WO2009031101A2

WO2009031101A2 - Beneficiation of coal

Info

Publication number: WO2009031101A2
Application number: PCT/IB2008/053552
Authority: WO
Inventors: Peter Dale Rose; Eric Egbe Igbinigie; Mark Patrick Horan; Joanna Felicity Dames; Thomas Tendo Mukasa-Mugerwa
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-09-04
Filing date: 2008-09-03
Publication date: 2009-03-12
Anticipated expiration: 2010-03-04
Also published as: WO2009031101A3; ZA201002354B

Abstract

A biological process (10) for treating coal and/or a coal derivative includes inoculating a body (16) of the coal and/or the coal derivative in particulate form, with at least one micro-organism. Plant growth is established on the surface of the body (16) by planting crops and/or grass (28) in the body (16). The coal and/or coal derivative in the body (16) is then allowed to degrade, resulting in the production of a humic particulate material.

Description

BENEFICIATION OF COAL

THIS INVENTION relates, broadly, to the beneficiation of coal. More particularly, it relates to the treatment of coal and/or coal derivatives. It relates in particular to a biological process for treating coal and/or a coal derivative.

Coal of low grade, such as roof coal, coal fines generated during coal mining and coal washing operations, and coal discard, e.g. coal discard left in the void following extraction of a main coal seam, is currently of little or no value, and handling and storage thereof present a problem. Thus far, attempts to beneficiate such low grade (low cost) coal on a commercial scale have been largely ineffective due to, amongst others, the cost of beneficiation, and the relatively low quality and value of products recovered. It is hence an object of this invention to provide a process of treating coal and/or coal derivatives whereby these drawbacks are at least alleviated. In other words, it is an object of this invention to provide a process of treating coal whereby value is imparted to waste coal by recovery and reprocessing thereof.

Coal is a complex material with many stages in its formation and its breakdown or weathering. The term 'coal derivatives' is thus intended to cover, generally, the products of the various stages of coal formation or coal breakdown.

Furthermore, it is usually difficult to pretreat coal and/or coal derivatives derived from higher rank coal such as bituminous or anthracitic hard coals, using biological processes. It is hence a further object of this invention to provide a process whereby coal and/or coal derivatives can more readily be treated biologically, to render them more amenable to further processing such as beneficiation. Thus, according to the invention, there is provided a biological process for treating coal and/or a coal derivative, which includes inoculating a body of the coal and/or the coal derivative in particulate form, with at least one micro-organism; establishing plant growth on the surface of the body; and allowing the coal and/or the coal derivative in the body to degrade, resulting in the production of a humic particulate material.

By 'degrade' is meant that the coal and/or the coal derivative is subjected, in a number of overlapping or non-distinct stages or steps, and in addition to surface attachment and/or attack by the microorganism, to a number of treatment mechanisms such as oxidation, fracturing of the coal/coal derivative substrate, weathering, reduction or breakdown into smaller particle size fractions, and/or depolymehzation and solubilization of the molecular structure of the coal/coal derivative, and is thereby transformed into the humic particulate material. Naturally, not all the treatment mechanisms specified need be present, nor need the treatment mechanisms occur in the order listed. Furthermore, the stage at which the treatment is terminated will determine the degree of degradation of the coal/coal derivative, and hence the quality and proportion of humic material that is formed.

While the invention, at least in principle, has application on any coal, including sub-bituminous coals and lignite, and even on high calorific organic minerals (coal derivatives or oil shales), it is believed that the process of the invention will find particular application in treating hard coals, particularly bituminous and anthracitic hard coals, and their derivatives.

The coal body may be inoculated with a plurality of micro-organisms, including at least one fungus. In particular, an isolate or innoculum comprising or containing a Neosartorya fischeri fungus, may be used for the inoculation. The isolate may include, in addition to the Neosartorya fischeri fungus, also other fungi such as Glomus clarum, Glomus mossea, Paraglomus brasilianum, Gigaspora gigantean, and various Phanerochaete, Trichoderma, Claviceps, Neosartorya, and Penicillium spp.

More specifically, the body may be inoculated with a fungal mixture comprising a fungal isolate, mycorrhizal strains and an inert particulate material, such as crushed brick. The fungal mixture is typically applied at a rate of about 75kg/Ha.

In principle, any suitable plants can be used to establish the plant growth. However, it is believed that particularly good results will be achieved when a grass is used. The grass may then, in particular, be Cynodon dactylon, ie so- called Bermuda or Kweek grass.

The plant growth may be established at a seeding rate of 10kg/Ha to 80kg/Ha, typically about 18kg/Ha.

Without wishing to be bound by theory, the Applicant believes that the mechanisms involved in the degrading of the coal and/or the coal derivative include (i) colonization of the roots of the plants by means of specific mycorrhizal strains added to the fungal mixture; (ii) breakdown of the coal or the coal derivative surfaces by means of coal degrading fungi and other microorganisms added to the fungal mixture; (iii) and interaction of the plants, fungi, other microorganisms, and the coal and/or the coal derivative, resulting in photosynthetic generation and release of organic carbon compounds in the root zones of the plants, thus enabling fungal attack on the coal and/or the coal derivative substrate; and (iv) the products of such fungal attack, probably in the form of mineral nutrients, are, in turn, made available to the plants to facilitate plant establishment and growth in an otherwise unanticipated or hostile environment.

The humic particulate material will thus contain complex organic acids, such as humic acid and/or fulvic acid, and/or will contain organic matter that can readily be transformed into such complex organic acids. The body may comprise a coal-containing layer in which the coal and/or the coal derivative is present. The coal-containing layer may comprise more-or-less fresh coal, i.e. recently mined coal. Instead, the coal-containing layer may comprise weathered coal, or a mixture of fresh and weathered coal. Still further, the coal-containing layer may also comprise non-coal substances, e.g. soil.

Still further, the process may include adding coal and/or coal derived material, e.g. weathered coal, to the layer, e.g. when the coal of the layer comprises fresh coal (recently mined coal), or when the layer initially contains no coal, e.g. initially contains soil only. In an embodiment wherein the layer initially contains soil only, the coal-containing layer may be formed by incorporation of coal and/or coal-derived material, preferably weathered coal, into a layer of top soil. When such addition of weathered coal is effected, it may typically be at a rate of 200tons/Ha to 400tons/Ha.

The process may further include adding a neutralizing agent to the layer for pH control, if necessary, e.g. if the coal contains a high level of sulphur which will result in excessive acid formation. Thus, agricultural lime, i.e. hydrated lime, can then be used, and may be added at a rate of 20tons/Ha to 30tons/Ha. Such neutralizing agent will normally be added to an upper surface layer, e.g. the upper 200mm, of the coal-containing layer.

If desired, a fertilizer, e.g. LAN, may be added to stimulate plant growth. The fertilizer may typically be added at a rate of about 300kg/Ha.

The process may also include watering the coal-containing layer, if desired, e.g. to speed up the weathering degradation processes.

The coal-containing layer may typically be 1 to 2 meters thick, and may be located above layers of coal and/or soil of indeterminate depth.

The degrading of the coal typically takes at least 10 weeks, e.g. from 10 to 20 weeks, depending on environmental conditions and irrigation regime. The longer the reaction time the further the degrading will proceed to the final humic particulate material and also the deeper it will progress into the underlying coal layer in stages. Areas affected may be >2m deep. This system will then contain the humic particulate material in the upper zones and partly degraded coal particles in the underlying zones. Thus, periods of 40-50 weeks will give a more complete reaction.

The process may include harvesting or recovering the treated coal, i.e. the humic particulate material, once sufficient degradation of the coal has taken place. The humic particulate material will normally contain organic acids and/or organic matter that can readily be transformed into such organic acids; the process may thus include processing the humic particulate material and recovering therefrom organic acids (such as humic acid) and/or organic matter.

In one embodiment of the invention, the coal-containing layer that is treated may be the upper layer of a coal heap or coal dump comprising particles of more-or-less fresh, i.e. recently mined, coal, typically in the particle size range of a few millimeters or even finer, up to a few centimeters. Once initial oxidative breakdown of the coal has taken place, typically after the elapse of a period of about 10-20 weeks after inoculation and grass planting has taken place, as hereinbefore described, the treated coal, i.e. the humic particulate material, can be harvested, together with the plant growth (including root material), and introduced into deep liquid fermentation reactors where methane gas production can be accomplished at relatively low hydraulic residence times, e.g. in similar fashion to the process described in US 6,143,534 which is hence incorporated herein by reference thereto.

Instead, the treated coal can be used as an organic carbon source in the treatment of mine drainage waste waters, where the oxidized coal provides the electron donor for sulphate reduction, in similar fashion to the processes described in US 6,197,196, US 6,228,263 and/or US 6,521 ,128, which are hence incorporated herein by reference thereto. In the above embodiments, the coal used may be either high grade or waste coal.

In another embodiment of the invention, the coal-containing layer may be the surface layer of a coal waste dump requiring cladding as part of rehabilitation of the coal waste dump. The coal-containing layer is then typically in the range 0.5-2m thick. Once the coal-containing layer has been converted into the humic soil-like particulate material, a range of other plant species can be established, or probably will establish naturally, to form a self-cladding surface. This self-cladding surface reduces the ingress of water into the dump, i.e. controls acid mine drainage formation, and also controls oxygen ingress into the dump, thereby inhibiting spontaneous combustion. Hitherto, such soil cladding has been effected by covering coal waste dumps with clay and top soils, and establishing different plants on the top soil. However, the cost of soil covering is significant; furthermore, over time, erosion results leading to loss of the dump cladding covers. These problems are at least avoided with the process of the present invention, which provides a self regenerating cladding process. It is believed that, when the process of the present invention is used for dump self-cladding, the humic material is responsible for absorption of water (in times of low rainfall) and by plant action enhances its transpirational loss over time. Furthermore, the grass layer controls water run-off and prevents surface erosion during high rainfall periods. There can also be a reduction in oxygen in the upper portion of the layer.

In yet another embodiment of the invention, the process of the invention also has application in open cast coal mine rehabilitation. Following an open cast coal mining operation, the void or pit that results from coal extraction, is filled with spoils as well as a layer of top soil which is typically 500-800mm deep. However, top soils lose their structure during storage and become compacted when replaced so that high quality agricultural land becomes more-or-less valueless. The Applicant has found that the compaction and fertility problems of such soils can be reversed by the addition of humic acids, utilizing the process of the present invention. Thus, in this application of the process of the invention, the coal-containing layer will first be formed by incorporating weathered coal into the top soil, typically up to a depth of about 200mm. Typically, weathered coal is then added to the soil at a rate of 200-400tons/Ha. In this embodiment of the invention, the coal-containing layer thus comprises weathered coal as well as soil. Inoculation of this layer with the micro-organisms and the establishment of the plant growth are effected as hereinbefore described.

In this embodiment of the invention, instead of weathered coal being used, or in addition thereto, humic particulate material generated by the process of the invention may be used. The humic particulate material is thus an example of a coal derivative that can be used in the process of the invention.

In yet a further embodiment of the invention, the process of the invention can find application in an integrated sustainable mine closure program. In practice, mines experience problems in achieving final mine closure licensing due to problems relating to the long-term sustainability of mine closure programs. These problems relate not only to soil rehabilitation, but also to ongoing generation and decanting of acid mine drainage waste waters into the environment. In this embodiment of the invention, weathered coal will also be admixed with a surface layer of soil as hereinbefore described so that the coal-containing layer comprises both weathered coal and soil. Once coal oxidation and breakdown has taken place resulting in the formation of the humic particulate material, crops can be planted in such material, so that high yield irrigated agricultural production can be practiced. Water used to irrigate the plants, accumulates in the mining void or pit below the layer, and which is filled with spoils, i.e. mining rubble. This results in the formation of acid mine drainage, which can be withdrawn or decanted from the void, and subjected to treatment in accordance with US 6,197,196, US 6,228,263 and/or US 6,521 ,128 with crop residues (from crops grown in the humic particulate material) providing the organic carbon source and electron donor for the process. The crops can also be subjected to further use, e.g. for production of biodiesel or bioethanol. With continued irrigation, there is thus continued flushing of the spoil-filled void, and it is believed that, over a period of years of such continued flushing, both sulphate acidity and heavy metals would be reduced to acceptable levels and thus contributing to sustainable mine closure. Still further, weathered coal or particulate humic material produced by the process of the invention can be used as a fertilizer in agriculture in situations where pure humic acid extracts could be used but are too highly priced for large scale application in row crop forming.

The invention will now be described in more detail, with reference to the accompanying diagrammatic drawings.

In the drawings,

FIGURE 1 shows a simplified flow diagram of a biological process according to the invention for treating coal in a coal-containing layer;

FIGURE 2 shows the process of the invention in a stacked-heap configuration;

FIGURE 3 shows, diagrammatically, laboratory apparatus used to carry out the soil column studies of Example 1 ;

FIGURES 4 and 5 show the results of penetromethc measurements of compacted soils treated with weathered coal and planted with Cynodon dactylon, in accordance with Example 1 ;

FIGURE 6 shows the results of column percolation, in accordance with Example 1 ;

FIGURE 7 shows the formation of humic acids in the experimental columns, in the presence of Cynodon dactylon, weathered coal, mycorrhiza and Neosartorya fischeri (84 strain), in accordance with Example 1 ;

FIGURE 8 shows biomass harvest results from 5 plots in the Klein Kopje large trial experiment, in accordance with Example 2;

FIGURE 9 shows the average runner length for various treatments of compacted soils, using differing concentrations of weathered coal, in addition to treatment in accordance with the process of the present invention, hereinafter also referred to as the 'Fungcoal Process', in accordance with

Example 2;

FIGURE 10 shows coal degradation in dump cladding studies showing a decrease in the large particle size fraction and an increase in the small particle size fractions for various treatments in pot trials of the Fungcoal Process applied to hard coal;

FIGURE 1 1 shows a molecular taxonomy dendrogram for the fungal isolate 84, showing it to be closely related to Neosartorya fischeri; FIGURE 12 shows a molecular taxonomy dendrogram of fungal species isolated from pot trials (of example 2) of the Fungcoal Process on hard coal - the relationship of clones (bold) to the nearest known species is shown;

FIGURE 13 shows a molecular taxonomy dendrogram of fungal species isolated from the pot trials (of Example 2) of the Fungcoal Process on hard coal with soil overlay - the relationship of clones (bold) to the known species is shown; and

FIGURE 14 is a gas chromatogram showing methane production from heap/dump coal treated in accordance with the process of the present invention.

Referring to Figure 1 , reference numeral 10 generally indicates a process according to the invention for treating coal in a coal-containing layer (hereinafter also referred to as the Fungcoal Process).

In the process 10, reference numeral 12 generally indicates an open cast coal mining void or pit filled with spoils or mining rubble 14, and having an upper or surface layer 16, which is 500-800mm thick, comprising a mixture of weathered coal and top soil. To form the surface layer 16, weathered coal is added to top soil at a rate of about 200-400tons/Ha.

An acid mine drainage (AMD) withdrawal or decant line 18 leads from the pit 14 to an AMD holding stage 20. From the holding stage 20, an AMD transfer line 22 leads to a biological sulphate reduction stage 24. A treated water withdrawal line 26 leads from the stage 24 and is arranged so that water passing along the line 26 can be used to irrigate crops 28 growing in the surface layer 16. A heavy metals, methane and hydrogen sulphide withdrawal line 30 leads from the stage 24.

A harvested crop line 32 leads from the mine pit site to a biodiesel/bioethanol production stage 34, with a product withdrawal line 36 leading from the stage 34. A crop or organic residue line 38 leads from the stage 34 to a holding stage 40, with a line 42 leading from the stage 40 to the stage 24.

In use, once the pit 12 is no longer actively mined, it is filled with spoils 14. An upper layer of top soil is applied to the pit, and weathered coal admixed with the soil at a rate of about 200-400tons/Ha. A coal-containing layer, typically 500-800mm thick, and comprising weathered coal and top soil is thus provided on top of the spoils 14.

The layer 16 is inoculated with a fungal mixture comprising (i) a fungal isolate comprising naturally occurring fungi including Neosartorya fischeh; (ii) mycorrhiza fungi; and (iii) a particulate carrier material, at a rate of about 75kg/Ha. The fungal isolate is that deposited in the EBRU (Environmental Biotechnology Research Unit at Rhodes University in Grahamstown, South Africa) Culture Collection under accession number 84. Cynodon dactylon is planted on the upper surface of the layer 16 at a seeding rate of about 18kg/Ha.

The Cynodon c/acfy/on/fungi/mycorrhia/weathered coal interaction results in degradation of the weathered coal as hereinbefore described, and also results in decompaction and enhanced fertility of the top soil, as also hereinbefore described. After a period of 10-40 weeks, and depending on climatic conditions, the layer 16 is ready for further processing.

At that stage, crops 28, for example maize or other crops, can be planted in the layer 16. The plants are cultivated using naturally occurring water, i.e. rain, as well as treated water supplied through the pipeline 26. Water that passes through the layer 16 accumulates in the pit 12, and becomes contaminated with sulphate acidity and heavy metals, and thus gives rise to acid mine drainage waste waters. This water is withdrawn and subjected, in the stage 24, to biological sulphate reduction as described in US 6,197,196, US 6,228,263 and/or US 6,521 ,128 with crop residues, which enter the stage 24 along the line 42, providing the necessary carbon and electron donor source. Heavy metals, methane and hydrogen sulphide are generated in the stage 24, and are withdrawn along the line 30. Treated water, which is thus effectively free of acidity and heavy metals, is used to irrigate the crops 28.

It is believed that, over a period of several years, sulphate acidity and heavy metal content of the water withdrawn along the line 18, will be reduced to acceptable levels.

From time to time, the crops 28 are harvested and transferred to the processing stage 34 along the line 32. In the stage 34, bioethanol (if the crops are, for example maize) or biodiesel (if the crops 28 are for example sunflower), can be produced, with the resultant ethanol or diesel withdrawn along the line 36.

Instead of, or in addition to, the crop residues which are passed into the stage 24 as carbon and electron donor source, the coal degradation product that is formed in the layer 16 can be used as carbon and electron donor source in the stage 24.

Alternatively, with reference to Figure 1 , the process 10 may be employed in rehabilitation of degraded agricultural land. In such an embodiment, a tract of degraded agricultural land 12, comprising degraded agricultural material 14, is provided with a top-layer 16 of weathered coal and optionally soil. The layer 16 is inoculated as described hereinbefore and, after conversion of the coal to a humic particulate material a product of humic acid (organic acid) and/or organic material which can readily be transformed to humic acid, is withdrawn from the layer along product stream 18. In the case that organic material is withdrawn, the process involves harvesting of the upper layer 16. The humic acid is re-introduced into the land 12 and the organic material is optionally treated further in a treatment stage 24. It will be appreciated that, in this embodiment, only a treatment stage 24 is required and not an AMD holding stage 22. It is expected that treatment of the organic material will typically involve extraction of humic acid therefrom and will be effected by well-known extraction methods, such as alkali extraction methods. The organic material may also be directly re-applied to the land 12, without further treatment, to be treated together with microbial inoculum and the reintroduced humic acid in situ. It is expected that by recovering and/or extracting and re-introducing the humic acids into the land, and by optionally applying another layer 16 and repeating the process, compaction and fertility of the soil will be beneficially influenced.

Crops 28 can be planted in the layer 16 and, when harvested, can be employed in the bioethanol/biodiesel production stage 34 in production of bioethanol/biodiesel.

It is envisaged that instead of, or in addition to the cultivation of crops 28 as hereinbefore described, high diversity grasslands can also be established in rehabilitated agricultural lands or open cast mining soils. In such an embodiment, produced biomass can be used in production of biofuels, as well as in carbon sequestration.

By this application of the invention it is envisaged that degraded agricultural lands can be rehabilitated by the reintroduction into such agricultural lands of organic (humic) acids and other organic material, which are fossilized in the coal contained in the coal layer 16 and which are recovered by application of the process of the invention.

This embodiment of the invention is, of course, not limited to agricultural lands and may be employed in any degraded soil lands.

Referring now to Figure 2, reference numeral 100 generally indicates an embodiment of the invention in a so-called stacked-heap configuration. It is envisaged that, in this embodiment, accelerated oxidation of coal can be effected thereby to produce products such as humic acids and weathered coal which may find application in rehabilitation of agricultural lands or waste coal dumps. In such an embodiment a coal substrate is comminuted to a convenient particle size and is arranged in a stacked heap 102 on a convenient site where decomposition thereof and product recovery therefrom can be effected. In another case, the stacked heap 102 may be located on a waste coal dump. It is expected that a wide range of particle sizes will be acceptable and will typically be dependent on field conditions. It is expected that typically 10-30mm particle diameter can be used. A surface layer 104 (typically 20-30cm deep) of the stacked heap 102 is inoculated with a fungal mixture, weathered coal, possibly also lime and fertiliser, and is then seeded with Cynodon dactylon (Kweek or Bermuda grass). The layer 104 is then irrigated to ensure good germination and take of the grass. Over a period of time, typically 20 to 40 weeks, the coal particles in an upper layer of the heap 108, i.e. the uppermost 0.5 to 2 m of the stacked coal heap, are broken down to smaller fraction sizes and are oxidised to produce a high yield of extractable humic acids (HA). It is expected that up to 40% yield can be achieved. The upper layer 108 may then be harvested and the process repeated by inoculating a newly exposed layer on the underlying coal material as described.

In an embodiment wherein the stacked heap 102 is a located on a waste coal heap, if the upper coal layer 108 is not harvested and is retained in position, the coal in the upper layer 108 eventually degrades to a soil-like humic material and forms a self-cladding layer on a surface of the waste coal dump. This forms a permanent layer enabling covering of waste coal dumps and thus facilitating sustainable rehabilitation thereof. It is once again envisaged that crops or grasses, such as Cynodon dactylon, may eventually be cultivated in the covering layers for the production of biofuels.

EXAMPLE 1

Laboratory experiments were conducted to prove some of the features of the process 10 of Figure 1 . Soil column studies were undertaken as follows:

PVC columns 50 (95x10cm) as shown in Figure 3 were used to simulate the soil capping used in strip mine rehabilitation and to evaluate the effect of the Fungcoal treatment process in these soils. Each column 50 was supported vertically by support struts 52. The lower end portion 54 of each column 50 was closed off with a plug 56 while drain openings 58 were provided in the end portion 54. A beaker 60 was placed below each column, to catch irrigated water. Each column was about 1 m long. The bottom 10cm was filled with stones 62; the next 60cm was filled with untreated soil 64; and an upper layer of treated soil 66 (20cm deep) was located on top of the untreated soil. These columns 50 were packed with soil 64 sourced from compacted strip mine rehabilitation areas, and the upper zone or layer 66 of the columns amended with various treatments and controls relating to the Fungcoal Process including weathered coal addition. Cynodon dactylon sprigs and also seeds were then planted in this upper zone. The columns were placed in a constant environment growth chamber with a 14:10 hour light:dark illumination regime. Plant growth, water retention and penetromethc readings were taken during the course of the experiments.

Figures 4 and 5 show changes in penetrometer resistance in the soil column studies and show that soil compaction is reduced by the Fungcoal Process.

Fig 6 shows improved water retention with change in weathered coal addition to the soil layer 66 in the soil column studies.

EXAMPLE 2

The application of the process of the invention for dump self-cladding was investigated on a laboratory scale using pot and column experiments as well as field studies.

The coal column and pot studies were undertaken as follows:

PVC columns 1.5xO.2m or pots 20cm deep were packed with hard dump coal and used to simulate the top 1 .5m of the coal dump when subjected to the Fungcoal treatment process. The top 20cm of the column was amended with various treatments and controls relating to the Fungcoal Process including weathered coal and inoculum addition. Cynodon dactylon sprigs and seeds were then planted in this upper zone. The columns were placed in a constant environment growth chamber with a 14:10 hour light:dark illumination regime. Plant growth was monitored during the course of the experiment. After 44 weeks the columns were unpacked and the following measured: plant biomass production, humic acid production from weathered coal and hard coal breakdown, change in particle size fraction, and total genomic DNA extraction and taxonomic phylogeny of the microbial population.

The results of these laboratory studies are shown in Figure 7. In Figure 7, "Cynodon" refers to "Cynodon dactylon", "WC" refers to "weathered coal", "AMF" refers to "arbuscular mycorrhizal fungi, and "84" refers to "Neosartorya fischeri fungus (84 strain)". Figure 7 thus shows the humic acid production (in mg/{) along the depth of the column used in the laboratory studies. Fig 6 shows increased humic acid production by the action of the Fungcoal Process applied in coal column studies. An increase in humic acid concentration (in the presence of the Fungcoal Process) translates into improved soil structure and fertility as is also well known in the prior art. From Figure 7, it is clear that the full Fungcoal Process treatment yields the greatest production of humic acid from the weathered coal.

Field trials of the dump cladding Fungcoal Process: Five 20x20m plots were prepared on the surface of a hard coal dump. Various treatments were applied as described below and then incorporated into the top 20cm of the dump surface. The plots were then irrigated to germinate seeded plots and to establish sprigs in the sprig-planted plots. Fig 7 shows improved Cynodon dactylon biomass yield for the various treatments comparing the full Fungcoal process (hard coal/weathered coal/lime/fungal inoculum) on plot 3. Plot 1 is Fungcoal without lime and sprig planted, plot 2 is the hard coal/lime control; Plot 3 is the full Fungcoal process seed planted, plot 4 is the full Fungcoal process without the weathered coal addition and seed planted, plot 5 is the full treatment seed planted with the exception of lime. Fig 8 also shows improved Cynodon dactylon growth when the Fungcoal Process is applied. Fig 9 shows coal degradation in the dump cladding study and indicates a decrease in the large particle size fraction and an increase in the small particle size fraction for various treatments of the Fungcoal Process applied to hard coal. This result indicates the weathering function that is considered to play a role in the degradation of the hard coal in this operation which results in an increase in the humic acid component.

EXAMPLE 3

Decompaction studies, also undertaken in column experiments, showed that compacted soils were expanded when humic acids were released due to the action of the plant and fungal inoculum on weathered coal. The experimental apparatus used was the same as in Example 1. The results are shown in Figure 4, which shows that treated samples revealed increased pressure due to expansion of the soils caused by humic acid release from the weathered coal.

EXAMPLE 4 Molecular taxonomy was carried out on the fungal isolate EBRU Culture Collection no 84, and was shown to be closely related to Neosartorya fischeri, as indicated in Figure 1 1 . Figures 12 and 13 report phylogenetic dendrograms showing the various clones isolated from the pot trials of the dump cladding study after 44 weeks without and with soil overlay respectively. It is important to note that clones closely related to Neosartorya and Paraglomus which were present in the initial inoculum were reisolated from the system after 44 weeks treatment indicating a relationship of these organisms to the processes taking place in the system.

EXAMPLE 5

As described hereinbefore, an application of the process of the present invention, ie the Fungcoal Process, is for heaped/dumped coal treatment, with the resultant treated coal being suitable for use for methane production. This was simulated on a laboratory scale by using hard coal from the top 0.5m layer after degradation in the dump cladding application of the Fungcoal Process (Example 2). The humic particulate fraction known as Fungcoal Product was added to flasks containing a basic mineral medium and a mixed microbial culture containing selected methane producing bacteria. The flasks were sealed and connected to a gasometer and incubated at 28⁰C. The volume of gas produced was measured and the gas analyzed using conventional gas chromatography. The results are shown in Figure 14 which clearly indicates the feasibility of producing methane from coal treated in accordance with the present invention.

The process of the invention, i.e. the Fungcoal Process, thus provides a novel coal beneficiation process. When it is used for coal heap/dump treatment, it can be considered to fall within the broad category of heap leach systems widely used for the beneficiation of various mined ores, in this case coal and/or coal derivatives.

By means of the Fungcoal Process, waste coal material, such as waste coal and/or coal derivatives, can thus be beneficiated, resulting in the production of humic particles which can be processed further, normally with little or no need for further comminution, eg crushing, thereof. Such further processing can include treating the humic particulate material to produce humic acid therefrom. Humic acid has a wide range of applications. Instead, the humic particulate material could find application as a product, without further processing thereof, in the humic acids market.

The Fungcoal Process can thus also be viewed as a type of mineral processing operation which has beneficiation and extraction objectives. By subjecting low grade coal and/or coal derivative to treatment in accordance with the Fungcoal Process, they are thereby beneficiated, permitting higher grade products to be recovered, eg by means of extraction.

Still further, the Fungcoal Process can be considered a form of heap leach biotechnology for coal beneficiation and product extraction, with applications to dump processing operation (to produce a humic product for further downstream treatment such as methane production, or as a final product in its own right, or to effect a dump self-cladding function) and to in situ extraction of humic acids from weathered coal added to a soil layer.

Thus, the Fungcoal Process provides a heap leach technology which provides a low-cost and low-tech methodology for the pretreatment of a coal.

Claims

1. A biological process for treating coal and/or a coal derivative, which includes inoculating a body of the coal and/or the coal derivative in particulate form, with at least one micro-organism; establishing plant growth on the surface of the body; and allowing the coal and/or the coal derivative in the body to degrade, resulting in the production of a humic particulate material.

2. The process according to Claim 1 , wherein the body is inoculated with a plurality of micro-organisms, including at least one fungus.

3. The process according to Claim 2, wherein the body is inoculated with a fungal mixture comprising a fungal isolate, mycorrhizal strains and an inert particulate material.

4. The process according to Claim 3, wherein the fungal mixture is applied to the body at a rate of about 75kg/Ha.

5. The process according to any one of Claims 1 to 4 inclusive, wherein a grass is used to establish the plant growth.

6. The process according to Claim 5, wherein the grass is Cynodon dactylon.

7. The process according to any one of Claims 1 to 6 inclusive, wherein plant growth is established at a seeding rate 10kg/Ha to 80kg/Ha.

8. The process according to any one of Claims 1 to 7 inclusive, wherein the body comprises a coal-containing layer in which the coal and/or the coal derivative is present.

9. The process according to Claim 8, wherein the coal-containing layer comprises recently mined coal.

10. The process according to Claim 8 or Claim 9, wherein the coal- containing layer comprises weathered coal.

1 1. The process according to any one of Claims 8 to 10 inclusive, wherein the coal-containing layer also comprises soil.

12. The process according to Claim 1 1 , wherein the coal-containing layer is formed by incorporation of coal and/or coal-derived material into a layer of top soil.

13. The process according to any one of Claims 8 to 12 inclusive, which includes adding a neutralizing agent to the coal-containing layer, for pH control.

14. The process according to any one of Claims 8 to 13 inclusive, which includes adding a fertilizer to the coal-containing layer to stimulate plant growth.

15. The process according to any one of the preceding claims, which includes harvesting the humic particulate material, once sufficient degradation of the coal has taken place.

16. The process according to Claim 15, wherein the humic particulate material contains organic acids and/or organic matter that can readily be transformed into such organic acids, with the process including processing the humic particulate material and recovering therefrom organic acids and/or organic matter.