Grantee Research Project Results
Final Report: Sustainable Algal Biofuels Solution: Sourcing Carbon and Recycling Nutrients from Waste Treatment Processing
EPA Grant Number: SU835717Title: Sustainable Algal Biofuels Solution: Sourcing Carbon and Recycling Nutrients from Waste Treatment Processing
Investigators: Bohutskyi, Pavlo , Shek, Coral F , Bouwer, Edward J. , Betenbaugh, Michael J. , Yacar, Dean , Dillon, Jacquelyn , Adams, Kameron , Chow, Steven
Institution: The Johns Hopkins University
EPA Project Officer: Hahn, Intaek
Phase: I
Project Period: August 15, 2014 through August 14, 2015
Project Amount: $15,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2014) RFA Text | Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Air Quality , P3 Challenge Area - Safe and Sustainable Water Resources , P3 Awards , Sustainable and Healthy Communities
Objective:
The objective of the P3 Phase I project and Phase II proposal is to develop, test and optimize a robust and sustainable process that converts agricultural and domestic waste run-off, carbon dioxide, and sunlight into energy in the form of biodiesel and biomethane.
Summary/Accomplishments (Outputs/Outcomes):
For the Phase I study, significant progress was achieved on the following Tasks and resulted in the preparation of 5 publications/presentations.
Task I: Obtain Nutrient-Rich Algal Growth Media from ATS™ Biomass.
We compared two alternative strategies for conversion of the ATS™ biomass into nutrient-rich growth media.
Subtask I.A: Conversion of Low-Cost Biomass into Sugar-Rich Substrates through
Thermochemical Hydrolysis
Several methods of algal biomass hydrolysis pretreatment have been tested to implement recovery of valuable sugars and nutrients from ATS™ biomass.Thermochemical pretreatment at 121°C with sulfuric acid was found to be superior to thermal pretreatment alone, thermochemical pretreatment with sodium hydroxide, and enzymatic treatment. The optimal chemical levels for thermochemical pretreatment were determined to be doses of H2SO4 in the range of 5-10 g/L, which achieved 50% hydrolysis of biomass to sugar. Moreover, milling of biomass reduced the H2SO4 dose to 5 g/L without reduction in hydrolysis efficiency.
Subtask I.B: Anaerobic Digestion of ATS™ Biomass for Biopower and Nutrient Recovery
ATS™ biomass was found to be a feasible substrate for methane production at a wide range of organic loading rates (OLR) from 1 to 5 gVS/L-day with steady specific methane yield nearly 0.2 L/gVS and volumetric methane yield up to 1 L/L-day. Importantly, a large fraction of essential elements from biomass was released into the AD effluent and became available for reuse as nutrient-rich fertilizer to grow microalga Chlorella sorokiniana, which may accumulate high-lipid content at the second cultivation stage. The highest nutrient recoveries were observed for nitrogen and phosphorus (40 – 50%), cobalt and magnesium (10 – 30%), and molybdenum and sulfur (5 – 10%). In contrast, less than 5% of calcium, iron, manganese, zinc, copper and boron content became available for reuse. The bioreactor operation parameters had strong effects on recovery efficiency, which decreased along with elevation of the OLR perhaps by stimulating precipitation and co-adsorption of most of the elements.
Task II. Cultivate Microalgae Using Nutrients Derived from ATS™ Biomass.
1. A variety of algal species were tested as candidates for cultivation in nutrient-rich algal growth media from ATS™ biomass. Two species – Chlorella sorokiniana (CCTCC M209220) and Chlorella sorokiniana (UTEX 1230) were found to have the highest growth rate and to be particularly suitable for cultivation. The optimal parameters for algae cultivation in wastewater media, which were grown in batch cultures, included percentages of hydrolysate or AD effluent. The 5-10% dilution of AD effluent was found to be the most appropriate for C. sorokiniana growth. The content for all nutrients except nitrogen in the 5-10% AD effluent-based medium was lower than in the Bold’s Basal Medium (BBM) typically used for algal cultivation. However, AD effluent was found to be superior for algal growth than BBM. These findings show that the filamentous algae generated in the ATS™ may be used as a feedstock for biofuel production and as a source of nutrients for microalga cultivation. Initial process scale-up was achieved by conducting algal cultivations at the 8-L and 150-L scale bioreactors. Cell density and nutrient concentrations were measured in order to determine growth rates and nutrient consumption demands for the scaled up process.
Conclusions:
Our results from Phase I demonstrated the technological viability and significant potential of integration of microalgal cultivation for biofuel into the Algal Turf Scrubber® wastewater processing technology. The nutrients assimilated from municipal wastewater can be used to support abundant algal growth and sustainable production of feedstocks for bioenergy. Our findings demonstrate that algal productivity can be significantly enhanced by selecting robust algal species and optimizing cultivation parameters. Furthermore, microalgae can uptake organic carbon, nitrogen, phosphorus and trace elements derived from low-cost biomass grown in wastewater. This could lead to a reduction of environment discharge of these nutrients and elimination of contamination from local watersheds. Especially exciting is the prospect that this technology can be expanded to processing of filamentous biomass generated in contaminated natural streams and agricultural wastes, including livestock manure and poultry litter. As an example, the poultry litter generated on the DelMarVa Peninsula alone contains about 24,000 and 9,000 tons of N and P yearly, respectively, much of which is deposited in the Chesapeake Bay. This technology will help to prevent release of this toxic pollution and convert it to a valuable energy or food source for improving people, planets, and prosperity locally and around the globe.
The filamentous algae generated during the phytoremediation of wastewater using the Algal Turf Scrubber® system were found to be suitable feedstock for generation of biofuels. One potential approach to biofuel production is to use filamentous biomass as a source of organic carbon (sugars) for efficient mixotrophic or heterotrophic cultivation of microalgae like Chlorella sorokiniana. These sugars together with other nutrients (N,P, and some trace elements) assimilated by the filamentous algae from wastewater and required for augmented microalgal growth can be extracted from ATS™ biomass by using thermochemical hydrolysis. A second potential approach is an application of anaerobic digestion (AD) to convert ATS™ biomass into methane. In addition, the nutrients can be partially recovered with the liquid fraction of the AD effluent and used for high-rate cultivation of high-quality Chlorella species. The results achieved in the current study prove the feasibility of the proposed technology, but additional pilot-scale investigation of the whole process combined with economical assessment is required prior large scale implementation.
Finally, productive collaborationswere established with commercial partners: producers of the ATS™ biomass Van Ert, Nemoto and Associates (VEN) Consulting, LLC and HydroMentia, Inc. and the local microalgal biotechnology startup company Clean Green Chesapeake (CGC). Intimate industrial and academic interactions will be essential for the successful translation of this technology to industry as well as for the development of a successful Phase II commercial process in large-scale bioreactors. Furthermore, CGC’s laboratory and demonstration-scale algal production facility provides a test bed for research on enhancing algal biofuel extraction methodologies and serves as a dynamic environment for graduate and undergraduate student training and engagement in research at a small business venture.
Journal Articles on this Report : 4 Displayed | Download in RIS Format
Other project views: | All 4 publications | 4 publications in selected types | All 4 journal articles |
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Bohutskyi P, Chow S, Ketter B, Shek C, Yacar D, Tang Y, Zivojnovich M, Betenbaugh M, Bouwer E. Phytoremediation of agriculture runoff by filamentous algae poly-culture for biomethane production, and nutrient recovery for secondary cultivation of lipid generating microalgae. BIORESOURCE TECHNOLOGY 2016;222:294-308 |
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Bohutskyi P, Phan D, Kopachevsky A, Tang Y, Betenbaugh M, Bouwer E, Lundquist T. Bioenergy from wastewater resources: Nutrient removal, productivity and settleability of indigenous algal-bacteria polyculture, and effect of biomass composition variability on methane production kinetics and anaerobic digestion energy balance. ALGAL RESEARCH 2018;36:217-228 |
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Bohutskyi P, Phan D, Spierling R, Kopachevsky A, Bouwer E, Lundquist T, Betenbaugh M. Production of lipid-containing algal-bacterial polyculture in wastewater and biomethanation of lipid extracted residues: Enhancing methane yield through hydrothermal pretreatment and relieving solvent toxicity through co-digestion. SCIENCE OF THE TOTAL ENVIRONMENT 2019;653:1377-1394 |
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Sarpong G, Gude VG. Codigestion and combined heat and power systems energize wastewater treatment plants-Analysis and case studies.RENEWABLE & SUSTAINABLE ENERGY REVIEWS2021;144(110937). |
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Supplemental Keywords:
sustainability, wastewater treatment, eutrophication, nutrients, resource recovery, waste-to-energy, carbon sequestration, renewable energy, algal biofuels, biodiesel, biogas, biomethane, anaerobic digestion, enzymatic pretreatment, thermochemical pretreatment, Algal Turf Scrubber, mixotrophic and heterotrophic algal cultivationThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.