Sustainable Energy, 2017, Vol. 5, No. 1, 32-37 Available online at http://pubs.sciepub.com/rse/5/1/5 ©Science and Education Publishing DOI:10.12691/rse-5-1-5 Optimization of Biogas Production in Dry Anaerobic Digestion of Swine Manure by the Use of Alkalinity Index to Monitor a Prototype Cylindrical Digester Ondiba Hesborn Andole 1,* , Zhongfang Lei 2 , Zhenya Zhang 2 , James Raude 3 , Christopher Kanali 3 1 Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan 2 Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan 3 School of Biosystems and Environmental Engineering, Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya *Corresponding author: hondiba@gmail.com Abstract Anaerobic digestion (AD) is one of the best alternative sustainable technologies for energy production and recovery from organic solid wastes. Up to now dry AD has been commercialized in the treatment of municipal solid wastes. Little information could be found on the practical application of dry AD to manure wastes or waste activated sludge. This study aimed at testing the feasibility of using alkalinity to manage dry AD system for swine manure treatment and clarify its effect on the stability and efficiency of the newly-developed prototype cylindrical digester system. A prototype cylindrical digester with a diameter of 40 mm and a volume of 1.3 liters was designed and fabricated. It was operated under mesophilic conditions (38°C). The alkalinity of manure was increased by 3000 g/L (R 1 ) and 6000 g/L (R 2 ) by adding sodium bicarbonate with the raw swine manure as the control (R 0 ). Results showed that R 1 and R 2 maintained a relatively higher level of alkalinity during the whole operation compared to the control (R 0 ). Only one peak appeared in biogas production for the control reactor (R 0 ) which almost ceased on day 12, whereas R 1 and R 2 exhibited two biogas peaks. The 30 days’ biogas yield for R 2 was 276.6 ml/g-VS added while R 1 was 204.8 ml/g-VS added which corresponds to an increase by 2.7- and 1.7- fold respectively as compared to the control (R 0 ). 2.2- and 4.1-fold increase in methane production was achieved in R 1 and R 2 respectively as compared to R 0 . This difference is most probably attributable to the high alkalinity in R 1 and R 2 that stabilized the digestion process and minimized the influence of pH variations on methanogenesis. Keywords: alkalinity, dry anaerobic digestion, prototype cylindrical digester, swine manure Cite This Article: Ondiba Hesborn Andole, Zhongfang Lei, Zhenya Zhang, James Raude, and Christopher Kanali, “Optimization of Biogas Production in Dry Anaerobic Digestion of Swine Manure by the Use of Alkalinity Index to Monitor a Prototype Cylindrical Digester.” Sustainable Energy, vol. 5, no. 1 (2017): 32-37. doi: 10.12691/rse-5-1-5. 1. Introduction Kenya, a sub-Saharan African country, has a national electrification level of 36% and thus only about 12.6% of the rural households have access to electricity [1]. Nationally, 69% of all households use firewood for cooking [2]. Inadequate power supply capacity due to rise in demand for electricity, which is growing faster than the ability to install additional generation plants is one of the greatest challenges. Furthermore, over-dependence on hydro-power, which exposes the country to power rationing due to extreme weather conditions that result in drought worsens this situation. The need for alternative energy resources is therefore imperative. Dry Anaerobic Digestion (AD) has attracted increasingly extensive attentions in the studies of biogas fermentation with advantages of water-saving, higher volumetric organic loading rate, higher biogasification performance, smaller reactor capacity requirement, less energy used for heating, easier handle ability of digestate, and higher energy recovery as compared to wet AD [2,3]. This process is more feasible to a wide range of organic wastes including waste water sludge from industries with the recovery of renewable energy and reduction in pollution load [4]. The process also results in a lower production of leachate and easy handlings of digested residues that can further be treated by aerobic composting processes and used as organic fertilizer [5]. In this regard, dry AD is a remarkable method that could offer potential by-products such as fertilizer for the large population of farmers as well as energy generation. It is the most promising technology based on its characteristics and advantages. Over the past 20 years, different commercialized dry AD systems have been developed and marketed by different companies in Europe. The Kompogas, Valorga and Dranco dry AD systems are the most prevalent and have been mainly used for commercially processing of municipal solid waste, kitchen waste, or yard waste [6]. However, up to now there is no commercial dry AD system for treatment of manure waste. Alkalinity is often referred to as buffer capacity in AD, which is the equilibrium of carbon dioxide and bicarbonate