Increased Methane productivity and organic matter removal efficiency in anaerobic digestion can be achieved by retaining microbial consortia inside the reactors using biofilm carriers. In this study, the performance of anaerobic reactors was assessed using natural organic materials i.e. luffa sponge, coconut husk fiber and wood chips as biofilm carriers. Anaerobic batch mode bioreactors comprising of carrier materials for biofilms and control bioreactor were run in parallel at mesophilic temperature (35 °C). Methane content, biogas yield, pH, volatile solids, chemical oxygen demand, VFA/alkalinity ratio and total organic carbon was measured before and after the experiment. Scanning electron microscopy was used to identify the morphology of the methanogenic bacteria present in the biofilms. Maximum methane concentration and volatile solids removal efficiency was obtained from luffa sponge reactor i.e. 77.7% and 82.6% respectively. Furthermore, determination of biokinetic parameters lag phase (ʎ) and production rate (R m ) was also performed using three kinetic models i.e. Modified Gompertz Model, Logistics growth model and Transference function model. Among the kinetic models, logistics growth model and modified Gompertz model provided the best fit with the experimental data providing the R 2 of 0.989 and 0.975 respectively.

Future energy and environmental issues are the major driving force towards increased global utilization of biomass, especially in developing countries like Pakistan. Lignocellulosic residues are abundant in Pakistan. The present study investigated the best-mixed proportion of mechanically pretreated lignocellulosic residues i.e., wheat straw and rice straw (WSRS), bagasse and wheat straw (BAWS), bagasse, and rice straw (BARS), bagasse, wheat straw, and rice straw (BAWSRS) through anaerobic co-digestion. Anaerobic batch mode bioreactors comprising of lignocellulosic proportions and control bioreactors were run in parallel at mesophilic temperature (35 °C) for the substrate to inoculum (S/I) ratio of 1.5 and 2.5. Maximum and stable biomethane production was observed at the substrate to inoculum (S/I) ratio of 1.5, and the highest biomethane yield 339.0089123 NmLCH4/gVS was achieved by co-digestion of wheat straw and rice straw (WSRS) and lowest 15.74 NmLCH4/gVS from bagasse and rice straw (BARS) at 2.5 substrates to inoculum ratio. Furthermore, anaerobic reactor performance was determined by using bio-kinetic parameters i.e., production rate (Rm), lag phase (λ), and coefficient of determination (R2). The bio-kinetic parameters were evaluated by using kinetic models; first-order kinetics, Logistic function model, Modified Gompertz Model, and Transference function model. Among all kinetic models, the Logistic function model provided the best fit with experimental data followed by Modified Gompertz Model. The study suggests that a decrease in methane production was due to lower hydrolysis rate and higher lignin content of the co-digested substrates, and mechanical pretreatment leads to the breakage of complex lignocellulosic structure. The organic matter degradation evidence will be utilized by the biogas digesters developed in rural areas of Pakistan, where these agricultural residues are ample waste and need a technological solution to manage and produce renewable energy.

Purpose In Pakistan, a major portion of population resides in rural areas that suffers severe energy shortage for agricultural and domestic need. Bio-digestion technology can play a significant role in the eradication of fuel energy shortage, given the socio-economic condition of rural communities. Despite of the efforts made by government organizations and NGOs for this technology promotion, it is still hampered by limited functionality and low rate of diffusion. Hence, this paper aimed at comprehensive systematic analysis to find out the underlying causes of slow technology dissemination. Design/methodology/approach In this paper, the authors have analyzed the case of bio-digestion technology using the technological innovation system (TIS) approach. They have identified the barriers that effect the widespread technology diffusion followed by studying their impact on each of TIS functional element. Findings The authors’ analysis points to the two main root causes which are lack of cohesive coordination between key stakeholders and poor functionality in legitimization, knowledge development and resource mobilization domain. Practical implications This paper also provided implications for national policy makers and key stakeholders for the attainment of well-functioning innovation system for bio-digestion technology by removing the existing barriers. Originality/value To the authors’ knowledge, this is the first study that has incorporated the comprehensive framework of TIS in the context of Pakistan to explain the malfunctioning of innovation system that is hindering the technology adoption and dissemination.