Esther Alvarez Godoy,
Susana Díaz Aguirre
and Marta Alessandrini Díaz
are researchers at the Centro de
Estudios de Biomasa Forestal
(Forest Biomass Study Centre),
Pinar del Río University, Cuba.
Research on methods for making products such as animal feeds, fertilizers, cosmetics and pharmaceuticals from the foliage and wood residues left over by the forest industry.
In some countries, disposal of residues from the forest industry, in-cluding foliage and wood residues, can pose a problem. Yet they have significant potential to be used economically and ecologically in the production of energy and of numerous products for which there is a high demand. A great deal of information has already been published on their use for alternative energy, e.g. in the production of renewable fuels such as ethanol and ETBE (ethyl tertiary butyl ether). This article instead focuses on the processing of forest residues into high-value products for various other sectors, including the pharmaceutical, chemical and cosmetics industries and the agriculture sector. It summarizes research carried out in Cuba by the Instituto de Investigaciones Forestales, the Instituto de Ecología y Sistemática and in particular the Forest Biomass Study Centre of Pinar del Río University.
Laboratory of the Forest Biomass Study Centre at Pinar del Río University, Cuba
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The Forest Biomass Study Centre explores the use of forest residues for four categories of products:
These products are currently in different stages of development (laboratory development, laboratory testing, pilot plant, industrial production). The research strategy is directed towards reaching the phases of production and marketing of the products in the region.
The foliage of felled trees represents a source of biomass which is useful for obtaining essential oils, wax, plant extracts (chlorophyll derivatives and food concentrates) and feeds (Yagodin, 1981; Díaz, 1998).
Although foliage remaining on the forest floor provides certain benefits such as nutrient recycling and protection from soil erosion, its excessive accumulation in forests can cause problems such as increased risk of disease and forest fire. This is especially true in felling areas, where Vidal (1995) estimates that about 35 to 45 percent of tree foliage usually remains. Conifers, for example, leave behind 2 to 4 tonnes per hectare per year. Removing some of the foliage after felling thus helps lessen the risk of fire and disease.
Biopreparations produced from the foliage of forest species contain high levels of chlorophyll and carotenoids and are therefore useful for a wide range of applications such as pharmaceuticals, cosmetics and veterinary medicines. The usefulness of chlorophyll derivatives arises from their capacity to stimulate the regeneration of tissues and their antimicrobial characteristics, as demonstrated by studies carried out with pine and fir (Pavlutskaya, 1983; Mednikov, 1985).
Researchers at the Study Centre have established a methodology (patent pending) to obtain vegetable wax, essential oils, chlorophyll-carotene paste and fodder from foliage on a laboratory scale. The extractive process makes it possible to vary the end products depending on the species, the production conditions and the demands of the economy. The method has been validated through the study of two species of conifers that grow in Pinar del Río - Pinus caribaea and Pinus tropicalis.
Foliage to be processed should be green and fresh; it should be processed within 24 hours after the tree has been cut. After the branches are separated manually, the material is processed using a machine designed at the Study Centre (Vidal, 1995) which separates the leaves from the wood and then crushes the leaves to produce a leaf extract. This machine can process 6 to 10 tonnes of foliage per day. (After this process the branches can be used for wood energy or other purposes.)
Study of the biochemical composition and nutritional value of the foliage after the extraction and drying process showed that it can be successfully used as a feed supplement for livestock and poultry.
From 1 tonne of foliage from a plantation of coniferous species, it is possible to obtain:
The extracted products are used in the preparation of ointments and creams with dermatological activity (which also have veterinary uses), toothpaste, medicinal soaps, lipsticks and perfumes - goods for which there is great demand in Cuba.
Of the species studied, Pinus caribaea var. caribaea gave relatively high yields of the various products (Díaz, 1998).
Economic analysis of the benefits of the process is still difficult. From the point of view of its raw material requirements, the commercial production of chlorophyll-carotene paste is a low-cost process. The main raw material is pine foliage, which at present has no commercial value and therefore no defined price. The other materials used are an organic solvent and sodium hydroxide. The process has been designed so that 60 percent of the organic solvent used in the extraction of these products can be recovered for reuse.
Based on the experimental results, the cost of 1 kg of chlorophyll-carotene paste has been estimated as US$5.70. (The other products are obtained as by-products of the technological process of obtaining the chlorophyll derivative.) The other direct and indirect costs of processing depend on the scale of production. However, given that the current price of 1 kg of chlorophyll-carotene paste in the market is US$65 to $75, it can be inferred that its commercial production should be economically feasible and also competitive at an international level.
Extractive methods have been developed through the study of these conifer species growing in Pinar del Río
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At present, chlorophyll derivatives have a high market value, both nationally and internationally, because of the trend to use natural products; the time seems ripe for a marketing study, as there is a universal trend to establish small pilot plants for the processing of biomass.
Wood residues have been defined in different ways depending on their uses. FAO (2000) has defined wood residues as:
"The volume of roundwood that is left over after the production of forest products in the forest processing industry (i.e. forest processing residues) and that has not been reduced to chips or particles [where chips and particles are defined as `wood that has been deliberately reduced to small pieces during the manufacture of other wood products']. It includes: sawmill rejects, slabs, edgings and trimmings, veneer log cores, veneer rejects, sawdust, residues from carpentry and joinery production, etc. It excludes: wood chips made either directly (i.e. in the forest) from roundwood or made from residues (i.e. already counted as pulpwood, round and split or wood chips and particles)."
Processing tree leaves to obtain chlorophyll derivatives
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In general, the average generation of residues in the sawn timber process, for conifers, is about 30 percent of the log input biomass, including sawdust (5 to 8 percent) and bark (10 to 14 percent) (Kalincha, 1978). The accumulation of residues in sawmills can become an obstacle to the production process, so they need to be removed quickly. Some producers sell them or give them to enterprises that exploit them for a variety of uses, but often they are discarded as rubbish or indiscriminately burnt, which is a waste of organic matter that is rich in nutrients.
Accumulated sawdust, whether in the forest or in sawmill yards, constitutes a reservoir and focus for the propagation of fungi (typically of the genera Fomes, Schyzophylum and Polyporus, among others) which provoke wood rot of moribund or dead trees with a relatively high moisture content. The sawdust is also a fire risk.
Furthermore, the accumulation of sawdust can have negative environmental effects:
Various products obtained from forest residues
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The question of how to use wood-processing residues, particularly in developing countries, is a complex one, tied to economic considerations and to the availability of transport.
Traditional uses of residues include fuel (Bintley and Gowen, 1994), industrial floor-cleaning agents, litter for poultry and other livestock (Oconnell and Meaney, 1997) and various artisanal or industrial products (Arends and Donkersloot, 1985). The pulp, chemical and panelling industries are the main users of wood residues. The chemical industry uses wood chips and sawdust as raw materials for production of alcohol, fodder yeast, furfural (a solvent which is also a precursor of furfuryl alcohol, used extensively in the foundry industry) and, more recently, carbohydrate, mineral and/or protein animal feed supplements (Jolkin, 1989). In the panelling industry, residues are used for particleboard, blockboard and medium-density fibreboard, to name a few examples.
Properties of saccharified sawdust cake from Pinus caribaea and Eucalyptus saligna (percent dry weight) | |||
Property |
P. caribaea |
E. saligna |
Standarda |
Free reducing sugars (%) |
11.4 |
11.9 |
|
Total reducing sugars (%) |
16.2 |
13.3 |
8 |
Water-soluble substances (%) |
23.0 |
18.0 |
|
Ether extract (%) |
1.6 |
0.3 |
|
Crude protein (%) |
3.9 |
5.1 |
4 |
Crude fibre (%) |
58.0 |
40.0 |
<60 |
Digestibility (%) |
32.0 |
49.0 |
|
Furfural (%) |
0.017 |
traces |
<0.1 |
Acetic acid (%) |
traces |
traces |
|
Ash (%) |
3.9 |
3.8 |
|
pH |
5-6 |
5-6 |
4-7 |
a Russian standard TU OP 64.11.105-86 for quality of carbohydrate feed supplements of vegetal origin. | |||
Animal feed supplement from pine and eucalyptus sawdust. Saccharified pine and eucalyptus sawdust cake for use as an animal feed supplement is produced through hydrolysis which transforms the wood cellulose complex.
In the pre-hydrolysis treatment, the sawdust (from Pinus caribaea var. caribaea and Eucalyptus saligna) is mixed with water in a proportion of one to three. The catalyst - solid-state calcium superphosphate - is added in sufficient quantities to reach a concentration of 4 percent. The mixture is placed in an autoclave for verification of the pre-hydrolysis reaction and heated in a glycerine bath according to a pre-established protocol specifying temperatures and durations. The resulting product is wood cellulose enriched in sugars (mono- and oligosaccharides). It is smooth and dun coloured, retains the appearance of the original material and has a pleasant smell. Its properties are acceptable for its use as a feed supplement; for example, it meets Russian quality standards for carbohydrate feed supplements of vegetal origin (see Table).
Studies have been carried out on the selection of white rot mould to increase the protein and digestibility of sacccharified pine sawdust. White rot moulds are the most efficient micro- organisms for breaking down wood and all its components, including lignin. The breakdown, which takes about one week, is achieved through the secretion of the enzymes lignin peroxidase and laccase as well as cellulase and xylanase. Trials have been carried out with species of Schizophillum, Pleurotus and Panus on various substrates to select the most active strains of white rot mould. The strains that developed best in saccharified sawdust of Pinus caribaea var. caribaea were strains of Schizophillum commune and Panus hirtus.
Fertilizer obtained through bioprocessing of pine sawdust with earthworms
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Fertilizer obtained through bio-processing of pine sawdust with earthworms. Fertilizer has been produced by using the worm Eisenia foetida to bioprocess cattle dung and Pinus spp. sawdust in the proportion 75:25. The earthworm humus is a mixture of chemical compounds produced by the enzymatic digestion of the organic substrate (dung plus sawdust) and the metabolism of microorganisms. It is dark in colour (almost black), uniformly granular, lightweight and porous.
The fertility and development of the earthworms, which depend on how they are nourished, were similar whether E. foetida was fed with cattle dung alone or with the combination of cattle dung and 25 percent Pinus caribaea sawdust.
The chemical characteristics of the 75:25 cattle dung and sawdust fertilizer are similar to those of other organic fertilizers produced in Cuba: 1.02 percent N; 0.67 percent P; 0.42 percent K; 40.51 percent organic matter; 35 percent moisture; pH 6.9; C/N 21:47.
The results obtained in Cuba have potentially far-reaching economic, environmental and social dimensions, opening up new prospects for the sustainable use of forest resources.
In economic terms, the identification of a method for obtaining high-demand products for agriculture, such as animal feed and biofertilizer from non-traditional sources, represents an important advance.
In environmental terms, such conversions offer a good solution for dealing with excessive foliage accumulating in the forest and the large amounts of sawdust that build up in sawmills as a residue of primary wood processing. Elimination of foliage and sawdust in a rational manner also helps to reduce the contaminating effects of carbon dioxide emission into the atmosphere, the risk of fire and the proliferation of disease.
In social terms, the use of these methods to obtain the products described in this article demonstrates to both producers and the general population the extent to which nature, if well cared for, can provide the products needed for human subsistence. This recognition can help develop awareness of the value of the rational use of natural resources.
It is important to stress, however, that while research has shown the technology to be feasible, activities of this kind often fail to be applied because of economic and operational factors (prices, market size, market logistics, consistency of raw material supply, etc.). Feasibility studies are needed to evaluate such factors before proceeding to a higher level, with pilot or even industrial plants. Steps in this direction would be in keeping with Cuba's national policy of increasing the representation of national products in the economy. The potential of this work is beginning to be realized through a joint project (already initiated) between the Ministry of Basic Industry, the Ministry of Agriculture and the University of Pinar del Río for the development of the technology described in this article.
Bibliography
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Bintley, W.R. & Gowen, M.M. 1994. Forest resources and wood-based biomass energy as rural development assets. Science Publishers, Inc. USA.
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Oconnell, J. & Meaney, W. 1997. Comparison of shredded newspaper and sawdust as bedding for dairy cows: behavioural, clinical and economic parameters. Irish Veterinary Journal, 50(3): 167-170.
Pavlutskaya, I.S. 1983. Poluchenie i ispolzovanie khlorofilcoderzhachikh preparatov iz drevesnoi zeleni. [Obtaining and use of foliage preparations containing chlorophyll.] Lesnoi Zhurnal, 4: 23-31.
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Yagodin, V.I. 1981. Osnovi khimii i tekhnologii pereravotki drevesnoi zeleni. [Chemical and technological foundation for the treatment of foliage.] Leningrad, Russian Federation, University of Leningrad.
