THE BAGACEIRA PROJECT

NATURAL BINDERS

Bio-based binders such as starch, chitin, algae, or mycelium have the potential to play a pivotal role in developing sustainable IAD materials because they are derived from natural, renewable sources sourced from diverse regions of the world and are safer and more sustainable than synthetic petro-chemical binders. These binders are sourced from different geographic regions, and vary in molecular composition and mechanical properties. Most binders are biodegradable, home compostable, or compostable in an industrial facility although the conditions and rates of biodegradation vary. All of these factors should betaken into account when selecting a binder for PF-based material development. Annex 12 lists and describes commonly used bio-based binders.

ALGAE
MYCELIA
CELLULOSE
GELATIN
NATURAL RESINS
CITRIC ACID
STARCHES
CALCIUM COMPOUNDS

Algae are a group of predominantly aquatic organisms that range in microscopic size to 60 meters (e.g., giant kelps). During photosynthesis, they produce 30 to 50 percent of the oxygen in the Earth’s atmosphere, store carbon, provide food for most aquatic life, and are economically important as a source of crude oil, human food, and pharmaceutical and industrial products. Some red and brown algae can be used as natural binders, thickening agents, or making bioplastic films. [279] For example, Agar and carageenan are gelatin-like products isolated from red algae and are used as binding agents for bioplastics as well as bacteriological culture media, food processing, cosmetics, and medicines [280] Sodium alginate that is derived from brown algae [281] is used as a binding agent for bioplastic films, bioplastics, or fiber-reinforced non-woven textiles.

Mycelium is comprised of masses of hyphae, the tubular filaments of fungi that may vary in size, from microscopic to large visible structures such as rhizomorphs or mushrooms. [268] Trametes versicolor, Fomes fomentarius, Ganoderma resinaceum are mycelium varieties with strong hyphae structures that are used in mycelium composites. [269] [270] [271]  Reishi strains (of the Ganoderma gensus) can feed on plant wastes at an industrial scale to produce a mycelium leather-like material. To create mycelium composite materials, the mycelium spores are mixed with organic substrates, such as hemp or wood chips, and then cast inside molds. As the mycelium grows, it feeds off of the organic material and acts as a binding agent. Once the mycelium grows throughout the molds, the composite material can be dried, yielding a strong, lightweight, and water-resistant material.

Cellulose, a complex carbohydrate provides structural support to plant cell walls. It is the most abundant naturally occurring organic compound, constituting approximately one-third of all plant matter. Herbivorous animals and some microorganisms rely on cellulose as a food source. Cellulose is processed to produce fibers and paper products, and after chemical modifications, can yield substances used to manufacture plastics (e.g., cellulose acetate, photographic film) and textiles (e.g., rayon). Cellulose derivatives are used to produce adhesives, coatings, and other products. [272] For example, carboxymethyl cellulose (CMC) is added to cement and other building materials due to its stabilizing and adhesive effects. It is also used for upholstery glues and wood glues. [273] Cellulose acetate is a bioplastic that can be used to create parts, fasteners, films, textiles, and packaging. Regenerated cellulose fibers are used to make rayon and lyocell fabrics.

Gelatin is a protein substance derived from collagen with gel-forming properties by boiling animal hides, skins, bones, and tissues. [267] Although its biocompatibility and biodegradability make it suitable for creating some bio-based materials, it is not commonly used in the IAD industry due to limited durability and longevity. PF can be mixed with the gelatin to reinforce bioplastic materials.

Natural resins, a class of noncrystalline or viscous liquids from trees or beetles, include pine resin, dammar, shellac, sandarac, turpentine, elemi, dragon blood resin, and amber resin. In the IAD industry, they are used in varnishes, lacquers, adhesives, additives to plaster, and decorative elements. [274] [275] Synthetic resins have largely replaced natural resins in most modern industries. [276]

Citric acid, an organic compound in the carboxylic acidfamily, is found in many plant, notably citrus fruits, and is also found invarious animal tissues and fluids. Citric acid is produced by fermenting canesugar or molasses, facilitated by the Aspergillus niger fungus. Its iswidely used in the food industry and as a cleaning agent. [282]Many researchers have also used citric acid as a binder for particle board. [152] [45] [153] [154]

Starch, an organic compound in many plants is obtained by crushing, mixing, purifying, and drying starch-rich seeds or tubers. such as corn, rice, wheat, tapioca, cassava and potatoes. Once extracted, it is a white powder that is insoluble cold water or alcohol. It excels as a natural binding agent for PF-based bio-materials by bonding components into cohesive structures. Starches can be dissolved in water, heated , mixed with plant fibers, and molded to create reinforced bioplastics. Starch is also used to strengthen paper and optimize surface sizing of corrugated paperboard, bags, boxes, gummed paper, and tape. For textiles, starch reinforces threads during weaving to improve durability and structural integrity. [262] [263] [264] [265] Starches can also be used as binding agents for particle boards or fiberboards or other compacted materials by heat pressing. In addition, starch mixtures can be extruded and 3D printed using paste printers. Dextrins, a class of carbohydrates created by heating or hydrolysis of starch are are used as adhesives and sizing agents in the textile and paper industries. [266] If starches are sourced from edible foods such as corn and rice, their production may compete with land and other resources for food supplies.

Calcium is a abundant alkaline earth metal that forms many compounds including calcium carbonate (CaCO3), calcium chloride (CaCl2), calcium hydroxide (Ca(OH)2), calcium oxide (CaO), and calcium sulfate (CaSO4).  [289] [290] Each of these compounds has different properties due to the nature of the bonds between the calcium and the other elements, and are used in a variety of industries such as construction, food, and agriculture.