EP4720402A1 - Mechanical non-wood pulp - Google Patents

Abstract

Disclosed are improved non-wood pulps, particularly non-wood pulps prepared from plants of the family Asparagaceae and more particularly one or more plants of the genus Hesperaloe, and methods of producing the same. The manufacturing processes generally comprise at least one mechanical treatment stage, such as mechanical refining, without the addition of chemicals to the biomass. In certain instances, the biomass may be subjected to two stages of refining where the consistency of the biomass differs between the stages, such that the first refining stage may be performed at a consistency ranging from about 8% to about 12% and the second stage may be performed at a consistency ranging from about 3% to about 4%. The resulting non-wood pulps have a high degree of Freeness, such as Freeness ranging from 500 mL to 600 mL and a relatively modest degree of tensile strength, such as a Tensile Index of about 50 or less.

Description

MECHANICAL NON-WOOD PULP BACKGROUND Pulp is a lignocellulosic fibrous material prepared by chemically and/or mechanically separating cellulose fibers from wood, or non-wood fiber sources. The pulping process, whether by mechanical, chemical, or a combination of mechanical and chemical, reduces the source material into its component fibers. In addition to separating the biomass into fibers, pulping removes a portion of the lignin from the fiber, while retaining the cellulosic and hemicellulosic portions. Chemical pulping achieves this by degrading the lignin into small, water-soluble molecules which can be washed away from the cellulose and hemicellulose fibers without depolymerizing them. Removal of lignin has the benefit of increasing the brightness of the pulp. Fibers derived from woody biomasses often contain greater concentrations of lignin compared to non-wood biomasses. As such, processes for pulping woody biomasses, particularly processes for producing high brightness woody pulps, are often highly chemically intensive. The same processes, when applied to non-wood biomasses, often result in significant depolymerization of cellulose and hemicellulose causing excessively weak pulps and unacceptably low yield. Thus, alternative pulping processes are often required to prepare non-wood pulps having sufficient strength and brightness as well as economically feasible yield. While certain alternatives to the chemical intensive pulping processes have been developed for use in the manufacture of non-wood pulps, there remains a need in the art for processes that produce pulps having desirable properties such as relatively long fiber length, low coarseness, low degree of fines, good dispersibility and high brightness. This is particularly true for non-woods having leaves or stems containing an epidermal layer, which are challenge to pulp using conventional processes because of their non-fibrous nature. SUMMARY The present invention provides novel processes for pulping non-woods and novel pulps produced thereby. The non-wood pulps of the present invention have several beneficial properties such as reduced tensile strength, relatively long fiber length, low coarseness, low degree of fines, good dispersibility, high brightness or a low degree of debris. To achieve the beneficial properties the biomass is mechanically pulped, at two different consistencies and without the addition of chemicals. The properties of the non-wood pulp may be further improved by treating the biomass prior to mechanical pulping to remove at least a portion of the water-soluble extractives. The properties of the non-wood pulp may also be further improved by further cleaning and bleaching of the mechanical pulp. Generally, the present invention provides a process for producing non-wood pulps, and non- wood produced thereby, where the non-wood biomass is pulped using a two-stage mechanical puling process where the consistency of the consistency of the biomass or bagasse being pulped differs for each of the stages. Further, both mechanical pulping stages are carried out without the addition of chemicals, such alkaline peroxide chemicals, and/or other chemicals known in the art to bleach or otherwise process lignocellulosic material into pulp or precursors of pulp, either before, during or immediately after, one or more stages of mechanical pulping. The foregoing process not only simplifies the pulping process and reduces costs, it also improves pulp yields and the physical properties of the resulting pulp. For example, the non-wood pulps of the present invention may be produced at yields of about 75% or greater, 80% or greater, such as about 85% or greater, such as about 90% or greater, such as yields from about 75% to about 95%. Accordingly, the present invention provides a method of manufacturing a non-wood pulp comprising the steps of: (a) providing a non-wood biomass; (b) cutting the non-wood biomass to a nominal length; (c) extracting water soluble solids from the cut biomass to produce a bagasse; (d) mechanically refining the bagasse at a first consistency to yield a refined bagasse; (e) mechanically refining the refined bagasse at a second consistency, wherein the second consistency is less than the first consistency, to yield a non-wood pulp. In other instances the present invention provides a method of manufacturing a non-wood pulp comprising the steps of: (a) providing a non-wood biomass; (b) cutting the non-wood biomass to a nominal length; (c) extracting water soluble solids from the cut biomass to produce a bagasse; (d) mechanically refining the bagasse at a first consistency to yield a refined bagasse; (e) mechanically refining the refined bagasse at a second consistency, wherein the second consistency is less than the first consistency, to yield a non-wood pulp; (f) cleaning the non-wood pulp to yield a cleaned pulp; and (h) bleaching the cleaned pulp to produce a bleached non-wood pulp. In still other instances the present invention provides a method of manufacturing a non-wood pulp comprising the steps of: (a) providing a non-wood biomass; (b) cutting the non-wood biomass to a nominal length less than about 20 mm; (c) extracting water soluble solids from the cut biomass; (d) washing the biomass to yield a washed biomass having a consistency ranging from about 8% to about 12% (e) refining the washed biomass under first refining conditions to produce a primary pulp; (f) diluting the primary pulp to yield a diluted primary pulp having a consistency ranging from about 3% to about 4%; and (g) refining the diluted primary under second refining conditions to produce a non-wood pulp. The non-wood pulp may be subjected to further treatment, such as cleaning to produce a cleaned pulp, bleaching to yield a bleached pulp, or drying to yield a dried pulp. While processes of the present invention are well suited for pulping of a wide range of non-wood biomass, the processes are particularly well suited for pulping biomass derived from a plant of the family Asparagaceae. Accordingly, in certain instances, the present invention provides a non-wood pulp comprising a plurality of fibers derived from a plant of the family Asparagaceae. The resulting pulps have or more physical properties that make them well suited for the manufacture of wet-laid fibrous products, such as tissue products. For example, pulps of the present inventio may have a relatively long fiber length, such as a fiber length of about 1.50 mm or greater, and are amendable to dewatering, such as having a Freeness of at least about 400 mL, such as at least about 450 mL, such as at least about 500 mL, such as from about 400 to about 700 mL and a modest degree of tensile strength, such as a Tensile Index less than about 50. DESCRITPION OF THE FIGURES Figure 1 is process flow diagram of a process for producing non-wood mechanical pulp. Figure 2 illustrates the relationship of Tensile Index and Freeness for four pulps (■) alkaline- peroxide mechanical hesperaloe pulp; (▲) bleached mechanical hesperaloe pulp prepared according to the present invention; (♦) unbleached mechanical hesperaloe pulp prepared according to the present invention and (●) bleached Northern Softwood Kraft pulp. Figure 3 illustrates the relationship of Tensile Index and Freeness for five pulps refined at two different levels – 100 revs and 500 revs – (x) bleached alkaline mechanical pulp prepared as described in Comparative Example xx; (■) alkaline-peroxide mechanical hesperaloe pulp; (▲) bleached mechanical hesperaloe pulp prepared according to the present invention; (♦) unbleached mechanical hesperaloe pulp prepared according to the present invention and (●) bleached Northern Softwood Kraft pulp. Figure 4 illustrates refining curves for four pulps (■) alkaline-peroxide mechanical hesperaloe pulp; (▲) bleached mechanical hesperaloe pulp prepared according to the present invention; (♦) unbleached mechanical hesperaloe pulp prepared according to the present invention and (●) bleached Northern Softwood Kraft pulp. DEFINITIONS As used herein, the term “substantially free” means less than 3 wt%, alternatively less than 2 wt%, alternatively less than 1 wt%, alternatively less than 0.5 wt%, alternatively less than 0.25 wt%, alternatively less than 0.1 wt%, alternatively less than 0.05 wt%, alternatively less than 0.01 wt%, and/or alternatively free of. As used herein, “free of” means 0 wt%. As used herein, the term “Biomass” generally refers to organic matter derived from a non-woody plant and includes both whole plants and plant organs (i.e., leaves, stems, flowers, stalks, roots, etc.). As used herein, the term “Bagasse” generally refers to biomass that has been subjected to a processing step such as, for example, pressing, milling, compression or maceration, to remove a portion of the biomass water soluble solids. Bagasse may be prepared by subjecting the biomass to compression and maceration using a plug screw, or other form of compression screw, to extract a portion of the biomass water soluble solids. As used herein, the term “Pulp” generally refers to a plurality of cellulosic fibers derived from biomass, the fibers having an elongate shape in which the apparent length exceeds the apparent width. Generally, pulps prepared according to the present invention are dispersible in water, have a measurable freeness, and may be used to form a handsheet. As used herein, the term “Fines” generally refers to fibrous water insoluble cellulosic material having a length to width aspect ratio of from about 1 to about 100 and wherein the length of the fibrous water insoluble material is less than about 0.2 mm. In certain instances, pulp prepared according to the present invention may comprise fines. In certain instances, the amount of fines present in pulp prepared according to the present invention may be about 2.0% or less, such as about 1.5% or less, such as about 1.0% or less, such as from about 0.5 to about 2.0%. The fines content of pulp, on a length weighted basis, may be measured using an OpTest Fiber Quality Analyzer-360 (OpTest Equipment, Inc., Hawkesbury, ON) as described in the Test Methods section below. Generally, the percentage of fines on a length weighted basis is the sum of the fines length divided by the total length of fibers and fines in the sample. As used herein, the term “Brightness” generally refers to the optical brightness of a pulp sample measured in accordance with ISO 2470-1:2016. Brightness is commonly expressed as a percentage (%). As used herein, the term “Debris” generally refers to the weight percentage of solids retained on a MasterScreen™ apparatus fitted with a screen having a slot size of 100 µm (0.004 inches). The amount of debris in a given pulp sample is generally measured as set forth in the Test Methods section below. As used herein, the term “Tensile Index” generally refers to the tensile strength of a sample, having units of grams force per 25.4 mm, divided by the bone-dry basis weight, having units of grams per square meter. For a given pulp sample, the tensile index is generally measured by dispersing the pulp in water to form a handsheet (as described in the Test Methods section below) and then measuring the tensile and basis weight of the handsheet. As used herein, the term “Caliper” is the representative thickness of a pulp sheet and is generally measured as described in the Test Methods section below. Caliper commonly has units of millimeters or microns. As used herein, the term “Freeness” refers to the Canadian Standard Freeness (CSF) determined in accordance with TAPPI Standard T 227 OM-94. Freeness commonly has units of milliliters (mL). As used herein, the term “Fiber Length” generally refers to the length weighted average fiber length (LWAFL) of fibers measured using an OpTest Fiber Quality Analyzer, model FQA-360 (OpTest Equipment, Inc., Hawkesbury, ON) as described in the Test Methods section below. Fiber length commonly has units of millimeters. As used herein, the term “Coarseness” generally refers to the weight per unit length of fiber measured using an OpTest Fiber Quality Analyzer-360 (OpTest Equipment, Inc., Hawkesbury, ON) as described in the Test Methods section below. Coarseness commonly has units of mass per unit length, such as milligrams per 100 meters (mg/100 meters). As used herein, the term “Very Long Fiber Fraction” generally refers to the percentage of fibers having a length (number average fiber length) greater than 6.0 mm and is generally determined using an OpTest Fiber Quality Analyzer-360 (OpTest Equipment, Inc., Hawkesbury, ON) as described in the Test Methods section below. As used herein, the term “Dispersivity Index” generally refers to the ratio of the length weighted average fiber length (Lw) to the number average fiber length (Ln). This ratio indicates the fiber length distribution of a given pulp. The length weighted average fiber length (L_w) to the number average fiber length (Ln) is generally determined using an OpTest Fiber Quality Analyzer-360 (OpTest Equipment, Inc., Hawkesbury, ON) as described in the Test Methods section below. As used herein, the term “Nominal Size” when referring to the size of biomass or bagasse, generally refers to the size of a given screen through which at least about 70% of the biomass or bagasse passes through. Generally, a screen is a member capable of sieving material according to size. Examples of screens include a perforated plate, cylinder or the like, or a wire mesh or cloth fabric. The preferred method of screening and sizing bagasse and biomass is described in the Test Methods section below. Ranges can be expressed herein as from “about” one particular value and/or to “about” another particular value. When such a range is expressed, another aspect includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another aspect. It should be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint and independently of the other endpoint. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint and independently of the other endpoint. Unless stated otherwise, the term “about” means within 5% (e.g., within 2% or 1%) of the particular value modified by the term “about.” Throughout this disclosure, various aspects of the disclosure can be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the disclosure. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, a description of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as individual numbers within that range, for example, 1, 2, 2.7, 3, 4, 5, 5.3, 6 and any whole and partial increments therebetween. This applies regardless of the breadth of the range. All percentages and ratios are calculated by weight unless otherwise indicated. All percentages and ratios are calculated based on the total composition unless otherwise indicated. Unless otherwise noted, all component or composition levels are in reference to the active portion of that component or composition, and are exclusive of impurities, for example, residual solvents or by-products, which may be present in commercially available sources of such components or compositions. DESCRIPTION This invention relates to non-wood pulps and processes for preparing non-wood pulps, particularly non-wood pulps produced from non-woody plants of the family Asparagaceae. Of particular interest are non-wood pulps produced from plants of the genus Hesperaloe, and more particularly one or more plants selected from H. funifera, H. parviflora, H. nocturna, H. chiangii, H. tenuifolia, H. engelmannii and H. malacophylla. The non-wood pulps are preferably produced by mechanical treatment, such as refining, of the non-wood biomass or bagasse, without the addition chemicals before, during or immediately after refining. In this manner the non-wood bagasse may be substantially free from chemical additives, or free from chemical additives, during mechanical refining of the bagasse. In certain instances, the non- wood bagasse may be subjected to separate mechanical refining stages where both stages are carried out without the addition of chemicals to the bagasse. The production of pulps by mechanical treatment without the addition of chemicals improves the overall pulp yield. In certain instances, the processes of the present invention may have yields of 90% or greater, such as about 92% or greater, such as about 94% or greater. Omitting chemicals during mechanical pulping generally may decrease the amount of lignin removed from the biomass during pulping. For example, the pulping process of the present invention may remove less than about 20% of the lignin, such as less than about 15% of the lignin, such as from about 10 to about 20% of the lignin. Bleaching of the pulp may further reduce the amount of lignin, however, the bleached pulp may still retain 50% or more of the lignin originally present in the biomass. Accordingly, in certain instances, Hesperaloe pulps may comprise at least 50%, by weight, of the original lignin contained in the biomass or more, such as about 60% or more, such as about 70% or more. Despite omitting chemical treatment during mechanical treatment, the pulps have desirable physical properties, such as a high degree of freeness, particularly compared to other non-wood pulps and pulps prepared using both chemical and mechanical treatment. The improved freeness is generally accompanied by a relatively low degree of tensile strength. This combination of high freeness and low tensile strength make the inventive pulps well suited for the manufacture of fibrous structures, particularly low basis weight tissue paper, that demand pulps that are easily dewatered and which develop only a moderate degree of tensile strength and maintain a high degree of softness. Accordingly, in certain instances, the inventive pulps may have a freeness, where a higher value is indicative of pulps that are more easily dewatered, of about 500 mL or greater, such as about 510 mL or greater, such as about 525 mL or greater, such as about 550 mL or greater, such as from about 500 mL to about 600 mL. The pulps may also have a relatively modest degree of tensile strength, such as a Tensile Index of about 55 or less, such as about 50 or less, such as about 45 or less, such as about from about 30 to about 55, such as from about 35 to about 50, such as from about 35 to about 45. Despite having moderate tensile strengths, the pulps of the present invention generally have a relatively long fiber length, such as a fiber length of about 1.50 mm or greater, such as about 1.55 mm or greater, such as about 1.60 mm or greater, such as about 1.65 mm or greater, such as about 1.70 mm or greater, such as about 1.75 mm or greater, such as from about 1.50 to about 2.50 mm, such as from about 1.50 to about 2.25 mm, such as from about 1.50 to about 2.00 mm, such as from about 1.60 to about 2.00 mm, such as from about 1.65 to about 2.00 mm. A comparison of the physical properties of pulps prepared according to the present invention and those prepared using both chemical and mechanical treatment are shown in Table 1, below. A comparison of the Tensile Index and Freeness of pulps prepared according to the present invention and those prepared using both chemical and mechanical treatment is shown in FIG.1. TABLE 1 Inventive APMP Hesperaloe Pulp Chemi-Mechanical Hesperaloe Pulp In other instances, the inventive pulps may have a moderate degree of tensile strength and a low degree of fibers having a fiber length greater than 6.0 mm, which can inhibit dispersion of the pulp in water and cause stringing or clumping when the pulp is used to manufacture wet-laid fibrous products. For example, the inventive pulps may have a Tensile Index of about 55 or less, such as about 50 or less and a Very Long Fiber fraction (VLF) of about 1.0% or less, such as about 0.75% or less, such as a about 0.50% or less, such as a VLF from about 0.05% to about 1.0%. In other instances, the inventive pulps may have a relatively long fiber length and a relatively low degree of Very Long Fiber fraction (VLF). For example, the inventive pulps may have a Fiber Length of about 1.50 mm or greater, such as about 1.55 mm or greater, such as about 1.60 mm or greater, such as about 1.65 mm or greater, such as about 1.70 mm or greater, such as about 1.75 mm or greater, such as from about 1.50 to about 2.50 mm, such as from about 1.50 to about 2.25 mm, such as from about 1.50 to about 2.00 mm, such as from about 1.60 to about 2.00 mm, such as from about 1.65 to about 2.00 mm and a Very Long Fiber fraction (VLF) of about 1.0% or less, such as about 0.75% or less, such as a about 0.50% or less, such as a VLF from about 0.05% to about 1.0%. Generally, the pulps of the present invention are prepared from one or more non-woody plants. Pulps may include fiber derived from a single plant species or, alternatively, fibers that originate from two or more different plant species. Biomass useful in the present invention may comprise freshly harvested non-wood plants, partially dried non-wood plants, fully dried non-wood plants or a combination thereof. The biomass may consist essentially of the above ground portion of the plant and more particularly the portion of the plant above the crown and still more preferable the leaves of the plant. Pulps of the present invention may be prepared from one or more non-wood plants of the family Asparagaceae, Suitable non-wood plants may include, but are limited to, one or more plants of the genus Agave such as A. tequilana, A. sisalana and A. fourcroyde, and one or more plants of the genus Hesperaloe such as H. funifera, H. parviflora, H. nocturna, H. chiangii, H. tenuifolia, H. engelmannii, and H. malacophylla. In certain instances, it may be preferable to prepare pulps from plants of the of the genus Hesperaloe such as H. funifera, H. parviflora, H. nocturna, H. chiangii, H. tenuifolia, H. engelmannii, and H. malacophylla. Pulp may be produced from non-woody plants by processing biomass, particularly the non-seed portion of the plant, more particularly the leaves and still more particularly the leaves above the crown of the plant, extracting water soluble solids from the biomass to generate a bagasse, impregnating the bagasse with a chemical, and mechanically refining the impregnated bagasse to produce a primary pulp. The primary pulp may be subjected to further processing, such as screening and bleaching to yield a bleached pulp suitable for a wide variety of end uses. In certain instances, prior to refining, the water- soluble solids may be removed from the non-wood biomass by compression and maceration. Compression and maceration may also be used to remove the epidermis from the biomass, as well as cut the biomass to size before refining. The inventive pulps are prepared by a mechanical pulping process without the addition of chemicals during, before, or immediately after the refining. In this manner refining may be carried out without treatment of the bagasse with an alkaline solution, such as sodium hydroxide, oxidative chemicals, such as hydrogen peroxide or sodium peroxide, or other chemicals commonly employed in pulping processes to facilitate the removal of lignin, such as sulfur dioxide, sodium sulfite, sodium bisulfite or sodium hydrosulfite. Because the pulps of the present invention may be prepared without the use of oxidative chemicals there is generally no need to add stabilizers, such as ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA) and nitrilotriacetic acid (NTA), before, during or immediately after, mechanical pulping. In certain instances, pulps prepared according to the present invention may be bleached to increase their optical properties, particularly brightness. For example, the present invention provides non-wood pulp derived from plants of the genus Hesperaloe having a brightness of 75% or more, such as about 77% or more, such as about 79% or more, such as from about 75 to about 92%. Bleaching may be carried out using any one of the well-known pulp bleaching processes. In certain instances, it may be preferable to perform bleaching without using elemental chlorine and more preferably without the use of chlorine containing compounds. Bleaching may be carried out in a single stage or may be performed in multiple stages. In certain instances, it may be preferable that the bleaching process comprises at least one non-chlorine bleach stage although any one or more conventional non-chlorine bleaching stages or sequences can be used, including those with oxygen (including oxygen delignification), ozone, peroxide, hydrosulfite, and the like. Although certain end uses may benefit from bleaching, the invention is not so limited and the pulps of the present invention may be unbleached and have a brightness less than about 75%, such as from about 50 to about 75%, such as from about 55 to about 70%. The pulp products of the present invention, while being produced from a non-wood fiber and produced by mechanical pulping, do not suffer the same freeness problems of prior art non-wood mechanical pulps. Indeed, in certain instances pulp products of the present invention have relatively high freeness, such as a Freeness of at least about 400 mL, such as at least about 450 mL, such as at least about 500 mL, such as from about 400 to about 700 mL, such as from about 450 to about 600 mL. Generally, “freeness” refers to the drainage rate of pulp, or how “freely” the pulp will give up its water. Freeness is important in papermaking in that, if the freeness is too low, it is not possible to remove enough water on the paper machine to achieve good sheet structure and strength. Often, mechanical pulps, particularly mechanical non-wood pulps, have low freeness due to the high degree of fines that inhibit drainage of the pulp when wet-formed into a sheet. The pulp products of the present invention may be provided as a wet lap, or in dried form as sheets, bales or rolled forms and are distinguishable from other fibrous products such as those intended for use in packaging, tissue, books, magazine, letters, and the like. The caliper of a pulp sheet may range from about 0.05 to 0.50 cm, such as from about 0.10 to about 0.25 cm. The bone-dry basis weight of pulp prepared according to the present invention may range from about 200 to about 1,000 grams per square meter. The pulp products of the present invention are generally subjected to further processing to convert the fiber into a final product to be used by a consumer. For example, the pulp products may be produced in a sheet having a consistency of about 40% or greater and which may subsequently be dispersed in water with agitation, pumped to a headbox and wet-laid to form a fibrous web. One non-limiting process for preparing non-wood pulps according to the present invention is illustrated in FIG. 1. The process comprises providing raw Hesperaloe biomass 10 and cutting the biomass 10 to size using a cutting apparatus 20. As discussed in more detail below, cutting may be achieved by a variety of means and preferably results in the cut biomass having a size of about 20 mm or less, such as at least about 10 mm or less. In addition to cutting, at least a portion of the water-soluble extractives are removed from the biomass prior to mechanical pulping. In certain instances, such as illustrated in FIG.1, the cutting and extraction of water-soluble extractives may be done in single stage using a screw press or the like while washing with an extraction solvent 25 to remove water soluble solids 27 from the biomass 10. The amount of water-soluble solids 27 removed from the biomass 10 may vary depending on the extraction process and conditions. In certain instances, at least about 40% of the water-soluble solids are removed from the biomass prior to mechanical pulping, such as at least about 50%, such as at least about 55%. With continued reference to FIG.1, the extracted and cut biomass, which is now generally referred to as bagasse 30, is subjected to washing 40 with a wash fluid 45. The washed bagasse 50 may be refined under first refining conditions without thickening of the washed bagasse 50, such that refining is carried out at a consistency ranging from about 8% to about 12%. The washed bagasse 50 is pulped using a first mechanical refiner 60 under first refining conditions to produce a refined bagasse 70. The first refining conditions may be selected to cause fibrillation of the bagasse 50 and to yield a refined bagasse 70 having a Freeness of at least about 600 mL, such as at least about 650 mL, such as at least about 700 mL, such as from about 600 mL to about 725 mL. After refining, the refined bagasse 70 may be diluted with dilution water 75 and may be subjected to cleaning or screening to remove debris prior to a second mechanical pulping stage using a second mechanical refiner 80. The consistency of the diluted refined bagasse 70 may range from about 3% to about 5%. The diluted refined bagasse 70 is pulped using a second mechanical refiner 80 under second refining conditions to produce a primary pulp 90. The primary pulp 90 may have a invention have relatively high freeness, such as a Freeness of at least about 500 mL, such as at least about 550 mL, such as at least about 600 mL, such as from about 500 to about 700 mL. The primary pulp 90 may also have a brightness of about 30% or greater, such as about 33% or greater, such as about 35% or greater such as from about 30% to about 40%. The primary pulp 90 may be subjected to further processing. For example, as illustrated in FIG. 1, epidermal debris 105 may be removed from the secondary pulp 90 by passing the pulp through a cleaning system 100. The cleaned secondary pulp 110 may then be transferred to a bleaching tower 120 and bleached by adding an alkaline peroxide solution 125 to produce a bleached pulp 130. Prior to processing, such as extracting, pressing, milling, or pulping, the biomass may be cut to size. In certain instances, the biomass may be cut to size and cleaned immediately prior to milling and extraction to remove the water-soluble fraction of the biomass. Alternatively, the biomass may be cut to size when harvested using harvesting equipment design to produce biomass chips of a desired size, particularly equipment designed to cut and chip biomass in a single operation. In certain instances, the biomass may be cut to size using a forage harvester. A forage harvester typically comprises a header and a cutter wheel or drum. The biomass may be cut directly by the harvester header, using reciprocating knives, discs or rotary mowers, or large saw-like blades. The header is configured such that the cut height is above the crown of the plant such as from about 10 to about 30 cm above the ground. From the header the biomass is fed to the cutter wheel. The cutter wheel is equipped with several knives fixed to it that chop and blow the silage out a chute of the harvester into a wagon that is either connected to the harvester or to another vehicle driving alongside. The configuration of the knives, the number of knives attached to the cutter wheel and the speed of the cutter wheel determines the cut size of the biomass. For example, the harvester may be configured to yield a nominal chop length from 5 to about 50 mm, such as from 5 to about 30 mm, such as from about 5 to about 20 mm. It should be noted that the nominal chop length is set by the harvester and the actual chop length of the material may vary depending upon the consistency of orientation of the biomass feeding into the cutter wheel as well as other factors. In other instances, the biomass may be cut to size after harvesting using a mechanical size reduction process such as a hammer mill, rotary shredder, shear shredder, knife hog, tub grinder, woodchipper, or any other device that reduces the nominal size of the entering biomass. Cutting may be preceded by grinding or chipping using a tub grinder, horizontal grinders/shredder, or simple woodchipper. These first stage systems typically have large rotating drums with large blunt hammers that quickly shear or shred the material into a less dense, loose format that can be easily milled to the desired size. Large screens are generally used in first stage grinding to prevent oversized material from exiting the grinding chamber. These screens may have openings that range in size from about 5 to about 15 cm. Chippers typically use rotating drums with fixed knives parallel to the drum axis. The size of the cut biomass is generally controlled by feed rate. Once the first stage grinding or chipping is completed, the feedstock is milled to the desired particle size using a hammermill. Hammermills use large rotating drums with protruding metal bars (i.e., hammers) that impact the material at high velocity to shatter and tear material particles. Typically, the metal bars swing freely from the drum, but fixed hammers are also common in hammer mill designs. The size of biomass exiting the hammermill may range from 5 to about 50 mm, such as from 5 to about 30 mm, such as from about 5 to about 20 mm. Generally cutting the biomass, particularly before the biomass is pulped or bleached, improves one or more physical properties of the resulting pulp. For example, cutting the biomass may reduce the fraction of long fibers in the pulp making the pulp more readily dispersible and amenable for use in the manufacture of wet laid paper products, particularly wet laid tissue products. In certain instances, the reduction in long fiber fraction may be achieved without a significant reduction in the fiber length, such that the pulp may have a fiber length of about 1.50 mm or greater, such as about 1.55 mm or greater, such as about 1.60 mm or greater, such as about 1.65 mm or greater, such as about 1.70 mm or greater, such as about 1.75 mm or greater, such as from about 1.50 to about 2.50 mm, such as from about 1.55 to about 2.00 mm. Cutting biomass prior to pulping may also reduce the fraction of pulp fibers having a fiber length of 6.0 mm or greater, referred to herein as the Very Long Fiber fraction (VLF). For example, pulps prepared according to the present invention may VLF of about 1.0% or less, such as 0.75% or less, such as 0.50% or less, such as 0.25% or less, such as 0.20% or less, such as 0.15% or less, such as 0.10% or less. In still other instances cutting the biomass prior to pulping reduces, or narrows, the distribution of fiber lengths such that the dispersivity index is about 2.00 or less, such as about 1.90 or less, such as about 1.80 or less, such as from about 1.50 to about 2.00, such as from about 1.50 to about 1.90, such as from about 1.50 to about 1.80. Having a dispersivity ratio less than about 2.00, and more preferably less than about 1.80, ensures that the length of the fibers is relatively uniform, improving dispersing the pulp in water, and reducing fiber clumping and stringing when forming wet-laid paper products. In certain instances, the biomass is processed to remove at least a portion of the water-soluble prior to pulping. Water-soluble solids may be removed using any one of several well-known extraction processes, such as a solvent extraction process, particularly processes using an aqueous solvent and more particularly an aqueous polar solvent such as water. One of skill in the art will recognize the ratio of extraction solvent to biomass will vary based on the solvent, the amount of biomass to be extracted, and the extraction procedure. In certain instances, the extraction solvent may be water and the ratio of extraction solvent to biomass, based on liters of extraction solvent to kilogram of bone-dry biomass, is from about 1:5 to about 1:100, such as from about 1:5 to about 1:50 and more preferably from about 1:5 to about 1:20. The pH of the extraction solvent can be between about pH 5.0 and 8.0, such as, for example, between about pH 6.0 and about 8.0, between about pH 6.5 and about 7.5. In those instances where the extraction solvent is water, the water may have a pH between about pH 6.5 and about 7.5. Where the extraction includes imbibition with a crude juice, the imbibition fluid may have a pH from about 4.0 to about 5.0. In those instances where the extraction process is a batch extraction process, the duration of extraction may range from about 0.25 to about 24 hours, such as, for example, from about 0.5 to about 2 hours, from about 1 to about 8 hours, or from about 1 to about 6 hours. In those instances where the extraction process is a continuous process, the duration of extraction may range from about 0.25 to about 5 hours, such as, for example, from about 0.5 to about 3 hours. A simple aqueous extract may be preferred for removal of the water-soluble extractives, although other extraction methods are within the scope of the present invention. For example, a simple water extraction of biomass may be suitable for achieving an insoluble biomass fraction, referred to herein as bagasse, which may be further processed according to the present invention. In other instances, the extractant solution may comprise, in addition to water, a surfactant, an additional solvent or extract-bearing juice. The extract-bearing juice can come from, for example, an earlier extraction step or an earlier milling step. In certain instances, it may be preferred to combine extraction with milling of the biomass. The biomass may be milled using a roll, screw, and other forms of presses. For example, the biomass may be passed between one or more nips of opposed counter-rotating rolls to maximize the mechanical removal of the water-soluble fraction and production of a bagasse that may be subjected to further processing as described below. Where bagasse is subjected to multiple pressings, the water-soluble fraction removed in one milling step, commonly referred to as juice, may be used to wash the bagasse in a subsequent milling step. In certain preferred instances, biomass may be harvested and cut to size, milled, and extracted with an aqueous solvent to remove water soluble extracts such as inorganic salts, saccharides, polysaccharides, organic acids and saponins. The milling step may be carried out prior to pulping using a screw press, optionally with imbibition, to both remove the water-soluble extractives and further reduce the size of the biomass. Generally, the extraction step, alone or in combination with milling, removes at least about 25% of the water-soluble solids from the biomass, more preferably at least about 50%, still more preferably at least about 75%, such as from about 25 to about 98%, such as from about 50 to about 90%, such as from about 75 to about 90%. Removal of water-soluble extractives from the biomass is preferably carried out prior to pulping and more preferably prior to bleaching. Removal of water-soluble extractives from the biomass may improve the efficiency of pulping and/or bleaching. For example, it has been demonstrated that removal of a significant portion of its water-soluble extractives from the primary pulp, such as at least about 85% and still more preferably at least about 90% of the water-soluble extractives, improves the brightness of the bleached pulp. In certain instances, the present invention provides removing at least 85% of the water-soluble extractives from the pulp prior to bleaching, such as at least about 90%, such as at least about 95%. By removing the water-soluble extractives prior to bleaching, the bleached pulps may have a brightness of about 80% or greater. Alternatively, the water-soluble solids may be removed from biomass prior to pulping by diffusion. In diffusion, the biomass is brought into contact with a solvent to extract the water-soluble solids. Usually, the biomass is prepared by first cutting, but not shearing or crushing, so as to minimize the damage to fibers, and avoid the creation of an excessive amount of fines. The prepared biomass is then washed repeatedly with a solvent in a diffuser to extract water soluble solids from the biomass. The solvent can be any of the foregoing solvents. An exemplary solvent is water, particularly hot water, more particularly water having a temperature from about 40 to about 90°C. Various types of diffusers are known in the art and can be adapted for use with biomass as described herein. Suitable diffusers include a ring diffuser, a tower diffuser, or a drum diffuser. Exemplary diffusion systems are discussed, for example, in U.S. Patent Nos.4,182,632, 4,751,060, 5,885,539 and 6,193,805 the contents of which are hereby incorporated in a manner consistent with the present disclosure. Numerous other diffusion methods and devices for the diffusion method are known and can be adapted for use in the methods described herein. One such diffuser is the continuous-loop, counter- current, shallow-bed Crown Model III Percolation Extractor, commercially available from Crown Iron Works, Blaine, MN. Alternatively, the water-soluble fraction of the biomass may be removed prior to pulping by compression and maceration. Compression and maceration may be carried out using multiple devices or a single compression and macerating device such as a plug screw feeder, for example an MSD Impressafiner® commercially available from Andritz, Inc. of Alpharetta, GA, or another device suitable to both compress and macerate the cut and washed biomass. For example, the cut biomass may be compressed by a device capable of at least a 2.5 to 1 compression ratio, such as a 4 to 1 compression ratio, such as a 5 to 1 compression ratio (including all compression ratios in between) to remove the water-soluble fraction and prepare the biomass for pulping. The compression ratio is defined as inlet volume of the compression zone related to the outlet volume of the compression zone. Such a compression ratio allows sufficient pressurization on the biomass to ensure proper chemical absorption during pulping. The device used for compression may be further used for maceration or a separate device may be used for the maceration phase. Maceration allows the softening and separation of biomass into fibers by the application of physical mechanical treatment. Maceration may also increase the surface area of bagasse available to absorb chemicals during subsequent pulping steps. The extracted bagasse is converted to pulp by mechanical refining without the addition of chemicals such as alkaline based chemicals. Mechanical pulping may be carried out by feeding the washed bagasse to a refiner having an inlet and a rotating disc within a casing. The diluted bagasse is mixed in the refiner by the rotating disc, refining the washed bagasse and producing a primary pulp. The refiner step may operate in continuous or batch mode. If continuous mode is used, a single refiner or multiple refiners in series or parallel may be operated. If batch mode is used, multiple refiners operating alternately to accommodate continuous transfer of bagasse to the refiner and continuous feed of primary pulp from the refiner. The refiner may be horizontal, vertical, or inclined orientation. The refiner operation may be optimized to fibrillate the hesperaloe bagasse without excessive cutting, fines generation or yield lose by subjecting the bagasse to a first and second mechanical refining stages where the first stage is carried out a first consistency and the second stage is carried out a second consistency, which is different than the first consistency. For example, the bagasse may be mechanically refined under first conditions where the bagasse consistency ranges from about 8% to about 12%, such as about 10% to yield a primary pulp. The primary pulp may be discharged from the refiner, diluted, and mechanically refined a second time under second conditions where the primary pulp consistency ranges from about 3% to about 6%, such as about 5% to yield a secondary pulp. The refiner conditions may be maintained such that the primary pulp has consistency ranging from about 8% to about 12%, a temperature ranging from about 20 °C to about 40 °C and pH ranging from about 6.5 to about 7.5. A The refiner may be operated under atmospheric pressure. After the first mechanical pulping stage, the primary pulp may be discharged from the first refiner to a second refiner to carry out the second mechanical refining stage. In those instances where the primary and secondary mechanical refining stages are carried out under similar conditions, such as a temperature ranging from and atmospheric pressure, it may not be necessary to quenched, such as by cooling, the refined bagasse as it is discharged from the first refiner to the second refiner. The second refiner conditions may be maintained such that the primary pulp has consistency ranging from about 3% to about 6%, a temperature ranging from about 20 °C to about 40 °C and pH ranging from about 6.5 to about 7.5. The second refiner may be operated under atmospheric pressure. The secondary pulp, which may have a brightness from about 50 to about 60%, may be subjected to further processing to yield a finished pulp. For example, the secondary pulp may be diluted, cleaned to remove debris, and bleached to produce a bleached pulp having a brightness of about 80% or greater. In certain instances, the secondary pulp may be bleached by reacting the secondary pulp with alkaline peroxide chemicals under conditions that allow the temperature of the secondary pulp to be maintained as the pulp is transferred to a bleaching tower for secondary bleaching. The temperature of the secondary pulp may also be thermally adjusted within the bleaching tower with the addition of liquids or gases or through use of heat transfer components if the secondary pulp is discharged directly to the bleaching tower. In certain instances, the secondary pulp may be transferred from the refiner to the bleaching tower under atmospheric conditions by a transfer screw, a chute, or the like. Where the refiner comprises a pressurized casing, the secondary pulp may be discharged to the bleaching tower via a blow valve. Bleaching may be carried out without the use of chlorine or chlorine containing compounds. The secondary pulp may be bleached using a non-chlorine oxidizing agent, such as peroxides, oxygen, and/or ozone with the addition of cyanamide or cyanamide salt. When secondary bleaching includes a peroxide as a bleaching agent, the process may also include one or more stabilizers or complex former to avoid decomposition of the peroxide. The addition of the stabilizer or complex former can be omitted if the heavy metal salts from the primary pulp are removed by washing prior to bleaching. In certain instances, it may be desirable to separate epidermal debris from the primary pulp prior to secondary bleaching. Epidermal debris generally originates from the cuticle of biomass leaves and may include additional layers of cellulosic epidermis. Epidermal debris may comprise cellulose, cutin, cutan, polysaccharides, lipids, and waxes. Epidermal debris may be hydrophobic and may have a color or hand feel that is undesirable in paper products. For example, the epidermal debris may have a brown or yellow color and a course hand feel. Removal of epidermal debris prior to secondary bleaching may improve secondary bleaching efficiency and increase the brightness of the finished pulp. Additionally, removal of epidermal debris may improve the physical properties of paper products made with the pulp. For example, removal of epidermal debris from the pulp may improve the hand feel and softness of tissue products made therefrom. In other instances, removal of epidermal debris from the pulp may reduce the amount of linting in the finished product as the often hydrophobic debris is not well suited for bonding with cellulosic fibers forming the paper product. In certain instances, it may be preferable for the debris content of the primary pulp to be about 5 wt% or less, such as about 3 wt% or less, such as less than about 2.5 wt% prior to secondary bleaching, such as less than about 2.0 wt%. Preferably the primary pulp has low debris content and as such there is generally no specific lower limit on the amount of debris. In certain instances, however, a certain amount of epidermal debris may survive processing and the primary pulp may have a debris content of about 0.5 wt% or greater, such as from about 1.0 to about 5.0 wt%. By reducing the debris prior to secondary bleaching, the resulting bleached pulp may have improved brightness and an acceptable level of debris. Such pulps are well suited for producing high brightness paper products, particularly tissue products that require a high degree of brightness and low lint. Accordingly, bleached pulps of the present invention have a brightness of 75% or more, such as from about 75 to about 92%, such as from about 75 to about 90%, such as from about 75 to about 85%, and a debris content of about 1.0 wt% or less, such as about 0.90 wt% or less, such as about 0.80 wt% or less, such as about 0.60 wt% or less. In certain instances, it may be desirable to remove substantially all of the debris from the pulp prior to bleaching such that the bleached pulp has no detectable debris. Non-limiting examples of devices useful for removing epidermal debris from primary pulp include one or more screens, cleaners, washers, or surge tanks. In certain instances, debris may be removed using a screen, particularly a pressure screen having a body equipped with a first screen having slots and a second screen having holes so that both slots and holes may be used to screen the primary pulp. Multiple screens may be used in a number of different configurations and flows. In certain instances, it may be preferable to remove debris by screening the pulp using a pressure screen having at least one slot. The slots may have a width dimension of about 0.3 mm or less, such as about 0.25 mm or less, such as from about 0.10 to about 0.15 mm. Debris may also be removed from the primary pulp by one or more conical cleaners, particularly one or more hydrocyclones. One skilled in the art will recognize that hydrocyclone is a generic description of cleaning equipment that uses centrifugal force, and other hydrodynamic forces, to separate insoluble solids based upon density. Generally, the conical cleaner has a geometry that provides decreasing (cross-sectional) diameter. Multiple cleaners may be combined in a variety of orientations so as to share common feed and discharge chambers. The conical cleaners may include one or more of a forward flow (conventional) cleaner; a low density cleaner, a reverse cleaner, a through flow cleaner, a core bleed cleaner, an asymmetrical cleaner, and a rotating body cleaner. In certain instances, it may be preferable to remove epidermal debris using at least one low density cleaner having a diameter from about 25 to about 120 cm, and an operated pressure drop from about 100 to about 210 kPa. The low-density cleaner may be operated in a forward feed configuration and at a pulp consistency from about 0.5 to about 2.0%. After cleaning, the cleaned pulp may be subjected to secondary bleaching. Secondary bleaching may be carried out at a medium or high consistency and may consist of one, two or three stages of bleaching depending on the desired brightness of the finished pulp. Generally, medium consistency bleaching is carried out at a pulp consistency less than about 16%, such as from about 8% to about 16%, such as from about 8 to about 12%. High consistency bleaching, on the other hand, may be carried out at a pulp consistency of about 16%, such as from about 16 to about 30%, such as from about 16 to about 22%. Secondary bleaching may be carried out in two stages at a consistency of about 10% with alkaline peroxide solution with or without the peroxide stabilizers: sodium silicate and DTPA. In other instances, secondary bleaching may be carried out in two stages where the first stage is carried out at a consistency of about 10% and the second stage is carried out at a consistency of about 20% and both stages are performed using an alkaline peroxide solution with or without the peroxide stabilizers: sodium silicate and DTPA. Secondary bleaching may also be carried out in a single high consistency stage, such as at a consistency of about 20%. Regardless of the number of stages or the consistency of the pulp, the overall peroxide dosage may range from about 8 to about 12% and the caustic to peroxide ratio may range from about 0.4 to about 0.6. Secondary bleaching may be carried out a temperature from about 75°C to about 85°C and the total retention time may range from about 1 to about 5 hours. The final pH of the bleached pulp may be from about8 to about 11, more preferably from about 9 to about 10. The bleached pulp may be fed to a further processing step, which may involve multiple operations including, but not limited to, mechanical refining, screening, and washing to produce a secondary bleached pulp suitable for final use, such as the manufacture of wet-laid paper products. For example, the bleached pulp may be diluted and refined at a low consistency, such as a consistency from about 3.0 to about 5.0% using a twin flow, non-pressurized, refiner. The refined bleached pulp may then be dewatered, dried, and formed into sheets. As an option, pulps, both bleached and unbleached, prepared according to the present invention may be formed into dried sheets or rolls. The pulp may be diluted with water resulting in diluted pulp that can be pumped via a fan pump to a headbox. The diluted pulp can be supplied to the headbox at consistencies ranging from about 0.1 to about 5% solids, such as from about 0.5 to about 3% solids, such as from about 1 to about 2.5% by weight solids. From the headbox the diluted pulp can be sprayed onto a wire and partially dewatered to form a partially dewatered pulp sheet. The wire may be a foraminous continuous metal screen or plastic mesh which travels in a loop. The wire can be, for example, a flat wire Fourdrinier, a twin wire former, or any combinations of these. Low vacuum boxes and suction boxes may be used with the wire in conventional manners. The consistency of the pulp sheet after dewatering on the wire may range from about 2 to about 35% solids, such as from about 10 to about 30% solids. The partially dewatered pulp sheet may be conveyed to a wet-press section. Additional water can be pressed and vacuumed from the pulp at the wet-press section. The wet-press section can remove water from the pulp with a system of nips formed by rolls pressing against each other aided by press felts that support the pulp sheet and can absorb the pressed water. A vacuum box may optionally be used to apply vacuum to the press felt to remove the moisture so that when the felt returns to the nip on the next cycle, it does not add moisture to the sheet. The wet-press section may increase the consistency of the partially dewatered pulp sheet to about 40% solids or greater, such as about 50% solids or greater. The pressed pulp may be dried by a thermal dryer section. The pulp sheet can be dried in the thermal dryer section at a temperature greater than about 100 °C to remove more water. The thermal dryer may comprise, for example, a series of internally steam-heated cylinders that evaporate the moisture of the pulp as the pulp is advanced over the heated cylinders. Generally, the thermal driers increase the consistency of the pressed pulp to about 80% or greater, such as about 90% or greater, such as from about 80 to about 95% by weight. The dried pulp exiting the thermal dryer may be in the form of a continuous dried pulp sheet, which may be unitized into sheets, bales, rolls, or other forms. In certain instances, the resulting pulp sheet has a moisture content of less than about 20%, more preferably less than 15% and still more preferably less than about 10%. Pulp sheets may be produced at any given basis weight, however, in certain instances the pulp sheets may have a basis weight of at least about 150 grams per square meter (gsm), such as from about 150 to about 600 gsm and more preferably from about 200 to about 500 gsm. The ability of the pulp sheet to disperse in water and drain during sheet formation is quite important since, if sufficient drainage does not take place, the speed of the paper machine must be reduced, or the wet-formed web will not hold together on the foraminous surface. A measure of this drainage parameter is freeness, and more particularly Canadian Standard Freeness (CSF). Accordingly, in certain instances pulps prepared according to the present disclosure have a Canadian Standard Freeness (CSF) greater than about 400 mL, and more preferably greater than about 450 mL, such as from about 400 to about 600 mL. Pulps produced according to the present invention may have one or more improved physical properties that make them well suited for use in the manufacture of wet-laid paper products and more particularly wet-laid tissue products. The inventive pulps may be blended with other wood and non-wood pulps as needed to form wet-laid products having the desired attributes. The blended pulps may comprise wood pulp fibers that have been produced by any one of several well-known methods such as chemical (sulfite, kraft), thermal, mechanical, or a combination of these techniques. In certain instances, the inventive pulps may replace one or more pulps, particularly wood pulps, in a conventional papermaking furnish. For example, the inventive pulps may replace Northern Bleached Softwood Kraft (NBSK) pulp fibers. In certain instances, the present invention provides a non-wood pulp, particularly a hesperaloe pulp prepared by at least one stage of mechanical treatment without the use of chemicals as described herein, having a Fiber Length of about 1.50 mm or greater, such as about 1.55 mm or greater, such as about 1.60 mm or greater, such as about 1.65 mm or greater, such as about 1.70 mm or greater, such as about 1.75 mm or greater, such as from about 1.50 to about 2.50 mm, such as from about 1.55 to about 2.00 mm. In certain instances the inventive non-wood pulps may have a coarseness less than about 10.0 mg/100 m, such as less than about 9.0 mg/100 m, such as less than about 8.0 mg/100 m, such as less than about 7.0 mg/100 m, such as less than about 6.0, such as less than about 5.0, such as from about 4.0 to about 10.0 mg/100 m, such as from about 4.0 to about 8.0 mg/100 m, such as from about 4.0 to about 6.0 mg/100 m. The pulps of the present invention generally have a modest degree of tensile strength, such as a Tensile Index of about 55 or less, such as about 50 or less, such as about 45 or less, such as about from about 30 to about 55, such as from about 35 to about 50, such as from about 35 to about 45. Further, the pulps may have only a modest degree of tensile strength even when subjected to refining. For example, as shown in FIG. 2, the pulps may have a Tensile Index less than hesperaloe pulps prepared by chemi-mechanical pulping over a wide range of refining levels. The freeness of the pulp may also be improved by foregoing the use of chemicals during pulping. For example, as shown in FIG.3, the inventive pulps may have a higher Freeness at a given Tensile Index, compared to Hespealoe pulps prepared by chemi-mechanical pulping. Therefore, in certain instances the non-wood pulps may have a freeness of about 500 mL or greater, such as about 525 mL or greater, such as about 550 mL or greater, such as from about 500 mL to about 600 mL. The non-wood pulp of the present invention may also have a low degree of fines and high freeness, such as a Fines content of less than about 2.0%, more preferably less than about 1.5% and still more preferably less than about 1.0%, such as from about 0.5 to about 2.0 and a freeness of about 500 mL or greater, such as about 525 mL or greater, such as about 550 mL or greater, such as from about 500 mL to about 600 mL. The non-wood pulp of the present invention may also be bleached non-wood pulps having a brightness of about 75% or more, such as about 77% or more, such as about 79% or more, such as about 81% or more, such as about 83% or more. In certain instances, the pulp brightness may range from about 75 to about 92%, such as from about 80 to about 90%, such as from about 80 to about 85%. At the foregoing brightness levels the pulp may have a debris content of about 1.0 wt% or less, such as about 0.90 wt% or less, such as about 0.80 wt% or less, such as from about 0 to about 0.80 wt%. In other instances, the non-wood pulps may comprise a low degree of water-soluble extractives, such as less than about 5.0 wt% water soluble solids, more preferably less than about 3.0 wt% water soluble solids and still more preferably less than about 2.0 wt% water soluble solids. The removal of water-soluble extractives during processing of the non-wood biomass into pulp may improve the bleaching of the fiber such that the bleached non-wood pulp has both a low amount of water-soluble solids, as less than about 5.0 wt%, and a high degree of brightness, such as a brightness of at least 80% or more, such as from about 80 to about 92%. TEST METHODS Pulp Handsheets Handsheets of pulp were prepared using a Valley Ironwork lab handsheet former measuring 8.5 inches × 8.5 inches. The pulp was mixed with distilled water to form slurries at a ratio of 25 g pulp (on dry basis) to 2 L of water. The pulp/water mixture was subjected to disintegration using an L&W disintegrator Type 965583 for 5 minutes at a speed of 2975 ± 25 RPM. After disintegration, the mixture was further diluted by adding 4 L of water. Handsheets having a basis weight of 60 grams per square meter (gsm) were formed using the wet laying handsheet former. Handsheets were couched off the screen, placed in the press with blotter sheets, and pressed at a pressure of 75 pounds per square inch for one minute, dried over a steam dryer for two minutes, and finally dried in an oven. The handsheets were cut to 7.5 inches square and subject to testing. Fiber Properties Fiber properties such as length, coarseness, percentage of fines, and fraction of very long fiber, are generally determined using an OpTest Fiber Quality Analyzer-360 (OpTest Equipment, Inc., Hawkesbury, ON) in accordance with the manufacturer's instructions. Samples are generally prepared by first accurately weighing a pulp sample. The sample mass may range from about 10 to about 50 mg (bone dry) and may be taken from a handsheet or pulp sheet. The weighed sample is diluted to a known consistency (between about 2 and about 10 mg/l). An aliquot of the diluted sample (usually 200 ml) is further diluted to a final volume of 600 ml and placed in the analyzer. The sample is then analyzed according to the manufacturer’s instructions and the output of the analyzer, such as the length weighted average fiber length, coarseness, length weighted fines, and a histogram illustrating the distribution of various fiber properties for a given sample are recorded. Generally, each reported fiber property is the average of three replicates. The output of the fiber quality analyzer is used to calculate the Very Long Fiber (VFL) fraction, which is the sum of fiber count from 6 to 14.95 mm divided by the total fiber count. Generally, the bin data output by the instrument, which provides the number of individual fibers counted within a given fiber length range, is used to determine VLF. The total number of individual fibers counted (N) and the total number of individual fibers counted having a length of 6 mm or greater (n) are determined from the bin data. The %VLF = n/N*100. The output of the fiber quality analyzer is also used to calculate the ratio of the length weighted average fiber length (Lw) to the number average fiber length (Ln). Lw and Ln are calculated by the FQA software using the following equations: ∑ ^ _{^^^ ^^^^^^} ^_^^_^ ^{^} ∑ _{^^^ ^^^^^^} ^_^^_{^ ^} = ∑ _{^^^ ^^^^^^} ^_^^_^ ^_^ = ∑ ^^^ ^^^^^^ ^_^ Where n and L The ratio of the length weighted average fiber length (Lw) to the number average fiber length (Ln) indicates the fiber length distribution of the sample. A higher ratio is indicative of a broader fiber length distribution. A value of 1 indicates that all of the fibers in the sample have the same length. Fiber coarseness is measured using the FQA instrument and is measured “as-is” without removal of fines. Consistency of the pulp sample is determined using TAPPI methods T-240 or the equivalent and the consistency (%) is recorded to the nearest 0.01%. Based upon the measured consistency, the amount of undried sample required to yield approximately 0.015 grams of oven dried pulp is calculated and weighed out and the weight recorded to the nearest 0.0001 g. The weighed undried pulp is transferred to a British pulp disintegrator or equivalent pulp disintegrator and the total volume of the sample is diluted to 2 liters with deionized water and disintegrated 15,000 revolutions according to the manufacturer’s instructions. The disintegrated sample is further diluted with deionized water to a total volume of 5 liters ± 50 mL and the volume is recorded to the nearest 10 mL. The diluted sample is agitated by stirring and approximately 600 grams are weighted out into a clean beaker. The mass of the sample weighed out to the beaker is recorded to the nearest 0.1 g. The oven dried weight of the pulp sample to be analyzed is then calculated as shown in the equation below and fiber analysis is carried out according to the manufacturer’s instructions. ^ ^ ^!"#$! %&'( ^)^* +,^-#-.$^/0 ,1 &^!"#$! -23('$ ^%^ * 52-- ,1623('$ ^)^ ^. ^. ^^^^ ^^ ^^^^ ^ = 7#'&.$! 623('$ 8,'&3$ ^3^^ * 9: sp-02. may as an or equivalent. The micrometer has a circular pressure foot having an area of 2.0 cm², a lowering speed of 1.0 mm/second and a pressure of 50 kPa. Generally, caliper is reported as the average of five samples. Basis Weight Generally, hand sheets are dried and prepared for testing as set forth in TAPPI T 205 sp-02. Pulp sheets may be tested as is. The bone-dry basis weight is generally measured by first cutting the samples to a specimen size of approximately 19.05 x 19.05 cm using an appropriate cutting tool. The cut sample is then placed on a balance in an oven preheated to 105 ± 2°C. Once the weight of the sample has stabilized, the weight is recorded to the nearest 0.01 gram. The bone-dry basis weight equals the measured weight (W) multiplied by 27.56. Tensile Generally Tensile is measured by forming a handsheet of a particular pulp, as described herein, and then testing the resulting handsheet. Generally, handsheets are dried and prepared for testing as set forth in TAPPI T 205 sp-02. Samples are preconditioned and tested under TAPPI conditions (50 ± 2% relative humidity and 72 ± 1.8°F) as set forth in TAPPI T 402. Tensile testing is carried out substantially as described in TAPPI T 494 om-01 using an MTS Systems Sintech 11S, Serial No.6233 tensile testing instrument. The data acquisition software was an MTS TestWorks® for Windows Ver. 3.10 (MTS Systems Corp., Research Triangle Park, NC). Generally, the tensile strengths of five samples are measured and averaged. Tensile strength generally has units of grams force per unit sample width, such as g/25.4 mm. Debris Debris is generally measured using a MasterScreen™ from Pulmac Systems International (Williston, VT). The MasterScreen™ is a low consistency screening device designed to mechanically separate fibers from contaminants. The MasterScreen™ is fitted with a screen (part no.3390P) having a slot size of 100 µm (0.004 inches). Screening of pulps using a MasterScreen type instrument is generally described in T-274. Approximately 5.0 bone dry grams of fiber are used for the analysis. The sample may be taken from a handsheet, a pulpsheet or from wet lap pulp. The 5.0 g sample is mixed with 2 L of water and disintegrate using a benchtop disintegrator at 15,000 Revolution prior to testing. In certain instances where the sample is known to have a fiber length in excess of 2 mm, a cationic debonder such as cationic oleylimidazoline may be added to the diluted sample to prevent the formation of clumps or strings. In those instances where a debonder is added, it is typically added at 160 kilograms of debonder per bone dry metric ton of fiber. The sample is screened according to the manufacturer’s instructions and the rejects are collected in a collection cup fitted with a 150 mesh stainless steel screen. A wash cycle is run after the initial cycle to ensure that all of the debris retained by the screen is captured. Finally, the collection cup is rinsed with water and the rinse fluid is collected in a beaker. The rejects and wash fluid collected in the beaker is filtered under vacuum using a pre-weighed filter pad. Debris is collected on the filter pad, which is dried in an oven preheated to 105°C overnight. The dried filter pad is weighed to the nearest 0.01 g and the weight percentage of debris is calculated. Generally, debris is reported as wt% and is the average of three samples. Water Soluble Solids Total biomass water soluble solids may be determined using an Accelerated Solvent Extraction system (ASE) such as a Dionex™ ASE™ 350 (Thermo Fisher Scientific, Waltham, MA). Approximately 10 grams of harvested biomass is dried to a constant weight in an oven, typically 4 hours at 125°C. After drying, approximately 0.2 grams of the bone-dry biomass is accurately weighed, and the weight (Wb) recorded to the nearest 0.001 gram. Using water as the solvent, biomass is extracted using the conditions set forth in Table 2, below. The ratio of biomass to solvent is generally 100:1 and two consecutive water extraction cycles are performed. TABLE 2 Pressure (psi) 1500 Tem erature (°C) 40 At the end of the extraction process the liquid phase is collected, dried under vacuum at approximately 80°C in a warm water bath and the weight of the dried material (Wi) is recorded to the nearest 0.001g. The total weight of water-soluble solids (W_e) is calculated by the weight of solids recovered from the extraction process (Wi). Total water-soluble solids as a percentage of bone dry biomass is then determined using the following equation: I Water Soluble Solids ^wt%^ = _$ K 100 I_J Size Classification The relative size of biomass and bagasse, as well as the nominal size, was determined using Williams screen analysis, using a TMI Chip Class™ Model 71-01 (Testing Machines Inc., New Castle, DE) substantially as described in TAPPI Useful Method 21, which indicates, by weight percentage, the relative proportion of biomass or bagasse retained on each of a series of screens having of varying size as set forth in Table 3, below. TABLE 3 Size Opening Screen No. Inch mm The Williams screen analysis nsverse dimensions of biomass or bagasse retained on a given screen. Two important values with regard to chip uniformity can be obtained from the above screen fraction data. The first value is the screen size through which at least 70% of the biomass or bagasse passes through, i.e, the nominal size. The second is the relative distribution of chips on each of the screens and the relative position of the screen at which the distribution is maximized. EXAMPLES Inventive pulps were prepared from H. Funifera biomass using a two-stage mechanical pulping process without the addition of chemicals to either of the pulping stages. Both bleached and unbleached pulps were prepared. The processes used to prepare exemplary pulps is summarized in Table 4, below. TABLE 4 Example Cut Water Soluble Solids Treated to Reduce Extracted Debris Bleached The biomass was cut and water soluble were removed using a two-stage screw press, which cut the biomass to a nominal size of about and 20 mm and removed about 55 wt% of the water-soluble extractives. The extracted and cut biomass was washed by mixing with water at a consistency ranging from 1% to 5%, dewatered to a consistency of 40% to 50%, and then diluted with hot water to a consistency of about 4%. The diluted bagasse was fed to an Andritz 36-1CP single disc refiner operating at atmospheric pressure, a temperature of about 130 F and rotational disc speed of 900 rpm. After the first refining the stage the refined bagasse was discharged into a retention tank and further diluted with hot water to a consistency of 3%. The diluted, refined bagasse was then fed to an Antritz TwinFlow IIIB refiner having a rotational disc refiner plate operating at 1,200 rpm. In certain instances, after secondary refining the pulp was diluted with water to a consistency of 2% and passed through a pressure screen. The pressure screen has a Dolphin rotor design equipped with a PG25-03 micro-slotted screen basket having 0.1 mm slots. The screen fractioned the pulp into accepts and rejects. In certain instances, the primary pulp was bleached using a single stage bleaching process. A 12% hydrogen peroxide solution, 4% NaOH, 3% Sodium Silicate, 0.5% DTPA was used to bleach the pulp. The fiber and tensile strength properties of the primary and bleached pulp are summarized in Tables 5 and 6, below. To further assess the physical properties of the inventive pulps, samples were subjected to refining and formed into handsheets as described herein. The handsheets were subjected to tensile and porosity testing as described herein. The results of the tensile and porosity testing are summarized in the tables below. TABLE 5 Inventive Sample 1 Inventive Sample 2 Brightness (%) 771 412 TABLE 6 PFI Refining Tensile Index Porosity (cfm) Tensile Index Porosity (cfm) Comparative Examples 1 A comparative sample of H. Funifera pulp was prepared using an alkaline-peroxide mechanical process substantially as described in Example 3 of PCT Application No. PCT/US2021/058196. The fiber and tensile strength properties of the bleached pulp are summarized in Tables 7 and 8, below. TABLE 7 Example Comparative Example 2 Bl h d Y PFI Refining Tensile Index Porosity (cfm) Rev 100 40.35 137.8 Comparative Examples 3 an A comparative sample of H. Funifera pulp was prepared using a three stage non-wood pulping process commercially available from Taizen America (Macon, GA). The pulping process involved both mechanical action as well as chemical treatment to defibrillate the plant material and produce pulp. Generally, fiber was cut to a nominal size of about 20 mm using a guillotine style cutter. The cut fiber was conveyed to a mechanical masher and diluted with water to a consistency of about 40%. The mashed fiber was conveyed to a kneader and the consistency was adjusted to about 30%. The mashed fiber was mechanically pulped with the addition of 7% NaOH to the first kneading cylinder and 5% H₂O₂ to the second kneading cylinder. The resulting pulp was washed and screened. The fiber and tensile strength properties of the unbleached pulp (Comparative Example 2) are summarized in Table 9, below. A portion of the unbleached pulp was subjected to bleaching with hydrogen peroxide. The fiber and tensile strength properties of the bleached pulp (Comparative Example 3) are summarized in Table 9, below. TABLE 9 S^{hort Description} Comparative Example 3 Comparative Example 4 Brightness *%) 82 40 1 _{2 4} m) bodiments thereof, it will be appreciated that those skilled in the art, upon attaining an understanding of the foregoing, may readily conceive of alterations to, variations of, and equivalents to these embodiments. Accordingly, the scope of the present invention should be assessed as that of the appended claims and any equivalents thereto and the following embodiments: Embodiment 1: A process for preparing pulp from non-woody species, the process comprising the step of: (a) cutting the non-woody species; (b) removing at least a portion of the water-soluble solids from the non-woody species to yield an extracted bagasse; (c) washing the extracted bagasse to yield a washed bagasse having a first consistency; (d) mechanically refining the washed bagasse under first refining conditions to yield a primary pulp, wherein step (d) is substantially free from added chemicals. Embodiment 2: A process for preparing pulp from non-woody biomass comprising the steps of (a) providing a non-wood biomass; (b) cutting the non-wood biomass to a nominal length; (c) extracting water soluble solids from the cut biomass to produce a bagasse; (d) mechanically refining the bagasse at a first consistency to yield a refined bagasse; (e) mechanically refining the refined bagasse at a second consistency, wherein the second consistency is less than the first consistency, to yield a non-wood pulp; (f) cleaning the non-wood pulp to yield a cleaned pulp; and (h) bleaching the cleaned pulp to produce a bleached non-wood pulp. Embodiment 3: A process for preparing pulp from non-woody biomass comprising the steps of (a) providing a non-wood biomass; (b) cutting the non-wood biomass to a nominal length less than about 20 mm; (c) extracting water soluble solids from the cut biomass; (d) washing the biomass to yield a washed biomass having a consistency ranging from about 8% to about 12% (e) refining the washed biomass under first refining conditions to produce a primary pulp; (f) diluting the primary pulp to yield a diluted primary pulp having a consistency ranging from about 3% to about 4%; and (g) refining the diluted primary under second refining conditions to produce a non-wood pulp. The non-wood pulp may be subjected to further treatment, such as cleaning to produce a cleaned pulp, bleaching to yield a bleached pulp, or drying to yield a dried pulp. Embodiment 4: The process of any one of embodiments 1-3 wherein the pulp yield is at least about 90%. Embodiment 5: The process of any one of embodiments 1-3 wherein the pulp has a fiber length from about 1.50 to about 2.50 mm and/or a coarseness from about 4.0 to about 10.0 mg/100 m. Embodiment 6: The process of any one of embodiments 1-3 wherein the pulp has a Tensile Index less than about 55. Embodiment 7: The process of any one of embodiments 1-3 wherein the biomass comprises one or more plants of the genus Hesperaloe. Embodiment 8: The process of any one of embodiments 1-3 wherein the biomass comprises one or more plants selected from H. funifera, H. parviflora, H. nocturna, H. chiangii, H. tenuifolia, H. engelmannii and H. malacophylla. Embodiment 9: The process of any one of embodiments 1-3 wherein the pulp has a Freeness from about 400 to about 600 mL. Embodiment 10: Embodiment 6: The process of any one of embodiments 1-3 wherein the pulp has a fines content of less than about 2.0% and a Freeness of about 400 mL or greater. Embodiment 11: The process of any one of embodiments 1-3 wherein the pulp has a Very Long Fiber (VFL) content of about 0.10% or less. Embodiment 12: The process of any one of embodiments 1-3 wherein the pulp is a substantially dry sheet having a moisture content of about 10% or less and a sheet bulk of at least about 2.0 cc/g. Embodiment 13: The process of any one of embodiments 1-3 wherein the pulp has a dispersivity index of about 2.25 or less, such as from about 1.50 to about 2.00. Embodiment 14: The process of any one of embodiments 1-3 wherein the pulp has a Tensile Index of about 50 or less, such as about 45 or less, such as about from about 30 to about 50, such as from about 35 to about 50. Embodiment 15: The process of any one of embodiments 1-3 wherein the dried pulp has a moisture content less than about 10%. Embodiment 16: The process of any one of embodiments 1-3 wherein the step of drying is carried out by contacting the bleached pulp with a cylindrical dryer surface having a temperature greater than about 100 °C. Embodiment 17: The process of any one of the embodiments 1-3 wherein the primary pulp or the non-wood pulp are substantially free from chemical additives. Embodiment 18: The process of any one of the embodiments 1-3 wherein refining is carried out without the addition of an alkaline solution, such as sodium hydroxide, or oxidative chemicals, such as hydrogen peroxide or sodium peroxide, or other chemicals commonly employed in pulping processes to facilitate the removal of lignin, such as sulfur dioxide, sodium sulfite, sodium bisulfite or sodium hydrosulfite. Embodiment 19: The process of any one of the embodiments 1-3 wherein refining is carried out without the addition of stabilizers, such as ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA) and nitrilotriacetic acid (NTA). Embodiment 20: The process of any one of the embodiments 1-3 wherein the bleaching step comprises adding a sodium hydroxide alkaline peroxide solution to the secondary pulp.

Claims

We claim: 1. A mechanical non-wood pulp comprising a plurality of fibers derived from one or more plants of the genus Hesperaloe and having a fiber length of about 1.50 mm or greater, a Freeness of at least about 400 mL and a Tensile Index of about 50 or less. 2. The mechanical non-wood pulp of claim 1 wherein the one or more plants are selected from H. funifera, H. parviflora, H. nocturna, H. chiangii, H. tenuifolia, H. engelmannii and H. malacophylla. 3. The mechanical non-wood pulp of claim 1 having a brightness of at least about 75%, 4. The mechanical non-wood pulp of claim 1 having a Tensile Index from about 20 to about 50. 5. The mechanical non-wood pulp of claim 1 having a Freeness from about 500 to about 650. 6. The mechanical non-wood pulp of claim 1 having a fiber length from about 1.50 to about 2.50 mm. 7. The mechanical non-wood pulp of claim 1 having a coarseness less than about 10.0 mg/100 m. 8. The mechanical non-wood pulp of claim 1 having a coarseness from about 4.0 to about 6.0 mg/100 m. 9. The mechanical non-wood pulp of claim 1 having a fines content of less than about 2.0% and a Freeness from about 550 mL to about 650 mL. 10. The mechanical non-wood pulp of claim 1 having a Very Long Fiber (VFL) content of about 0.10% or less. 11. The mechanical non-wood pulp of claim 1 having a Debris content of about 2.0 wt% or less. 12. The mechanical non-wood pulp of claim 1 comprising about 2.0 wt% water soluble solids or less. 13. A method of manufacturing a non-wood pulp comprising the steps of: a. providing a non-wood biomass derived from a plant of the family Asparagaceae; b. feeding the non-wood biomass to a refiner comprising a refining disc encased in a housing having an inlet and an outlet; c. refining the non-wood biomass under first refining conditions having a pH ranging from 6.5 to 7.5 and a first consistency to produce a primary bagasse; d. feeding the primary bagasse to a refiner comprising a refining disc encased in a housing having an inlet and an outlet; and e. refining the primary bagasse under second refining conditions having a pH ranging from 6.5 to 7.5 and a second consistency, wherein the second consistency is less than the first consistency, to yield a primary pulp. 14. The method of claim 13 further comprising the step of cleaning the primary pulp to yield a cleaned pulp having less than about 5% debris; 15. The method of claim 13 further comprising the step of bleaching the primary pulp. 16. The method of claim 15 wherein the bleaching step comprises adding a sodium hydroxide alkaline peroxide solution to the secondary pulp. 17. The method of claim 13 further comprises the step of selectively cutting the biomass. 18. The method of claim 13 further comprises the step of extracting water-soluble solids from the biomass. 19. The method of claim 8 wherein the biomass is derived from one or more plants of the genus Hesperaloe. 20. The method of claim 15 wherein the one or more plants are selected from H. funifera, H. parviflora, H. nocturna, H. chiangii, H. tenuifolia, H. engelmannii and H. malacophylla. 21. The method of claim 8 wherein the first refining conditions comprise a biomass consistency ranging from about 8% to about 12% and the second refining conditions comprise a primary bagasse having a consistency ranging from about 3% to about 4%. 22. The method of claim 8 wherein the pulp yield is at least about 90%. 23. The method of claim 8 wherein the primary pulp is substantially free from chemical additives. 24. The method of claim 8 wherein the high yield pulp has a Fiber Length of about 1.50 mm or greater, a Tensile Index less than about 50 and a Freeness of about 500 mL or greater.