MATHEMATICAL MODELLING OF TECHNOLOGICAL PROCESSES AND SYSTEMS
Optimal design of an integrated 1st generation biodiesel / diesel supply chain based on solid waste management for energy efficiency improvement
- 1 Bulgarian Academy of Science, Sofia, Bulgaria
The transport sector is a major consumer of diesel fuel, which ranks it among the main greenhouse gas (GHG) emissions generators. They can be reduced by gradually introducing biofuels into transport fuels and their share is expected to increase over the years. However, full sustainability can only be achieved by simultaneously consideration of all stages of the product life cycle with a tendency to close it, by utilization of solid waste by-products to improve the energy efficiency of considered biofuel production.
This study proposes an approach for optimal design of an Integrated Biodiesel/Diesel Supply Chain (IBDSC) based on 1st generation feedstock, taking into account the impact of the used feedstock for its energy efficiency improvement. It based on mathematical models of the environmental and economic impact of the considered IBDSC. The latter are included in an optimization problem for determination of optimal number, size and location of bio refineries and solid waste facilities; areas and quantities of raw materials needed for the production of biodiesel and mode of transport. Two optimization criteria are defined: environmental – minimum generated GHG emissions from IBDSC operation and economic – the total annual costs optimization criteria. The problem is solved if either at one of the two criteria, or at an integrated environmental and economic criterion. The approach involves an additional analysis of different feedstock as well as useful byproducts. Based on this analysis, the sunflower has been selected as the most appropriate feedstock which can be used as a generator of a useful by-product – sunflower husks. The obtained optimal amount of sunflower husks generated in the production of tons of biodiesel is 0.431(/.). They are used to produce the required amount of heat in biorefineries, where there are plants for burning flakes and is 0.215(/.). The remaining amount of sunflower husks is used for the production of pellets. When using an integrated environmental-economic optimization criterion, the following results are obtained – 33.4% of sunflower husks are used for the production of pellets, and 66.6% for the production of heat in biorefineries. This would have a positive impact on the formation of the final price of biodiesel.
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