Abstract:
The fire log comprises an organic fibre base that is over-saturated with vegetable cooking oil. The vegetable oil is contained and sealed therein by a casing made of the vegetable wax. More specifically, the fire log is over saturated with 65%-75% by weight of vegetable oil. The vegetable oil is used vegetable cooking oil. The organic fibre base represents about between 20%-30% by weight and consists of compressed paper-based products such as cardboard, newsprint and recyclable paper. The vegetable wax casing represents about between 1-5% of its weight. In another aspect of the present invention, the organic fibre base is made of broken fibres and interstices, and the vegetable oil is infused therein while these fibres are dilated from their natural states. In yet another aspect, the organic fibre base is formed in a perforated cylinder whereby a bark-like appearance is imprinted on its surface.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention pertains to artificial fire logs and other fuel elements made of organic fibrous materials mixed with vegetable oil and encased in vegetable wax. More particularly, the invention pertains to a fuel element containing an organic fibrous material that is over-saturated with vegetable oil, and to a process and an apparatus for manufacturing such fuel element.  
       BACKGROUND OF THE INVENTION  
       [0002]     Manufactured fire logs are normally used as substitutes for cordwood in fireplace and small wood stoves during power outages for example or simply for pleasure. Synthetic fire logs can be purchased one at the time and are generally wrapped neatly, making them more attractive than natural wood blocks to the occasional user. Their clean-burning characteristics are advantageous over natural wood, and therefore these logs are also preferred by the environment-conscious people.  
         [0003]     Fire logs currently available to consumers are dividable in two types. The first type contains about 40-60% wax with the remaining portion being sawdust, wood chips or wood shavings. The second type contains wood fibers in various forms impregnated with vegetable, animal or petroleum oil. In both types, the wax and the oil are the primary source of heat with the fibrous material being the substratum of the product. Typically, fire logs have a heat capacity of almost twice as much as cordwood and their moisture contents are much lower, providing a more complete combustion.  
         [0004]     In regard to prior art in this field, the inventions described in the following documents represent good examples of the types of fire logs preceding the present invention.  
         [0005]     U.S. Pat. No. 1,484,302 issued to C. Y. Garrett on Feb. 19, 1924, discloses a combustible block which is used as a fire kindling material. The block is made of pieces of wood, or wood pulp impregnated with resin and coated with wax. Different compositions are proposed. For example, the wood shavings content is 25% to 75% and the resin content is 25% to 58%.  
         [0006]     U.S. Pat. No. 4,120,666 issued to S. R. Lange on Oct. 17, 1978, discloses an artificial fireplace log made of shredded paper and wax. The preferred proportions are 32% to 45% paper and 55% to 68% wax.  
         [0007]     U.S. Pat. No. 4,326,854 issued to J. D. Tanner on Apr. 27, 1982 discloses a synthetic fire log made of 35%-40% by weight of cellulosic material such as wood or paper, a suitable liquid combustible by-product such as vegetable or animal oil, and a gelling agent to solidify the liquid by-product therein.  
         [0008]     U.S. Pat. No. 5,244,472 issued to J. J. Simmons on Sep. 14, 1993 discloses a method to manufacture cellulosic fuel from wood chips impregnated with vegetable oil. The wood chips are immersed in hot vegetable oil and heated to reduce the moisture content in the wood chips to less than 10%, and until the oil content of the wood chips is between 10% to about 30%.  
         [0009]     U.S. Pat. No. 6,017,373 issued to G. Frisch on Jan. 25, 2000 discloses an artificial log which contains coriander seeds to create a crackling sound. The log is made of 35% to 55% by weight of a combustible material such as wood chips, sawdust, cardboard, and 45% to 65% by weight of a flammable wax binder material such as paraffin or stearic acids derived from vegetables.  
         [0010]     U.S. Pat. No. 6,458,177 issued to M. Cox on Oct. 1, 2002, discloses a synthetic fire logs made of wood waste and wax in a ratio of 40:60.  
         [0011]     Emissions from residential wood stoves, furnaces and fireplaces contribute significantly to particulate matters (PM) and volatile organic compounds (VOC) released in the air. The adverse effects of these and other pollutants on human health and on the environment have resulted in the development and implementation of the Kyoto Accord™, and associated preventative actions to reduce these emissions.  
         [0012]     It is believed that the moisture content in a fire log is a first cause of pollution. The moisture content of the log prevents a full combustion of the log. Such incomplete combustion creates emissions containing large quantities of particulate matters and carbon oxides (CO). Also, it is known that the burning of logs containing petroleum by-products such as paraffin wax causes emissions that could contain carcinogens.  
         [0013]     The type of synthetic fire logs which is of interest herein contains primarily fibrous organic materials, and vegetable oil as the primary fuel element. It is known that vegetable oil is more combustible than wood resins and wax, and therefore the oil burns more efficiently with less pollution than natural wood or paraffin wax. Therefore, it is believed that air polluting emissions, including particulate matters, carbon oxides, benzene, an formaldehyde, can be reduced significantly by burning manufactured fire logs containing vegetable oil, instead of cordwood or synthetic logs containing petroleum oils or paraffin wax.  
         [0014]     Many attempts have been made in the past to infuse as much vegetable oil as possible in wood fibers or in other organic fibers to make synthetic fire logs. Vegetable oils and especially used cooking oils are easily available from restaurants and hotels for examples, and therefore this product is a preferred ingredient for making synthetic fire logs. However, it has been generally accepted that the maximum oil-absorption capacity of wood fibers is about 60% by weight of the product. Therefore the heat content of a synthetic fire log has been limited by the fibre mass of the log, basically.  
         [0015]     As such, it is believed that a market demand still exists for a synthetic fire log having a better heat content than the prior art fire logs, and which produce less pollution. It is believed that a need exists for a manufacturing process whereby vegetable oil is infused in a fire log in a proportion that is greater than 60% of the weight of the log.  
       SUMMARY OF THE INVENTION  
       [0016]     The composition of the fire log according to the present invention is different from those currently available commercially as it basically comprises recyclable organic fibers over-saturated with vegetable cooking oil. The vegetable oil is infused into the organic fibres and is contained and sealed therein by an envelope made of the vegetable wax.  
         [0017]     More specifically, the fire log according to the present invention is over-saturated with vegetable oil in a proportion of 65%-75% by weight. The vegetable oil is used vegetable cooking oil. The organic fibrous substratum thereof represents about between 20%-30% by weight and consists of compressed paper-based products such as cardboard, newsprint, and other recyclable paper. The vegetable wax envelope represents about between 1-5% of the weight of the log.  
         [0018]     Testing of the fire log according to the present invention has determined that the fire log has a calorific value of 33 MJ/kg, and the burning thereof produces emissions that contain 84% less particulate matters and 94% less carbon oxides than cordwood.  
         [0019]     In another aspect of the present invention, there is provided a method to manufacture the fire log mentioned above. The method comprises the step of providing recyclable paper material and causing this recyclable paper material to decompose by exposing it to sunlight, rain and wind. The decomposed paper material is then mixed with water and further broken down until an homogenous slurry is obtained. Water is removed from the slurry until the water content of the slurry is at a saturation point of the slurry. A measure of this slurry is compressed in a perforated cylinder until a solid fuel block is formed. The solid fuel block is dried by heat, and while it is still warm, the solid fuel block is immersed in warm vegetable oil, thereby causing vegetable oil to be absorbed therein. The fire log is then encased in a vegetable wax cover to retain the vegetable oil therein.  
         [0020]     This method is advantageous for obtaining an organic fibrous block that has broken fibres and interstices to retain the oil component therein. Furthermore, it is believed that the heating of the solid fuel block prior to infusing the vegetable oil therein causes the fibres to dilate from their natural state, thereby causing larger surfaces and larger pores on these surfaces to which vegetable oil can adhere. It is believe that the large quantity of interstices and the porous dilated surfaces of the organic fibres are important contributing factors in increasing the oil-absorption capacity of the solid fuel block beyond the maximum oil-absorption capacity stated in the prior art.  
         [0021]     In yet another aspect of the present invention, there is provided an apparatus for manufacturing a fire log and for making dimples and streaks on its surface. This apparatus comprises basically a perforated cylinder mounted vertically and having means to received a measure of fibrous slurry therein. A top piston is mounted above the upper end of the cylinder in such a way that it can move downward inside the perforated cylinder through the upper end of the cylinder. A bottom piston is mounted inside the bottom end of the perforated cylinder and is movable upward a first distance inside the perforated cylinder. The downward movement mentioned above and the first upward distance are respectively about one third of the length of the perforated cylinder, in order for the pistons to compress a measure of fibrous slurry inside the perforated cylinder and to form a solid fuel block out of this measure of slurry, having one third of the initial volume of slurry. The bottom cylinder is further movable a second distance to eject a formed solid fuel block through the upper end of the perforated cylinder.  
         [0022]     During the compression of the solid fuel block inside the perforated cylinder, the fibrous material expands into the perforations of the cylinder. Numerous dimples are thereby formed on the surface of the fuel block. Some of these dimples are compressed inward during the ejection of the solid fuel block from the perforated cylinder and spring back later, while others are sheared off causing streaks to appear on the surface of the solid fuel block. These dimples and streaks simulate a bark appearance on the surface of the fire log.  
         [0023]     This brief summary has been provided so that the nature of the invention may be understood quickly. A more complete understanding of the invention can be obtained by reference to the following detailed description of the preferred embodiment thereof in connection with the attached drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]     One embodiment of the present invention is illustrated in the accompanying drawings, in which like numerals denote like parts throughout the several views, and in which:  
         [0025]      FIG. 1  is a partial and cutaway side view of a press used for manufacturing the fire logs according to the preferred embodiment of the present invention;  
         [0026]      FIG. 2  is a perspective end and side view of a fire log according to the preferred embodiment in an intermediate stage of its manufacturing;  
         [0027]      FIG. 3  is a partial side view of a live bench used for drying the wax cover applied to the preferred fire logs. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0028]     While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will be described in details herein one specific embodiment, with the understanding that the present disclosure is to be considered as an example of the principles of the invention and is not intended to limit the invention to the embodiment illustrated and described.  
         [0029]     The fire log according to the preferred embodiment of the present invention is made of organic fibers obtained from waste paper and card board, impregnated with used vegetable oil and encased in vegetable wax. The vegetable oil is the primary fuel element and is comprised in the final product in a proportion of about 65%-75% by weight. The waste paper is the secondary fuel element and is comprised in the final product in a proportion of about 20%-30% by weight. The vegetable wax is athird fuel element and is used as a casing to prevent the leakage of the vegetable oil from the fibrous base. Its content in the final product is about 1-5% by weight.  
         [0030]     The high content of vegetable oil and the advantageous combustion characteristics of the preferred fire logs are attributable to various factors which will be explained in the following method.  
         [0031]     Preparation of the Vegetable Oil  
         [0032]     The preferred vegetable oils consist of used cooking oils gathered from restaurants and hotels. The preferred oils are canola oil, soy oil, corn oil, peanut oil, and other vegetable oils. If desired, essential oils may be added to the vegetable oils to provide a pleasant aroma when the log is burning. Additions of essential oils to the vegetable oil should be limited to about between 1% and 24% by weight of the vegetable oil.  
         [0033]     The first step in the preparation of the vegetable oil consists of screening the oil to remove any food particles and other impurities from it. The oil is then heated to about 212° F. (100° C.) and maintained at that temperature for several minutes to evaporate any water that may be present in it. The oil is kept at this temperature until there is no bubble rising to the surface. It was found that if the oil is not filtered and the water is not removed, the fire log made with it will not burn as cleanly and efficiently as in the case of a log made with clean oil. The filtered oil is then stored in a holding tank and kept at a temperature slightly above room temperature until the solid fuel block is dipped into it.  
         [0034]     Preparation of the Solid Fuel Block  
         [0035]     The preferred organic fibrous substratum or solid fuel block, is made of waste paper such as box board, corrugated board, cardboard, newsprint, paper-based egg cartons, paper-based coffee-cup trays, brown paper bags, bond paper, and any other recyclable paper. The types of paper that should not be used in the preferred fire log according to the preferred embodiment are catalogue and magazine paper having a glossy finish, and wrapping paper having a metallic coating such as Christmas gift wrapping paper, candy bar wrappers and potato chip bags.  
         [0036]     A first step in the preparation of the paper stock consists of removing all staples, tapes, plastics and labels from it. The paper stock is then wetted and laid in the outdoors on a clean surface, so that it remains exposed to sunlight, rain and wind for 4-5 days. If there is no rain during that period, the paper stock is preferably wetted at least twice per day using a garden hose. The exposure of the paper stock to the elements helps to degrade the paper and to break the fibers in the paper. During winter, the paper stock is preferably laid in a heated greenhouse for at least 5 days or more and wetted regularly until its pieces break down when pulled up lightly.  
         [0037]     The preferred proportion of paper in a typical batch is about 70% box board, corrugated board, cardboard and brown paper; 20% newsprint, and 10% other types of paper such as bond paper.  
         [0038]     The paper stock is taken from outside and transferred into a hydra-pulper™ for further breaking down its fibers. The re-pulping process is carried out with a water-fiber ratio of about 4:1 by weight. For yet better results in breaking down the fibers, warm water should be used in the re-pulping process.  
         [0039]     The high water content as specified above is advantageous for washing out industrial contaminants in the paper such as inks, dies and glues. It is believed that the initial exposure of the paper to the elements prior to re-pulping contributes to a better breaking down of the fibers as well as a better breaking down of the bond between the fibers. It is believed that the breaking down of the paper fibers from the initial exposure of the paper to water, wind and sunlight, increases the available surfaces and the interstices in the solid fuel block to absorb more vegetable oil therein.  
         [0040]     Re-pulping is carried out until the paper stock has a consistency and appearance of thin sludge, free of lump. Re-pulping should be carried out until the fibre stock has a homogeneous furry feeling to the touch.  
         [0041]     The sludge is then taken out of the re-pulper in batches and laid on a screen having a mesh size of about ⅛ inch (3 mm), such that the excess water can drip out. When dripping substantially stops, the batch is ready to be processed through the next step. The water content of the sludge at that time is at a saturation point.  
         [0042]     Another portion of the water present in the sludge is extracted during subsequent compression and extrusion steps, which are carried out in a press. The purpose of the compression step is to obtain a moisture content of approximately 15%.  
         [0043]     A preferred press is illustrated schematically in  FIG. 1 . The press comprises a double-wall cylinder with a piston in each end. The press is made of stainless steel or a similar metal resistant to corrosion. The inside cylinder  22  is perforated with ⅛ inch (3 mm) holes spaced apart at ½ inch (12.7 mm) intervals and is referred to as the perforated cylinder  22 . The outside cylinder  24  which is shown in a cutaway view in  FIG. 1 , has a solid wall and forms a vessel around the perforated cylinder  22 . A drain pipe  26 extends from the bottom of the outside cylinder  24 . A first piston  28  is mounted above the perforated cylinders  22  and is movable into the perforated cylinder  22  from the top end thereof. A bottom piston  30  is mounted below the cylinders and is movable inside the perforated cylinder  22  from the bottom end thereof. The perforated cylinder  22  has a preferred length of 30 inches (76.2 cm) or slightly more and a preferred inside diameter of 3 inches (7.62 cm). The top and bottom pistons  28 ,  30  are movable inside the perforated cylinder  22  over a distance of 10 inches (25.4 cm) respectively toward each other. The mechanisms used for operating the top and bottom pistons  28 ,  30  have not been illustrated. These mechanisms are well known in the art and do not constitute the essence of the present invention.  
         [0044]     In use, the inside cylinder  22  is filled completely with wet sludge from the drip screen mentioned above. The perforated cylinder can be filled manually using a hand-held scoop and a funnel for example. The top piston 28 is inserted into the top end of the perforated cylinder  22  as is forced downward over a distance ‘A’ of about one third of the total length of the perforated cylinder  22 . The force applied to the top piston  28  should be limited to about 100 psi. While the top piston  28  remains at that position, the bottom piston  30  is forced upward and is moved upward over a distance ‘B’ of about one third of the length of the perforated cylinder  22 , compressing the solid fuel to a total length ‘C’ of about one third of the total length of the perforated cylinder  22 . This compression process removes the water from the sludge and brings the water content of the solid fuel block to about 15% by weight.  
         [0045]     The perforations in the perforated cylinder  22  produces dimples on the surface of the solid fuel block. As the solid fuel block is extruded from the perforated cylinder  22  these dimples are compressed inward and some are partly torn away, leaving streaks on the surface of the block. These dimples and streaks produce a rough surface on the block, which simulates the appearance of natural bark.  
         [0046]     The top piston  28  is then retracted as the lower piston  30  continues to move upward to eject the solid fuel block  32  from the top end of the perforated cylinder  22 . The solid fuel block  2  thus formed has a length of about 10 inches (25.4 cm) and a diameter of about 3 inches (7.62 cm).  
         [0047]     The amount of compression described above should not be exceeded to ensure that the solid fuel block will not separate before it is fully dried. The extruded solid fuel block is then dried in a kiln to a moisture content of approximately 1%.  
         [0048]     All the water extracted from the solid fuel block during the compression step is piped to a separate holding tank for reuse. The water is filtered again to further remove any contaminants separated from the paper fibers during the re-pulping and extrusion steps.  
         [0049]     Infusion of the Vegetable Oil in the Solid Fuel Block  
         [0050]     The solid fuel block is taken out of the kiln and is dipped into the warm vegetable oil when it is still at a temperature of about 100° F. (38° C.). The solid fuel block is left in the oil until bubbling therefrom substantially stops. Immersion of the solid fuel block into the warm oil should be limited to no less than 20 minutes and no more than 30 minutes. It is believed that the warm fibers are dilated and have larger interstices there between. It is believed that because of the dilatation of the fiber, the solid fuel block can absorb more oil therein. When bubbling stops, the solid fuel block contains an amount of vegetable oil that is about 65%-75% by weight. Then the fuel block is removed from the oil tank and is left on a table to cool down.  
         [0051]     Preparation and Application of the Vegetable Wax.  
         [0052]     The preferred vegetable wax is soy wax. The vegetable wax is heated to a temperature of or above its melting point. The wax is then applied onto the solid fuel block to form a jacket over the block and to contain the used vegetable cooking oil inside the solid fuel block. The wax is applied to the fuel block when at least the outside surface of the fuel block is at room temperature. The wax can be applied by spraying, by painting it on the solid fuel block, or by dipping the solid fuel block therein. The vegetable wax consists of approximately 1%-5% of the weight of the final product. This jacket or casing acts a containment vessel to retain the vegetable oil inside the fire log.  
         [0053]     As soon as the wax coating as been applied to the fire log, the coated fire log  34  is laid on a live table  36  for keeping the log  34  in a rotational motion until the wax solidifies. This live table  36  is illustrated in  FIG. 3 , and consists of a belt conveyor in motion in which the top segment of the belt  38  is sagging a sufficient amount to retain the coated fire log  34  thereon. This motion prevents the wax from building up in one area, and the oil from accumulating in one region of the log.  
         [0054]     Packaging  
         [0055]     When the wax has solidified on the fuel block  34 , this coated fuel block is wrapped in a wax-coated wrapper which preferably contains materials that are entirely biodegradable. This wrapper provides additional protection for preventing any vegetable oil from leaking out of the coated fuel block  34 .  
         [0056]     The logs are then packaged into boxes containing twelve logs per box. The logs are kept in a cool place and away from temperatures exceeding 86° F. (30° C.).  
         [0057]     Test Results  
         [0058]     Testing was carried out on samples of fire logs made using the method described herein above. These sample logs had a length of 7.48 inches (19 cm) and a diameter of 2.95 inches (7.5 cm). The weight of each fire log was about 1.76 lbs (0.8 kg). The results of these tests were as follows:  
                             TABLE 1                       Fire log Analysis                                    Proximate Analysis   (wt % as received)                       Moisture   0.55           Ash   1.14           Volatiles   94.95           Fixed Carbon   3.36                       Ultimate Analysis   (wt % dry)                       Carbon   69.58           Hydrogen   10.25           Nitrogen   0.01           Sulphur   0.03           Oxygen (diff.)   18.98                       Calorific Analysis   (dry)                       MJ/kg   33.05                      
 
         [0059]     For reference purposes, the calorific value of dry wood is estimated at 14.4 to 17.4 MJ/kg. The calorific value of wood chips impregnated with vegetable oil as described in U.S. Pat. No. 5,244,472, has a BTU content of 9,000 to 12,000 BTU per pound. (20.9 to 27.8 MJ/kg). It will be appreciated that the calorific value of the fire log according to the preferred embodiment constitutes a substantial improvement over cordwood and over at least some of the synthetic fuel products of the prior art.  
                                                                 TABLE 2                           Combustion Tests                Run 1   Run 2   Run 3   All                    Combustion Tests            Fire log Weight (kg)   0.82   0.80   0.73           Total Run Time (hr)   2.17   2.17   2.23       Burn Rate (kg/hr)   0.38   0.37   0.34       Average Chimney Conditions       Temperature (° C.)   61.3   56.8   57.8       Oxygen (%)   20.7   20.7   20.7       Carbon Monoxide (ppm)   47   55   59       Other observations       Maximum Flue Gas Temp.               82° C.                  
 
         [0060]    
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                   
               
               
                 Emission of Particulate Matters and Carbon Oxides. 
               
             
          
           
               
                   
                 Emissions 
                 Run 1 
                 Run 2 
                 Run 3 
               
               
                   
                   
               
             
          
           
               
                   
                 PM g/hr 
                 — 
                 8.6 
                 3.9 
               
               
                   
                 PM - g/kg of fuel 
                 — 
                 23.3 
                 11.5 
               
               
                   
                 PM - g/MJ 
                 — 
                 0.70 
                 0.35 
               
               
                   
                 CO - g/hr 
                 11.4 
                 14.0 
                 12.7 
               
               
                   
                 CO - g/kg of fuel 
                 30.4 
                 38.1 
                 36.9 
               
               
                   
                 CO - g/MJ 
                 0.92 
                 1.2 
                 1.1 
               
               
                   
                   
               
             
          
         
       
     
         [0061]     The following Table 4 compares the average particulate matter and carbon oxide emissions from the fire logs according to the preferred embodiment of the present invention, to the fireplace emissions from three types of fuel; cordwood, pressed wood fire logs and wax fire logs. This study concluded that replacing “dirtiest” cordwood with the “cleanest” fire logs according to the preferred embodiment reduced fireplace emissions by up to 84% for particulate matters and by up to 94% for carbon oxide emissions.  
                                     TABLE 4                           Emission Analysis                    Pressed                       Wood Fire   Wax Fire   Present       Emissions   Cordwood   Log   Log   Invention               PM - g/hr   37.3 ± 20.3   20.1 ± 5.6    14.2 ± 5.6    6.2 ± 3.3       PM - g/kg   14.5 ± 5.5    7.9 ± 2.2   18.1 ± 3.9    17.4 ± 8.4        PM - g/MJ   0.73 ± 0.27   0.39 ± 0.11   0.51 ± 0.11   0.53 ± 0.25       CO - g/hr   215 ± 40    155 ± 24    21 ± 6    13 ± 1        CO - g/kg   75 ± 5    81 ± 14   31 ± 10   35 ± 4        CO g/MJ   3.9 ± 0.2   3.9 ± 0.7   0.89 ± 0.24   1.06 ± 0.25                  
 
         [0062]     Flue gases were analyzed to determine the volatile organic compounds (VOCs) present. Only benzene, toluene, ethylbenzene, styrene and xylene were found at detectable levels. The emission factors for the VOCs produced by the fire log are listed in Table 5. For reference purposes, these emissions factors are compared to the flue gas analyses where pine cordwood was burnt in a fireplace. Comparison of the fire log and pine cordwood emissions indicate that a reduction in VOC emissions from fireplaces can be achieved through the use of the fire log according to the preferred embodiment.  
                                                               TABLE 5                                       Comparison of the               VOC Emissions           Emission Factor (mg/kg)                Compound   Present Invention   Pine Cordwood                            Benzene   183   383           Ethylbenzene   &lt;32   22.9           Styrene   &lt;31   13            Toluene   71   158           Xylene (total)   &lt;48   78.1                      
 
         [0063]     The tests recorded in Tables 1-5 demonstrate that the fire log according to the preferred embodiment of the present invention has better calorific value and produces less pollution than cordwood and at least some of the fire logs of the prior art.  
         [0064]     While one embodiment of the present invention has been illustrated and described herein above, it will be appreciated by those skilled in the art that various modifications, alternate constructions and equivalents may be employed without departing from the true spirit and scope of the invention. For example, it will be appreciated that the fuel elements according to the present invention can take the shape of pellets, hockey-puck-like discs, bricks or other shapes, and can be used in commercial boilers and industrial applications such as for power generation. Therefore, the above description and the illustrations should not be construed as limiting the scope of the invention which is defined by the appended claims.