Methane enhancement and asynchronism minimization through co- digestion of goose manure and NaOH solubilized corn stover with waste activated sludge Muhammad Hassan a , Weimin Ding a, * , Muhammad Umar b , Kunlun Hei c, d , Jinhua Bi c, d , Zhendan Shi e a College of Engineering, Nanjing Agricultural University, Nanjing, Jiangsu 210031, China b Department of Food Engineering, University of Agriculture, Faisalabad 38000, Pakistan c College of Resource and Environmental Science, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China d Institute of Agricultural Resources and Environment, Jiangsu Academy of Agricultural Science, Nanjing, Jiangsu 210014, China e Institute of Animal Science, Jiangsu Academy of Agricultural Science, Nanjing, Jiangsu 210014, China article info Article history: Received 9 March 2016 Received in revised form 29 October 2016 Accepted 2 November 2016 Available online 15 November 2016 Keywords: Alkali solubilized corn stover Asynchronism minimization Carbon to nitrogen ratio optimization Methane enhancement abstract Anaerobic co-digestion of corn stover (CS) and goose manure (GM) was carried out in the present study at four composition levels. Corn stover was pretreated to enhance its lignocellulosic digestibility. The NaOH pretreatment effect on the chemical composition of the corn stover was also determined and the methane production from all the composition levels was found significant (P < 0.05) as compared with the control. The cumulative methane production of treatment C2 (0.6 CS: 0.4 GM), C3 (0.4 CS: 0.6 GM) and C4 (0.2 CS: 0.8 GM) were 86.1%, 92.1% and 83.1% enhanced as compared with the control respectively. On the basis of the experimental results, it was concluded that a C/N ratio between 20 and 30 was found optimum to enhance methane production. Asynchronism minimization was observed for all the treat- ments. Process chemistry of the whole co-digestion process like total volatile fatty acids (TVFAs), alcohol production pattern, pH, soluble chemical oxygen demand (CODs), total available ammonia (TAN) and free available ammonia (FAN) were deeply monitored. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction With the growing population of the world and huge urbaniza- tion in the developing countries, waste generation trends have multiplied during the past decades. In addition to agricultural ac- tivities, commercial poultry production is also a common rural life style within the rural areas worldwide. Goose meat is considered one of the most favorite protein sources in China and almost 93% of the world goose is reared in China [1], resulting in the annual production of millions of tons of goose manure. As the leader of the agricultural production, China also produces 216 million of tons of corn stover annually, and about half the straw production is burnt in the fields in standing conditions [2]. Burning of these crop resi- dues and direct use of livestock manure as fertilizer in the agri- cultural fields emits a high concentration of methane, carbon dioxide and nitrogen oxides that contribute greatly to greenhouse gas (GHG) emissions [2,3]. In such a situation anaerobic digestion technology emerges as a promising option with useful by product as methane [3,4] and is gaining more importance than the other conventional energy re- sources used on a commercial scale. Anaerobic digestion is basically a microbial and biochemical process [5,6] where a mixture of gases consisting mostly of methane and carbon dioxide is produced [7]. Anaerobic digestion process consists of four steps; hydrolysis, acidogenesis, acetogenesis and methanogenesis while hydrolysis is considered as AD rate limiting step in agricultural biomass utili- zation [6,8]. All types of agricultural biomass are rich in organic contents, protein, fats, carbohydrates and cellulose that can be a suitable feedstock for anaerobic digestion and hydrolyzed further to produce methane as a final product with the help of different microbial activities [9]. Anaerobic digestion is the most suitable and environmental friendly option [4] to reduce the risk of carbon and nitrous oxide emissions from organic waste along with the energy and bio-fertilizer production [7,10,11]. * Corresponding author. E-mail address: wmding@njau.edu.cn (W. Ding). Contents lists available at ScienceDirect Energy journal homepage: www.elsevier.com/locate/energy http://dx.doi.org/10.1016/j.energy.2016.11.007 0360-5442/© 2016 Elsevier Ltd. All rights reserved. Energy 118 (2017) 1256e1263