Due limited natural resources and increased greenhouse gas emissions, substitution of fossil fuels with renewable bio-energy has been encouraged United Nations Framework Convention on Climate Change (UNFCCC). According to the United Nations, by the year 2050, up to 77% of the world's energy demand could be supplied by renewable energy sources [1]. However, because biomass has gained economic interest, further expansion of biogas production is increasingly dependent on the exploitation of new sources of biomass.Biomass is composed of carbon-rich materials including plant residues, animal excrements and bio-waste from households and industry [2]. Unused or discarded biomass residues from agriculture are a potential energy resource, even though those materials can be a source of green house gas (GHG) emissions causing climate change. The potential energy production from crop residues and animal wastes is globally estimated at about 34 EJ (exajoule = 10 18 joules) out of a total 70 EJ [3]. Biomass is a renewable energy resource derived from all organic materials produced by both human and natural activities. It is a complex mixture of carbohydrates, fats and proteins. Plant residues are regarded as the main source of biomass because they usually contain 40%-50% cellulose, 20%-35% hemi-cellulose, and 15%-30% lignins. Therefore, biomasses like the plant residues of grapeseed, rice, barley and wheat could serve as alternative bio-energy resources.The grand total of generated waste from livestock, agro-industrial waste and crop residues is estimated at 58,010 kt yr -1 in Korea. Potential methane production from agricultural wastes including livestock, crop residues and agro-industrial wastes is estimated at 436 kt yr -1 [4]. Anaerobic digestion (AD) for methane production using crop residues in the agricultural sector is becoming necessary in areas with limited natural resources like Korea. Over the past decade, AD of biomass originating from agriculture to produce methane gas has attracted much attention from government authorities, academia, and industry in Korea.AD is a biological process that converts the solid or liquid biomass into a gas in the absence of oxygen. Many studies on AD in Korea have focused on swine manure and food wastes as substrates [5][6]. AD has many environmental benefits including the production of a renewable energy carrier, nutrient recycling and the reduction of waste volumes [7][8][9]. Therefore, different types of organic wastes such as sewage sludge, industrial wastes, slaughterhouse waste, fruit and vegetable wastes, manure and agricultural biomass have been successfully digested under anaerobic conditions. Each of these wastes has been digested separately or co-digested with other wastes [10][11][12].However, not many papers have been published on the mono-digestion of crop residues [13][14][15][16], while thermophilic AD has been mainly the subject of more recent studies.The organic loading rate and hydrologic retention time (HRT) are two major parameters used for sizing a digester, an...