Performing Department
(N/A)
Non Technical Summary
Demand for seafood has steadily increased due to increasing population and per capita consumption. Recirculating aquaculture systems (RAS) intensively produce aquatic products; however, their operations require high energy input and create considerable nutrient-rich wastewater, leading to significant environmental impacts. Using algae to treat wastewater (also known as phycoremediation) can assimilate nutrients and carbon to produce algal biomass for conversion into bioenergy, leading to the overarching goal of this project: Integrating RAS with phycoremediation and anaerobic digestion (AD) for nutrient reuse, energy production and carbon dioxide sequestration to develop an intensive aquaculture production system with near-zero emissions. Specific project objectives include: (1) Screening of algae for effective nutrient removal from RAS wastewater; (2) Developing AD strategies for algal biomass, and wet scrubber for air pollution mitigation; (3) Kinetic modeling and life cycle assessment of integrated near-zero-emission aquaculture production system; (4) Disseminating project results and products to stakeholders. The RAS-algae-AD integration is expected to close the nutrient loop to a higher degree that can be adopted by smallholder aquaculture farmers as a promising approach to reducing energy demand and waste output. This novel aquaculture production system features more efficient nutrient use, reduced operating costs, and improved environmental quality, and thus will play a major role in sustainably enhancing food security.
Animal Health Component
0%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
(N/A)
Goals / Objectives
The overall goal of the proposed project is to enable a sustainable intensive aquaculture production system that combines the benefits of nutrient reuse, energy production and CO2 sequestration by integrating algae cultivation and anaerobic digestion (AD) with recirculating aquaculture systems (RAS) to achieve near-zero emission to the hydrosphere and atmosphere. To test our central hypothesis, and thereby attain the overall objective through interconnected research and Extension activities, we have built a multidisciplinary team and will partner with the Aquaponics Association to pursue four objectives: Obj. 1, 2 and 3 for research, and Obj. 4 for Extension.Objective 1. Screening of algae and cultivation conditions for effective removal of dissolved nutrients from fish RAS wastewater.Objective 2. Developing co-digestion strategies to enhance AD of algae, and wet scrubber for pollution mitigation.Objective 3.Kinetic modeling of integrated phycoremediation-anaerobic co-digestion (AcoD) wastewater treatment and life cycle assessment (LCA) on the environmental performance of near-zero-emission aquaculture production system.Objective 4. Disseminate project results and products to various stakeholders via Purdue and multi-state Extension networks.
Project Methods
RAS wastewater samples will be collected from tilapia growing units to start a continuous-flow algae-bacterial bioreactor and optimize its operating parameters, including hydraulic and solid retention times, organic loading rates, and light intensity. The bioreactor will be run as a suspended growth system and algae will be harvested once they reach optimal growth conditions for compositional analysis. Several different algal cultures will be tested and based on growth rate the best performing algal strain will be selected for AD.Algae will be harvested and concentrated for AD at mesophilic temperature. The digester feedstock will include RAS sludge, algae, and livestock manure for optimal biogas production. The digestate will be used as nutrients for algal cultivation. The produced biogas will supply fuel to the biogas boiler to produce hot water via direct combustion. The hot water will be cycled first to heat the lower-temperature-required anaerobic digester and fish tanks. Hot exhaust air from the biogas boiler will be supplied to algae bioreactor to provide carbon source and heat for algal growth. A wet scrubber will be developed using cycling algae water from the algae bioreactor. Aerial pollutants in the enclosed production system will be removed from the air and captured during the scrubbing process to provide nutrients and micronutrients for algal growth.The kinetics in the proposed integrated system will be modeled and its environmental performance will be evaluated using LCA. The kinetic model combined with LCA can predict the system performance (nutrient recovery and energy generation) and determine the operating conditions of subsystems to minimize the life cycle emissions. The proposed model is a compilation of multiple sub-models for the subsystems which are combined through the fluxes of nutrients and energy. Mass balance equations will be established to integrate all the sub-models, and all the constants and coefficients in the integrated model will be calibrated and validated using experimental data. A system energy balance will also be calculated to assess the potential energy saving by the proposed integration. A cradle-to-gate LCA will be conducted. Foreground data of the life cycle inventory on the operation of subsystems and the associated material and energy use will be mainly collected from experiments and complemented by the results of kinetic modeling where needed. Background data will be taken from databases. Life cycle impact assessment will be performed using the TRACI 2.1 method.In the early stage of the project, we will locate interested farmers in the Midwest willing to test the effectiveness of our new wastewater treatment system at their farms. Further, we will engage anaerobic digester owners to evaluate the potential of AcoD of aquaculture waste and algal biomass with their existing feedstocks. Upon completion of the experiments, we will publish Extension Factsheets and articles to disseminate our project findings to stakeholders to explain the technical feasibility and environmental benefits of the integrated waste management system over conventional treatments. The research results will also be shared with scientific communities and the public in Indiana via Purdue Extension network. All the Extension materials developed will be made available in Purdue Extension Education Store Website, and websites of AD and agricultural waste management. We will also pilot-test our Extension materials through aquaculture and AD workshops and field days at Purdue. We will demonstrate our experimental systems in the workshops, which will be helpful for participants to get hands-on training with its operation and evaluate its performance. Additionally, we will develop an innovative and interactive tool for on-line use. This web tool will enable stakeholders to learn the novel RAS-algae-AcoD production system and design a potential new system.