Performing Department
Biological Systems Engineering
Non Technical Summary
Agriculture faces a challenging future due to soil degradation, water quality, and scarcity problems, and climate change impacts driven by greenhouse gas (GHG) emissions. Concurrently, growing populations will continue to drive food demand and, thus, land and farm productivity. Farmers historically responded to demand increases with expansion and intensification, often at the expense of environmental sustainability. The ongoing shift in livestock-crop systems toward consolidation, compounded by decreases in agricultural land has created local areas of imbalance between the cropping and animal systems. With rapidly depleting ecosystem services, it will be critical to adopt agricultural practices which can meet these demands more sustainably. One practice that is of interest is finding more valuable uses of dairy manure to improve profitability and improve nutrient management.The current value-added uses of dairy manure are largely limited to use biochemical processes such as anaerobic digestion and fermentation to produce biomethane and bioethanol and to use thermochemical processes such as pyrolysis and gasification to produce bio-oil, biochar and combustible gases. Moreover, the biochemical process can only utilize part of cellulose and hemicellulose in dairy manure; while the thermochemical process typically requires high temperature. In general, these processes primarily produce relatively low value-added products such as methane and ethanol. Therefore, there is a critical need for additional research devoted to developing new efficient, economically feasible and environmentally benign approaches to tackle the underutilization problem of dairy manure and help enhance farmer benefits and agricultural sustainability.Dairy manures (undigested and anaerobically digested) are abundant, aggregrated, and low-cost lignocellulosic resources as compared to others like wood. The United States Department of Agriculture (USDA) inventory reported that the number of dairy cows is currently about 9.40 million. In average, dairy cattle can produce about 12 gal of manure per 1000 lb. live weight per day with 14.4 lb. total solids. It was estimated that more than 110 million tons of animal manure are annually produced in the United States. Dairy manure is enriched in cellulose (about 20% - 35%), depending on the diet of cow, separation, process method and conditions of anaerobic digestion if the manure is processed in a digester.Anaerobic digestion systems for dairy farms are growing in popularity across the United States, which can yield a significant mass of cellulose fibers. The anaerobically digested fiber typically contains about 35% cellulose, 9% hemicellulose (xylose, galactose, arabinose and mannose) and 28% lignin, which accounts for approximately 40% of the anaerobic digested effluent total solid.This fiber can be an important low-cost source for value-added products. However, most of the anaerobically digested cellulose fibers is currently underutilized as soil amendment or animal bedding.Previous studies have considered using the carbohydrates in dairy manure to produce monomeric sugars which can be further upgraded into fuel ethanol and other value-added chemicals. However, our studies and others have shown that enzymes can only partially convert cellulose fibers in dairy manure to fermentable sugars due to high levels of ash and lignin both which are enzymatic inhibitors. Instead this research looks to use the cellulose in the manure fibers to produce nanocellulose materials.Nanocellulose materials are nanometer-sized fibers obtained from lignocellulosic biomass obtained from either hydrolysis of cellulose in concentrated acid solution (typically sulfuric or hydrochloric acid) or obtained by mechanical fibrillation of cellulose, or a combination of chemical or enzymatic treatment and mechanical fibrillation of cellulose. Numerous uses for nanocellulose materials have been proposed, including incorporation in fiber-reinforced polymer composites, substrates for flexible electronics and organic solar cells, coatings, membrane systems, and networks for tissue engineering.One of the most promising early uses of nanocellulose materials is in the papermaking industry. These materials may be incorporated as a binder material to improve the strength properties of paper.Nanocellulose can also serve as a renewable and sustainable alternative to synthetic latex and binders in most coating formulation to improve the barrier properties. Finally, cellulose nanofiber can be directly made into cellulose nanopaper, which can surpass ordinary paper in the mechanical, optical and barrier properties and can be used for many high-tech applications such as flexible energy storage and conversion devices, and printed flexible electronics.There is a critical need for additional research devoted to developing new efficient, economically feasible and environmentally benign approaches to tackle the underutilization problem of dairy manure and help enhance farmer benefits and agricultural sustainability. The proposed research will address the underutilization challenge of dairy manure and anaerobically digested dairy manure via effectively extracting nanocellulose products and exploring these materials in paper coating applications. This research will advance the utilization of manure waste generated in an agricultural system and improve sustainable agriculture.
Animal Health Component
0%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
(N/A)
Goals / Objectives
Research and develop technically feasible, economically viable and environmentally sustainable technologies to convert biomass resources into chemicals, energy, materials in a biorefinery methodology including developing co-products to enable greater commercialization potential.
Project Methods
Task 1: Manure Processing and PurificationAlong with the primary lignocellulosic components, dairy manure usually contains impurities such as odors, metals, proteins, urea, microbes, etc. The methods for task 1 include:(1) Solid/liquid separation. Solid/liquid separation will be carried out using a Boch centrifuge with a 100 mesh screen located in the Wisconsin Energy Institute. Previous work has shown this method to be able to achieve approximately 40 % solids content.(2) Alkaline treatment. The manure solids will be mildly treated by alkaline protease under ambient temperature to further remove the residual proteins (Ibarra et al., 2004). The treated manure then will be separated and washed using the centrifuge, producing a product that is primarily comprised of carbohydrates.(3) Analysis. Samples of the initial and separated manure will be analyzed using for C, H, O, N, S using a Perkin Elmer Elemental Analyzer. Phosphorus will be analyzed using a UV-Vis spectrophotometer at 645 nm. Potassium will be measured using an ICP-OES spectrophotometer. Ash, extractives, and acid-insoluble lignin will be analyzed according to National Renewable Energy Laboratory Analytic Procedures (Sluiter et al., 2010). Total solid and volatile solid will be analyzed according to published standards (APHA 2006). Monosaccharides (glucose, galactose, arabinose, mannose, and xylose) will be measured by a high-performance liquid chromatography (HPLC).Task 2: Produce Nanocellulose This task is to efficiently produce a nanocellulose product at high yield and minimal energy inputs. The methods for task 2 include:(1) Cellulose Nanofiber Extraction. The extracted manure sample in Task 2 will be further delignified through bleaching to partially or completely remove the residual lignin using alkaline hydrogen peroxide, producing the lignin-containing or pure cellulose fiber. The amount of lignin in cellulose fiber will be controlled by adjusting the bleaching conditions. The obtained cellulose fiber will be firstly treated by enzymes then followed by the microgrinding, producing the cellulose nanofiber. Enzyme treatment will be used to reduce the respective energy consumption.(2) Bleaching. The manure sample will be treated in a reactor with alkaline (pH =11.5) hydrogen peroxide (0.05 wt%, based on the dry manure) at 70 °C for approximately 1 hour. After the bleaching, cellulose fiber will be washed with water and neutralized.(3) Enzymatic Pretreatment. The manure sample will be treated with commercially available enzymes (xylanase and cellulase) following Tarrés et al. (2016). Briefly, the never-dried manure sample at a 3% consistency will be treated with enzymes under different dosages (0.05-50 activity unit /g dry cellulose fiber) in a phosphate buffer at 50 °C for varying times (30-90 min).(4) Microgrinding. Briefly, the manure sample at an initial 2%-3 % (w/v) solid consistency will be dispersed in distilled water for 2 h. Then, the resultant suspension will be processed using microgrinding equipment available at the Forest Products Laboratory (SuperMass Collider). The gap between the grinding stones (stator and rotor) will be adjusted to control the defibrillation. defibrillated cellulosic fibers will be periodically sampled for measuring the yield and size.(5) Cellulose Nanofiber Yield. Cellulose nanofiber yield will be determined through a centrifugation method. Briefly, the diluted fiber suspension with a 0.2% (w/w) concentration will be centrifuged at 4500 rpm for 20 min to isolate cellulose nanofiber (contained in the supernatant) from the non-fibrillated and partially fibrillated one retained in the sediment fraction. After the supernatant fraction is removed, the sediment fraction is dried at 100 °C in the oven.(6) Characterization and Analysis. Nanocellulose samples will be characterized for morphology, length, diameter, length distribution, aspect ratio, and nano-scale material properties of cellulose nanofiber will be characterized using the combined microscopy techniques of Field Emission Scanning Electron Microscopy and Transmission Electron Microscopy. Crystallinity will be measured using an X-ray diffractometer. Rheological properties will be analyzed using a shear rheometer. Monosaccharides (glucose, galactose, arabinose, mannose, and xylose) will be measured by high-performance liquid chromatography.Task 3: Evaluate Performance of Produced Nanocellulose This task is to test the ability of the produced hemicellulose as a binder for paper coating and the abilities of cellulose nanofibers as strengthening agents for papermaking. Additionally, the properties of the manure produced nanocellulose will be compared to wood pulp produced nanocellulose available from the Process Development Center at the University of Maine.The methods for task 3 include:(1) Paper Coating. Coating formulations will be formulated with different levels of nanocellulose along with the typical binders and opacifying agents. A minimum of three produced nanocellulose and one conventional nanocellulose product from wood pulp will be used. To test the coating performance, the gel/paste will be spread over the wire side of an uncoated free sheet (a base paper with grammage of 60 g/m2) with a manual laboratory draw-down rod coater. The coating formulation will be manually metered onto the wire side of the sheet and then coated with the rod. After coating, the samples will be air-dried overnight and then conditioned at TAPPI conditions (50% relative humidity and a temperature of 25 °C) prior to characterization.(2) Papermaking. The extracted cellulose nanofibers (5-10%) will be incorporated into the pulp slurries following the method described by Tarrés et al. (2016). Briefly, the pulp will be disintegrated in water and then cellulose nanofiber will be added. Polymer additives such as cationic starch as retention aids will be added as well. Handsheet with grammage of 60 g/m2 will be fabricated using a semi-automatic laboratory handsheet maker equipped with a vacuum dryer (T205 om-88 TAPPI).(3) Characterization. Strength properties (tensile, bursting tearing resistance, and folding endurance), gloss, surface roughness, and optical properties (brightness, color, opacity) will be measured according to TAPPI standard methods (T-403, T-414, T-423, T-441, T-460, T-494, T-452, T-530, T-538). Water vapor transmission rate will be determined according to ASTME 96-95 using the water method.