Bioprocess systems applied for the production of bio- ethanol from lignocellulosic biomass of cocoa pod husk (Theobroma cacao L.) and other agricultural residues: A review

Bioenergy is fast becoming one of the most dynamic and rapidly changing sector of the global energy economy. The associated accelerated growth in the production, supply, conversion and use of bioenergy especially in the liquid bio-ethanol sector present a new reality that is attracting interest from key stakeholders in developed and developing countries alike. Petroleum, in addition to being the main source of transportation energy, has also been the mainstay of the Nigeria economy up to date. This feedstock is, however, not sustainable since it is not renewable over the period of time over which we use them. Present technologies to produce bioethanol largely depend on food-based materials and this has caused significant stress on food prices and food security. The growing interest in the use of biomass-based materials like cocoa pod husk (CPH) for bio-ethanol production especially when accruing as wastes from the agricultural sector is generally a welcomed development. Biomass feedstock are considered to be the most abundant renewable resource in the world, not only as an alternative source of energy but also hold remarkable potentials to mitigate greenhouse gas emission and for the development of organic chemical industries. However, before lignocellulosic materials can be effectively utilized, there is need for some conversion processes. Currently, enzymatic saccharification and acid hydrolysis are the main conventional methods for breaking these complex materials into smaller units prior to fermentation. The inability of Sacharomyces. cerevisiae to fully utilize pentose sugars present in biomass have been pointed out as one of the bottlenecks for the commercialization of cellulosic ethanol production. To circumvent this limitation, gene cloning techniques are used to adapt yeast for the bioconversion processes. Keywords : Biomass, bio-ethanol, cocoa pod husk, greenhouse gas. African Journal of Biotechnology Vol. 12(35), pp. 5375-5388