Superstructure development of lignocellulosic biomass from empty fruit bunch of palm for optimal design of bio-based chemical productions

Abstract

Apart from palm oil, the left-over parts of palm trees such as leaves, trunks and empty fruit brunches are low in value that typically used for producing fertilizer. In fact, considering the constituents in these wastes, they comprise of valuable components including cellulose, hemicelluloses and lignin. Recovery of these components is beneficial since they can be used as precursors for a wide range of productions of other chemicals such as bio-ethanol, succinic acid, lactic acid and other aromatic compounds. In this work, therefore, we gather experimental works in the literature in order to establish a super-structure, the network of processes that links the waste obtained from palm trees to the higher-value products. This super structure development is of importance for 1) the selection of produced chemicals and 2) the optimal process design since it provides the whole possible products and production alternatives. However, the constructed structure can be complicated specifically the selection of the best pathway which depends on the objective functions. To remedy this, we utilize mixed integer nonlinear programming (MINLP) in GAMS to search for the best pathway subject to the specified objective functions. According to the obtained results succinic acid provides the highest profit margin - about 89 %profit relative to the investment cost followed by lactic acid and ethanol. In addition, the optimal pathways of synthesis specific to each product, e.g. lactic acid, succinic acid and bioethanol are determined given variability of the product prices. Lastly, the sensitivity of product price has been investigated. It is found that the only possibility that would shift the production from succinic acid to lactic acid is when lactic acid is more expensive than succinic acid. The results obtained from the optimization of this superstructure will be served as the potential alternatives for the next step of process design.