Recipient Organization
UNIV OF IDAHO
875 PERIMETER DRIVE
MOSCOW,ID 83844-9803
Performing Department
Biological Engineering
Non Technical Summary
The dairy industry is a very important sector of agriculture in Idaho and in the United States. Nutrient cycling from dairy production systems has long been a challenging topic for both the industry and the research community. The goal of this project is to provide dairy farmers an alternative technology for dairy waste management and value-added utilization of byproducts from dairy operations. This goal will be achieved through a systematic engineering research on nutrient cycling and carbohydrates/ sugars production.There are multiple anticipated benefits from this research. First, the outcomes from this project would benefit Idaho's dairy industry by providing an alternative technology for managing dairy manure while producing a nutrient-rich hydrochar that has resale value and can be marketed to crop farmers, especially those practicing organic farming, for increased profits. Secondly, nutrient cycling achieved by the hydrochar would not only benefit crop farmers with an organic fertilizer and a soil amendment agent with improved nutrient retention capacity, humic substance contents, and carbon sequestration, but also provide a tremendous environmental benefit by transporting the nutrients in manure to croplands that have a high demand for organic fertilizers. Thirdly, carbohydrates/sugars produced from duckweed biomass cultivated on the nutrients in dairy wastewater not only treat the wastewater but also produces sugar feedstock for biofuel production in a value-added manner. Ultimately, this project creates meaningful long-term economic and environmental impact by supporting the sustainability of the agriculture and food systems of Idaho and the U.S.The expected outputs from this project will include multiple deliverables of scientific research findings for knowledge advancement, a data collection of technological developments in new dairy waste management practices, technology for hydrochar production for nutrient cycling and carbon sequestration, and technology for sugar production from duckweed for biofuel production.
Animal Health Component
80%
Research Effort Categories
Basic
20%
Applied
80%
Developmental
(N/A)
Goals / Objectives
The goal of this project is to provide dairy farmers in Idaho, and other states in the U.S., an alternative technology for dairy waste management and value-added utilization of byproducts from dairy operations. The goal will be achieved through a systematic engineering research on nutrient cycling and carbohydrates/ sugars production. Accomplishment of this goal would greatly contribute to the rural economy, healthy growth of dairy industry, and the welfare of farmers, and our society in general, by managing dairy waste more effectively, utilizing and cycling the nutrients more efficiently, producing a value-added and nutrient rich hydrochar as an organic fertilizer and a sugar feedstock for biofuels, and ultimately protecting our environment for everybody's better life.To accomplish this goal set by this 5-year project, specific studies will be conducted with the following objectives.1.1 Objective 1To develop an aquatic biomass production system for cultivating strains of duckweed on wastewater from anaerobically digested dairy manure for optimal biomass productivity and sugar accumulation (to be conducted during Year 1 - Year 4).1.2 Objective 2To investigate and optimize the process on duckweed biomass harvesting and processing, carbohydrate/ sugar extraction from duckweed biomass, analysis of sugar profiles and purification of fermentable sugars (to be conducted during Year 2 - Year 5).1.3 Objective 3To develop a hydrothermal carbonization process to convert the activated sludge from anaerobic digestion of dairy manure, and the residual duckweed biomass after sugar separation into hydrochar which is a solid product, rich in nutrients, as an organic fertilizer for nutrient cycling and high in carbon content as a soil improver for carbon sequestration (to be conducted during Year 1 - Year 4).1.4 Objective 4To develop a conceptual process design of a pilot system that integrates the findings of objectives 1-3 in hydrochar production, N and P recovery/retention, and sugar production, for implementation and practical on-farm application in R&D of next stage (to be conducted during Year 4 - Year 5).
Project Methods
Methods for Objective 1To accomplish this objective, process parameters, including limiting nutrient (e.g., N and P) concentrations, requirement of minimal and optimal lightening intensity, and suitable pH and its control of the cultivation medium, will be studied systemically on duckweed' growth rates and carbohydrate/ sugar accumulation for maximized sugar production. Three strains of duckweed, i.e., Landoltia punctata 0128, Lemna gibba 7589, and Lemna minuta 9517, will be used as the candidates based on the findings of our preliminary studies.A walk-in chamber will be used as the controlled environment for conducting the experiments in this study. This environmental chamber is capable of controlling temperature, lightning, and humidity if needed. The ranges of cultivation temperature, light intensity, nutrient dilution rate, and medium pH are preliminarily determined at 20-30°C, 1,000-10,000 lux, 1:10-1:30 v/v, and 6.5-9.0, respectively. The photo-period will be 16:8, i.e., 16 hours of lightning and 8 hours of dark period.Laboratory experimental trials will be conducted in rectangular PET containers (4.5 x 3.5 x 4.0 in) with lids in batch mode. Experimental data to be analyzed/collected include total nitrogen (TN), total kjeldahl nitrogen (TKN), ammonia nitrogen (NH3-N), total phosphorous (TP), ortho-phosphate-phosphorous (o-PO4-P), pH, chemical oxygen demand (COD), dissolved oxygen (DO) and electric conductivity.Biomass productivity and sugar accumulation will be used as the process evaluation parameters, which will collectively give the sugar productivity in g/m2·day. The biomass productivity on wet biomass basis, sugar accumulation on dry biomass basis, and sugar productivity on dry biomass basis are targeted at 15 g/m2·day, 35 g/g of biomass, and 50 g/m2·day, respectively.Methods for Objective 2The focus of this objective is to identify the fermentable sugars so they can be used for bioethanol production. To obtain the carbohydrates, mainly starch, biomass harvesting and processing (e.g., collecting, de-watering, drying, and de-sizing) are an important first step for a high process efficiency. Getting the starch out of the biomass is also important and potentially challenging due to the unique properties of aquatic biomass. Identification and purification of fermentable sugars are also important because non-fermentable sugars not only reduce the process efficiency/product yield, but also are potentially toxic/inhibitive in sugar fermentation to bioethanol.Carefully designed harvesting schedules will ensure a healthy and productive duckweed crop. The means of harvesting depends on the ways of cultivation. In this stage of laboratory investigation, duckweed harvesting will be performed by simply scooping a carefully determined quantity of the plants out of the containers so that the duckweed growth will be at an approximately steady rate. The wet duckweed will be centrifugated by a low rpm spinning machine to remove the free water from biomass. Then the samples are carefully lay on absorbent paper towel in thin layers to remove additional surface water before the wet biomass productivity is determined.Methods for Objective 3In Task 3.1, an efficient process will be identified with optimized operating conditions to produce hydrochar that will be used for further evaluation of the efficiency on N and P reutilization. The focus will be process development and optimization. The feedstock will be the sludge from anaerobic digestion of dairy manure and residues of duckweed biomass after sugar extraction. For investigation on process parameters, an existing high-temperature, high-pressure PARR reactor system (Parr Instruments) consisting of a 300-mL pressure reactor will be used, which is capable of handling up to 20 MPa of pressure and 350°C of temperature. The reactor is equipped with a controller to regulate and monitor the operating temperature, pressure, and agitation motor speed. The process control and data acquisition are computerized, in addition to manual control and data recording. Once the process is optimized and the operating condition established, hydrochar will be produced in a 4-L reactor system to provide adequate hydrochar for further characterization.As found from our preliminary studies, the influential process parameters include the processing temperature (180-250°C), residence time (15-60 minutes), level of solid content (5-35%), and acidity or alkalinity of feedstock (pH 5-8). Additional process parameters that have not been tested in our preliminary experiments are the nature of the feedstocks (e.g., fresh manure vs. solid sludge) and the makeup of the feedstock (e.g., raw manure, activated sludge, and/or duckweed biomass). In the process development, we will systematically investigate the effects of process parameters on the hydrothermal carbonization of the targeted feedstocks for hydrochar production. The yield of hydrochar will be used as an indicator of process efficiency. Feedback on N and P contents in hydrochar as determined in Task 3.2 will be taken into consideration in evaluating the process parameters. Research will also be conducted on the engineering aspects of the process development, such as feeding and discharge mechanisms, and data will be collected for a future scale-up project. For process control purposes, elemental analyses of carbon, hydrogen, and sulfur will also be conducted on feedstock and hydrochar. Mass balances of N and P will be performed for evaluating the N and P reutilization efficiency.Task 3.2 will be on evaluating the performance and efficiency in N and P reutilization. Characterization of hydrochar on N and P contents will be conducted. Mass balances of N and P in hydrochar, water-soluble, and gaseous products will be conducted and documented. The analyses of N and P contents, as well as carbon and sulfur, including proximate and ultimate analyses, of the feedstock and hydrochar will be conducted. Examples of analytical techniques include CNS analyzer, sulfur analyzer, and ICP spectrometer. Electron microscopy and x-ray photoelectron spectroscopy will also be used to characterize the hydrochar for its potential as a soil fumigant and N and P slow release media. The efficiencies of N and P reutilization will be evaluated by computing the N and P recovery rates after the processing as opposed to the initial N and P input.Methods for Objective 4This objective will be fulfilled by evaluating the overall efficiency of the integrated process on optimal nutrient cycling and sugars production, and developing a conceptual process design for a demonstration dairy farm of 2,500 cows/year capacity, which is estimated to produce approx. 100 million lb of total wastes annually. The outcome from objective will be a database that will provide the information of N and P reutilization efficiencies, and a complete conceptual process design of the technology that will be used in further investigation and implementation at a pilot project in future.Once the preliminary results are obtained from Objectives 1-3, process integration will be started and experimental results will be systematically analyzed. Data processing will be achieved on N and P cycling efficiencies via mass balances through spreadsheets.A conceptual process design will be developed, based on the outcomes of this project, for a dairy farm of 2,500 cows/year capacity. The conceptual process design will include a detailed flowchart that illustrates 1) key process equipment and components, 2) mass balances of nutrient streams, 3) piping and control schemes, and 4) utility requirements. The capacities of the waste volumes treated, hydrochar produced, and the N and P cycled will be specified. A preliminary techno-economic analysis will be conducted, which is an important component in the process design and one of the key investigation topics in future pilot testing.