Automatic process control for stable bio-hythane production in two-phase thermophilic anaerobic digestion of food waste

Abstract The paper reports the results of a long term (310 days) pilot-scale trial where food waste as sole substrate was treated in a two-phase thermophilic anaerobic digestion process. This was optimized for concurrent hydrogen and methane production. First phase's optimization for hydrogen production was obtained recirculating the effluent coming from the methanogenic phase and without the addition of external chemicals. A drawback of such approach is the recirculation of ammonia into the first phase reactor for hydrogen production with possibility of consequent inhibition. Therefore this study was focused on the development of a control protocol based on ammonia concentration. The first part of this paper illustrates how the use of a variable recirculation flow makes possible to control the whole process, preventing the ammonia inhibition in the system. In order to lay down the groundwork for an automatic control of the process, in the second part of the study a preliminary statistical study is presented. In the latter are developed models to predict ammonia levels in system using the measure of Electrical Conductivity, Volatile Fatty Acids and Alkalinity. During steady state conditions, managed by a variable recirculation flow, the system produced a mixture of gas that met the standards for the biohythane mix with an average composition range of 7% H2, 58% CH4 and 35% CO2. The overall average specific gas production (SGP) reached 0.69 m3Biogas/kgTVS and gas production rate (GPR) of 2.78 m3/m3rd.

[1]  David M. Bagley,et al.  Improving the yield from fermentative hydrogen production , 2007, Biotechnology Letters.

[2]  Bruce E Logan,et al.  Inhibition of biohydrogen production by ammonia. , 2006, Water research.

[3]  Paolo Pavan,et al.  Bio-hythane production from food waste by dark fermentation coupled with anaerobic digestion process: a long-term pilot scale experience , 2012 .

[4]  Masoud Kayhanian,et al.  Ammonia Inhibition in High-Solids Biogasification: An Overview and Practical Solutions , 1999 .

[5]  C. Gallert,et al.  Mesophilic and thermophilic anaerobic digestion of source-sorted organic wastes: effect of ammonia on glucose degradation and methane production , 1997, Applied Microbiology and Biotechnology.

[6]  Yu-You Li,et al.  Continuous H2 and CH4 production from high-solid food waste in the two-stage thermophilic fermentation process with the recirculation of digester sludge. , 2010, Bioresource technology.

[7]  A. Zeng,et al.  Growth inhibition by ammonia and use of a pH-controlled feeding strategy for the effective cultivation of Mycobacterium chlorophenolicum , 1995, Applied Microbiology and Biotechnology.

[8]  Greg Rideout,et al.  Greenhouse gas emissions from heavy-duty vehicles , 2008 .

[9]  Dipankar Ghosh,et al.  Microbiological and engineering aspects of biohydrogen production , 2009, Indian Journal of Microbiology.

[10]  Sonia Heaven,et al.  Trace element requirements for stable food waste digestion at elevated ammonia concentrations. , 2012, Bioresource technology.

[11]  René H. Wijffels,et al.  Bio-methane and bio-hydrogen: status and perspectives of biological methane and hydrogen production. , 2003 .

[12]  I. Valdez‐Vazquez,et al.  Hydrogen production by fermentative consortia , 2009 .

[13]  Paolo Pavan,et al.  Mesophilic and thermophilic anaerobic co-digestion of waste activated sludge and source sorted biowaste in pilot- and full-scale reactors. , 2013 .

[14]  D Bolzonella,et al.  Optimization of two-phase thermophilic anaerobic digestion of biowaste for hydrogen and methane production through reject water recirculation. , 2011, Bioresource technology.

[15]  Irini Angelidaki,et al.  Anaerobic thermophilic digestion of manure at different ammonia loads: Effect of temperature , 1994 .

[16]  Godfrey Kyazze,et al.  The potential for hydrogen-enriched biogas production from crops: Scenarios in the UK , 2007 .