(363c) Integrated Modeling of Agricultural and Industrial Processes for Intensifying Cane Sugar Industries

We developed a process model of cane sugar industries, which consist of agricultural and industrial processes and produce raw sugar, ethanol and some residues from sugarcane. This model enables to simulate mass and energy flow overcoming the gap between agricultural and industrial processes and to analyze the effects of operational and technological options on the performance of the whole system.

In the previous studies analyzing the life cycle of sugarcane-derived ethanol, the potential of its sustainable production has been confirmed. Although various kinds of research on elemental technologies as well as on their integration approach such as process intensification have been devoted to improving production efficiency, it is difficult to achieve the implementation within engineering fields because cane sugar industries can be represented as complex systems. Various decision-makers are involved in this industry; sugarcane is an agricultural product yielded by farmers, while it is processed into raw sugar and/or ethanol in industrial sectors. The industrial process performance have high sensitivities to changes in the components and conditions of sugarcane, while cultivar choices, environmental conditions such as climate and soil type, and farm operations influence on those properties. Industrial processes also have strong influences on agriculture. For example, many farmers have chosen cultivars which contain much sucrose to meet the demands of the industrial processes. In addition, the material transportation from industrial to agricultural processes is also confirmed. The residues from industrial sectors such as filter cake contain abundant fertilizer nutrients such as nitrogen, phosphorus and potassium, and, therefore, it is implemented worldwide that they are returned to farmlands to maintain the soil fertility.

It is challenging to introduce new technology to achieve high-efficiency production into such complex systems where agricultural and industrial processes are interweaved with each other. The whole system should be regarded as the objective of intensification and the integrated analysis considering the linkage between them is required to fulfill the potential of the introduced technology sufficiently. Nevertheless, elemental technologies have been developed in the respective sectors up to date. Simulation-based analysis which can visualize the phenomena of agricultural and industrial processes simultaneously is effective to understand the linkage between them. In this study, we have tackled the challenges described above with the development of an integrated model and a case study.

In the agricultural part of the developed model, the relationship among chosen cultivars, cropping type, environmental conditions such as climate and soil, and farm operations such as irrigation, soil pH control, and fertilization was modeled based on the results of the existing reports. The yield of sugarcane and its composition are estimated by this agricultural part. The modeled sugarcane is composed of five components: sucrose, reducing sugars, minerals, fiber and water. The process performance is calculated by the industrial part of the model based on the amount and the ratio of these components. Sucrose and reducing sugars can be converted into ethanol, while reducing sugars affect the efficiency of raw sugar crystallization. Fiber is not a raw material for sugar and ethanol but emitted as bagasse. This is used as a fuel for providing the processes with heat and electricity. The surplus bagasse is generated under some conditions and can be used as a biofuel for other facilities.

A case study using the constructed model demonstrates that an introduction of the new industrial technology into the existing system can achieve significant increase in both sugar and ethanol production as well as the reduction of environmental impacts by choosing appropriate cultivar in agricultural sectors. In other words, the concept of the integrated design proposed in this research can intensify cane sugar industries. This concept offers us a wider range of solutions and help us to improve the performance of the system significantly. The results shown by the model can be used to motivate the real stakeholders such as sugarcane farmers, plant managers and operators of sugar mills, and policy makers to modify their decision-makings in order to increase their profitability and to reduce environmental impacts.