Ramin Yazdani

Ramin Yazdani

University of California at Davis, Ph.D.
EREF Scholar 2008

Factors Limiting Aerobic Degradation During Aerobic Bioreactor Landfilling

Project Description (while EREF Scholar):
The goal of my research project is to analyze the data gathered over the past eleven years of research for the anaerobic and aerobic bioreactor landfills. The analysis of the experimental data collected as discussed below will aid in understanding the performance of bioreactor landfills. Unless the performance of full-scale bioreactor landfills are well understood, they will continue being built and functioning on an “ad hoc” process, making it difficult to predict under what operating conditions they “work” or they “fail.”

Dissertation Organization
The objective of my study will be to carry out data analysis which will be organized and appear in a separate chapter and each chapter will be prepared as a technical, peer-reviewed journal article. Each paper will be written and published in peer-reviewed technical journals. A brief description of each chapter is presented below.

Technical Chapter 1 – The Influence of Leachate Recirculation on Anaerobic Bioreactor Performance
The main objective of this research project is to develop better methods for management of solid waste disposed in landfills, to reduce long-term environmental impacts, and to maximize the amount of renewable energy produced from landfill gas while minimizing the fugitive gas emissions.

Methane generation and waste stabilization are accelerated by improving biological reaction within a demonstration test cell and two full-scale demonstration cells while leachate is added and recirculated. A control cell is operated in parallel with no liquid addition or recirculation. Landfill gas capture is maximized, and emissions reduced to minimal levels, by a combination of surface membrane containment and gas collection system under vacuum. Each bioreactor cell is highly instrumented to gather data and determine system performance.

In this paper, data collected from the anaerobic bioreactor landfills constructed at the Yolo County Central Landfill for the past eleven years will be used to evaluate the performance of the anaerobic bioreactor landfills. The data will be analyzed to determine whether the expected benefits of anaerobic bioreactor have actually been achieved.

Technical Chapter 2 – The Influence of Leachate Recirculation and Air Flow on Aerobic Bioreactor Performance
The primary objective of aerobic landfill operation is to control air and moisture conditions such that aerobic waste degradation occurs throughout the landfill. The aerobic degradation of waste in landfill can rapidly increase the rate of waste decompisition and settlement, decrease the production of methane gas, improve leachate quality, and decrease the quantity of leachate that needs treatment.

In this project, a bioreactor cell at the Yolo County Central Landfill was operated aerobically for five years intermittently to evaluate the influence of air-flow operations and liquid addition on aerobic refuse degradation. This 2.5-acre landfill cell was filled with 15,000 tons of MSW and instrumented with temperature, resistivity moisture sensors, and small-diameter tubes for collecting gas samples and measuring fluid pressures throughout the landfill. An array of horizontal wells located in three vertical layers was used to add liquid (fresh or recirculated) or to pull air into the landfill. Because air entered the landfill through the landfill surface and was collected in a central vacuum line, the “effluent” gas from the landfill could be easily monitored during aerobic operations. In this chapter, data collected from the aerobic bioreactor will be analyzed to determine if the expected benefits of aerobic bioreactor have actually been achieved.

Technical Chapter 3 – Economics and Cost-Benefit Analyses of Anaerobic and Aerobic Bioreactors
In this chapter, economic analyses of bioreactors will be evaluated based on the actual costs and benefits. Cost of a bioreactor landfill will include the following:
1. Costs of bioreactor landfill design, construction and operation.
2. Construction costs associated with the installation of enhanced leachate recirculation devices and landfill gas collection systems.
3. Operating costs resulting from increased leachate recirculation, gas generation, permitting fees, and equipment/manpower needs.
4. Changes in waste management costs, such as comparisons of additional operating costs against savings.

Potential benefits of bioreactor landfills will include the following:
1. Reduced leachate treatment/disposal costs.
2. Saved landfill space.
3. Extended landfill life.
4. Deferral of new cell construction.
5. Post-closure savings from fewer monitoring and financial assurance requirements.
6. More efficient gas collection with potential for revenues from energy production.
7. Avoided methane emissions, including revenues from energy production and greenhouse gas credits for avoided emissions.
8. Potential value of carbon credits.

Ramin moved from Iran to the United States in 1978. He received an A.S. degree from West Valley College in Saratoga, CA and then attended California Polytechnic State University in San Luis Obispo, where he majored in BioResource and Agricultural Engineering. He then earned his M.S. at the University of California at Davis, after which he accepted a job with the Soil Conservation Service in Santa Maria, CA. After a year Ramin, his wife and two children moved back to Davis where he accepted a position with the Yolo County Public Works Department as a civil engineer in design and construction of roads and landfills. After obtaining his California professional civil engineering registration, Ramin was promoted to Associate and then Senior Civil Engineer. By 1993 he was in charge of the design, construction and overall management of the first landfill Bioreactor demonstration project at the Yolo County landfill. Later he was promoted to Chief County Engineer and then the Assistant Director of Public Works position. In 2001 Ramin initiated the design and permitting of the full-scale Bioreactor EPA XL Project for the Yolo County landfill. This project was one of the first Bioreactor projects which was approved by the federal EPA and Cal-EPA in both the state of California and in the U.S. In 2002, Ramin left his position as an assistant director of public works to pursue his Ph.D.

Research Publications:
Ramin Yazdani. Quantifying Factors Limiting Aerobic Degradation During Aerobic Bioreactor Landfilling and Performance Evaluation of a Landfill-Based Anaerobic Composting Digester for Energy Recovery and Compost Production