Enhancing performance in anaerobic high-solids stratified bed digesters by straw bed implementation.
Anaerobic high-solids single-stage stratified bed digesters have been found to be simple and flexible design candidates for small-scale reactors located in medium- to low-technology environments. In the present study, wheat straw was used as the starter material for the stratified bed. Upon green mass feeding, the anaerobically stabilised straw bed functioned both as a biofilm support and as a particulate filter. It enabled a direct onset of 7 kg VSm(-3) batch loads, added twice a week, and permitted a low but consistent bed permeability during feeding at an average superficial flow velocity of 1 m d(-1) to be achieved. Fed-batch tests with sugar beet tops in pilot- and laboratory-scale setups at an average loading rate of 2 kg VSm(-3) d(-1) resulted in average biogas production rates of 1.2-1.4 m3 m(-3) d(-1) and methane yields of 0.31-0.36 m3 kg(-1) VS(added). At the end of the laboratory-scale feeding trial, the 200 day old straw bed had compacted to 50% of its initial volume, without any negative effects on performance being detectable.
Svensson
Lars Mattias
LM
Department of Biotechnology, Lund University, PO Box 124, SE-221 00 Lund, Sweden. mattias.svensson@biotek.lu.se
Björnsson
Lovisa
L
Mattiasson
Bo
B
D000383:Agriculture; D000693:Anaerobiosis; D019149:Bioreactors; D018547:Plant Stems / Q000737:chemistry*; D012037:Refuse Disposal / Q000295:instrumentation* / Q000379:methods; D014908:Triticum