’s leading countries in terms of production, management, and technologies for the Eucalyptus forest plantations, as well as for the most different uses of the woods produced by them.
Our acknowledgement and special admiration for its companies, research centers, universities, public and private entities and for all South-African technicians and researchers, for believing in the Eucalyptus as a basis for a strong, healthy, and sustainable economy.
The genus Grevillea is probably the most popular and widely cultivated of all of Australia's plant genera. The reasons for this are not difficult to find. The plants occur in numerous shapes and sizes so that there is a Grevillea for almost any conceivable garden situation. Added to this are the colourful flowers which, in many cases, attract birds.
Grevillea is a member of the Protea family (Proteaceae) and its close relatives include Banksia, Hakea, Isopogon and Telopea (the Waratah). Grevillea is named after Charles Francis Greville who was one of the founders of the Royal Horticultural Society in 1804. There are over 300 species in the genus.
Scientific name:Grevillea robusta
Common name: Grevillea, Silky oak
The flowers of Grevillea species are quite small but they occur in clusters (an inflorescence) which, in some species, may consist of perhaps 100 or more individuals. The sequence of opening of each flower is similar to other members of the Proteaceae and goes through several stages:
Grevilleas are propagated by three principal methods; seed, cuttings and grafting. Tissue culture has also been used with a few species and cultivars but this is a more specialist method which is not of practical interest to most amateur growers. To maintain desirable characteristics of a particular plant, vegetative propagation (e.g. cuttings or grafting) must be used. This also applies to propagation of named cultivars.
As seed is shed annually, plants need to be kept under observation and seed capsules collected when they first begin to open.
Germination of seed of grevilleas can be slow and sometimes difficult. To assist germination a variety of seed pre-treatments have sometimes been attempted. Some of these work on some species but not on others.
The most usual method of pre-treatment is to 'nick' or peel off the seed coat with a sharp blade to allow moisture to reach the embryo. This needs to be done with care to avoid damage to the embryo. For seed with thin walls, pouring hot (not boiling!) water over the seed and allowing it to soak for a day or so is sometimes successful.
Seed can be sown in normal seed raising mixes and seedlings could be expected to appear in anything from 2 weeks to a year after sowing, depending on the species and the time of sowing. Those species native to temperate areas may not germinate in the heat of summer (this may be an ecological factor to enhance the chance of survival of the seedling in the wild). These species are best sown in autumn or early spring.
Propagation of Grevilleas from cuttings is generally a reliable method and is preferred over seed because of both the scarcity of seed and problems in germination. In addition, cutting-grown plants will usually flower at an earlier age than seedlings.
Cuttings about 75-100 mm in length with the leaves carefully removed from the lower half to two-thirds seem to be satisfactory. "Wounding" the lower stem by removing a sliver of bark and treating with a "root promoting" hormone both seem to improve the success rate. No special propagating mixes or treatments are required.
In conclusion Grevillea robusta is mainly propagated through seeds and wildings from natural regeneration. A kilogram of seed may contain 70,000-100,000 seeds. Seeds can be stored in air-tight containers in a cool dry place for up to two years without significant loss of viability. Seeds germinate within 8 – 20 days with expected germination of 55,000 seedlings from 1 kg of seed
CULTIVATION AND ECOLOGICAL REQUIREMENTS
Grevillea robusta originated from Eastern Australia. The species was introduced in Kenya as a coffee shade and is now naturalized in the country. Grevillea robusta grows well in areas between 850 to 2500 metres above sea level with a mean annual rainfall of 600 to 1500 mm and mean annual temperatures of 13 degree Celsius to 21 degree Celsius.
Grevillea robusta trees can be planted; along boundaries, as woodlots, on terraces, in alleys, and scattered among crops such as tea, coffee, maize, bananas and beans. Planting along farm boundaries is done in single rows at 2–2.5 m spacing but in small farms it is can be planted closely spaced at about 1.5 m between trees. A spacing of 2.5 x 2.5 m is recommended for plantations and woodlots. The species performs best on well drained fertile soils but also grows moderately well on medium textured soils (loam, clay-loam to light sandy soils). However, it does not tolerate water logged soils. The species is widely grown on farms in the coffee and coffee-tea zones of central highlands eco-region with high populations of the species in; Meru, Embu, Kirin-yaga, Muranga and Kiambu counties. Grevillea robusta is a fast growing tree. On suitable sites, Grevillea can attain a height of 20 m and diameter of up to 25 cm in 15 to 20 years.
Grevillea is used for sawtimber, firewood, poles, in agroforestry applications, as fodder and bedding for livestock, and as shade for tea and coffee.
In conclusion Grevillea has deep roots and tolerates heavy pruning and pollarding, meaning it doesn’t compete for water, nutrients or sunlight with surrounding crops. It is easily propagated from seed and grows well even without fertilizer and in soil prepared by hand implements, meaning farmers can plant it without great cost or labor. Most people typically plant grevillea around their homes, to demarcate fields, as wind breaks between fields, as single trees, and in small woodlots.
What are greenhouse gases?
Most of the Earth's atmosphere is made up of nitrogen and oxygen, which do not have much effect in regulating the climate. Other gases that occur in trace amounts (<1% of the atmosphere) have a much bigger impact even though they occur in relatively small quantities. These are known as the greenhouse gases.
Energy (light) from the sun passes through the Earth's atmosphere and is not absorbed by the greenhouse gases (due to its short wavelength). The Earth absorbs this energy and radiates heat energy at a longer wavelength (infrared radiation) back into the atmosphere. The greenhouse gases absorb some of this energy and radiate much of it back towards the surface whilst the rest is radiated out to space. This plays an important role in keeping the Earth's surface warm and able to sustain life. Without this greenhouse effect the Earth would be much colder and life on this planet would be very different. This effect is called the greenhouse effect, because it acts a bit like a glass greenhouse that traps heat creating a warmer environment inside the greenhouse
Greenhouse gases include water vapour (H2O), carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), ozone and halocarbons. Some greenhouse gases, such as water vapour and carbon dioxide, occur naturally and enter the environment though natural processes as well as through human activity. Some greenhouse gases, such as fluorocarbons, are created solely through human activities.
Since the industrial revolution (about 150 years ago), human activities have led to emissions and an increase in the levels of greenhouse gases. An increase in these gases in the atmosphere means the atmosphere traps more heat and allows less heat to escape to space, leading to an increase in the average temperature of the Earth's surface.
Why is this important?
Rising temperatures may lead to changes in weather, sea levels and affect how land can be used. These changes are commonly referred to as climate change. Scientists predict even a small increase in the average temperature (about 1°C) could lead to increases in more extremes of weather including increased rainfall in some places, rising sea levels and more heat-waves and decreases in some such as cold spells. There could also be greater risk of drought in some countries in Africa and Asia and possibly more intense hurricanes.
Although it is already too late to stop climate change completely, making changes now could prevent it getting much worse.