Dana Kirk

Effects of coffee processing residues on anaerobic microorganisms and corresponding digestion performance

The objective of this study was to delineate the effects of different coffee processing residues on the anaerobic microbes and corresponding digestion performance. The results elucidated that mucilage-rich feed enhanced the accumulation of methanogens, which consequently led to better digestion performance of biogas production. Fifty percent more methane and up to 3 times more net energy (heat and electricity) output were achieved by the digestion of the mucilage-rich feed (M3). The microbial community and statistical analyses further elucidated that different residues in the feed had significant impact on microbial distribution and correspondingly influenced the digestion performance.

Corrigendum to “Effects of coffee processing residues on anaerobic microorganisms and corresponding digestion performance” [Bioresour. Technol. 245 (2017) 714–723]

a Agricultural Engineering, University of Costa Rica, San José, Costa Rica Agronomy Research Center, University of Costa Rica, San José, Costa Rica National Institute for Innovation and Transfer of Agricultural Technology, Ministry of Agriculture, San José, Costa Rica d Fabio Baudrit Experimental Station, University of Costa Rica, San José, Costa Rica Microbiology and Molecular Genetics, Michigan State University, MI, USA Danish Genome Institute, Aarhus, Denmark g Cellular and Molecular Biology Research Center, University of Costa Rica, San José, Costa Rica Anaerobic Digestion Research and Education Center, Biosystems and Agricultural Engineering, Michigan State University, MI, USA

Construction, Start-Up, and Operation of a Plug Flow Anaerobic Digester on the Michigan State University Dairy Farm

In September of 2011, construction was completed on a 225,000 gallon plug flow anaerobic digester at the Michigan State University Dairy Teaching and Research Farm. The anaerobic digester is part of an integrated research complex intended to advance waste to resource projects. Start-up of the digester commenced in late September 2011 with the system utilizing dairy manure mixed with wood shavings as bedding. In November the feedstock blend was expanded to include cafeteria food waste as well as other agricultural waste products (poultry eggs). Biogas was scrubbed of hydrogen sulfide and then utilized to fuel a boiler that supplied the operation with the necessary heat to maintain the digester at mesophillic temperatures. New feedstock is preheated by passing through a heat exchanger prior to entering the digester. This digester was built with a limited amount of monitoring equipment resulting in the need for frequent manual observations to ensure successful operation. Topics addressed in this paper include start-up of the digester, modifications to the system, and how a combination of lab analysis, engineering calculations, and visual observations were used to manage the digester. Lab analysis consisted of regular pH, electrical conductivity (EC), alkalinity, volatile fatty acid (VFA), as well as total and volatile solid measurements. Gas chromatography (GC) was also conducted on a regular basis to ensure an adequate methane concentration for boiler operation, detect changes in system stability, and verify that hydrogen sulfide levels did not become excessive. The result of this research will be the development of a protocol for the start-up and operation of an anaerobic digester especially in situations where automated data collection is limited.

Statistical Verification of a Biochemical Methane Potential Test

The Biochemical Methane Potential (BMP) assay is commonly used for determining the viability of feedstocks for anaerobic digestion (AD). The results from these tests have been adopted for a variety of applications; including preliminary screening, toxicity testing, as well as the design and prediction of biogas production from full-scale operational digesters. The use of the BMP as the foundation for making the aforementioned decisions is problematic because of the variation in BMP protocols available and a lack of statistical analysis to verify accuracy of the results. This paper will detail selected results from a series of BMP assays conducted on several dairy manure and milking center wastewater samples, collected over a period of six weeks from three New Mexico dairy farms. The manure and wastewater samples were characterized individually and also as an array of blends. Each blend was set up in triplicate in serum bottles with the contents of each bottle being tested individually for a series of parameters both pre and post-digestion (pH, alkalinity, chemical oxygen demand (COD), total solids (TS), total volatile solids(VS) and ammonia). At the end of the BMP, a biogas potential ratio was calculated based on the initial VS and COD (mL per mg VS Fed and mL per mg COD Fed derived from pre-digestion analysis. A statistical analysis was completed to compare this method for calculating the biogas potential ratio with a more traditional method.