A Sustainable Bioenergy Future for Puerto Rico - Feedstock Potentials, Production Costs, Environmental Impact. A Spatially Explicit supply chain optimization using GIS and a Mixed Integer Linear Programming Model.
Summary
This research investigates the best suitable configuration for a bio-ethanol sector that is most suited for the island of Puerto Rico. The supply chain presented here includes a series of three feedstocks, three types of ethanol conversion technologies, an array of locations for these plants, and an array of the size or capacities of these plants. This optimization procedure has a twofold result: first the ethanol supply chain will be optimized for its economical and emission performance, i.e. the highest Net Present Value (NPV) and according Greenhouse Gas (GHG) emission performance. Simultaneously a multi-period, spatially specific designation of biomass and biofuel production sites will result from the detailed geographical data input.On ethanol terms, the total land potential of 82,320 ha can be used to substitute an amount of 16.5% (k3) or 41% (k7) of Puerto Rico’s gasoline consumption, depending on the technology used (k3 or k7). An energy cane-based supply chain configuration k3 (ec.1GEN) resulted in a benefit of 14.07 $/GJ (0.50 $/Liter ethanol) and thus good business case for Puerto Rico. The second-best option is also a supply chain based on energy cane (ec.SSCF) with a cost of 26.98 $/GJ (0.92 $/Liter ethanol) and must be subsidized. The first option thus shows the best performance in economic terms, but also on emissions terms. This energy cane-based configuration has an emission factor of -790 kg CO2 eq/GJ, if emission credits from excess electricity is allocated to ethanol production. A combination of k3 and k7 configurations is presented as the preferred ethanol supply chain for Puerto Rico, using the high electricity revenues to keep the costs down of the whole system over the timeperiod 2014-2030. At a marketing price of 12 $cents/kWh, configuration k3-k7 has a Cost of Energy of 12.48 $/GJ (or 0.43$/Liter). For the timeframe 2014-2030 are built 4 ethanol conversion plants dispersed over the region, and satisfying an island wide 11,2-22,4% gasoline substitution with ethanol.