Anaerobic biogasification of undiluted dairy manure in leaching bed reactors G.N. Demirer a, * ,1 , S. Chen b a Department of Environmental Engineering, Middle East Technical University, 06531 Ankara, Turkey b Department of Biological Systems Engineering, Washington State University, Pullman, WA 99163, USA Accepted 3 November 2006 Available online 16 January 2007 Abstract Dry anaerobic digestion of high solids animal manure is of increasing importance since conventional slurry digestion is not an effec- tive system for these manures. The investment costs for large-size reactors, costs for heating these reactors, handling, dewatering, and the disposal of the digested residue decrease the benefits of conventional slurry anaerobic digestion for high solids animal manure. Even though leaching bed reactors (LBR) constitute a promising option for dry anaerobic biogasification of animal manure, no study is cited in the literature for animal manure, excluding a single study on cattle waste which utilized a similar concept in a different experimental set-up, namely a packed bed digester. Therefore, this work was undertaken to investigate the anaerobic biogasification of undiluted dairy manure in LBRs. To this purpose anaerobic leaching bed reactors (ALBR) packed with a mixture of dairy manure, anaerobic seed and wood powder/chips were operated. The ALBRs were fed with water, and the leachate that was collected from their effluents was sub- jected to biochemical methane potential (BMP) experiments to determine the biogas production. The results revealed that LBRs can successfully be applied to anaerobic digestion of undiluted dairy manure with around 25% improvement in biogas production relative to conventional (slurry) anaerobic digesters. Ó 2006 Elsevier Ltd. All rights reserved. 1. Introduction Concentrated animal feeding operations along with a cor- responding absence of suitable manure disposal methods have been shown to cause significant environmental and public health problems (Gilliam, 1995; Sa ´nchez et al., 1995; Bouwman and Van Der Hoek, 1997). Continued sus- tainability of animal agriculture and its allied industries will be largely dependent on improvements being made in man- aging these problems. Moreover, diminishing supplies of conventional energy sources have increased the need for alternative and renewable energy sources. In recent years, anaerobic biogas production has gained attention as a waste management technology capable of meeting both of the above mentioned environmental and energy concerns. The dual benefits from environmental pollution control and energy production include microbiological degradation of organic pollutants, greater inactivation of pathogens and weed seeds, reduction of global warming potential, diminish- ment of odor, and of course the meeting of national energy and economic needs by reducing the reliance on foreign oil imports (Gu ¨ngo ¨ r-Demirci and Demirer, 2004; Harikishan and Sung, 2003). Additionally, energy taxes on fossil fuels and a growing interest in governmental measures and credits for sustainable environmental and energy solutions further encourage the exploitation of anaerobic digestion and place it as a highly competitive alternative for the treatment of ani- mal manure (Salminen and Rintala, 2002). Even though anaerobic digestion (AD) is an established farm animal manure bioconversion technology (Hall et al., 1985; Hobson, 1991; Hobson and Wheatley, 1993; Lusk, 1998; Demirer et al., 2000; Misi and Forster, 2001; Ahring 0956-053X/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.wasman.2006.11.005 * Corresponding author. Tel.: +90 312 210 58 67; fax: +90 312 210 26 46. E-mail address: goksel@metu.edu.tr (G.N. Demirer). 1 At the time of the study, the author was affiliated with the Department of Biological Systems Engineering, Washington State University, Pullman, WA 99163, USA. www.elsevier.com/locate/wasman Available online at www.sciencedirect.com Waste Management 28 (2008) 112–119