New Biofuels on the Horizon for the Great Green Fleet

RIMPAC 2012USNS Henry J. Kaiser (T-AO 187) refuels USS Princeton (CG 59) during the Great Green Fleet demonstration in 2012. Photo by MC3 Andrew M. Jandick.

By Patric Petrie

The Navy has committed to the deployment of a “Great Green Fleet” by 2016, a carrier strike group fueled by alternative sources of energy such as new-generation biofuels.

Biofuels are drop-in replacements for petroleum-based fuels such as JP-5, used in aircraft, and F-76, used in ships. These biofuels are derived from lipid-rich plants or algae, which are highly renewable energy sources that produce lower greenhouse gas emissions than typical Navy fuel sources and consume carbon dioxide as they grow.

By seeking alternative and renewable fuel sources, the Navy can reduce its dependence on foreign oil while furthering its environmental stewardship, a key element of the Navy’s Energy Vision.

Two biofuels currently being tested by Naval Air Systems Command as blends with existing petroleum-based fuels include HRJ-5, a jet fuel made from camelina plants, and HRD-76, a ship diesel made from marine algae. Although these fuels have passed recent fit-for-purpose tests in Navy aircraft and ships, their fate and effects in the marine environment remain unknown.

Prototype energy-efficient technologies have been designed to enhance the combat capability of Navy warships. These include solid-state lighting, which is more efficient and lasts longer than incandescent or fluorescent fixtures; stern flaps designed to help reduce hull resistance when under way; a shipboard energy dashboard that displays energy usage to the operators in real time and informs energy efficient decisions; and gas-turbine online water wash that improves engine efficiency. Similarly, new ship fuels must meet performance specifications, as well as environmental compliance requirements, both of which are essential to operational readiness.

Space and Naval Warfare Systems Command (SPAWAR) scientists are currently assessing the potential ecological risks of these new-generation fuels in the event of fuel spills during storage or transport. Ensuring that the Navy adopts alternative fuels that are no more hazardous in the underwater environment than current petroleum-based fuels will reduce the potential for fines associated with spills and the need for costly assessment and cleanup actions.

Assessing the Ecological Risk 

Over the past year, SPAWAR scientists have completed preliminary laboratory studies that investigated the toxicity and chemical characterization of new-generation fuels compared to traditional petroleum-based fuels in marine environments.

Initial range-finding tests evaluated acute toxicity (mortality in short-term exposures of four days) for juvenile mysid shrimp and topsmelt (a small Pacific fish) larvae and chronic/sublethal toxicity (exposures of two to four days) for sea urchins and mussel embryos.

To assess toxic effects, marine organisms were exposed to seawater saturated with water-soluble fuel extracts from alternative renewable or traditional petroleum-based fuels.

Results displayed rapid mortality of mysid shrimp and topsmelt in petroleum-based fuels, while no mortality was observed in alternative fuel samples. Similar responses were observed with embryonic urchins and mussels.

These results suggest that alternative fuels are far less toxic than their petroleum-based counterparts. Differences in toxicity are most likely driven by much higher concentrations of toxic compounds such as volatile organic carbons and polycyclic aromatic hydrocarbons in petroleum-based fuels.

Looking Ahead

Future studies will more definitively determine toxicity concentrations with complementary chemical analyses. In addition, SPAWAR scientists will be working on identifying and developing of data for key parameters for fate and effects modeling, such as biodegradation, photodegradation, and oceanographic mixing rates of alternative fuels.

Determination of the chemical components of alternative renewable and petroleum-based fuels will provide guidance for forthcoming management and certification decisions in selecting less toxic fuels with similar performance specifications.

About the author:

Patric Petrie is the lead staff writer for Space and Naval Warfare Systems Center Pacific.

 

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