Grantee Research Project Results
Final Report: Closing the Carbon Loop: Growing Algae Using Sustainable CO2 from Bio-waste
EPA Grant Number: SU833931Title: Closing the Carbon Loop: Growing Algae Using Sustainable CO2 from Bio-waste
Investigators: Venable, Mark E. , Porras, Erica , Ramsdell, Jeff
Institution: Appalachian State University
EPA Project Officer: Page, Angela
Phase: I
Project Period: August 15, 2008 through August 14, 2009
Project Amount: $10,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2008) RFA Text | Recipients Lists
Research Category: P3 Challenge Area - Air Quality , Pollution Prevention/Sustainable Development , P3 Awards , Sustainable and Healthy Communities
Objective:
Unstable oil prices , depleting reserves (Koppelaar, 2005), and the threat of global warming (Solomon et al., 2007) have made the development of renewable domestic transportation fuels a high priority in the U.S . However, the conventional biofuel crops used in the U.S. such as soybeans and corn are limited by their yielding potential. Even if the U.S. switched to growing canola oil seed for biodiesel (the highest oil yielding crop producible in the U.S.) some estimate it would require 122% of the current U.S. crop area to meet 50% of the total U.S. fuel consumption needs (Chisti, 2007, p. 296).
Microalgae is a next generation feedstock that has the potential to significantly offset fossil fuel usage. Studies show that microalgae strains can range between 1-40% triglyceride content by dry weight, and can more than double its biomass each day (Sheehan, Dunahay, Benemann, & Roessler, 1998). The oil can be extracted and chemically converted into biodiesel, which can be used in diesel vehicles with few modifications. Projections show that an area equivalent to 1-3% of the total U.S. cropping area would be sufficient to supply all the U.S transportation fuel needs (Chisti, 2007, p. 296).
In order to achieve the significant algae production rates required, large sources of concentrated carbon dioxide must be supplied to the algae . Almost all algae-to-biofuels propose utilizing the fossil fuel emissions from central power stations and industrial plants for C02. However, upon combustion of the algae-based biodiesel, the carbon dioxide is released, ultimately resulting in a net gain of C02 in the atmosphere. This design does not close the carbon loop and the health and environmental impacts of fossil fuel mining and extraction persist.
The algal culture system proposed in this P3 project utilizes sustainable sources of C02 from the abundant and untapped resource of biowaste. Through the anaerobic digestion of community food waste, agricultural waste, animal waste, and municipal solid waste, biogas may be produced, which can be combusted for energy production, and the emissions can then be utilized for algae production. This results in net zero gain of C02 in the atmosphere.
This model more completely closes the carbon loop for transportation fuels, and at the same time makes possible a highly distributed fuel production model that empowers local communities and their economies. This model also presents the concept that a community’s organic waste may be able to sustain its transportation needs, and algae can be grown at any organic waste source (farms, livestock operations, landfills, hotels, schools). According to a study funded by the ASP, the amount of available C02 from anaerobic digestion of biomass waste (type of biomass was not specified) in the U.S. was 230 X 106 kg/year in the year in which the study was conducted (Sheehan et al., 1998). This quantity was comparable to the total C02 resource from fossil steam plants, a promising indication that anaerobic digestion of biomass is itself an abundant source of C02 for microalgae culturing.
The purpose of Phase I of this project is to design, build, and implement a scalable model of an algal culture system that utilizes sustainable C02 sources, rather than C02 emissions from fossil fuels, which is the more widely proposed model. The system was designed to provide real data for insight into the true feasibility of this closed loop concept. In addition, by building a small research system in Phase I, a more effective design may be implemented in Phase II.
The research focus of Phase I was three-fold: (1) explore anaerobic digestion of bio-waste as a renewable C02 source for algae growth, (2) collect and quantifying community bio-waste for anaerobic digestion, (3) and study and optimize algae cultivation.
Proposed Phase II Objectives and Strategies
The Phase II goals will be to extend the Phase I efforts by building upon relationships built during Phases I to create a permanent and long term research facility dedicated to ongoing investigation into algae and in particular this sustainable model. The Phase II funding will provide the resources to build up a permanent and better equipped research facility with the necessary devices and equipment to carry out an effective feasibility study of all the processes associated with the system including anaerobic digestion, algae cultivation, algae harvesting, and oil extraction. In phase II, we will implement system improvement recommendations gathered in Phase I, greatly improve measurement equipment and sensors, test and optimize the entire system and all processes, and utilize the space for long term programs for student research and educational tours.
Summary/Accomplishments (Outputs/Outcomes):
We designed a hybrid algal culturing system that incorporated both a closed photobioreactor and open ponds. The system was sized to theoretically produce enough oil to supply one 40 mpg car 100% of its biodiesel needs, as well as fit within a 24’ X 80’greenhouse. Previously published literature was used to determine algae and oil productivities and extrapolate the systems annual oil productivity.
Using volumetric productivity levels reported in the literature, the estimated oil output of the system was 211 gallons per year. This would provide enough fuel for the annual needs of one energy efficient vehicle. With a footprint of only 576 square ft, this would be equivalent to 75 cars fueled per acre of algae system, requiring 100 lbs of organics/acre/day to be anaerobically digested to produce the C02 necessary for this productivity. These numbers are based off of the expected output of our current small scale design, which is not yet optimized for maximal space utilization, so they are most likely conservative.
Preliminary, non-optimized runs of the photobioreactor showed that the chambers that were purged with C02 grew well, approximately tripling in three days ending at 0.442 g/L while those not given C02 did not grow at all. Those that were stressed with C02 deprivation, however, accumulated oil. Stressors of various types, including carbon deprivation stimulates algae to switch from growth phase to oil production. Those that were stressed contained 0.33g/L triglycerides while those unstressed contained 0.067 g/L.
Supplemental Keywords:
Biogas, bio-based feedstocks, anaerobic remediation, renewable feedstocks, waste to value, energy recovery, Global climate, innovative technologies, waste reduction, atmosphere, cleaner production/pollution prevention, renewable fuels, petroleum, Environmental Engineering, alternative energy source, alternative to petroleum diesel fuel, waste minimization, sustainable infrastructure design;, RFA, Scientific Discipline, Sustainable Industry/Business, POLLUTION PREVENTION, Sustainable Environment, Energy, Environmental Chemistry, Technology for Sustainable Environment, Environmental Engineering, sustainable development, environmental sustainability, alternative materials, biomass, alternative fuel, biodiesel fuel, energy efficiency, energy technology, alternative energy sourceThe 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.