(259c) Renewable Transport Fuels, Heat and Electricity from Miscanthus: Optimisation for Design, Planning and Operation of Sustainable Value Chains

Authors: 
Grubb, R., University of Bath
Samsatli, S., University of Bath
Biofuels and bioenergy (i.e. bio-heat and bio-electricity) can play a prominent role in decarbonising the energy system. Biofuels are compatible with existing vehicles and transport fuel supply infrastructure and they are one of the most affordable alternatives to fossil fuel. Currently, they are the only viable replacement fuels for the aviation and shipping sectors since hydrogen fuel cells and electric batteries have not yet advanced sufficiently to power aircrafts and ships. Further, production of heat and electricity from biomass is a mature and proven low-carbon technology, which when combined with carbon capture and storage can result in negative GHG emissions. However, biofuels and bioenergy are one of the most complex and controversial alternative sources for energy. If not properly planned and managed, they can heighten competition with food production and cause detrimental effects on the environment and biodiversity. Therefore, their supply chains need to be carefully designed, planned and operated in order to ensure that their production and utilisation are sustainable, do not contribute to global warming and do not result in water and land use conflicts. A biomass supply chain typically consists of growing and harvesting biomass feedstocks, pre-processing and pre-treatment, conversion to intermediates, final products and energy services, logistics and inventory and waste management.

There has been a lot of research into biomass supply chain modelling and optimisation. However, most them considered production of bio-ethanol from arable crops, which can cause competition with food production, as well as being water and energy-intensive. In Great Britain (GB), energy crop such as Miscanthus × giganteus (hereafter Miscanthus) are promising alternatives to arable crops as feedstocks for biofuel and bioenergy production. Miscanthus is a perennial grass that can be cultivated in marginal and degraded land, which is not used for food production; it requires low input (in terms of energy, water and fertilisers); it is fast-growing and high yielding and once established it can provide biomass feedstock for up to 20 years without the need for replanting. To date, no optimisation model has been developed for biofuel and bioenergy supply chains based on Miscanthus.

The aim of this project is to examine the large scale utilisation of Miscanthus to satisfy transport fuel, electricity and heat demands in GB. A mixed integer linear programming (MILP) model is developed that can simultaneously determine the design, planning and operation of the supply chains. GB is divided into 50 km × 50 km squares, in order to capture the suitable land for Miscanthus cultivation and the variation in productivity/yield, distribution of product demands, as well as to model the transport of resources. To avoid competition with food production, only grassland in GB is considered. GIS modelling is performed to exclude grassland areas that are not suitable for cultivation and harvesting based on elevation, slope and soil organic carbon, as well as those that do not comply with a number of environmental and social constraints (e.g. protected areas, urban areas etc.). Different conversion technologies, at different scales, are modelled including pelletising, torrefaction, gasification, Fischer-Tropsch (FT) synthesis, di-methyl ether (DME) synthesis, lignocellulosic fermentation, pyrolysis and pyrolysis oil upgrading, and integrated gasification combined cycle (IGCC) for combined heat and power generation. The valuable products in the supply chain include: FT-jet (aviation fuel); upgraded pyrolysis oil (UPO, marine fuel); DME, FT-diesel and ethanol (road transport fuel); and heat and electricity. The spatial distributions of the demands for these products across GB are modelled. The planning horizon considered is from 2018 to 2050.The optimisation determines where to grow Miscanthus, what technologies to invest in and where to locate them and which products to produce in order to maximise the net present value (NPV) of the supply chains. It also decides between centralised and distributed processing or a combination of the two; whether to densify or pre-process the biomass before transportation; how the biomass is transported to the processing facilities and the products distributed to customers; and how to manage inventory to balance Miscanthus availability and demands for products. In this conference, we will present the optimisation model as well the sustainable and profitable Miscanthus supply chains identified using the model.

References:

[1] S. Samsatli, N.J. Samsatli (2018). A multi-objective MILP model for the design and operation of future integrated multi-vector energy networks capturing detailed spatio-temporal dependencies. Applied Energy. DOI: 10.1016/j.apenergy.2017.09.055.

[2] S. Samsatli, N.J. Samsatli, N. Shah (2015). BVCM: a comprehensive and flexible toolkit for whole-system biomass value chain analysis and optimisation - mathematical formulation. Applied Energy, 147, pp. 131-160.

[3] S.M. Jarvis, S. Samsatli (2018). Technologies and infrastructures underpinning future CO2 value chains: a comprehensive review and comparative analysis. Renewable & Sustainable Energy Reviews, 85, 46-68.

[4] S. Samsatli, N.J. Samsatli (2015). A general spatio-temporal model of energy systems with a detailed account of transport and storage. Computers and Chemical Engineering, 80, 155-176.

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