Synthesis of a sustainable integrated rice mill complex

• A new mathematical model for process screening and product portfolio planning.
• A sustainable, resource-efficient rice mill with process-utility system integration.
• Multi-objective optimisation to maximise profit and minimise environmental impact.

A rice mill produces many by-products that can be further utilised into value-added products. For instance, rice bran can be further processed to produce rice bran oil. On the other hand, rice husk can be utilised as biomass in the cyclonic husk furnace or cogeneration system to supply thermal energy for paddy drying. Alternatively, rice husk can be the raw material to produce bio-char, bio-oil and biofuel. This paper presents a framework to synthesise the sustainable pathways for an Integrated, Resource-Efficient (IRE) rice mill aimed at maximising its profitability while minimising the environmental impact of its by-product utilisation. The key factors considered include the availability of resources, the cost-effectiveness of the available technology options and the trade-off between profitability and environmental impact such as global warming, photochemical ozone production and eutrophication. The developed model was applied on a case study where five different scenarios representing different economic and environmental objective functions were analysed. The proposed model allows rice millers to target for the maximum profit and synthesise the sustainable process pathways prior to the detailed design of the IRE rice mill complex.