Producer gas fermentation is a technology which has not yet reached the market,
because of low productivity of the bioreactor. This is due to several factors, such as
(Ungerman and Heindel 2007):
– Low cell density
– Lack of regulation of metabolic pathways to yield only the desired product
– Inhibition of the biological catalysts by products and substrates
– Low gas–liquid mass transfer
At mild temperatures, CO and H 2 have aqueous solubilities of 60% and 4%, with
respect to oxygen, on a mass basis. This results in low concentration gradients and,
hence, low mass transfer rates. Higher mass transfer rates can be achieved using:
– An agitator system
– Increasing the operating pressure
– Producing micro-bubble dispersions (bubbles with diameters of about
50–100 mm have been used to provide a large gas transport area at low power
consumption (Lewis et al. 2006))
1.5
BTL (FT-Diesel, Methanol and DME)
1.5.1 Introduction
The term “BTL” is applied to a liquid fuel obtained through thermo-chemical
processes, such as pyrolysis and gasification, applied to biomass.
Fig. 1.9 Microbial fermentation of syngas (Vohra et al. 2014)
18
P. Bartocci et al.