Recipient Organization
UNIVERSITY OF ILLINOIS
2001 S. Lincoln Ave.
URBANA,IL 61801
Performing Department
Agri Engineering
Non Technical Summary
Many processes using agricultural commodities and biomass as inputs use water intensively. As a result, process streams carry nutrients consisting of proteins, carbohydrates, lipids, bioactive compounds, vitamins and minerals. While containing potentially valuable components, these process streams are large in volume and are dilute. These conditions create challenging recovery and low or negative economic value of recovered solids. For example, thin stillage from ethanol production is produced at a rate of 7 L per 1 L ethanol and has 5% total solids for an industry producing about 60 billion L ethanol per year. Other process streams in industry include steepwater and process water from corn wet milling.Conventional drying processes are inherently energy intensive because of the phase change with evaporation of water and other solvents. Impact of drying methods on coproduct nutritive value largely are undetermined. For the case of thin stillage, water is removed by evaporation to concentrate solids from 5 to 35%. Thin stillage is usually mixed and dried with other process solids to form distillers dried grains with solubles (DDGS), which has value similar to that of corn.As the biofuels industry grows, sustainable use of water and recovery of nutrients will become increasingly important. In the US, more than 200 biorefineries are in operation; nearly all of these plants use corn, an important crop for Midwestern states. Plant capacities range from 40 to 120 million gallons ethanol per year (mmgy). With a thin stillage recycle rate of 35%, a 40 mmgy plant will remove 140 mmgy water using evaporation. As the use of biomass to produce ethanol becomes commercially viable, new process streams will result, increasing the need to sustainably recover water and nutrients.Fuel ethanol plants use multiple effect evaporators to concentrate thin stillage. Evaporators must be cleaned at intervals of 1 to 2 weeks, resulting in economic and capacity losses at the plant. Labor and chemical costs are incurred to clean the evaporators, a plant must reduce processing or shut down entirely during cleaning, and additional evaporator capacity must be installed if the plant wants to continue operating during cleaning. Cleaning procedures add water to the process; water and cleaning chemicals must be routed appropriately, either for reuse or disposal. When processing difficulties arise, such as during poor fermentation or incomplete liquefaction, evaporators can be expected to foul more rapidly.Separation processes upstream from the evaporator affect its efficiency. Process designs to produce valuable coproducts also affect process efficiency and long term sustainability. As the biorefinery industry grows and matures, long term economic operations will become increasingly important and impact the communities where they are located. Developing new uses and, more importantly, higher value for coproduct solids in process streams is needed to retain bioprocessor competitiveness and can be accomplished through new process designs, incorporation of new technology or combinations of both.
Animal Health Component
50%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
(N/A)
Goals / Objectives
1.Develop processes that enhance the value of agricultural materials, especially grain processes, such as membrane separations.2.Use emerging technologies or technologies from other industries in bioprocesses to dewater, dry or convert solids into higher valued coproducts.3.Gain understanding of mechanisms that hinder or enhance separations of nutrients in process streams, including fouling of heat transfer surfaces.
Project Methods
Various process systems and unit operations will be studied in an effort to improve the economic and nutritive value of process streams. Methods to convert agricultural materials, such as grains, into food and industrial products, and recover, dewater, and dry solids from these processes will be investigated. Development of new processing systems will be emphasized.Membrane filtration technology will be applied to grain and biofuels processes to conserve water and recover nutrients, thus reducing flows to waste treatment facilities. Microfiltration and ultrafiltration unit operations, focusing on commercially available membrane materials and using a range of pore sizes, will be applied to process streams such as thin stillage and the solids separations studied (Objective 1).It is expected that membrane filtration will improve compositions of retained solids as well as reduce the amount of water to be removed by thermal methods such as evaporation (Objective 2). Information on improved coproduct composition (e.g., improved phosphorus content) will be collected with processing information (e.g., water removal and recycle possibilities) that could be used in other research. Based on previous work (Agbisit et al 2003, Arora et al 2009, 2011a,b, Wilkins et al 2006a,b) the role of membrane filtration in reducing heat transfer fouling will be investigated further and coupled with recent expertise in using our fouling test apparatus and model fluids.Membrane filtration, due to its selective separations, can be incorporated in experimental designs that will increase our understanding of the causes of heat transfer fouling, leading to reduced evaporator fouling (Objective 3). By use of model process streams, insights can be gained regarding causes of accelerated fouling (Challa et al 2017, Rausch et al 2013, You et al 2019) and the desired effect from membrane separations. Although not a direct outcome of this work, it is anticipated that the information gathered during the project could be used to develop economic simulations and cost analyses for improved bioprocesses (e.g., Arora et al 2011).