Location: Bioproducts Research
2015 Annual Report
Objectives
The demand for agricultural feedstocks is growing as global demand for food is ever increasing and efforts mount to create alternatives to petroleum products that feed global warming. The goal of this project plan is to use biopolymers to develop sustainable technologies and bioproducts that will benefit the U.S. and that will not negatively impact food reserves. This plan highlights the use of nonfood fibers and crop waste to create new bioproducts and help improve the efficiency in utilizing agricultural commodities via the following objectives:
Objective 1: Enable, from a technological standpoint, new commercial value-added biobased materials.
a. Utilize conventional and novel processing technologies to produce and characterize nanofibers from biopolymers and investigate potential applications.
b.Utilize biopolymers to encapsulate/deliver beneficial soil microbes that improve crop production.
Objective 2: Enable new commercial materials based on biopolymers and biobased fillers.
a. Develop fiber-reinforced composite materials.
b. Develop value-added bioproducts from torrefied crop waste.
c. Develop value-added bioproducts from almond, grape and citrus waste.
Approach
The overarching approach will be to provide data, technology and prototypes that will not only result in novel bioproducts but also address important agricultural needs including the need for higher crop production, the need for more sustainable farming practices, the need for alternatives to petroleum-based products and the need for new innovations such as nanotechnology. The first approach is development of composite materials that encapsulate beneficial microbes to be used to reduce the inputs of conventional fertilizers and petroleum-based pesticides. A co-development as part of this approach is production of humic acid from renewable resources such as torrefied crop waste to augment soil health. Humates will be used as soil amendments to improve soil fertility and crop production. Also, nanofibers from aqueous solutions of biopolymers will be made and characterized by developing new processes to make nanofibers from a wide array of biopolymers. Bioproducts made using the nanofibers will include controlled-release devices and sensors.
Objective 2 is aimed at developing bioproducts from nonfood agricultural products, namely plant fibers and crop waste. The group will apply expertise in dispersing plant fibers in biopolymer matrices and in inorganic binders. The anticipated bioproducts developed in Objective 2a include compression molded food service products containing more than 60% fiber using biopolymers as binders. We will also create lightweight rigid foam products by dispersing plant fibers in inorganic binders including Portland cement and gypsum.
California has one of the most diverse agricultural industries in the world and ranks first in production in terms of cash receipts ($43 billion), but also leads in the output of crop waste and residues. Diverse agricultural byproducts such as almond hulls, grape pomace, citrus peel waste, etc., which are concentrated at processing plants and often carry a cost for disposal, will be converted into higher value products. Objectives 2b, and 2c specifically address this need. The anticipated products include black filler for PET plastics and pelletized coal dust made using inexpensive biopolymer binders such as citrus waste and gums from almond hulls. Other bioproducts include essential oils and antioxidants extracted from seeds processed from grape pomace.
Progress Report
This is the first report for this new project which continues research from “Bioproducts from Agricultural Feedstocks”, 2030-41000-056-00D. Please see this report for further information.
Objective 1. Cellulose nanofibers are typically extracted from cellulose by acid hydrolysis or purified enzymes. However, microbes that excrete extracellular enzymes have the potential to be a useful, low cost tool for extracting nanofibers or nanofibrillated fibers from fibers. We exposed bleached eucalyptus pulp fibers to an anaerobic microbial-rich digestate for different incubation periods (5, 10 and 20 days) to determine the treatment effect on morphology, crystallinity, and thermal stability of cellulose pulp fibers. The six most abundant bacteria in the AD-supernatant were determined by 16S analysis. The bacteria population was comprised mostly of Bacteroides graminisolvens (66%) and Parabacteroides chartae (28%). Enzymatic activity from the bacteria partially removed the amorphous components and increased the crystallinity and crystallite size of the cellulose substrate. The X-ray diffraction data provided evidence that the amorphous portion of the cellulose was more readily and quickly hydrolyzed than the crystalline portion. The longest incubation times resulted in substantial damage to the cellulose structure and decreased the thermal degradation temperature. This information is being published and provides a unique, low cost method of extracting nanofibrillated cellulose.
Phosphorus (P) is one of the three macronutrients that are essential for plant growth and development. Insoluble and inorganic phosphorus can make up to 70% of the total P content in the soil and are unavailable for plant use. The existence of microorganisms that can solubilize phosphate has been known for decades but, until recently, the Pantoea genus has been overlooked. In collaboration with our industrial partner, we have been able to show how the bacteria from the Pantoea genus can solubilize tricalcium phosphate, aluminum phosphate, and iron phosphate in quantitative laboratory experiments. Additionally, the most efficient bacterium in the set, Pantoea vagans C9-1, can solubilize tricalcium phosphate at a record high rate of 955 mg/L and can also show the same solubilization functionality in the greenhouse setting to promote tomato plant growth. The goal is to encapsulate the bacteria in the patented starch/gypsum matrix developed in our laboratory. The original method of making the matrix through extrusion was rather inefficient. A granulation process was developed that scaled much better for making the matrix material. The granulation process was simple and produced granules with a moisture content of about 20%. Approximately two hundred pounds of product can be made per day at our facility using this process. Two companies have licensed this technology and field trials of tomatoes, onions, and strawberries are being tested to determine their effect on yields when fertilization is decreased.
Objective 2. Film composites made with polylactic acid (PLA) with a high pulped fiber content are difficult to produce because the fiber is not compatible with the plastic matrix. Uniform fiber dispersion in a PLA matrix is difficult to achieve, especially with high fiber content. We are investigating the method of producing a porous fiber matrix that can be infiltrated with a polymer solution that can then be dried to form a high-fiber composite film. We have been successful in dispersing pulped fiber in water and collecting the fiber on screens. The fiber is removed from the screens and dried to form a porous fiber sheet. The sheets will be infiltrated with a polymer solution and the properties compared with films made of PLA containing no fiber.
Torrefied almond shells and wood chips were incorporated into polypropylene as fillers to produce torrefied biomass-polymer composites. The composites were prepared by extrusion and injection molding. Response surface methodology was used to examine the effects of filler concentration, filler size, and lignin factor (relative lignin to cellulose concentration) on the material properties of the composites. The heat distortion temperatures, thermal properties, and tensile properties of the composites were characterized by thermomechanical analysis, differential scanning calorimetry, and tensile tests, respectively. The torrefied biomass composites had heat distortion temperatures of 8–24°C higher than that of neat polypropylene. This was due to the torrefied biomass restricting mobility of polypropylene chains, leading to higher temperatures for deformation. The incorporation of torrefied biomass generally resulted in an increase in glass transition temperature, but did not affect melting temperature. Also, the composites had lower tensile strength and elongation at break values than those of neat polypropylene, indicating weak adhesion between torrefied biomass and polypropylene. However, scanning electron microscopy results did indicate some adhesion between torrefied biomass and polypropylene.
A milling technique was developed that allow the removal of the outer layers of grape seeds that are especially rich in antioxidants. The remainder of the seeds is oil-rich and is a commercially viable source of grape seed oil. This work is being done in collaboration with an industrial partner who is interested in commercializing the process.
Accomplishments
1. Torrefied crop waste as a replacement for carbon black. Carbon black is used as a filler in plastic composites to improve the heat resistance and appearance. ARS scientists at the Western Regional Research Center in Albany, California, used ground torrefied crop waste from almond shells and wood chips as a replacement filler for carbon black. The composites had greater heat stability than the plastic by itself but the strength and elongation of the composites, although adequate for many applications, were inferior. The results indicate that torrefied crop waste could be a viable filler for plastic composites for many applications.
2. Low cost treatments for making fibrillated nanofibers. Fibrillated nanofibers have been shown to improve the strength of plastic composites but are prohibitively expensive. ARS scientists at the Western Regional Research Center in Albany, California, in collaboration with Brazilian scientists, have demonstrated that degradative enzymes from crude digestate are effective in making fibrillated nanofibers from pulp fiber. Different incubation times yielded correspondingly varied degrees of fibrillation. This research could lead to greater production of low-cost fibrillated nanofibers that can improve the strength of fiber composites and increase their renewable material content.
