A new study has found that an integrated seawater energy and agriculture system (ISEAS) can produce biofuel for the aviation sector with fewer greenhouse gas emissions than its fossil counterpart.
The research project conducted by a team of researchers from Qatar University (QU) and Masdar Institute of Science and Technology (Masdar Institute) has found that the aviation biofuel produced from this ISEAS system emits up to 68 percent less greenhouse gases compared to fossil jet fuel and yields an overall positive net energy balance.
The study is funded by Boeing Corporation. In a new article appearing online in the International Journal of Life Cycle Assessment (http://link.springer.com/article/10.1007/s11367-016-1215-5), which was co-authored by QU Center for Sustainable Development (CSD) Research Assistant Professor Dr J Jed Brown, a life cycle assessment (LCA) of a potential ISEAS was conducted. The team quantified the energy and material flows throughout the system and calculated the resulting net greenhouse gas emissions.
In the ISEAS, seawater is pumped into ponds where high value shrimp and fish are grown for human consumption. The nutrient-rich effluent exits the ponds and flows into fields of salt-tolerant plants (halophytes). The team examined a Salicornia bigelovii halophyte — commonly known as glasswort or samphire — which produces oilseeds similar to soybeans.
The oil extracted from the seeds can be processed into a drop-in biofuel for aeroplanes, Dr Brown said, adding, “The portion of the seed that remains after oil extraction is high in protein and can be recycled into feed for fish and shrimps. The dried straw that remains after the oilseeds can also be used to generate electricity. Water that leaves the halophyte fields flows into a mangrove wetland where most of the remaining nutrients will be absorbed into mangrove biomass. Branches and leaves from the mangroves can be periodically trimmed to generate electricity with the Salicornia straw.”
Dr Brown also highlighted the environmental benefits of the ISEAS system, saying, "In the ISEAS system, the nutrient-rich effluent from the aquaculture ponds serves as a fertiliser source for the halophytes and mangroves, which clean the water by removing nutrients. Mangroves are also used in many parts of the Gulf region to stabilise erosion-prone coastal regions."
