Pretreatment for cellulosic ethanol production in the developing world

In the context of the Developing World, it is challenging to implement technological schemes with large-scale, high-performance technologies, due to i.e. the poor biomass infrastructure, which in most cases are not able to support collection, storage and transport of huge amounts of the biomass needed for a large-scale facility. Therefore, pretreatment for cellulosic ethanol should be optimized within the constraints of a smaller scale than envisioned in most scientific studies. On the other hand, it might be conceivable to employ methods that are more labor intensive than methods developed for the industrialized world.

In the current study, a thorough investigation of three alternative pretreatment methods applicable for small-scale low-tech conditions is described (boiling pretreatment, soaking in aqueous ammonia, and white rot fungi pretreatment). These methods are benchmarked against well-known hydrothermal treatment. The pretreatments is tested on 11 West African biomasses, i.e. cassava stalks, plantain peelings, plantain trunks, plantain leaves, cocoa husks, cocoa pods, maize cobs, maize stalks, rice straw, groundnut straw and oil palm empty fruit bunches. The raw and pretreated biomasses are screened in an enzymatic convertibility assay where after the most promising biomasses are subjected to compositional analysis and ethanol fermentation.

We find that the alternative methods are viable, especially when looking at the overall utilization of the biomasses, even though only less than half of the tested biomasses are suitable for cellulosic ethanol production with sufficiently high yields. Furthermore, we elaborate on the mode of action of the pretreatment methods and their effect on the different biomasses.