Sustainable pilot-scale production of a Salicornia oil, its conversion to certified aviation fuel, and techno-economic analysis of the related biorefinery

The 2 ha pilot-plant Seawater Energy and Agriculture System (SEAS) in Abu Dhabi, United Arab Emirates (UAE), integrates aquaculture ponds, which produce fish and shrimp, with fields of Salicornia and mangrove used as a natural filter to clean the waste seawater from the ponds. The SEAS is a sustainable solution that addresses the food security issues of countries with large deserts or arid regions. At the same time, it produces economically viable fuels from biomass, using non-arable lands and non-drinkable water. After harvesting and pressing Salicornia seeds (2 t ha⁻¹ year⁻¹), a custom-made process serves to pre-treat the vegetable oil (0.7 t ha⁻¹ year⁻¹) containing 85 wt% C₁₈ and 10 wt% C₁₆ fatty acids as triglycerides. The first step of the UOP Ecofining® process produces an oil composed of linear C₁₅-C₁₈ alkanes. Analytical data suggest the oil feed converts at 60 wt% by hydrodeoxygenation and at 40 wt% through decarboxylation/decarbonylation. The subsequent hydrocracking/isomerization step provided 3.4 wt% C₁–C₄, 34.8 wt% green naphtha, 47.5 wt% sustainable aviation fuel (SAF), and 14.2 wt% green diesel. After distillation, the SAF has been certified following ASTM D7566 before being blended with conventional jet fuel and used successfully on a commercial passenger flight in January 2019. The techno-economic study shows that the biorefinery part is economically sustainable when reaching a production scale of 900bbd, required for a SEAS surface of 20 000 ha. At this scale, expected revenue and conversion costs per MT of feed are, respectively, $589 and $290. The resulting benefit, associated with a CAPEX of $115M, would lead to a payback time of 6.9 years.