In Asian countries, highly intensive agriculture has been popular since ancient times because of high population density, limited area of arable land and rice cultivation. Therefore, various traditional cultivation techniques had developed in order to raise the productivity of crops. Any kinds of wastes, the excretions of human and live stocks, straw, leaf litter, grassAsewages and rice husk charcoal have been used as fertilizers and soil amendments, not only in agriculture but also for gardening or revegetation. Wood ash containing some cinders was especially used as an important material for soil amendment and mineral supply.
In Japan where the domestic supply of energy sources has been limited, the forest resources, fire wood and charcoal were most important energy sources until the beginning of 20th century. Charcoal production and consumption increased with the increase of population and reached a maximum, 2.7 million ton per year in 1947. It has been estimated that wood, mainly broad leaved trees, of about 10 million ton was carbonized by traditional kiln at that time (1).
However, due to the rapid increase of imported fossil fuels in the 1960s, the so called gFuel Revolutionh occurred, and the production of charcoal decreased to a minimum of about 30 thousand ton per year in 1980s. The abrupt changes in peoplefs daily life and the changed relationships between humans and forest caused the decrease of Matsutake mushroom, mycorrhizal fungus production and the outbreak of pine wilting disease (2).
Under such circumstances, late Dr. S. Kishimoto and G. Sugiura who were experts of charcoal and wood vinegar production began the movement to make revive charcoal and to encourage the new use of charcoal in 1970fs. In 1980 they published a book gIntroduction to charcoal making on Sundayh (3) and distributed the knowledge of popular charcoal making and use. They contributed considerably toward the present prosperity of the charcoal business in Japan and Asia.. The author, M. Ogawa and his colleagues began the studies on the utilization of charcoal in agriculture and forestry on their requests in 1980 and reported the effects of bark charcoal on soy bean and pine tree in 1983 (4) (5).
encouraged by the activities of Kishimoto, Sugiura and Ogawa and the extension
of organic farming in
Due to the report, the
effects of charcoal and wood vinegar were recognized in public and authorized as
a specific material for soil amendment by MAFF (Ministry of Agriculture,
Forestry and Fishery) in 1990. However, contrary to the
government expectation of increasing the charcoal production in rural area, the
cheaper charcoals have been imported from
1. Charcoal Utilization in Agriculture and Gardening
1) Rice husk charcoal
The oldest description on charcoal use in agriculture is found in a text
book, gNogyo Zensho (Encyclopedia of Agriculture)h written by Yasusada
Miyazaki in 1697 (7). He described in it; gAfter roasting every wastes, the dense excretions
should be mixed with it and stocked for a while. This manure is efficient
for the yields of any crops. It is called the ash manureh. Probably similar
knowledge had been popular in
In Asian countries, rice husk charcoal which can be carbonized by simple methods in field soon after harvesting has been one of the most common materials for soil amendment. It seems that rice husk charcoal has been used for several thousand years since the beginning of rice cultivation in Asia, because rice husk with high content of silica is decomposed a little in soil and useless as a compost material.
The custom using rice husk charcoal mixed with excreta had been very popular among farmers particularly in wheat cultivation until about 60 years ago. There seemed to be reasonable benefits, because the charcoal can absorb and keep chemical nutrients and deodorize the excreta. However, this method was too popular to investigate for scientists. This led to the roles of charcoal in agriculture being neglected for long time. After the information on wood charcoal use was circulated in1980fs, the roles of rice husk charcoal were recognized and investigated by agricultural researcher again.
For instance, recently Ezawa et al. (8) reported that rice husk and its charcoal enhanced A (arbuscular) mycorhiza formation of some crop plants and improved soil physical properties when each material was added top soil. Ishii et al. (9) also reported the same effects on the A mycorrhiza formation of citrus seedlings. Komaki et al. (10) suggested that a small amount of rice husk charcoal could increase the growth of Catharanthus roseus, but the browning of leaves appeared with the excessive application because of high concentration of potassium and higher pH of rice husk charcoal than wood charcoal. Takagi et al. (11) proposed a practical method to reduce the outflow of pesticides and herbicides from paddy field utilizing the absorbing ability of rice husk charcoal. Also he tried to fix the bacteria with high decomposing ability of pesticide into rice husk charcoal and succeeded to reduce the outflow of herbicide simazine from a golf course (12).
@At present, carbonizing
methods have developed from the traditional kiln to the sophisticated facilities
equipped at rice mill. Dried rice husk can be carbonized automatically and
continuously in a self-fuel kiln and the extra heat is utilized for small scale
power generation (13). Recently the facility
and system has been exported to
In Asian countries, the studies of charcoal use in agriculture have
been mostly carried out by JICA (Japan International Cooperation Agency) experts.
2) Wood and bark charcoal
In 1983, Ogawa et al. (4, 5) reported that the bark charcoal powders containing a small amount of chemical fertilizers were efficient for the mycorrhiza formation of pine tree and the A mycorrhiza and root nodule formations of soy bean plant. In the experiments with soy bean plants (19), the bark charcoal of broad leaved trees was mixed with 1 % (W / W) of the inorganic fertilizer (N: P: K (8: 8: 8)), urea, super lime phosphate, ammonium sulfate and oil cake powder respectively. These charcoal fertilizers were stocked for one week and scattered over soil surface at 500 g / m2 and 1500g / m2 each before plowing. Soy bean seedlings without root nodules were planted in each plot. The plots in which inorganic chemical fertilizer was applied, 100 g / m2 and 200 g / m2 and control plots without any treatments were established to compare the efficiency.
Soy bean yields harvested from the plots with charcoal fertilizers of 500 g / m2 were mostly equal to those from the plots with 100 and 200 g of chemical fertilizer. By this method the amount of chemicals could be reduced to 1/20th. Root nodule formation was stimulated by charcoal fertilizers, but it was suppressed by the ones with ammonium sulfate and synthetic chemical fertilizer. A mycorrhiza infection rates and the spore numbers increased in the plots treated with charcoal fertilizers. It seems that the better growth of soy bean plants resulted from the enhanced root growth and propagation of symbiotic microorganisms being activated by the charcoal.
The soil microbial flora in each plot changed with the application of charcoal fertilizers. Charcoal fertilizers with higher pH than 8 inhibited the propagation of soil fungi, but enhanced that of bacteria and Actinomycetes soon after the treatment and then returned to the normal state gradually. It was hypothesis that the emission of carbon dioxide increased temporarily being caused by the high microbial activity. At the same time, the free living nitrogen fixing bacteria could be isolated on the nitrogen free medium. From the inoculation test of the charcoal which was sterilized and buried in soil for a week, it was certain that the charcoal became the habitat for root nodule bacteria (19).
The charcoal which was carbonized under high temperature is usually alkaline and porous substance, and there is no substrate for saprophytic microorganisms. When the charcoal was added into soil, at first plant roots grow toward the charcoal with enough water and air. Next some microorganisms which can endure under high alkalinity can propagate in or around charcoal. It seems that the charcoal provides a better habitat for the root and symbiotic microorganisms.
These research results were also confirmed in the TRA. Wood charcoal could improve the soil properties, but mixtures with chemical fertilizers, zeolite, wood vinegar and organic fertilizer exhibited better effects than charcoal itself on tea plant, citrus and vegetables (20), rice plant and apple tree (21) and some leguminous plants and grass for revegetation (22).
It was found that root nodule bacteria could often be immobilized with high frequency in white and hard charcoal with fine pores. So, Takagi (23) proposed the method to make the inoculum of root nodule bacteria of leguminous plants utilizing charcoal. On the other hand, A mycorrhizal fungi showed the better growth on black charcoal which was carbonized at 400-500 degree Celsius. The spore of Gigaspora margarita was formed in black volcanic soil with high carbon content (24). The application of wood charcoal to the plant associated with Frankia was effective also for the actinorhiza formation (25). In general, it is certain from these results that the white charcoal with fine pores and high pH is suitable for the immobilization of bacteria and the black one more suitable for fungi. After the study of TRA Oohira et al. (26) reported that the oak charcoal with finer pores than that of pine was more suitable for the immobilization of bacteria and Actinomycetes than that of pine. Meanwhile, the immobilizing ability of pine charcoal could be improved by mixing with acetic acid. Matsubara et al. (27) reported that coconut shell charcoal and the inoculation of A mycorrhizal fungi were effective to suppress the infection of soil born pathogen Fusarium spp..
These research results of charcoal use in
various fields were distributed not only in
3) Charcoal compost and wood vinegar
In 1980s, a private company Kingukouru invented the method to produce charcoal compost which was made from fresh chicken dung and pal shell charcoal (31). In the process of compost making, the more the charcoal is used, the faster the decomposition progresses with exothermic reaction. Under aerobic conditions the Bacillus group became dominant and produced antibiotics. Kobayasi (32) reported that these antibiotics inhibited the growth of some soil born pathogens, Pythium, Rhizoctonia, Phytophtra and Fusarium and were effective to suppress root diseases of various plants. At present the charcoal compost has been sold as a biological fungicide by the company. Following this instance, various kinds of organic composts have been produced from other livestock excretions and charcoal and sold commercially.
It had been also well known that the liquid (wood vinegar) flowing out of charcoal kiln was useful. It had been used in forestry nursery beds as a pesticide and on road sides as a herbicide. Kishimoto et al. (33) published a text book in which they recommended the use of wood vinegar in agriculture, forestry, animal husbandry and food processing describing the methods for purification, distillation and filtration.
Wood vinegar is a byproduct which is obtained from the carbonization process by cooling the smoke with air or water. This liquid contains the volatile substances emitted with pyrolysis; the water soluble fraction is wood vinegar and the oily one is wood tar. The chemical composition is different depending on raw materials. Major components of broad leaved trees are 81 % water, acetic acid 8-10 %, methanol 2.44 %, acetone 0.56 % and soluble tar 7 %, and that of conifers are rich in water, acetic acid 3.5 % and the others concentrations are lower than that of broad leaved trees (34). The chemical components of wood vinegar containing many organic substances are unstable, so it has been sold as the material complex.
It has been recognized since 1960s that the wood vinegars extracted from broad leaved trees are more efficient for the growth and rooting of various plants than that of conifers. The effects were confirmed also in the study of TRA (35) (36) (37). The concentrated liquid of wood vinegar with strong acidity can kill microorganisms, plants and some larvae, but the diluted form stimulates rooting, plant growth and microbial propagation. There are many reports of the application in field practice and generally the effects have been well known by users, but there are a few available scientific reports on the mechanisms associated with the chemical properties.
2. Utilization in Forestry and Revegetation
1) Rehabilitation and reforestation of trees and pine forest by charcoal and mycorrhiza
In 1980, Ogawa et al. (38) tried to apply the bark charcoal powders with a small amount of chemical fertilizers and succeeded to promote the growth of pine, Pinus thunbergii and cultivate the mycorrhizal fungi, Rhizopogon rubescens which is a dominant mycorrhizal species in the young stand with infertile basic sand
Some chemical fertilizers, urea, ammonium sulfate, super lime phosphate and synthetic chemical fertilizer, were added to bark charcoal powder with 0.1-1.0% (W / W) respectively. These materials were buried into the trenches 30 cm in depth and width after cutting the roots and then covered with sand. The regenerated fresh roots grew inside the charcoal layers vigorously after 3 months and the mushrooms appeared abundantly along the trenches 9 months later. After a year, the amounts of pine root and mycorrhiza increased considerably in the charcoal layers. In addition, the growth of shoots and the color of needles became better than before treatment. These apparent effects probably resulted from the regeneration of roots and the formation of mycorrhiza. It might be caused from the enhanced nutrient uptake and the water absorption through mycorrhiza. The water content in the charcoal was remarkably higher and it was kept at 40 % even in mid summer comparing with 5 % outside the charcoal layer (39).
After publishing the experiment results, similar
phenomena were confirmed by many researchers in local forest experiment
stations, because it is an edible mushroom in
The same method has been widely accepted by professional gardeners and applied to various kinds of tree species to revive famous old trees in shrines, temples and parks. Usually the charcoal powder, maximum 1 cm in diameter, has been buried in trenchs or holes together with a small amount of phosphate fertilizer and the spores of suitable mycorrhizal fungi to host plant. Sometimes the root system was exposed removing top soil and covered by charcoal powder as well. Also in nurseries, the charcoal fertilizer is mixed with pot soil to improve soil properties and inoculate the mycorrhizal fungi (41).
Both pine wilting disease by the insect and
nematode and oak wilting by the insect and fungi have been spreading mainly in
Mycorrhiza formation is essential to Pinus species which generate the forests as a pioneer plant at dry sites with infertile soil. These fungi also prefer to propagate in dry and infertile soil conditions. Therefore, it has been well known through the ecological study of pine forest (2) that the man-made pine forest should be kept at the primary stage of plant succession by cutting all of under shrubs and raking out the litter layer.
M. Ogawa proposed to rehabilitate and reforest the coastal pine forest using charcoal and mycorrhizal fungi publishing a monograph (41). In the established forest, the same methods described previously have been applied. Meanwhile, in a place from which all of pine tree were destroyed, the under shrubs and top soil must be completely removed before planting. Then pine seedlings with the inoculated mycorrhizal fungi, Rhizopogon, Pithoritus, Suillus species, are planted together with the charcoal powder. The survival rates of these seedlings were much higher than that without mycorrhiza and charcoal.
As such a trial, growing tree and burying charcoal, seems to be one of the practical methods for carbon sequestration, Ogawa M. and his colleagues have promoted the movement to make revive gWhite Sand and Green Pineh which is one of the symbolic scenery of Japan islands in order to contribute the prevention of natural disasters and the countermeasure for global warming.
2) Rehabilitation of tropical rain forest and forestation in semiarid region
M. Ogawa who was working in the rehabilitation project of tropical rain forest in 1989 found that a dominant species, Dipterocarpaceae, forms the ectomycorrhiza with several fungal species among which Scleroderma columnare enhanced the seedling growth efficiently in nursery. He tested the effect of charcoal powder on the growth of Shorea species and found that the small amount of charcoal 2 % in volume was effective to stimulate the mycorrhizal formation and the growth (42). Kikuti J. and M. Ogawa (43) devised the practical inoculation method in which several saplings with the mycorrhiza were planted inside the nursery beds and the pots were set under the canopy. By this method the mycelium of mycorrhizal fungi penetrates through holes of the pot and naturally infected. Mori et al. (44) found rice husk charcoal is also effective and established the more convenient method. Rice husk charcoal is not so harmful even if it was added excessively.
The nursery technique to inoculate the
mycorrhizal fungi with charcoal was also used in the forestation project of
pine in northern
3. Utilization of charcoal and wood vinegar in animal husbandry and fishery
Charcoal powder had been commonly used to cure the intestinal disorders of animals. In 1980s the utilization of charcoal and wood vinegar extended into the fields of animal husbandry and the fish aquaculture. In the 1970fs one of the wood vinegar makers invented a tablet of charcoal powder containing wood vinegar and sold as a medicine for livestocks ; this was formally recognized by MAFF (33). When animals take the drug with the feed, it is said that the quality of meat, fat and egg can be improved because of effect on activity of intestinal microorganisms (47). Recently the use for pig and poultry increased to avoid antibiotics and to prevent epidemics.
In general, charcoal powder has the strong ability to absorb the smell of excretions and liquid. The charcoal carbonized under lower temperature than 300 degree Celsius especially shows the strong adsorption of ammonium (48). The mixture of charcoal and wood vinegar has been used in barn of housed livestock as the deodorant and absorbent of liquid. It seems that these effects result from the complex reactions of charcoal and wood vinegar, but there has been little available scientific investigation (33).
The material containing wood vinegar also is used in the aquaculture of eel and fish to keep water clean (33). Sometimes high quality charcoal which is carbonized under higher temperature has been also used for water purification in the fish tank. From experiences it is said that fish likes to spawn around the charcoal, probably because some algae propagate on the wood charcoal and carbon fiber
4. Trials of carbon sequestration by charcoal use in agriculture and forestry
1) Developing charcoal industry
In 2000, the
fundamental law concerning the establishment of a recycling social system was
The function of charcoal for humidity control was studied intensively several decades ago (49) (50). Recently the construction companies have begun to spread the charcoal bag not only over the under floor but also above the ceiling (51). Meanwhile it was also reported that the treatment was efficient to reduce asthma and atopic dermatitis by diminishing the population of molds and ticks (52) (53).
With the development of charcoal utilization, carbonization technology is developing from the simple kiln to the automatic mass production facilities. The newly devised carbonizers including various kinds of movable batch type kiln, rotary kiln, swing kiln and etc has been sold for the mass production of waste wood charcoal. In some cases the extra gas has been used for thermal electric power generation. At the same time, the studies to establish the industrial standards and function of carbonized materials have started, and the charcoal industry begins to be renewed in the 21st century.
2) New materials of charcoal
Recently the raw
materials of charcoal are ranging from waste woods to some flammable substances.
Among them the carbonization of bamboo and its utilization has been widely
noticed as one of the management methods of bamboo forest which occupies wide
ranges in southwest
Up to several years ago, all of garbage from urban life had been burned in incineration plants, but now some cities began to carbonize the garbage and try its utilization. But there are some problems to be solved, because the water content is usually so high that it consumes too much energy for desiccation, and some products are unsuitable for agricultural use because of the high concentration of heavy metals and salt (54). Therefore, the thermal electric power plants have tried to burn the garbage charcoal mixing with coal and oil (55). The wastes disposed from food processing and live stock excretions have been also carbonized and used in agriculture with compost (55).
3) Carbon Sequestration by Forestation and Carbonization (CFSC)
On January 8 in 1991, M. Ogawa puts forward a new idea gThe earthfs green saved with charcoalh writing an article in Nihon Keizai Shinbun (Nikkei). He described in this paper the outline of this concept; The carbon dioxide emitted into air can be fixed by photosynthesis into the planted tree; If the waste wood will be carbonized and used in agriculture and other fields, a vast amount of carbon will be stored for a long term in soil, and at the same time sustainable production of crops and trees will be achieved.
In 1990s it has been recognized gradually in Japan that the carbonization are meaningful as a counter measure against global warming through the production of renewable energy and the uses for soil amendment in agriculture. However, the raw materials of carbonization in this project must be restricted only the plant residues, because it induces large scale deforestation as well as other biomass energy productions.
After COP3 (The 3rd
Session of the Conference of the Parties to the United Nations Framework
Convention on Climate Change), Ogawa (56) (57) proposed the idea gCarbon
Sequestration by Forestation and Carbonization (CSFC Project)h in
If charcoal is easily
weathered (oxidized) in field, the idea may be meaningless. But it has been actually
exhibited that the charcoal has remained for one thousand years or more without
weathering at the ruin of ancient coin studio and in the old tombs in
After the observation of stability in sulfuric acid, sodium hydrate or under ultra violet light for short term (personal communication), Kawamoto et al. (59) examined the durability of wood charcoal against ozone and estimated the half-life of the charcoal in air. The weight of saw dust charcoal carbonized at 400oC was not affected with 8.5% ozone, while the one done at 1000oC burned with 4.9% ozone. There were observed minute pores on the surface of charcoal carbonized at 1000oC. The half-life of charcoal which was carbonized at 1000oC and treated by ozone in air was about 50,000 years. From these results it is suggested that wood charcoal is stable on a geological time scale.
On the other hand, Yamato et al. (60) reported the changes in soil chemical properties and the crop yields when
the bark charcoal of Acacia mangium, which was made of waste from pulp
industry, was applied as soil amendment for the cultivation of maize, cowpea
and peanut in
Formerly it was reported that the population of free living nitrogen fixing bacteria increased around the charcoal buried in tropical soil (28). Probably a small amount of nitrogen seems to be accumulated into soil by charcoal application also in slash burn cultivation.
According to these
A similar trial was conducted also in Indonesian JICA project as a small scale example, and the research result was reported by JICA (62). In this project it was confirmed that the applications of charcoal were effective both for the seedling growth of Acacia and tree growth in field.
she feasibility study of carbon sequestration in which various kinds of waste wood out of construction, saw mill, trimmed branch and others were recycled by carbonization was conducted by RITE (Research Institute of Environment and Industry) as summarized in the previous paper(64). It was focused on the effective use of surplus heat from a garbage incinerator for carbonizing woody materials. It was prospected from the study that the waste wood of 936.0 Mg-C / year would be converted into the net carbon sink of 298.5 Mg-C / year by carbonization, with the fixed carbon recovery of the system being 31.9 %.
The life cycle
assessment has been conducted also in
From these research
results, it is expected that CSFC project will be recognized as a concrete,
easy and low cost counter measure when the global warming will intensify more
seriously in the near future. Today the charcoal uses in various fields are
extending through the release of technical information, and the charcoal production
industry is growing as one of the environment businesses not only in
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