Grantee Research Project Results
Final Report: An Innovative Design for Anaerobic Co-Digestion of Animal Wastes for Sustainable Development in Rural Communities
EPA Grant Number: SU834318Title: An Innovative Design for Anaerobic Co-Digestion of Animal Wastes for Sustainable Development in Rural Communities
Investigators: He, Qiang , Hawkins, Shawn A. , Cox, Chris D. , Sneed, Caroline , Jacobs, David , Ko, Edward , Zamudio, Esteban , Hsu, Julia , Hsueh, Michael , DeBlois, Reese , Stephens, Timothy , Zhang, Yan , Zhu, Zhenwei
Institution: University of Tennessee
EPA Project Officer: Page, Angela
Phase: I
Project Period: August 15, 2009 through August 14, 2010
Project Amount: $10,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2009) RFA Text | Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Sustainable and Healthy Communities , P3 Challenge Area - Air Quality , P3 Awards , Sustainable and Healthy Communities
Objective:
Animal waste poses one of America's most serious pollution problems, because the natural decomposition of livestock manures releases large quantities of pathogens, excess nutrients, and greenhouse gas methane, among other pollutants. Anaerobic digestion technology offers great potential in sustainable animal waste management with the capacity for 1) destruction of pathogens, 2) production of biogas/methane as a renewable fuel, and 3) reduction of greenhouse gas emission by harvesting methane gas. However, in the United States, the economics of anaerobic digestion using animal wastes as a primary feedstock remain unattractive due to technical challenges, such as the low biogas yield of dilute dairy manure, and process inhibition characteristic of poultry waste.
The Phase I project aims to develop an innovative design for anaerobic co-digestion of dilute dairy waste and poultry manure, which are difficult to treat as the sole substrate with anaerobic digestion, to greatly enhance the process efficiency and biogas yield. This innovative design exploits the potential synergistic effects of mixing these two waste streams of complementary characteristics: the high solids content of poultry manure makes up for the low solids content of dilute dairy waste, while the dilution effect of dairy waste minimizes the potential for ammonia inhibition of the nitrogen-rich poultry manure. We expect that this synergy will result in considerable improvement in anaerobic digestion performance.
This innovative anaerobic co-digestion design will significantly enhance the treatment efficiency of animal waste and the production of biogas as a renewable energy. This will meet not only the need of livestock producers for a sustainable animal waste management strategy, but also the need of the public and society for improved environmental quality. The production of biogas as a renewable energy also will enhance the energy security and ultimately the prosperity of our society. Moreover, the ability of the proposed design to reduce greenhouse gas emission will help to protect our planet by mitigating the risk of global climate change.
The specific objectives of the Phase I project are to:
- Design and develop an innovative anaerobic co-digestion process for the treatment of dairy manure and poultry waste;
- Assess the technical feasibility of anaerobic co-digestion in lab-scale systems;
- Assess the economic feasibility of anaerobic co-digestion of dairy manure and poultry waste in local rural communities;
- Implement the P3 project as an educational tool.
The results from the Phase I project provide the optimized design concept and process parameters for the implementation of a pilot-scale anaerobic co-digestion model system as a sustainable solution to animal waste management.
Summary/Accomplishments (Outputs/Outcomes):
With the aim of the Phase I project to develop an innovative anaerobic co-digestion design for the treatment of dairy manure and poultry waste, our Phase I team has evaluated the technical and economic feasibility of the anaerobic co-digestion design concept with a thorough investigation into the waste characteristics, batch treatability tests, continuous digestion optimization, and economic feasibility analysis.
Analyses of waste composition show poultry waste contained much higher total solids (~56%) than dairy manure (2.3%), an indication of higher organic content and biogas potential. In contrast, the higher nitrogen content of poultry waste suggests potential inhibition of the digestion process by excess ammonia, which supports the expectation of the co-digestion design concept that the dilution of nitrogen-rich poultry waste by nitrogen-poor dairy manure would reduce the risk of inhibition of ammonia from poultry waste. These results suggest that the use of dairy manure and poultry waste as co-substrates in anaerobic digestion would have the benefit of enhanced process efficiency and biogas yield. Batch treatability tests confirmed that poultry waste has higher methane potential than that of dairy manure. Thus, better process anaerobic digestion performance could be achieved by maximizing poultry waste loading. Moreover, complete digestion of animal wastes was shown to be accomplished with a retention time of 20 days at operational temperatures above 20°C.
Building upon the operational parameters from batch tests, multiple lab-scale continuous anaerobic co-digesters were developed and operated for more than 5 months to determine critical process parameters such as hydraulic retention time and organic loading rates. Optimal hydraulic retention time was selected as 20 days as biogas yield and organic removal did not improve when hydraulic retention time was greater than 20 days. As a result, a 20-day hydraulic retention time was selected in all subsequent continuous digesters. Optimal organic loading rates of dairy manure and poultry waste were determined by step-wise increase in the organic loading of manure-fed continuous digesters by the addition of organic-rich poultry waste. Our results show that the addition of organic-rich poultry waste as a co-substrate resulted in increases in biogas production, with the highest biogas production rate observed at the organic loading of 1.5 gVS/L·d. However, organic loading rates higher than 1.5 gVS/L·d led to the collapse of digester performance, likely a result of process inhibition by excess levels of ammonia produced during the breakdown of poultry waste in anaerobic digestion, which is consistent with the high nitrogen content of poultry waste. Furthermore, the volatile fatty acids (VFA) concentrations also rose dramatically from less than 5 mg/L to greater than 1,000 mg/L when organic loading reached 1.8 gVS/L·d, another evidence that the digestion process was inhibited at higher loadings of poultry waste. These results indicate that the optimal organic loading rate is 1.5 gVS/L·d, which corresponding to the optimal ratio of approximately 2:1 (gVS/gVS) between dairy manure and poultry waste in the feed. Overall, the addition of organic-rich poultry waste improved biogas yield by more than 75% at optimal conditions.
While the anaerobic co-digestion design is shown to be technically feasible, the economic feasibility is paramount in the decision-making process for the implementation of this innovative design in rural communities. Our Phase I team has collaborated with USDA Natural Resources Conservation Services (NRCS) EQIP grant program and Farm Credit Services of Mid-America to determine the economic feasibility of the anaerobic digestion design developed in the Phase I project. The EPA AgStar Farmware analysis indicates that the anaerobic digestion design was, in general, more feasible in larger farms with a payback period of less than 10 years. The recovery of bedding material from anaerobic digestion was a key factor that would strengthen the economic feasibility of anaerobic digestion with the current green energy rates and financial terms. Given the importance of the scale of farms to the economic feasibility, it is critical that the design developed in this project is implemented as a centralized facility that serves multiple farms to improve economic sustainability.
Conclusions:
The Phase I project has been very successful in developing the innovative anaerobic co-digestion design for the treatment of animal waste. Our team has demonstrated both technical and economic feasibility of this design as a sustainable solution to the challenges of environmental pollution from animal wastes. Results from Phase I clearly show that the anaerobic co-digestion design has successfully balanced the P3 elements. People will benefit from the educational value inherent in the collaborative design process used and the concept of sustainable development. The people also will benefit directly from improved environmental protection and sustainable development of the communities. Agricultural communities will gain prosperity because the P3 design is shown to provide a cost-effective waste management strategy for the sustainable development of the livestock industry in rural communities. The sustainable design developed in the Phase I project can be readily replicated for application in communities around the globe and will definitely be of benefit to the planet in reducing environmental pollution and increasing the use of renewable energy—biogas. More importantly, the innovative design and process parameters optimized in the Phase I project will serve as the basis for the Phase II project to implement the anaerobic co-digestion design concept at the pilot scale.
Phase II Objectives and Strategies:
The objectives of Phase II project are to: 1) design and build a pilot-scale continuous anaerobic co-digestion system for the treatment of dairy manure and poultry waste; 2) operate and monitor the performance of the continuous anaerobic co-digestion system; 3) develop a user-friendly economic feasibility model to evaluate anaerobic co-digestion processes; and 4) partner with government agencies and local livestock and poultry producers to promote and design a full-scale anaerobic co-digester for dairy waste and poultry manure. The primary output of the Phase II project is an efficient pilot-scale anaerobic digester system designed with guidelines developed in Phase I. To achieve these objectives, specific milestones have been set in the project schedule and the success of the project will be evaluated by achieving the following:
- Design and construction of a pilot-scale anaerobic co-digester system that is simple, efficient, and readily replicable.
- Operation of a well-functioning digestion system with optimal operational conditions: co-digestion ratio, organic loading rate, hydraulic loading rate, and operational temperature.
- Development of an economic feasibility model capable of assessing anaerobic digestion of multiple substrates.
Journal Articles on this Report : 5 Displayed | Download in RIS Format
Other project views: | All 6 publications | 5 publications in selected types | All 5 journal articles |
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Chen S, Zhu Z, Park J, Zhang Z, He Q. Development of Methanoculleus-specific real-time quantitative PCR assay for assessing methanogen communities in anaerobic digestion JOURNAL OF BIOSCIENCE AND BIOENGINEERING 2014;116(6):1474-1481. |
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Chen S, He Q. Persistence of Methanosaeta populations in anaerobic digestion during process instability. JOURNAL OF INDUSTRIAL MICROBIOLOGY AND BIOTECHNOLOGY 2015;42(8):1129-1137 |
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Chen S, He Q. Enrichment and specific quantification of Methanocalculin anaerobic digestion. JOURNAL OF BIOSCIENCE AND BIOENGINEERING 2015;120(6):677-683 |
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Chen S, He Q. Distinctive non-methanogen archaeal populations in anaerobic digestion. APPLIED MICROBIOLOGY AND BIOTECHNOLOGY 2015;100(1):419-430. |
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Zhang Y, Zamudio Canas EM, Zhu Z, Linville JL, Chen S, He Q. Robustness of archaeal populations in anaerobic co-digestion of dairy and poultry wastes. Bioresource Technology 2011;102(2):779-785. |
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Supplemental Keywords:
bio-methane, agricultural waste, sustainable development, bioenergy, climateThe 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.