If the biomass concentration in the digestor is increased, it would be a corresponding increase in the viscosity of the digestor contents. This could possibly be detrimental to the flow distribution in the digestor, leading to dead zones and poor mixing. Hence, it would be necessary to increase the concentration of the full-scale digestor and monitor the effects on the flow distribution. This would be done using tracer studies, i.e. the Residence Time Distribution technique. If any significant maldistribution is identified, investigations will focus on whether these could be engineered out.