EP1594668A4

EP1594668A4 - Pelletizing yew biomass for extraction of taxanes and other natural products

Info

Publication number: EP1594668A4
Application number: EP03815018A
Authority: EP
Inventors: Rex T Gallagher; Edward M Desimone; Brian A Bucher; Christopher D Howe; Barry S Hand
Original assignee: Natural Pharmaceuticals Inc
Current assignee: Natural Pharmaceuticals Inc
Priority date: 2002-12-31
Filing date: 2003-12-30
Publication date: 2006-06-07
Also published as: CA2512170A1; EP1594668A1; WO2004060626A1; AU2003303565A1

Abstract

A process of making Yew pellets from Yew tree material is disclosed herein. The process comprising the steps of (i) adding from about 1% to about 20% w/w water to the Yew tree material; and (ii) compressing the Yew tree material in a die to from a pellet whereby the resulting pellet has a final moisture content of less than 10% by weight. The yew pellets produced herein are suitable for extracting taxane molecules from the pellets.

Description

I. TITLE

Pelletizing Yew Biomass For Extraction Of Taxanes And Other Natural Products

II. CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §119 from U.S. Provisional Appl. Ser. No. 60/437,434, filed December 31, 2003. This prior application is incorporated herein by references in its entirety.

This patent application is also co-pending with U.S. Appl. No. 60/437,237, filed

December 31, 2002, and PCT Appl. No. , filed December 30, 2003. Both applications are entitled "Harvesting Yew Biomass for Extraction of Taxanes and Other Natural Products". Both of these prior applications are incorporated herein by reference in their entirety.

III. BACKGROUND OF INVENTION

In one alternative embodiment, the present invention is directed to making Yew pellets from Yew tree material. The process comprising the steps of (i) adding from about 1% to about 20% w/w water to ground Yew tree material; and (ii) compressing the Yew tree material in a die to form a pellet. In one embodiment, the resulting pellet has a final moisture content of less than 10% by weight. The Yew pellets produced herein are suitable for extracting taxane molecules from the pellets.

Yew trees contain a family of natural diterpenoid compounds called taxanes. One of these taxanes in particular, taxol, has been developed as a major anticancer drug which successfully treats a number of human cancers. The name taxol was given to the compound by the original discoverers of this material. Subsequently the name was registered as a trademark, and the compound is now referred to in the scientific literature as 'Paclitaxel.' However, a large body of scientific and industry publications still refer to the natural compound as taxol.

Large-scale extraction of plant biomass has been practiced, and a number of patents have been granted for various extraction and purification processes. These patents generally fall into two categories: (1) animal feed; and (2) fuel. For example, U.S. Patent 6,375,447 is directed to a feed pellet mill that has one inlet for the feed, one outlet for the pellet, and one outlet for water expressed from the forming pellet. This allows for excess water to be removed from the biomass as the pellet is being formed. U.S. Patent 4,613,339 is directed to a process that pelletizes spent sorghum residue, "bagasse," by storing and then pelletizing the residue. U.S. Patents 5,682,683 and 5,728,447 describes process for forming pellets of grains and cereals with a waved-brick structure, providing the pellet with better handling properties.

Paclitaxel was initially discovered in the bark of the Pacific Yew tree. A number of patents described processes for removing the bark from the trunk-wood of the tree. For example, U.S. Patent 3,826,433 describes a process for separating the bark from the shipped wood through steam, mechanical compression, milling, and screening. U.S. Patent Application US2002/0114853 describes the use of pelletization in the extraction of a variety of compounds (including taxanes) using selective extraction of components using acidic and basic solvents from Taxus yunnaneusis bark, or Yew tree needles. Other patents that are relevant to extractions from biomass may use powdered, pulverized, or shredded material (See U.S. Patents 6,1751,035 Bl, 6,264,998 Bl, 6,392,070 B 1).

Yew is a name ascribed to a number of trees which are Taxus species; Taxus being the main genus in the family Taxaceae. Originally isolated from the bark of the Pacific Yew (Taxus brevifolia) collected from Washington State, beginning in 1962, taxol was subsequently reported as occurring in two other Taxus species, including Taxus baccata (European Yew) and Taxus cuspidata (Japanese Yew), in 1971. Following intensive investigations, taxol was further reported to occur in a number of other Taxus species and cultivars. These include, but are not limited to: Taxus globosa (Mexican Yew), Taxus floridana (Florida Yew), Taxus canadensis (Canadian Yew), Taxus wallichiana (Himalayan Yew), Taxus yunnanensis, Taxus chinensis, and also a number of ornamental hybrids, such as Taxus media cultivars, e.g.: T.media 'Densiformis', T.media Ηicksii', T.media 'Brownii', T.media 'Dark Green Spreader', T.media 'Runyan', T.media 'Wardii', T.media 'Tautonii', Tcuspidata 'Capitata', etc.

In the present invention, Yew biomass material may be derived from any Taxus species, including but not limited to the species and cultivars described above. Other Taxus species for use in the present invention are identified in: Chadwick, L.C. and Keen, R.A. May 1986, "A study of the Genus Taxus", Res. Bull. 1086, Ohio Agricultural Research and Development Center; Appendino, G. 1995, "The Phytochemistry of the Yew Tree": Phytochemistry, Natural Products Reports 12(4): 349-360; Convention On International Trade in Endangered Species of Wild Fauna and Flora: Eleventh meeting of the Plants Committee, LangKawi (Malaysia), 3-7 September 2001, Document PCI 1 DOC. 22-p.l, United States of America; and Greer, C.E., Schutzki, R.E., Fernandez, A. and Hancock, J.F. Oct./Dec. 1993. "Electrophoretic Characterization of Taxus Cultivars": HortTechnology, 3(4): 430-433. Each of these references are incorporated herein by reference in their entirety.

Therefore, in one alternative embodiment, the starting material for this invention may be derived from a plant material selected from the group of plants commonly referred to as Yew trees. Suitable plants of this group are species of Taxus. Among Taxus species, Taxus x media cultivars are preferred. For example, preferred cultivars include, but are not limited to, T.media 'Hicksii' or T.media 'Dark Green Spreader'. While it is convenient to use certain parts of the Yew tree in this invention, the Yew biomass for pelletization can be derived from the whole plant or from separated parts such as wood, stems, roots, leaves (needles), seeds, or any combination thereof. The material to be pelletized are derived from the bark or the needles are used. In one preferred embodiment, the material to be pelletized is dry ground yew tree root biomass (powder).

The large-scale processing of Yew tree biomass typically involves some kind of size- reduction processing. This is done to produce a more-or-less homogeneous ground powder which can be extracted with organic solvents in suitable, large-volume containers. Problems arise with handling the ground biomass material, particularly with transportation, safety, and ease and efficiency of solvent extractions. Solvent extraction problems arise from poor solvent contact due to channeling, 'clumping', or poor solvent circulation.

In the present invention, pellets can be readily made from ground biomass materials using commercially available pelletizing mills. Suitable large-scale pelletizing machinery is available from various sources, which include California Pellet Mill Co, Crawfordsville, Indiana; Sprout-Bauer, Muney, PA; Bliss Industries, Ponca City, OK. Typically, very large and heavy duty machinery is used for the process of pelletizing biomass materials such as hay, alfalfa, etc. The machinery used usually involves engines that can range in capacity up to 10 tons/hour throughput which utilize massive engines of several hundred HP. The associated drying and mass transporting systems involve large facilities and equipment, often including large storage sheds, silos, semitrailer and rail wagon transportation, etc. Suitable methods of harvesting and processing yew biomass material is provided in PCT Appl. No. , entitled "Harvesting Yew Biomass for Extraction of Taxanes and Other Natural

Products," filed December 30, 2003. The advantages of using pelletized Yew biomass materials over non-pelletized materials include but are not limited to the following: (i) ease of bulk handling; (ii) shipping/ transportation / storage; (iii) freedom from dust (cleaner, safety factor, environmental factor, reduced product loss); (iv) greater density of solids leads to less volume required in shipping and storage; (v) greater density of solids requires smaller processing vessel volumes; (vi) non-packing nature of pellets resists volume-unloading issues after transport (flour can pack into a cement); (vii) larger size of pellets allows for greater range of equipment use in processing (larger filters); (viii) uniform size-diameter distribution vs. ground biomass; (ix) extraction of biomass lends itself to faster / easier operation due to non-packing nature of the pellets (higher throughput of solvent through bed of pellets); (x) use of pellets decreases channeling and loss of contact between pellets and extraction solvent; (xi) use of pellets decreases pockets of biomass with low solvent-turnover rates; (xii) stability of product, including reduced oxidation due to smaller surface area exposed to the atmosphere; reduced microbial fermentation problems (toxins, heat); and (xiii) use of continuous extraction equipment including automated counter-current extraction equipment (e.g. Crown Extractors).

In one alternative embodiment of the present invention, it was discovered that pelletizing ground powdered Yew biomass offers substantial advantages in the handling, processing and, most importantly, extraction of taxanes and other material products from the biomass. In particular, efficiency and ease of solvent extraction is a major advantage in processing the pelletized Yew biomass. Thus, the present invention provides a process for manufacturing pelletized Yew material without significant reduction of the available taxane content in the biomass. Also, such process does not adversely impact the extraction process, such that additional purification and/or extraction steps are required. Further, in another alternative embodiment, the present invention provides stable pellets from ground, dried Yew roots, at both the laboratory scale and at the industrial scale. No significant loss/degradation of extractable paclitaxel resulting from the present pelletization process was observed. IV. SUMMARY OF THE INVENTION

It is an object of the present invention to provide a process for producing pelletized Yew biomass for extracting taxanes and other natural products.

Another object of the present invention is to provide an efficient and economical process for producing Yew pellets from Yew tree material, including ground material (powder).

Another object of the present invention is to provide a process for making pellets from Yew tree material (including powdered material) which are easily handled, stored, and used.

A further object of the present invention is to provide a process for making Yew pellets from Yew tree material (including powdered material) wherein the resulting pellets have appropriate amounts of water for the extraction process.

A further object of the present invention is to provide a process for making Yew pellets with appropriate amounts of water to minimize undesirable microbal growth of the pelletized material.

These and other objects and advantages of the present invention will become more readily apparent from the following detailed description.

In one alternative embodiment, the foregoing objects and advantages of the invention are achieved in accordance with the present invention in which a pelletized product is produced from, for example, a finely ground pelletizable Yew tree material, or a mixture of finely ground Yew tree materials and water, by pressing the material through appropriate die openings in a commercial or laboratory scale pelletizer such as, for example, a California pellet mill, or a Bliss pellet mill. While the invention may be utilized in the processing of various raw materials, it has been found especially useful in producing a pelletized Yew from a finely ground material. V. DETAILED DESCRIPTION OF THE INVENTION

In many commercial pelletizing operations, the resulting pellet is a product of a controlled manufacturing process. For example, it is well known that variations in the amount of water or liquid in the raw material will have a marked effect both on the ability to form the material into pellets and on the strength and integrity of the pellets formed. The present invention provides a process that forms a stable Yew pellet for transportation and extraction of taxanes and other natural products contained therein.

The present invention is suitable for pelletizing Yew biomass at different scales, including but not limited to: (i) Laboratory/Pilot Scale Pelletizing Runs; and (ii) Industrial- Scale/Large-Scale Pelletizing Runs. A description of each type of run is described below. The Yew pellets produced herein are suitable for extracting taxane molecules from the pellets. Laboratory / Pilot-Scale Pelletizing Runs

Pelletizing may be carried out on Taxus media x "Densiformis" ground root material. Here, pellets can be made with a California Pellet Mill ("CPM"), Crawfordsville, IN. This pelletizing mill comprises dies having 1/8" and 3/16"extrusion holes. During the pelletization process, the mill speed may be adjusted to prevent the temperature from exceeding 200°F, preferably less than 180°F, more preferably 140°F to 160°F. Water can be added to the powdered biomass material before pelletization. Other adjustments to the pellet mill can be made to facilitate the pelletization process, such adjustments are known to those skilled in the art.

Industrial-Scale / Large-Scale Pelletizing Runs

Pellets can be made using a CPM pellet mill. A large CPM pellet mill can pelletize approximately 55 metric tons of 'Densiformis' roots biomass during a one-day run. The resulting pellets can be ^lA inch in diameter. Preferably the resulting moisture content in the pellets can be approximately 5 to 6 wt% water. Industrial-Scale/Large-Scale Pelletizing Runs

Pellets can also be made using a Bliss Hammer Mill. The Yew ground material biomass can be dried in a rotating drum and ground further by using this mill. The pelletizing can be done in two Sprout pelletizers with smaller dies. The dies can have 1/4" holes with tapered relief. The throat length for compression can be 1 1/4" long. Water can be added to the Yew ground material before pelletization. Each pelletizer mill can process 3,500 lb ground biomass/hr. Each mill may consume 200 A at 460N 3 phase. Pelletizing Process

The biomass, after reaching the appropriate conditions of size and content, are first harvested. After harvesting, the Yew tree material may be ground by conventional means. Suitable equipment for harvesting the tops of yew plants include those developed by Dr. Peter Felker (Texas A&M University - Kingsville) using a flail harvester (http://www.newuses.orR EG/EG-19/19harvester.html'). or http://www.woodyciOps.org/ mechconf/mclaughl. html).

/ In one alternative embodiment, the harvesting is directed to the roots of the Taxus plant. After the roots have been removed from the soil, they may be piled on a concrete slab, and washed using a high pressure hose and a shovel or other suitable device to turn the mass over. The roots may be dried through an alfalfa drier and then ground by conventional means. In one embodiment, approximately 5% to 6% w/w water is added to the Yew biomass. The water content should be carefully monitored. Too much water in the pellets could encourage microbial growth, which is undesirable. Also, excess water may adversely affect the taxane extraction process, causing a reduction in the extraction efficiency. In one embodiment, the water content may be controlled by a water or steam bleed steam. This is more desirable.

In another embodiment, the following ranges of water (w/w) may be added to the Yew tree material: from about 0.25% to about 0.5%; about 0.5% to about 1.0%; about 1.0% to 1.5%; 1.5% to about 2.0%; 2.0% to about 3.0%; 3.0% to about 4.0%; 4.0% to about 5.0%; 5.0% to about 6.0%; 6.0% to about 7.0%; about 7.0% to about 8.0%; 8.0% to about 9.0%; about 10.0% to about 11.0%; about 11.0% to about 12.0%; about 12.0% to about 13.0%; about 13.0% to about 14.0%; about 14.0% to about 15.0%; about 15.0% about to 20.0%. Other ranges of water include: about 1% to about 5%; about 5% to about 10%; about 10% to about 15%; about 15% to about 20%.

In one preferred embodiment, the pellets are made using a CPM pellet mill. The speed/capacity of the CPM Pelletizing Mill is affected by the moisture content of the wetted biomass. The normal capacity rating of the CPM laboratory pelletizing mill is about 125 lbs/hr. However, if the moisture content of the wetted biomass is about 30% to about 36% by weight, an additional 30-60 lbs/hr additional capacity may be achieved. If the moisture content of the wetted biomass is too low, it will plug the dies. Conversely, if the materials are too wet, unpelletized material will flush out the die.

The ground solids may be wetted using either water or steam, and then pelletized to a diameter of about 4 to 6 mm (3/16 to 1/4 inch). This diameter is preferred for further processing the biomass. Smaller diameters may clog the dies, increase the processing temperature, and also increase the wear on the dies. After the pellets are formed, they may be allowed to cool, and then transported. The pellets formed from the process of the present invention show no loss of taxanes over the course of this treatment.

The finished pellets can be stored or used as desired. In the present invention, it is preferred that the pellets be substantially cylindrical or parallelepiped. The maximum cross section of each individual pellet should be about 3/16 to about 1/4 inch. While the production of cylindrically shaped pellets is preferred, the invention in its broadest aspects contemplates producing pellets of any suitable configuration. For example, the pellets may be cube-shaped. In one alternative embodiment, the bulk density of pellets produced in the present invention can be at least 30 lbs/ft.³, up to 50 lbs/ft.³ In one alternative embodiment, the bulk density of the resulting pellet may include the following ranges: about 30 lbs/ft.³ to about 35 lbs/ft.³; about 35 lbs/ft.³ to about 40 lbs/ft.³; about 40 lbs/ft.³ to about 45 lbs/ft.³; about 45 lbs/ft.³ to about 50 lbs/ft.³ Equipment Used for Pelletizing

The following is a list of pelletizing equipment suitable for pelletizing Yew biomass.

1. CPM (2975 Arline Circle, Waterloo IA)

A large range of suitable industrious equipment is available from this company.

2. Andritz Sprout-Bauer (Sherman St, Muncy, PA) Hammermills with a range of power (22 - 255 kW)

Pellet mills with varying power (30 - 560 kW) and die press area (620 -14313 cm²).

3. Bliss Industries (1415-T W. Summit Ave, Ponca City, OK) Hammermills with a range of power (6 - 447 kW, 10 - 600 H.P.)

Pellet mills with varying power (50 - 300 kW, 80 - 500 H.P.) and die press area (1500 - 7800 cm²). Taxanes Extracted from Yew Pellets

An important component of manufacturing pellitized Yew material is to produce the pellets without reducing the available taxane content inside the pellet, and adversely affecting the taxane extraction process from the pellets. As used herein, "taxane or taxane molecule" include but are not limited to a molecule that contains a basic baccatin III structure with a (2R,3S)-C₆H₅CH(Rx)CH(OH)C(0)- group forming an ester with the hydroxyl group located at the C-13 position of the basic baccatin III structure. The group represented by Rx can be an amino group, a salt of an amino group (e.g., an ammonium salt), an amino group which is protected with an amino protecting group, or a substituent which may be converted into an amino group. Various isomers, homologues, and analogues of the basic baccatin III structure, and of the (2R,3S)-C₆H₅CH(Rx)CH(OH)C(0)- group also are included in the definition of a taxane molecule.

Also, a 10-deacetylbaccatin III structure is contemplated within the scope of a taxane molecule. Included within the definition of a taxane or taxane molecule include, but are not limited to, primary taxanes, for example taxol A (paclitaxel), taxol B (cephalomanninc), taxol C, taxol D, taxol E, taxol F, and taxol G. Further, the definition of a taxane or taxane molecule includes docetaxel (TAXOTERE^®). (See, e.g., PCT Ser. Appl. No. PCT/US03/105566, which is incorporated herein by reference). As used herein, a "basic baccatin III structure" means a compound having the formula as shown in the aforementioned application, where each of Ri, R₂, R₄, R₇, Rio and Rι₃ independently is hydrogen, an alkyl group, an acyl group, an aryl group, an arylalkyl group, a vinyl group, an ether group, an ester group, a glycoside group, an oxo group, or a hydroxyl protecting group. Included within the definition of a basic baccatin III structure is baccatin III, which has the formula as shown in the aforementioned application, and 10-deacetylbaccatin III, which has the formula as shown in the aforementioned application, where Ac is an acetyl group (CH₃C(0)-), and Bz is a benzoyl group (PhC(O)- or C₆H₅C(0)-).

In one alternative embodiment, the present invention is directed to a process for making Yew pellets comprising the following steps: (a) adding from about 1% to about 20% w/w water to ground Yew tree material; and (b) compressing the wetted Yew tree material in a die to form a pellet whereby by the resulting pellet has a final moisture content less than 10% by weight. In one alternative embodiment, the Yew tree material is ground into a powder. In another embodiment, the Yew material is derived from roots.

In another alternative embodiment, the process of the present invention provides a resulting pellet having a bulk density from about SOlbs/ft³ to about 501bs/ft³. In another embodiment, the present process provides a resulting pellet having a final diameter from about 1/16 inch to about 1 inch, or from about 3/16 inch to about ^lA inch or the final diameter is VA inch.

In another embodiment, in carrying out the present process the diameter of the extrusion holes of the die is from about 1/16 inch to about 1 inch, or from about 3/16 inch to about inch. Further, in another embodiment, the temperature of the resulting pellet as it emerges from the die is from about 100°F to about 212°F, or from about less than 180°F or from about 130°F to about 160°F.

In another alternative embodiment, the present invention is directed to a Yew pellet having a final moisture content less than 10% by weight. In another embodiment, the pellet has a final moisture content from about 1% to about 6% by weight, or from about 4% to about 6% by weight. In another embodiment, the pellet of the present invention has a final bulk density from about 30 lbs/ft³ to about 50 lbs/ft³. In another embodiment, the diameter of the pellet is from about 1/16 inch to about 1 inch or 3/16 inch to about ^lA inch or VΛ inch. Turning the pellet mill to higher throughput can reduce the quality of the pellets. Also, as the thickness of the die is increased, the resulting pellets become harder and the capacity and ability of the mill to run are adversely affected. In one alternative embodiment, the die is made of high carbon steel. Carbon steel is more preferable than chrome or stainless steel dies.

The use of additives can be important with powered biomass materials. In the case of ground root biomass, the use of additives is less important, and in some instance is not required. With Yew tops, for example, it is advantageous to use binder additives to facilitate production of pellets suitable for extraction. Such binders may include, but are not limited to, guar gum, starches, vegetable oils, alginates, xanthan gums, locust bean gum and other suitable binders.

The invention is further demonstrated by the following examples. The examples are for purposes of illustration and is not intended to limit the scope of the present invention. VI. Examples Example 1 -Pelletizing Process

1. 2000 grams of dry ground Yew tree root biomass (powder).

2. 200 g water added to the Yew biomass.

3. The biomass and water were mixed in a HOB ART blender with eccentric drive/paddle.

4. The die is first purged with oats, forming pelletized oats.

5. The wetted biomass was run through a CPM 'CL3' Laboratory pellet mill. This mill had a 3 HP motor (220 Volts). The temperature of the resulting pellets were approximately 160° F. The pellets were dark in color, ranging in length of about . inch tol inch. 6. After 20 minutes, the moisture content of the pellets was approximately 10.3%. After

30 minutes, it was approximately 10.4%. The bulk density of the pellets was 39 lb./ft³' The bulk density of the biomass powder was approximately 18 lbs/ ft³'

Capacity tests were run on the pellet mill to determine the mill's capacity for the biomass material. For example, to produce 1/8 inch pellets, the capacity for the mill was 117 lbs hr. Example 2 -Additives

In some instances, additives can be used to facilitate production of pellets suitable for taxane extraction. The following examples describe an additive (Guar Gum) that can be added to the wetted biomass. Each pelletizing run followed the general protocol shown in Example 1. To evaluate the amount of fines, the die was heated beforehand.

1% Guar Gum

Guar gum run: 3/16" pelletizing; 2000 g of ground Yew root biomass; 200 g H₂0; 20 g guar gum;

Guar Gum Source - *non-food grade Rawtec UFF-MN (5/21/01 RX 1036)

Temperature higher: more fines in 155°F; 128 lb/hr

Bulk density: 40 lb/ft³; and

Wgt. fines 208 g; wgt pellets 1822 g; 10.2% fines; 90% conversion.

1/2 % Guar Gum

Guar gum run: 1/8" pelletizing;

2000 g of ground Yew root biomass; 200 g H₂O;

10 g guar gum ( = VJVo) (added as powder);

Temp l50°F to l63°F;

Rate: 136 lb/hr.; Wgt. pellets: 1894 g; wgt fines. 139 g; or 7% fines; and

Bulk density: 35 lb/ft³.

2% Guar Gum

Guar gum run: 1/8" pelletizing;

2000 g ground Yew root biomass; 200 g H₂O;

40 g guar gum (=2%) (added as powder);

Temp l62°F to l74°F;

Rate Capacity: 145 lb/hr.

Fines 140 g; pellets 193° g; 7% fines;

Bulk density: 37 lb/ft³.

Control Run (No Guar Gum Added)

2000 g ground Yew root biomass; 200 g H₂O;

1/8" pelletizing;

Temp: 148°F to 170°F;

Rate: capacity 95 lb/hr;

Wgt fines: 95 g; wgt of pellets 2000 g;

4.5% fines; and

Bulk density: 34 lb/ft³. Example 3 - Extraction of Taxanes From Pellets

A series of experiments were run to confirm that paclitaxel and other taxanes survive the pelletizing process of the present invention. Specifically, Yew pellets were extracted using hotmethanol in a Soxhlet apparatus: 1/8" pellets (no additives), 3/16" pellets (no additives), and non-pelletized biomass powder (from which the pellets were made). Table 1 shows the recovery of taxanes. TABLE 1

HPLC analysis showed good recovery of total taxanes approximately (approximately 0.02% w/w) for both pellets and non-pellets. HPLC analysis also showed good recovery of paclitaxel (approximately 0.01% w/w) for both pellets and non-pellets. These tests showed no significant loss/degradation of extractable paclitaxel as a result of the pelletization process.

The invention, as described above, may be varied in certain aspects. For example, pellet production may be accomplished continuously or in separate batches. In addition, operating parameters may be varied, depending on many factors. These factors include available materials, economic considerations and energy needs of specific consumers. However, it is to be understood that these and other factors can be made by those skilled in the art without distracting from the sprit and scope of the invention.

Throughout the description, where the present invention is described as having, including, or comprising specific components, or where processes are described as having, including, or comprising specific process steps, it is contemplated that the present invention also consists essentially of, or consists of, the recited components or processing steps. Further, it should be understood that the order of steps or order for performing certain actions are immaterial so long as the invention remains operable. Moreover, two or more steps or actions may be conducted simultaneously so long as the invention remains operable. Also, one or more steps or elements may be omitted from the claimed invention, or the invention described herein suitably may be practiced in the absence of any component or step which is not specifically disclosed herein, so long as the invention remains operable.

Further, the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The foregoing embodiments are therefore to be considered illustrative rather than limiting the invention described herein.

The content of each patent and non-patent document referred to herein is expressly incorporated herein by reference in its entirety.

Claims

We claim:

1. A process of making Yew pellets from grounded Yew tree material comprising the following steps: a. adding from about 1% to about 20% w/w water to the ground Yew tree material; . b. compressing the Yew tree material in a die to form a pellet whereby by the resulting pellet has a final moisture content less than 10% by weight.

2. The process according to claim 1, wherein the resulting pellet has a final moisture content less than 8% by weight.

3. The process according to claim 1, wherein the resulting pellet has a final moisture content from about 1% to about 6% by weight.

4. The process according to claim 1 , wherein the resulting pellet has a final moisture content from about 4% to about 6% by weight.

5. The process according to claim 1, wherein the final bulk density of the resulting pellet is from about 301bs/ft³ to about 501bs/ft³

6. The process according to claim 1, wherein the final diameter of the resulting pellet is from about 1/16 inch to about 1 inch.

7. The process according to claim 1, wherein the final diameter of the resulting pellet is from about 3/16 inch to about ^XA inch.

8. The process according to claim 1, wherein the final diameter of the resulting pellet is ^γA inch.

9. The process of claim 1, wherein the diameter of the extrusion holes of the die is from about 1/16 inch to about 1 inch.

10. The process of claim 1, wherein the diameter of the extrusion holes of the die is from about 3/16 inch to about ^lA inch.

11. The process of claim 1 , wherein the temperature of the resulting pellet as it emerges from the die is from about 100°F to about 212°F.

12. The process of claim 1, wherein the temperature of the resulting pellet as it emerges from the die is from about less than 180°F.

13. The process of claim 1 , wherein the temperature of the resulting pellet as it emerges from the die is form about 130°F to about 160°F.

14. A Yew biomass pellet produced by a process comprising the following steps: a. adding from about 1% to about 20% w/w water to ground Yew tree material; and b. compressing the wetted Yew tree material in a die to form a pellet whereby by the resulting pellet has a final moisture content of less than 10% by weight.

15. A Yew biomass pellet having a final moisture content of less than 8% by weight.

16. The Yew biomass pellet of claim 15, wherein the pellet has a final moisture content from about 1% to about 6% by weight.

17. The Yew biomass pellet of claim 15, wherein the pellet has a final moisture content from about 4% to about 6% by weight.

18. The Yew biomass of claim 15, wherein the bulk density of the pellet is from about 301bs/ft³ to about 501bs/ft³

19. The Yew biomass of claim 15, wherein the diameter of the pellet is from about 1/16 inch to about 1 inch.

20. The Yew biomass pellet of claim 15, wherein the diameter of the pellet is from about 3/16 inch to about % inch.

21. The process according to claim 1, wherein the final diameter of the resulting pellet is inch.