WO2025245519A1

WO2025245519A1 - Methods for stabilizing aggregates and sequestering carbon dioxide utilizing non-bituminous binders and biochar, and compositions resulting therefrom

Info

Publication number: WO2025245519A1
Application number: PCT/US2025/030917
Authority: WO
Inventors: Robert Jason DYKE; Hans Arne FLATO; Tonje NORHEIM; Haakon BRUNELL; Kristoffer RØIL; Benoit LORANGER
Original assignee: Carbon Crusher Inc
Current assignee: Carbon Crusher Inc
Priority date: 2024-05-24
Filing date: 2025-05-26
Publication date: 2025-11-27
Anticipated expiration: 2026-11-24

Abstract

An aggregate stabilization process includes locating a layer of granular material distributed over a stabilization area and characterized by a layer depth, wherein the granular material is characterized by a granular porosity; obtaining a quantity of biochar characterized by a biochar density; calculating a biochar area density based on the layer depth, the granular porosity, and the biochar density; dispersing the quantity of biochar over the stabilization area approximating the biochar area density; dispersing a lignin-based binder over the stabilization area, wherein the lignin-based binder includes a lignin-based polymer and water and exhibits an aqueous mass ratio of the lignin-based polymer and the water; mixing the granular material layer, the quantity of biochar, and the lignin-based binder to produce an aggregate-filler-binder layer; and compacting the aggregate-filler-binder layer.

Description

METHODS FOR STABILIZING AGGREGATES AND SEQUESTERING CARBON DIOXIDE UTILIZING NON-BITUMINOUS BINDERS AND BIOCHAR, AND COMPOSITIONS RESULTING THEREFROM

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This Application claims the benefit of U.S. Provisional Application No. 63/651,942, filed on 24-MAY-2024, and U.S. Provisional Application No. 63/743,273, filed on 09-JAN-2025, each of which is incorporated in its entirety by this reference.

TECHNICAL FIELD

[0002] This invention relates generally to the field of aggregate stabilization and, more specifically, to new and useful methods for stabilizing aggregates utilizing non-bituminous binders and biochar and compositions resulting therefrom in the field of aggregate stabilization.

BRIEF DESCRIPTION OF THE FIGURES

[0003] FIGURE 1 is a flowchart representation of one variation of an aggregate stabilization process.

[0004] FIGURE 2 is a schematic representation of one variation of a stabilized aggregate composition.

[0005] FIGURE 3 is a graphical representation of a grading curve of an example granular material.

[0006] FIGURE 4 is a graphical representation of an unconfined compressive strength progression of multiple examples of the stabilized aggregate material and a control composition not including a biochar filler proportion.

[0007] FIGURE 5 is a graphical representation of an unconfined compressive strength relationship to moisture content for multiple examples of the stabilized aggregate material and a control composition not including a biochar filler proportion.

[0008] FIGURE 6 is a flowchart representation of one variation of an aggregate stabilization process.

[0009] FIGURE 7 is a flowchart representation of one variation of an aggregate stabilization process.

[0010] FIGURE 8 is a flowchart representation of one variation of an aggregate stabilization process. DESCRIPTION OF THE EMBODIMENTS

[0011] The following description of embodiments of the invention is not intended to limit the invention to these embodiments but rather to enable a person skilled in the art to make and use this invention. Variants, variations, configurations, implementations, example implementations, and examples described herein are optional and are not exclusive to the variants, variations, configurations, implementations, example implementations, and examples they describe. The invention described herein can include any and all permutations of these variants, variations, configurations, implementations, example implementations, and examples.

[0012] Generally, the term “set,” as utilized herein, can include a single instance or multiple instances of an associated object. Descriptors such as “first,” “second,” “third,” etc., as utilized herein, do not imply a sequence or order unless otherwise specified but do imply separate instances of the associated object.

[0013] Generally, the term “include,” as utilized herein, can mean “comprise,” “consist of,” or “consist essentially of’ and is not restricted to any one of the above interpretations throughout.

[0014] Generally, various components of the various compositions are described herein as percentages or proportions of the whole composition. In these circumstances, the terms “percentage” or “proportion” or the symbol “%” refer to mass percentages or proportions unless otherwise specified.

[0015] Generally, the term “distribution,” as utilized herein, represents any characterization of data that approximates a true distribution of the data and is not intended to imply any degree of accuracy

[0016] Generally, the terms “approximate” or “approximating,” as utilized herein, indicate an attempt to effect a particular quality or outcome within some margin of error (e.g., ±25%).

[0017] Generally, the term “technical lignin,” as utilized herein, refers to lignin-rich material derived from biomass fractionation, such as lignosulfonate, Kraft lignin, soda lignin, and hydrolysis lignin.

[0018] Generally, the term “non-bituminous,” as utilized herein, refers to a composition that does not contain, and is not derived from, bitumen or similar petroleum-based products.

[0019] Generally, the term “filler,” as utilized herein, refers to any material that fills voids within a stabilized aggregate composition, “fillers” can include materials that do not necessarily increase density or stiffness of the stabilized aggregate composition, and, additionally or alternatively, modify other characteristics of the stabilized aggregate composition.

[0020] Generally, the term “stabilized aggregate composition,” as utilized herein, refers to a heterogeneous and compacted mixture of materials. Therefore, characteristics, properties, or attributes of the stabilized aggregate composition described herein refer to bulk characteristics, properties, or attributes of the stabilized aggregate composition on the resolution of the square meter or cubic meter scale and may vary locally within smaller samples of the stabilized aggregate composition.

[0021] Generally, the term “road composition,” as utilized herein, is one example of a stabilized aggregate composition and refers to a heterogenous and compacted mixture of road materials that form one or more of a set of road layers, including a sub-base, a base course, a binder course, and/or a surface course. Therefore, characteristics, properties, or attributes of the road composition described herein refer to bulk characteristics, properties, or attributes of the road composition on the resolution of the square meter or cubic meter scale and may vary locally within smaller samples of the road composition.

1. Aggregate Stabilization Process

[0022] As shown in FIGURE 1, one variant of an aggregate stabilization process Pl 00 includes locating a layer of granular material distributed over a stabilization area and characterized by a layer depth, wherein the granular material is characterized by a granular porosity in Step SI 10; obtaining a quantity of biochar characterized by a biochar density in Step S120; calculating a biochar area density based on the layer depth, the granular porosity, and the biochar density in Step SI 30; dispersing the quantity of biochar over the stabilization area approximating the biochar area density in Step S140; dispersing a lignin-based binder over the stabilization area, wherein the lignin-based binder includes a lignin-based polymer and water and exhibits an aqueous mass ratio of the lignin-based polymer and the water in Step SI 50; mixing the granular material layer, the quantity of biochar, and the lignin-based binder to produce an aggregate-filler-binder layer in Step SI 60; and compacting the aggregate-filler-binder layer in Step SI 70.

[0023] As shown in FIGURE 6, another variant of the aggregate stabilization process Pl 00, the lignin-based polymer includes carboxylated technical lignin. In this variant, the aggregate stabilization process includes: isolating a quantity of technical lignin from a quantity of black liquor byproduct in Step S 151 ; calculating a target sodium hydroxide concentration and a target hydrogen peroxide concentration for an oxidative solution based on a set of granular material characteristics of the granular material in Step S152; immersing the quantity of technical lignin in the oxidative solution characterized by the target sodium hydroxide concentration and the target hydrogen peroxide concentration in Step S153; and precipitating the quantity of carboxylated technical lignin from the oxidative solution in Step SI 54. [0024] As shown in FIGURE 7, yet another variant of the aggregate stabilization process P100 includes calculating the aqueous mass ratio based on the granular porosity of the granular material, a moisture content of the granular material, and a set of environmental parameters including an ambient humidity distribution, an ambient temperature distribution, and a target application temperature in Step S155.

[0025] As shown in FIGURE 8, yet another variant of the aggregate stabilization process P100 includes: calculating a binder area density based on the layer depth of the granular material, the granular porosity of the granular material in Step S156; and dispersing the lignin-based binder over the stabilization area, approximating the binder area density in Step SI 57.

2. Stabilized Aggregate Composition

[0026] As shown in FIGURE 2, one variant of a stabilized aggregate composition 100 includes: a granular mass proportion 110 comprising granular material 112 characterized by a granular porosity and granular density; a biochar filler mass proportion 120 including biochar 122 characterized by a biochar density, wherein the biochar filler mass proportion 120 is based on the biochar density, the granular density, and the granular porosity of the granular mass proportion; and a lignin-based-binder mass proportion 130 between 0.3% and 4.0% of the granular mass proportion.

[0027] In another variant, the stabilized aggregate composition is produced via the aggregated stabilization process Pl 00.

3. Applications

[0028] Generally, a stabilized aggregate composition utilizes a combination of a lignin-based binder and biochar filler to stabilize a granular material, thereby exhibiting a high rate of carbon sequestration, high stiffness, and thermal stability without requiring petrochemical products such as bitumen or the use of hydraulically bound materials such as cement. More specifically, the stabilized aggregate composition incorporates a quantity of biochar based on the porosity of the granular materials being stabilized in the stabilized aggregate composition. The stabilized aggregate composition includes a quantity of biochar that approximately fills voids in the granular material, acting as a drying accelerator to the stabilized aggregate when compared to a control composition without biochar due to the desiccant nature of the biochar.. Thus, stabilized aggregate compositions incorporating biochar as a filler in combination with a lignin-based binder improve curing times and therefore early compressive strength of the stabilized aggregate composition, while also sequestering carbon.

[0029] Additionally, an aggregate stabilization process for the stabilized aggregate composition can include mixing and compacting components of the stabilized aggregate composition in situ to crush the biochar to a filler particle size of less than 250 microns in average diameter. By sequestering carbon in both lignin-based polymers and biochar, the stabilized aggregate composition can exhibit a low or even negative carbon footprint depending on material sources. Furthermore, because lignin-based polymers and biochar are derived from renewable natural biomass, the stabilized aggregate composition functions as a more environmentally friendly alternative to stabilized aggregate compositions including petroleum-based binders. Additionally, the inclusion of biochar within the polymer matrix of the lignin-based binder facilitates long-term sequestration of carbon within the stabilized aggregate composition, enabling the stabilized aggregate composition to have a negative emissions impact in some circumstances.

[0030] In one application, the stabilized aggregate composition is produced in situ to resurface an existing road. In this application, the existing road is crushed or ground to a depth of up to 35 centimeters or more for reuse as the granular material in the stabilized aggregate composition. In this application, a biochar filler proportion and a lignin-based binder are mixed into the granular material from the existing road to produce a new road surface course and/or base layer that sequesters carbon and does not require additional petrochemicals or cement.

[0031] In another application, the stabilized aggregate composition includes biochar sources generated from biomass directly adjacent to the road via the production of biochar at the road construction location. In this application, trees and other biomass that may have been removed to create a path for the road can be utilized as a filler for the road, thereby reducing material transportation costs from other sources of biochar.

[0032] In one variant, the aggregate stabilization process includes the production of carboxylated technical lignin (e.g., carboxylated Kraft lignin) as the lignin-based binder. In this variant, the degree of carboxylation and the molecular weight are tuned to the particular characteristics of the granular material and the environment of the stabilized aggregate composition to improve the material strength and durability of the stabilized aggregate material. Thus, the stabilized material composition can include an application- specific, biologically-derived binder produced from over-abundant waste feedstocks from various biomass fractionation processes (e.g., the Kraft pulping process).

[0033] In this variant, the process P100 can produce a lignin-based binder that exhibits high solubility and low viscosity, suitable for dispensation into granular materials that can effectively replace foam bitumen, other non-renewable road binding materials, and other biologically derived binders including lignosulfonates. The process P100 can produce stabilized aggregate compositions (including between 0.25% and 5.00% of the lignin-based binder by mass) exhibiting unconfined compressive strength (hereinafter “UCS”) greater than 2.0 newtons per square millimeter after five days of curing. Additionally, the carboxylated technical lignin in the lignin-based binder (e.g., derived from a softwood feedstock) exhibits the tendency to crosslink over time at higher molecular masses. In some implementations, the lignin-based binder includes a crosslinker proportion to increase the rate of crossfinking within the road composition, and/or a co-binder proportion to increase binding capability within the road composition, thereby increasing the curing rate and improving the durability of the road composition..

[0034] In another example of this variant, the process P100 produces a lignin-based binder that exhibits a relatively low viscosity (e.g., between 20 and 100 centistokes) at typical ambient temperatures at a target stabilization area (e.g., between 0 and 40 degrees Celsius). More specifically, the process P100 produces a lignin-based binder specific to the expected temperature at the stabilization area to ensure the binding composition can be easily distributed into the aggregate materials without additional on-site heating. For example, in a road binding application, the process P100 can produce a road binder capable of distribution via a standard binder distributor (e.g., typically used for bitumen distribution) without requiring an on-site heating unit.

4. Composition Characteristics and Test Data

[0035] Generally, the stabilized aggregate composition exhibits favorable material properties for its intended application, offering equal or better cure time and unconfined compressive strength when compared to control compositions including the lignin-based binder without biochar. Additionally, the stabilized aggregate composition sequesters between 4 to 21 kilograms of carbon dioxide per square meter of stabilized aggregate composition (at 20 to 25 centimeters of depth).

[0036] A 0/4 mm gabbro aggregate from Vassfjell Quarry (Norway) was stabilized using 1.2% lignin-based binder and different biochar content. The theoretical maximum biochar content to fdl the voids for the highly compacted gabbro was estimated at 3%. Four levels of biochar (0%, 3%, 6%, 12% as a mass percentage of the granular material mass) were tested to determine the mechanical behaviour when maximizing the biochar in the mix.

4.1 Granular Material

[0037] The granular material used for testing was a crushed gabbro aggregate, 0/4 mm in grading, sourced from the Vassfjell quarry near Trondheim, Norway. The Vassfjell gabbro material is characterized by known mechanical consistency and suitability for road construction.

[0038] The 0/4 mm graded aggregates from the Vassfjell quarry were first split into seven individual sieve fractions. The sieve fractions were then recombined using the Fuller- Thompson relation, which defines the ideal particle size distribution that minimizes voids in a granular assembly. It follows the formula:

P(«) = (T)" where P(d) is the percentage passing a sieve of diameter d, D is the maximum particle size, and n is the Fuller exponent. In this study, a Fuller exponent of 0.4 was used, a value previously validated by the author in related material studies. A Fuller exponent of 0.4 provides a well-balanced distribution of fines, yielding approximately 20% passing the 0.063 mm sieve, which enhances packing density while preserving workability, but leaving it as a non-ideal material (high fine content). The resulting grading curve is represented in FIGURE 3.

4.2 Lignin-Based Binder

[0039] The lignin-based binder used in this study was dosed at 1.2% by dry mass of the granular material. This dosage, when scaled to field conditions for road stabilization, corresponds to an application rate of approximately 4.0 L/m² for a 20 cm layer depth and 5.0 L/m² for a 25 cm layer depth, assuming a compacted granular material density of 2000 kg/m³ and a lignin-based binder density of 1.2 kg/L. However, the above values for application rate, layer depth, granular material density, and lignin-based binder density were selected for purposes of experimentation and do not limit the properties of these materials with regard to the process Pl 00 or the stabilized aggregate composition.

4.3 Biochar Addition

[0040] As described below with respect to Step SI 30 of the process Pl 00, a biochar filler proportion was calculated based on the granular porosity (p) for the granular material (in this case, the crushed gabbro aggregate). Granular porosity quantifies the volume fraction of voids within the material structure and represents the theoretical space available for fillers such as biochar. p = 11 - ^p"

P_S where represents a dry density of the compacted granular material (equal to 2.40 g/cm³ under high compaction for the purpose of this test), and represents a particle density of the granular material (equal to 3.02 g/cm³ for the Vassfjell gabbro).

[0041] The granular porosity of the granular material was calculated at 20.5%, indicating 0.205 m³ of voids per cubic meter of compacted granular material. In accordance with Step SI 30, further described below, the mass proportion of biochar filler is calculated according to the following equation:

Thus, the mass proportion of biochar filler is calculated based on a ratio of biochar density to granular density multiplied by the granular porosity. In this test, values of 350 kg/m³ for biochar density, 2400 kg/m³ for granular density, and 20.5% for granular porosity were used, yielding a biochar filler proportion of 2.99%.

[0042] The biochar filler was added to the granular material in increasing dosages of 0%, 3%, 6%, and 12% of the granular material proportion in accordance with Step S140. Samples characterised by biochar filler proportions greater than 3% (i.e., 6% and 12%) were produced to test the material properties of the stabilized aggregate composition at levels of biochar higher than the amount calculated in accordance with Step S130.

[0043] The samples of the control composition (0% biochar filler proportion) and variants of the stabilized aggregate composition were mixed in accordance with Step SI 50. More specifically, water was added to reach target moisture levels for compaction. Based on post hoc calculations, the water contents at mixing were estimated at 6.5%, 8.6%, 10.6%, and 14.9% for the 0%, 3%, 6%, and 12% aggregate-filler mixes, respectively. These values align with the expected trend, as increased fine content typically requires more moisture to achieve the optimum water content (OWC). All specimens achieved good compaction without visible water loss and reached high dry densities, suggesting effective moisture control and compaction across all mixes.

[0044] The biochar filler used for this study was made out of good-quality hardwood, with an average particle size below 250 microns. However, in other applications, the stabilized aggregate composition can include larger average particle sizes, which can be crushed down to smaller sizes during compaction.

4.4 Sample Preparation

[0045] Cylindrical samples were compacted in standardized molds to dimensions of approximately 49 mm in diameter and 78-86 mm in height. Wet mass was recorded, and samples were cured under laboratory conditions (21 °C ±2°C) for up to five days. After curing, dry mass and volume were measured to determine density and residual water content.

4.5 Testing Procedure

[0046] Unconfined Compressive Strength (UCS) tests were performed using a strain-controlled loading frame. The loading rate was held constant across all specimens, set at 2 mm/min. The UCS was calculated from the peak load and sample cross-sectional area.

4.6 Theoretical Sequestration Potential

[0047] A theoretical mass-balance approach was used to estimate the carbon sequestration potential of each mixture. The calculation is based on the following equation: CO ₂ = p hbf -77

2 e/m ^r d ^s c 12 where h represents the layer depth, f represents the carbon fraction of biochar (assumed 85% for the purposes of this calculation), and — represents the stoichiometric ratio for converting carbon to CO based on molar mass. This calculation represents the maximum potential estimate for carbon sequestered and does not account for oxidation or degradation losses. TABLE 1 below shows the results of this sequestration calculation for the samples produced.

TABLE 1 :

4.7 Results

[0048] As shown in TABLE 2 below, results for dry density, water content, curing time, residual water content, and UCS were collected.

TABLE 2:

[0049] These results are additionally represented in part by FIGURE 4 and FIGURE 5, which show the relationships between UCS and curing time, and UCS and water content.

[0050] The progression of UCS in the samples is directly influenced by moisture loss over time. In stabilized aggregate material, where curing can occur through drying rather than chemical hydration, the residual water content at the time of testing provides a more accurate measure of lignin-based binder activation than curing time alone.

[0051] The results of TABLE 2 show a general increase in UCS with curing time across all samples. However, this increase closely followed the reduction in water content. Samples tested with lower residual moisture consistently exhibited higher UCS, indicating that strength development is governed more by drying progression than by elapsed time.

[0052] The influence of biochar content on this relationship is also evident. In the control composition (0% biochar filler proportion), strength increased rapidly with both time and moisture loss. Notably, the 3% biochar filler proportion sample performed comparably to the control composition, and in several cases, even exceeded the UCS of the control composition at comparable times. This suggests that low-level biochar addition may enhance drying, potentially through improved water distribution or increased pore connectivity — a behavior that could prove beneficial under field conditions.

[0053] For samples with a biochar filler proportion greater than 3%, the rate of strength gain relative to curing time decreased. This trend can be attributed to the moisture-retention capacity of biochar, which can slow down drying and may delay binder activation at quantities greater than the void capacity (granular porosity) of the granular material. Nevertheless, UCS values at 12% biochar remained within acceptable limits for early stabilization, reaching 1.9 MPa after five days. Additionally, the final residual water content in the 12% biochar filler proportion samples after five days was comparable to that of the 0%, 3%, and 6% mixes after just one day. This indicates that additional UCS gain is likely if further drying were allowed beyond the five-day window.

[0054] These results confirm that residual moisture is the principal factor controlling early-age strength in examples of the stabilized aggregate material. Curing time alone may not sufficiently describe UCS evolution unless evaluated in parallel with the stabilized aggregate material’s moisture condition. The biochar filler proportion can modulate drying behavior within the stabilized aggregate material by altering the internal moisture retention and drying dynamics of the mix — accelerating drying at low proportions approximating the void capacity or granular porosity of the granular material (3%) and retarding drying at higher proportions (6% and 12%).

5. Composition: Granular Material Proportion

[0055] Generally, the stabilized aggregate composition includes a granular material proportion, which forms the majority of the mass of the stabilized aggregate composition and is the primary component of the structural matrix of the stabilized aggregate composition, supported by the lignin-based binder proportion and the biochar filler proportion. More specifically, the stabilized aggregate composition can include a granular material proportion of greater than 96% and up to 99.7%. The granular material proportion can include aggregates such as crushed stone, gravel, sand (river or ocean), silt, recycled concrete aggregate, slag, crushed brick, crushed gravel, stone dust, crushed shells, pea gravel, clay, shale, perlite, mud, or any synthetic or geosynthetic aggregate. Additionally, the granular material proportion can include native soil, recycled binder material from an existing road, or other impurities not typically utilized as a standalone granular material. Furthermore, the measured weight of the granular material proportion can include the weight of water within the granular material proportion. The granular material proportion can exhibit various densities typically ranging between 1800 kilograms per cubic meter and 2700 kilograms per cubic meter. However, the granular material proportion can exhibit any density outside of this range without diminishing the effects derived from the lignin-based binder and the biochar proportions. Thus, the granular material proportion forms the majority of the mass of the stabilized aggregate composition, but the cohesion and stiffness of the stabilized aggregate composition can be enhanced by the lignin-based binder and/or the biochar filler.

[0056] Additionally, the granular material is characterized by a layer depth when distributed over a stabilization area. More specifically, the layer depth indicates the depth to which the granular material remains homogenous and granular before reaching an underlying material. Thus, when executing the process Pl 00, Step SI 50 can include mixing to the layer depth of the granular material. The layer depth also influences area density calculation for both the biochar filler proportion and the lignin-based binder proportion in Steps S130 and S156 respectively. [0057] Further, the granular material is characterized by a granular porosity, which, as described above, is calculated based on the following equation:

P = - 11 -

^P _s where represents a dry density of the compacted granular material (i.e., granular density), and represents a particle density of the granular material (i.e., the density of the average individual particle in the material). The granular porosity indicates the void capacity of the material when compacted and influences the biochar area density calculation in Step S130 and/or lignin-based binder calculations in Steps SI 55 and/or SI 56.

6. Composition: biochar filler Proportion

[0058] Generally, the stabilized aggregate composition includes a biochar filler proportion to act as a drying accelerator, fill a certain part of the overall porosity within the structural, and sequester carbon from waste biomass. More specifically, the stabilized aggregate composition can include a biochar filler proportion of up to 4.0% or more based on the granular porosity of the granular material and the density of the biochar. The biochar filler proportion can include biochar sourced from wood and wood residues, agricultural residues, forestry residues, animal manure, green waste, food waste, industrial biomass byproducts (e.g., paper byproducts, beer byproducts, or any other industrial organic waste), aquatic biomass, energy crops, (e.g., switchgrass, miscanthus, bamboo), coconut husks, peat, rice husks, bagasse, or any other source of biochar. Thus, the biochar filler proportion maintains rigidity and durability to the structural matrix of the stabilized aggregate composition while also sequestering carbon.

[0059] The stabilized aggregate composition includes a biochar filler proportion sufficient to fill voids within the structural matrix of the stabilized aggregate composition without significantly disrupting the structural matrix of the stabilized aggregate composition. The biochar filler proportion is calculated during Step S130, further described below. In one example, the stabilized aggregate composition includes a biochar filler proportion of less than 1.8%. In another example, the stabilized aggregate composition includes a biochar filler proportion of between 1.12% and 1.13%. In yet another example, the biochar filler proportion is equal to 3% or more of the granular material proportion.

[0060] In implementations in which maximizing the quantity of carbon sequestered is a design priority, the stabilized aggregate composition can include a biochar filler proportion greater than the calculated amount, thereby increasing the quantity of carbon sequestered within the stabilized aggregate composition, potentially at the expense of the stiffness and durability of the stabilized aggregate composition due to disruption of the structural matrix by more compressible biochar particles.

7. Composition: Lignin-Based-Binder Proportion

[0061] Generally, the stabilized aggregate composition includes a lignin-based binder proportion to enhance cohesion and stiffness of the stabilized aggregate composition while maintaining flexibility and thermal stability. More specifically, the stabilized aggregate composition includes a lignin-based binder proportion between 0.3% and 4.0%. The lignin-based binder proportion can initially include a lignin-based polymer within an aqueous solution to improve workability. The aggregate stabilization process Pl 00 includes compaction of the stabilized aggregate composition in Step SI 70, thereby evacuating water from the stabilized aggregate composition. The compaction process leaves behind an enriched lignin-based polymer matrix, which enhances the cohesion and stiffness of the stabilized aggregate composition. The stabilized aggregate composition can include a lower proportion of the lignin-based binder relative to bitumen proportions in conventional stabilized aggregate compositions, indicating that the lignin-based binder can be more effective than bitumen on a per-mass basis. Thus, the lignin-based binder is an environmentally friendly and cost-effective alternative to bitumen.

[0062] In one implementation, the lignin-based binder proportion includes lignosulfonate as the lignin-based polymer. In this implementation, the lignin-based binder includes lignosulfonate exhibiting a sulfonation degree between 0.5 and 2.0 to reduce water solubility of the lignin-based binder proportion. In one example of this implementation, the lignosulfonate exhibits a sulfonation degree between 0.65 and 1.00.

[0063] In implementations in which the lignin-based binder proportion includes a lignosulfonate-based binder, the lignosulfonate-based binder can be characterized by a number-average molecular weight between 5,000 and 80,000 grams per mol. In this implementation, the lignosulfonate-based binder proportion enables favorable stiffness and compressive strength due to greater adhesion caused by the relatively high molecular weight of the lignin-based polymer.

[0064] In another implementation, the lignin-based binder proportion includes Kraft-lignin-based polymer as the lignin-based polymer. Because Kraft lignin is more widely available as a byproduct of the Kraft process for paper production, Kraft lignin may be easier to source for the production of the stabilized aggregate composition. More specifically, the lignin-based binder can include chemically modified Kraft lignin as the lignin-based polymer in the lignin-based binder. One variant of the process Pl 00, further described below, includes the production of a carboxylated Kraft-lignin-derived polymer specific to the particular granular material of the stabilized aggregate composition and the environment of the stabilization area. Thus, the stabilized aggregate material can include targeted lignin-based polymers for particular applications.

[0065] The lignin-based binder proportion can include other chemical amendments, such as catalysts, crosslinkers, and/or co-binders in addition to the lignin-based polymer to improve properties of the lignin-based polymer within the stabilized aggregate composition or during dispersion of the lignin-based binder.

8. Process: Granular Material Location and Deposition

[0066] Generally, the aggregate stabilization process P100 includes sourcing granular materials to a target road area and producing a stable layer of the granular material in Step SI 10. More specifically, the aggregate stabilization process can include depositing or otherwise locating the granular material over the target road area to a depth of up to 35 centimeters or more. In particular, the aggregate stabilization process Pl 00 can include locating a layer of granular material distributed over a stabilization area and characterized by a layer depth, wherein the granular material is characterized by a granular porosity. The process P100 can additionally include measuring the granular porosity of the granular material, the granular density of the granular material, and/or the layer depth of the granular material. Thus, the process Pl 00 can include locating the granular material of the stabilization area and characterizing certain aspects of the granular material.

[0067] In one implementation, the aggregate stabilization process can include crushing an existing road to a depth of at least 10 centimeters in situ, thereby locating the granular material over the stabilization area by crushing existing material into the granular material. In some implementations, the aggregate stabilization process can include crushing the existing road to a depth of 35 centimeters or more. Thus, the aggregate stabilization process includes preparing the granular material to receive the biochar filler and the lignin-based binder by locating the granular material over the target road area.

9. Process: Obtaining Biochar Filler

[0068] Generally, the aggregate stabilization process Pl 00 can include obtaining the biochar filler in Step S120. More specifically, the aggregate stabilization process P100 can include obtaining milled or partially milled biochar ready for dispersion over the stabilization area and mixing the biochar into the granular material. As described above, the biochar filler can be sourced from a variety or combination of sources including but not limited to: wood and wood residues, agricultural residues, forestry residues, animal manure, green waste, food waste, industrial biomass byproducts (e.g., paper byproducts, beer byproducts, or any other industrial organic waste), aquatic biomass, energy crops, (e.g., switchgrass, miscanthus, bamboo), coconut husks, peat, rice husks, bagasse, or any other source of biochar.

[0069] In one implementation, the aggregate stabilization process Pl 00 can include characterizing the biochar filler by measuring an average density of the biochar filler and/or measuring an average particle size of the biochar filler. Thus, in instances where the biochar has not been pre-characterized, the process Pl 00 includes characterizing the biochar to inform subsequent Step SI 30.

10. Process: Biochar Area Density Calculation

[0070] Generally, the aggregate stabilization process P100 can include calculating the quantity of biochar per area for dispersion or distribution of the stabilization area. More specifically, the aggregate stabilization process Pl 00 includes calculating a biochar area density based on the layer depth, the granular porosity, and the biochar density in Step S130. In particular, the aggregate stabilization process Pl 00 can include evaluating the following equation: b =pp_bh where b represents the biochar area density in kg/m², p represents the granular porosity expressed as a percentage, represents the biochar density of the biochar filler proportion in kg/m³, and h represents the layer depth in meters. Generally, b indicates the maximum area density for the biochar filler prior before the void capacity of the granular material is occupied by the biochar filler.

[0071] In implementations for which carbon dioxide sequestration capacity is the primary design criterion, the process Pl 00 can include selecting a biochar area density greater than or equal to b. More specifically, the process Pl 00 can include: calculating a void-filling biochar area density, as described above; and selecting a biochar area density greater than the void-filling biochar area density.

11. Process: Biochar Filler Dispersion

[0072] Generally, the aggregate stabilization process Pl 00 includes dispersing the biochar filler onto the layer of the granular material to produce an aggregate-filler mixture (i.e., a heterogeneous mixture). More specifically, the aggregate stabilization process P100 includes dispersing the quantity of biochar over the stabilization area, approximating the biochar area density in Step S140. In this context, the term “approximating” indicates dispersing the quantity of biochar roughly evenly over the stabilization area, or ±25% on a per square meter basis. In particular, the aggregate stabilization process Pl 00 can include dispersing the quantity of biochar over the stabilization area, approximating a selected biochar area density greater than the void-filling biochar density. Thus, by dispersing the quantity of biochar filler over the stabilization area, the process P100 prepares the stabilization area for the subsequent mixing step.

[0073] In one example, the aggregate stabilization process can include dispersing greater than 8 kilograms of biochar filler per square meter of granular material, which corresponds to a mass proportion of up to 1.8%, depending on the density and depth of the layer of granular material. In one implementation, the aggregate stabilization process includes dispersing the biochar filler onto the layer of the granular material, wherein the biochar filler is characterized by an average particle diameter of less than 2.0 millimeters. In another implementation, the aggregate stabilization process includes pre-grinding the biochar filler to an average particle diameter of less than 1.0 millimeter and as small as 250 microns prior to dispersion onto the layer of granular material. In yet another implementation, the aggregate stabilization process includes the use of a spreader to ensure even dispersion of the biochar over the layer of granular material. Thus, the aggregate stabilization process ensures that biochar is evenly distributed over the surface and ready for subsequent incorporation into the road via mixing.

12. Process: Lignin-Based Binder Preparation

[0074] One variant of the process P100, includes preparing a lignin-based binder targeted to the particular characteristics of the granular material and the expected conditions of the stabilization area, including but not limited to binding parameters the granular porosity of the granular material, a particle size distribution of the granular material, a moisture content of the granular material, an ambient air temperature distribution of the stabilization area, an ambient humidity distribution of the stabilization area, an expected amount of precipitation at the stabilization area, and/or a target application temperature at the stabilization area. Thus, by preparing a target lignin-based binder, the process P100 can improve material characteristics of the stabilized aggregate composition. This variant of the process Pl 00 is described in further detail below.

12.1 Accessing Binding Parameters

[0075] Generally, this variant of the process P100 includes accessing a set of binding parameters including characteristics of the target aggregate material and the stabilization area. More specifically, the process P100 can access a granular porosity of the granular material, a particle size distribution of the granular material, a moisture content distribution of the granular material, an ambient temperature distribution at the stabilization area, an ambient humidity distribution at the target site, and a target binder application temperature. The process P100 utilizes the binding parameters to adjust reaction parameters for the carboxylation reaction of technical lignin, as is further described below. 12.2 Obtaining and Isolating Technical Lignin

[0076] Generally, this variant of the process Pl 00 includes obtaining technical lignin resulting from a biomass fractionation process in Step S151. In one implementation, the process P100 can include obtaining the technical lignin from a third-party feedstock. In another implementation, the process P100 can include precipitating technical lignin from black liquor via acid precipitation by lowering the pH of the black liquor to below 3.0 (e.g., via the addition of a strong acid). In yet another implementation, the process Pl 00 can include the addition of coagulants or flocculants to cause agglomeration of the technical lignin prior to isolation. After precipitation, the process P100 can include isolating the technical lignin via filtration or centrifugation.

12.3 Calculating Reaction Parameters

[0077] As shown in FIGURE 6, the process P100 can include calculating a set of reaction parameters such that the carboxylation reaction produces a quantity of carboxylated technical lignin that exhibits a target degree of carboxylation and a target molecular mass in Step SI 52. More specifically, the process P100 can: calculate a target degree of carboxylation and a target molecular mass based on the set of binding parameters; and calculate a target sodium hydroxide concentration and a target hydrogen peroxide concentration of an oxidative solution based on the target degree of carboxylation and the target molecular mass. Thus, the process P100 can adapt the properties of the lignin-based binder based on known characteristics of the stabilization area. [0078] The process P100 includes preparing an oxidative solution including a technical lignin proportion between 5% and 20% by mass, a sodium hydroxide concentration between 20% and 30% by mass, and a hydrogen peroxide concentration between 5% and 20% by mass with the remaining proportion being water. However, the process Pl 00 can also include calculating a target concentration of sodium hydroxide and hydrogen peroxide within the aforementioned ranges.

[0079] The sodium hydroxide in the oxidative solution functions to increase the solubility of the technical lignin and enable the oxidative cleavage of phenolic rings (yielding two carboxyl groups per cleaved phenolic ring) and/or the oxidation of hydroxyl and aldehyde groups in the technical lignin to produce carboxyl groups. Additionally, as the concentration of sodium hydroxide in the oxidative solution increases, the pH of the oxidative solution also increases. This increase in pH, in turn, causes a decrease in the rate of crosslinking via radical elimination, which effectively decreases the molecular mass of the resulting carboxylated technical lignin, while still increasing the molecular mass of the carboxy lated lignin relative to the input technical lignin. Thus, by increasing the target sodium hydroxide concentration, the process P100 can effectively lower the molecular mass and, therefore, the viscosity of the lignin-based binder.

[0080] The hydrogen peroxide in the oxidative solution functions as a mild oxidizing agent that effectively increases the conversion of phenolic rings to carboxyl groups in the technical lignin. Thus, increasing the concentration of hydrogen peroxide in the oxidative solution increases the resulting degree of carboxylation and, therefore, the solubility of the resulting lignin-based binder.

[0081] Therefore, to calculate the target sodium hydroxide concentration and the target hydrogen peroxide concentration, the process P100 can include calculating a target solubility of binding composition based on the moisture content of the aggregate materials and the humidity at the stabilization area. Generally, lower solubility is desirable in higher moisture and humidity applications to prevent the binder from reentering the aqueous phase during the curing process. On the other hand, higher solubility can increase the mass proportion of carboxylated technical lignin within the lignin-based binder, thereby enabling the use of less water in the mixing process, which can improve compaction of the bound aggregate materials (e.g., a road). The process Pl 00 can include calculating a target solubility based on a look-up table, given the moisture content of the aggregate materials and the humidity distribution of the stabilization area.

[0082] Additionally, in order to calculate the target sodium hydroxide concentration and the target hydrogen peroxide concentration, the process P100 can initially calculate a target viscosity at the target binder application temperature and a target solubility at the target application temperature. Generally, the process Pl 00 can utilize the particle size distribution of the target aggregate material, the target application temperature at the stabilization area (i.e., the target temperature for applying the binding composition), and/or the viscosity constraints of the distribution device (e.g., a road distributor in a road-building application) to calculate a target viscosity for the lignin-based binder at the target application temperature. In one implementation, the process P100 includes utilizing a look-up table based on the particle size distribution, the target application temperature, and any viscosity constraints of the distribution device to identify a target viscosity that satisfies all of these conditions. Alternatively, the process P100 can utilize a physics-based computer simulation to identify a target viscosity for the lignin-based binder, such that the lignin-based binder can be evenly distributed into the aggregate material at the target application temperature via a reclaimer, pulverizer, pulvimixer, road tiller, and/or any other suitable equipment or combination of equipment. In instances in which all performance targets cannot be satisfied (e.g., at low application temperatures, it may be impossible to satisfy the viscosity constraints of the distribution device), the process Pl 00 can prioritize the distribution device and modify the viscosity to remain inside the viscosity constraint despite potentially negative effects on the process of mixing the lignin-based binder with the aggregate material. Alternatively, the process Pl 00 can prioritize the mixing properties of the binder and rely on limited heating of the binding composition prior to distribution into the aggregate material to maintain a sufficiently low viscosity for distribution.

[0083] In one implementation, the process P100 can include receiving the target viscosity and the target solubility as a user input instead of calculating these target values.

[0084] Upon receiving the target viscosity and target solubility for the lignin-based binder, the process Pl 00 can evaluate an optimization algorithm to calculate a target molecular mass and target degree of carboxylation of the carboxylated technical lignin and a mass proportion of the carboxylated technical lignin within the lignin-based binder that most closely approximates the target viscosity and target solubility. For example, the process P100 can include utilizing gradient descent, constrained optimization methods, grid search or sampling methods, metaheuristic algorithms, or any other machine learning method to select a target molecular mass and a target degree of carboxylation.

[0085] Upon identifying the target molecular mass and the target degree of carboxylation, the process Pl 00 can utilize a look-up table to obtain a corresponding sodium hydroxide concentration and a target hydrogen peroxide concentration effective to produce carboxylated technical lignin characterized by the target degree of carboxylation and the target molecular mass. Alternatively, the process Pl 00 can include a second optimization step to calculate a set of reaction parameters including but not limited to: sodium hydroxide concentration, hydrogen peroxide concentration, reaction temperature, reaction duration, hydrogen peroxide addition rate, technical lignin mass proportion, and/or any other reaction parameters. In this second optimization step, the process Pl 00 can utilize a similar optimization algorithm to calculate the set of reaction parameters that maximizes yield while producing carboxylated technical lignin characterized by the target molecular mass and the target degree of carboxylation.

12.4 Carboxylation Reaction

[0086] Generally, the process P100 includes preparing an oxidative solution exhibiting the calculated sodium hydroxide concentration, the calculated hydrogen peroxide concentration, and/or the calculated technical lignin proportion. More specifically, the process Pl 00 can include immersing the quantity of technical lignin in the oxidative solution characterized by the target sodium hydroxide concentration and the target hydrogen peroxide concentration to produce a quantity of carboxy lated technical lignin in Step S153. In particular, the process Pl 00 can include: creating a basic solution of sodium hydroxide based on the target sodium hydroxide concentration; dissolving the quantity of technical lignin in the basic solution; heating the basic solution to a reaction temperature between 70 and 90 degrees Celsius (e.g., with a condenser and reflux apparatus to prevent mass loss in smaller batches); consistently adding hydrogen peroxide at a hydrogen peroxide addition rate (to prevent overboiling) until the target hydrogen peroxide concentration is reached; and holding the oxidative solution at the reaction temperature for the reaction duration. Thus, the process P100 can produce a quantity of carboxylated technical lignin exhibiting the desired molecular mass and degree of carboxylation.

[0087] In one implementation, process P100 also includes precipitating the quantity of carboxylated technical lignin in Step S154. In this implementation, the precipitation process includes: lowering the pH to approximately 2.5 (e.g., via the addition of sulfuric acid); remove residual inorganics by aqueous extraction from the lignin-precipitate; and adjusting the pH of the aqueous solution to approximately neutral (pH of approximately 7) via addition of a base (e.g., sodium hydroxide). The resulting carboxylated technical lignin can be added to an aqueous solution for use as a binder.

[0088] In another implementation, the carboxylated technical lignin is added to an aqueous solution directly without precipitation from the oxidative solution. In this implementation, the lignin-based binder can include additional salts remaining in the oxidative solution.

12.5 Binder Production

[0089] As shown in FIGURE 7, the process P100 can include producing the lignin-based binder by combining technical lignin with water in an aqueous solution. More specifically, the process P100 can include calculating an aqueous mass ratio of carboxylated technical lignin to water based on the binding parameters and/or target viscosity characteristics. In particular, the process P100 can include adding the quantity of carboxylated technical lignin to an aqueous solution to produce the lignin-based binder exhibiting the aqueous mass ratio in Step S155. In one implementation, the process P100 utilizes an aqueous solution characterized by a pH between 6 and 8, capable of dissolving the quantity of carboxylated technical lignin. Thus, the process P100 produces a lignin-based binder with application- specific properties by adjusting the characteristics of carboxylated technical lignin. 12.6 Resulting Lignin-Based Binder

[0090] Generally, the lignin-based binder includes a carboxylated technical lignin proportion at least partially dissolved in an aqueous solution or suspension. More specifically, the lignin-based binder can include an aqueous proportion, a lignin-based polymer proportion (e.g., carboxylated technical lignin), and a crosslinker proportion. Additionally, the lignin-based binder can also include co-binders, plasticizers, and/or flow-aids/chaotropic agents.

[0091] In one implementation, the lignin-based binder includes a carboxylated technical lignin proportion greater than 10% by mass. In this implementation, the carboxylated technical lignin proportion can define a water solubility greater than 90%.

[0092] In another implementation, the carboxylated technical lignin proportion is characterized by a degree of carboxylation greater than 1.0 millimole per gram. In some examples of this implementation, the carboxylated technical lignin proportion is characterized by a degree of carboxylation greater than 2.5 millimoles per gram. Generally, higher degrees of carboxylation increase the solubility of the carboxylated technical lignin proportion at a neutral pH. Thus, in this implementation, the lignin-based binder can remain sufficiently water soluble at room temperature to facilitate dispersal into the granular material (e.g., during road construction).

[0093] In another implementation, the carboxylated technical lignin proportion is characterized by a degree of carboxylation between 1.5 and 2.5 millimoles per gram. Thus, in this implementation, the carboxylated technical lignin proportion maintains a balance of solubility and dispersion properties that enable the use of carboxylated technical lignin as a binder.

[0094] In yet another implementation, the carboxylated technical lignin proportion is characterized by a molecular mass (e.g., as measured by gel permeation chromatography) between 20 and 400 kilodaltons, which enables an effective balance of solubility and binding characteristics. In one example of this implementation, the carboxylated technical lignin proportion is characterized by a molecular mass between 300 and 350 kilodaltons, further refining the target solubility and binding characteristics of the lignin-based binder.

[0095] However, the carboxylated technical lignin proportion can be characterized by any combination of carboxylation degree and molecular mass that results in the target solubility, dispersion, and binding properties in the lignin-based binder, as described above.

[0096] In yet another implementation, the lignin-based binder can include a crosslinker proportion configured to to accelerate the curing process of the lignin-based binder when dispersed within the aggregate materials and improve the material properties of the resulting material (e.g., by increasing the UCS or stiffness and decreasing the propensity of the binder to wash out of the resulting aggregate material). The lignin-based binder can include one or more crosslinkers from a number of crosslinker categories, including aldehydes, carboxylic acids, anhydrides, epoxides, amines, isocyanates, and/or oxidizing agents.

[0097] Within the aldehyde group, the lignin-based binder can include aldehyde crosslinkers such as: formaldehyde, furfural, hydroxymethylfurfural, glyoxal, malondialdehyde, succinaldehyde, glutaraldehyde, phthalaldehyde, benzaldehyde, hydroxybenzaldehyde, 1,4-terephthaldehyde, and/or 4,4-oxybenzaldehyde. These aldehyde crosslinkers couple to the aromatic rings (and potentially other reactive sites) in the quantity of carboxylated technical lignin, thereby forming covalent linkages between lignin molecules.

[0098] Within the carboxylic acid group, the lignin-based binder can include carboxylic acid crosslinkers such as: oxalic acid, malonic acid, succinic acid, glutaric acid, and/or citric acid. These carboxylic acid crosslinkers couple to the hydroxyl groups of the quantity of carboxylated technical lignin, thereby forming ester linkages between lignin molecules. Carboxylic crosslinking reactions can also be mediated via catalysts or other coupling agents included in the lignin-based binder.

[0099] Within the anhydride group, the lignin-based binder can include anhydride crosslinkers such as succinic anhydride and maleic anhydride. These anhydride crosslinkers couple with the quantity of carboxylated technical lignin via a hydroxyl group, thereby generating ester linkages between the anhydride and the lignin molecule. During this process, the anhydride is converted to expose a carboxylic acid group, which can further bind to hydroxyl groups on other lignin molecules.

[0100] Within the epoxide group, the lignin-based binder can include epoxide crosslinkers such as: bisphenol A diglycidyl ether, ethylene glycol diglycidyl ether, and/or polyethylene glycol diglycidyl ether. These epoxide crosslinkers bind available hydroxyl groups of the quantity of carboxylated technical lignin.

[0101] Within the amine group, the lignin-based binder can include amine crosslinkers such as: hexamethylene tetramine, ethylenediamine, and polyethyleneamine. These amine crosslinkers react in a Mannich reaction between formaldehyde and a coupling agent, which contains at least two amine groups.

[0102] Within the isocyanate group, the lignin-based binder can include isocyanate crosslinkers including: tolylene diisocyanate, diphenylmethane diisocyanate, methylenediphenyl diisocyanate, and isophorone diisocyanate. These isocyanate crosslinkers bind with technical lignin via substitution of polyols of polyurethanes with the hydroxyl groups of the lignin, forming covalent linkages.

[0103] Within the oxidizing agent group, the lignin-based binder can include oxidizing agents such as: sodium periodate, iron chloride, iron chloride and hydrogen peroxide, silver nitrate, sodium hypochlorite, calcium hypochlorite, sodium percarbonate, chloramine, ammonium persulfate. These oxidizing agents cause oxidative activation of the phenolic ring of the carboxylated technical lignin molecules, yielding crosslinking via radical elimination.

[0104] Additionally or alternatively, the lignin-based binder can be configured to crosslink via click-chemistry reactions by further functionalizing the carboxylated technical lignin with reactive end groups. The stabilized aggregate composition can include a catalyst that induces crosslinking between the functionalized groups as the lignin-based binder cures in situ. In one example, the click-chemistry reaction includes functionalizing the quantity of carboxylated technical lignin with bromobutyryl chloride and propargyl bromide, such that the carboxylated technical lignin can participate in click reactions via copper-catalyzed azide-alkyne cycloaddition. In another example, the click-chemistry reaction includes functionalizing the quantity of carboxylated technical lignin with allyl bromide. In yet another example, the quantity of carboxylated technical lignin is functionalized with 11-maleimidoundecaoyl chloride.

[0105] Generally, the lignin-based binder is an aqueous suspension. More specifically, the lignin-based binder can include a water proportion greater than 40% by mass. In particular, the lignin-based binder is produced by mixing solid constituents, including the crosslinker and/or emulsifier, into an aqueous solution of the carboxylated technical lignin proportion and water. The lignin-based binder can be mixed onsite or offsite via a continuous or batch drum mixer, planetary mixer, twin shaft mixers, ribbon blenders, or any suitable mixing machinery that produces a sufficiently homogenous mixture of the constituents of the lignin-based binder.

13. Process: Dispersion of the Lignin-Based Binder

[0106] Generally, the process P100 includes dispersing the lignin-based binder over the stabilization area in Step S150. More specifically, the process P100 can include dispersing 3-18 liters of binder per square meter of aggregate-filler mixture, corresponding to a mass proportion in the stabilized aggregate composition of between 0.3% and 4.0%. In one implementation, the process Pl 00 can include calculating a binder area density based on the layer depth of the granular material, the granular porosity of the granular material in Step S156; and dispersing the lignin-based binder over the stabilization area, approximating the binder area density in Step S157. In this implementation, the process P100 can include calculating a binder area density, based on the compound aggregate-filler porosity based on the combination of the biochar proportion and the granular material proportion, such that the volume of lignin-based binder fills the void capacity of the aggregate-filler mixture. Thus, in this implementation, the addition of the lignin-based binder does not substantially disrupt the structural matrix of the stabilized aggregate material.

[0107] Upon execution of the compaction step of the process P100, further described below, the water in the lignin-based binder may subsequently evaporate from the stabilized aggregate composition, leaving a polymer matrix of the lignin-based binder within the stabilized aggregate composition in addition to some remaining moisture content. The process Pl 00 can include distributing the lignin-based binder via a distributor device equipped with a spray bar, emulsion applicator, or any other means. Thus, the process Pl 00 includes evenly distributing the lignin-based binder to prepare the layer of aggregate-binder mixture for subsequent mixing and grading.

14. Process: Mixing the Lignin-Based Binder

[0108] Generally, the process P100 includes mixing the granular material, the biochar filler, and the lignin-based binder to an approximately homogenous consistency effective to ensure consistent mechanical properties within the stabilized aggregate composition in Step SI 60. More specifically, the process Pl 00 can include mixing the granular material, the biochar filler, and the lignin-based binder via a reclaimer, pulverizer, pulvimixer, tiller, and/or any other suitable equipment to produce the aggregate-filler-binder layer. The process Pl 00 can include mixing the aggregate-filler-binder mixture to a depth consistent with the initial layer of the aggregate material. In one implementation, the process Pl 00 can include mixing to a shallower depth than the layer of the aggregate material to enable separation formation of a base course or sub-base course upon compaction. Thus, the process Pl 00 includes mixing the aggregate-binder mixture in preparation for compaction to ensure consistent properties within the stabilized aggregate composition in multiple dimensions.

14.1 Process: Grading

[0109] In one implementation, the process P100 includes grading the aggregate-filler-binder mixture based on a target profile for the stabilized aggregate composition. More specifically, the process Pl 00 can include grading the aggregate-filler-binder mixture via motor graders, bulldozers, scrapers, excavators, compact track loaders, skid steer loaders, tractor-towed graders, and/or any other type of grading equipment commonly used in construction. In another implementation, the process Pl 00 includes simultaneous grading and compaction via equipment such as vibratory rollers (including padfoot and/or drum rollers) or any other type of compactor graders.

15. Process: Compaction

[0110] Generally, the process P100 includes compacting the aggregate-filler binder layer to produce the stabilized aggregate composition. More specifically, the process Pl 00 includes compacting the mixed aggregate-filler-binder mixture with a compaction pressure of at least 30 kilogram-force per square meter (427 pounds per square inch) to voids within the structural matrix of the stabilized aggregate composition and to increase the bulk density of the stabilized aggregate composition. In particular, the process Pl 00 includes compacting the aggregate-binder mixture via smooth drum rollers (single and/or double drum), padfoot rollers, vibratory plate compactors, grid rollers, and/or oscillating rollers. Additionally, the process P100 includes compacting the stabilized aggregate composition to the maximum dry density of the stabilized aggregate composition as established in the design specification or as established via a proctor test (e.g., between 95% and 98%). In one implementation, the process Pl 00 includes compacting the mixed and graded aggregate-binder mixture with a compaction pressure of 60 to 65 kilogram-force per square meter. Thus, the aggregate stabilization process includes compaction to remove voids in the stabilized aggregate composition and increase the bulk density of the stabilized aggregate composition.

Claims

CLAIMS We Claim:

1. An aggregate stabilization process comprising:

• locating a layer of granular material distributed over a stabilization area and characterized by a layer depth, wherein the granular material is characterized by a granular porosity;

• obtaining a quantity of biochar characterized by a biochar density;

• calculating a biochar area density based on the layer depth, the granular porosity, and the biochar density;

• dispersing the quantity of biochar over the stabilization area, approximating the biochar area density;

• dispersing a lignin-based binder over the stabilization area, wherein the lignin-based binder: o comprises a lignin-based polymer and water; and o exhibits an aqueous mass ratio of the lignin-based polymer and the water;

• mixing the layer of granular material, the quantity of biochar, and the lignin-based binder to produce an aggregate-filler-binder layer; and

• compacting the aggregate-filler-binder layer.

2. The aggregate stabilization process of Claim 1, wherein calculating the biochar area density further comprises multiplying the biochar density, the granular porosity, and the layer depth.

3. The aggregate stabilization process of Claim 1, wherein compacting the aggregate-filler-binder mixture further comprises compacting the aggregate-filler-binder mixture with a pressure greater than 30 kilogram-force per square meter.

4. The aggregate stabilization process of Claim 1, wherein dispersing the lignin-based binder comprises dispersing lignin-based binder between 0.3% and 4.0% of a total dry mass of the layer of granular material per cubic meter of the layer of granular material over the stabilization area.

5. The aggregate stabilization process of Claim 1, wherein the lignin-based polymer comprises lignosulfonate.

6. The aggregate stabilization process of Claim 1, wherein the lignin-based polymer comprises carboxylated technical lignin.

7. The aggregate stabilization process of Claim 5, further comprising producing the carboxylated technical lignin by:

• isolating a quantity of technical lignin from a quantity of black liquor byproduct;

• calculating a target sodium hydroxide concentration and a target hydrogen peroxide concentration for an oxidative solution based on a set of granular material characteristics of the granular material;

• immersing the quantity of technical lignin in the oxidative solution characterized by the target sodium hydroxide concentration and the target hydrogen peroxide concentration; and

• precipitating the quantity of carboxylated technical lignin from the oxidative solution.

8. The aggregate stabilization process of Claim 1, further comprising calculating the aqueous mass ratio based on the granular porosity of the granular material, a moisture content of the granular material, and a set of environmental parameters comprising:

• an ambient humidity distribution;

• an ambient temperature distribution; and

• a target application temperature.

9. The aggregate stabilization process of Claim 1, wherein dispersing the lignin-based binder comprises:

• calculating a binder area density based on the layer depth and the granular porosity of the granular material; and

• dispersing the lignin-based binder over the stabilization area, approximating the binder area density.

10. A stabilized aggregate composition comprising:

• a granular mass proportion comprising granular material characterized by a granular porosity and granular density;

• a biochar filler mass proportion comprising biochar characterized by a biochar density, wherein the biochar filler mass proportion is based on the biochar density, the granular density, and the granular porosity of the granular mass proportion;

• a lignin-based binder mass proportion between 0.3% and 4.0% of the granular mass proportion.

11. The stabilized aggregate composition of Claim 1, utilized as a binder course in a road.

12. The stabilized aggregate composition of Claim 1, utilized as a base course in a road.

13. The stabilized aggregate composition of Claim 1, wherein the biochar exhibits an average particle diameter less than 250 microns.

14. The stabilized aggregate composition of Claim 1, wherein the lignin-based binder comprises lignosulfonate.

15. The stabilized aggregate composition of Claim 7, wherein the lignosulfonate is characterized by a sulfonation degree between 0.5 and 2.0.

16. The stabilized aggregate composition of Claim 7, wherein the lignosulfonate-binder mass proportion exhibits a number-average molecular weight between 5 kDa and 80 kDa.

17. The stabilized aggregate composition of Claim 1, wherein the lignin-based binder mass proportion comprises:

• an aqueous proportion; and

• a carboxylated technical lignin proportion.

18. The stabilized aggregate composition of Claim 17, wherein the carboxylated technical lignin is characterized by:

• a molecular mass between 20 kDa and 400 kDa; and

• a degree of carboxylation between 1.5 millimoles and 2.5 millimoles per gram.

19. The stabilized aggregate composition of Claim 17, wherein the carboxylated technical lignin proportion is between 45% and 55% of the lignin-based binder mass proportion.

20. A stabilized aggregate composition produced via an aggregate stabilization process comprising:

• obtaining a quantity of biochar characterized by a biochar density; • calculating a biochar area density based on the layer depth, the granular porosity, and the biochar density;

• dispersing the quantity of biochar over the stabilization area approximating the biochar area density;

• mixing the quantity of biochar and the layer of granular material to produce an aggregate-filler layer;

• mixing the aggregate-filler layer and the lignin-based binder to produce an aggregate-filler-binder layer; and

• compacting the aggregate-filler-binder layer.

21. The stabilized aggregate composition of Claim 20, wherein the lignin-based binder is a lignosulfonate binder.

22. The stabilized aggregate composition of Claim 21, wherein the lignosulfonate binder exhibits a sulfonation degree between 0.5 and 2.0.

23. The stabilized aggregate composition of Claim 21, wherein the lignosulfonate binder exhibits a number-average molecular weight between 5,000 grams per mol and 80,000 grams per mol.

24. The stabilized aggregate composition of Claim 20, wherein the lignin-based binder is a carboxylated Kraft lignin binder.

25. The stabilized aggregate composition of Claim 20, wherein the lignin-based binder is a hydrolysis lignin binder.

26. The stabilized aggregate composition of Claim 20, wherein the aggregate stabilization process comprises compacting the aggregate-filler-binder mixture such that the biochar filler is crushed to an average particle diameter of less than 250 microns.

27. The stabilized aggregate composition of Claim 20, exhibiting a stiffness greater than 20 meganewtons per square meter.