DoT Algal Fuel Test Results Show Potential
June 6, 2012
he Maritime Administration (MARAD) of the U.S. Department of Transportation has released its analysis of a test conducted with algae-based biofuel on one of its large commercial-size vessels. This research used marine engines aboard the Great Lakes Maritime Academy training ship, the TS State of Michigan, to measure algal biofuel performance and emissions reduction impacts. The project is part of a joint effort by the Departments of Defense and Transportation to reduce the nation’s dependence on petroleum.
The main objective of this project was to test algal-derived hydrotreated renewable diesel (HRD) fuel, currently being tested by the U.S. Navy for consideration as a “drop-in” fuel, in a commercial type shipboard application. The fuel, which was provided by the Navy, was tested in one of the vessel’s engines for more than 400 hours. Researchers measured the fuel’s emissions, efficiency and effect on engine performance.
MARAD specifically designed a test plan to evaluate the 50/50 blend of Ultra-low-sulfur diesel (ULSD) and Algal HRD fuel to determine whether it is acceptable for commercial marine use. Accomplishing this objective required a comparison of emissions and operational performance of the 50/50 blend test fuel with the baseline ULSD, and an assessment of the blended fuel and its impact on the engine.
The current Navy HRD test program includes a complete Qualification Protocol including property testing, component and full-scale engine tests, and platform testing. The Navy plans to test a Green Strike Group of ships in summer 2012. The Navy has also provided MAERSK Lines (a commercial shipper) with some HRD fuel. MAERSK tested this fuel on a container ship using an auxiliary diesel generator and special tankage and piping.
While many tests have been performed on first generation Fatty Acid Methyl Ester (FAME) biodiesel fuels, the opportunity for MARAD to test a second generation HRD renewable fuel onboard a ship was an important milestone given the various drawbacks of the first generation biofuels. Although the Navy is laboratory testing the fuel on diesel engines as part of the Qualification Protocol, this was the first full-scale ship platform test of the HRD renewable fuel in a shipboard diesel generator over multiple days of operation with pre- and post-test material condition assessments, performance, endurance and emissions testing.
The test plan also provided an opportunity to determine the feasibility of field blending smaller quantities of fuel as well as delivery and shipboard storage and transfer. Also, because the T/S STATE OF MICHIGAN is a T-AGOS 1 Class ship it has engines that are still in active use in MARAD, 38 NOAA, and Navy vessels.
The Number 4 SSDG was used for the baseline and blend fuel exhaust emission testing and also for the remainder of the testing. Testing commenced on September 10, 2011 and was concluded November 17, 2011. After 17 underway days and 31 pier-side test days of operating Number 4 SSDG engine on the 50/50 blend fuel, the engine was inspected and found to be in good operational condition.
The Number 4 SSDG was operated for over 440 hours on the test fuel. The engine consumed about 9,500 gallons of the test fuel over this span of time. The remaining 3500 gallons were transferred into a storage tank and will be part of an ongoing U.S Coast Guard/MARAD long-term storage stability test to be completed in 2012.
Modifications to the exhaust stack were accomplished to accommodate the exhaust emission test equipment. Exhaust emission testing was performed while underway on Lake Michigan using the baseline ULSD and then the 50/50 blend fuel on two consecutive days. A detailed test profile for emission testing was developed to comply with the test protocol of ISO 8178 D2 cycle. The same profile was run using both fuels.
Emission tests were performed by UCR for a period of two days at the start of the test. The same generator engine was used for both fuels. The UCR report concludes that the 50/50 blend test fuel produces lower measured emissions of NOx, CO, CO2, and Particulate Matter (PM).
ISO 8178 calls for the measurement of exhaust emissions at five test points and then using the defined weighting factors a weighted emission factor is created. The weighted emission of NOx, CO, and CO2 were 10, 18, and 5 percent lower respectively for the 50/50 blend test fuel than for same engine operated on the ULSD. The switch in fuel also resulted in a 25 percent reduction in the weighted emissions of PM and a lower volumetric fuel consumption for the same power output.
These results indicate that if a 50/50 blend of this HRD and ULSD were made available to the commercial marine marketplace at a similar delivered price to ULSD, lower emissions would be achieved. Most significant would be the reduced PM, which is currently a major clean air issue. Likewise, the reduced greenhouse gas emissions would slightly reduce the carbon footprint of a vessel that used this fuel.
Underway and Pier side operations were also run to accumulate the necessary engine operating hours to evaluate the impacts of the fuel on the engines. Post testing, the engine conditions were assessed using a combination of visual inspection and testing and compared to the initial pre-test engine inspection. The conclusion of the Service Representative was: “After all the inspections were done I did not see anything abnormal. The effects of the biofuel were the same as running on Number 2 ultra low sulfur diesel.”
After review of the operating data, material condition reports, and from onsite observation, it appears that the 50/50 blend test fuel appeared to perform better than neat ULSD. Visual inspection of exhaust emissions from the SSDGs operating at the same load, emission from Number 4 SSDG appeared to be clearer than that of the others. The engine parts examined were in a condition consistent with engine parts of a similar engine age.
This leads to the conclusion that after over 440 hours of operation at various engine loads there is no indication of any adverse effect of the fuel on the engine and fuel systems. The long-term stability test will be concluded in 2012. The test results are encouraging and MARAD believes that the 50/50 blend test fuel used for this test would be an acceptable drop-in replacement fuel to replace ULSD that is used on the T/S STATE OF MICHIGAN, and more broadly on other commercial vessels with this type of engine.
The testing successfully demonstrated all facets of drop-in fuel performance – from fuel husbandry (loading, transferring, and supply to the engine) to superior exhaust emission performance. Addition of the HRD to the ULSD also provided an improvement in heating value that resulted in slightly better fuel consumption performance as well.
This project provided valuable performance data and results suggesting that further drop-in fuels testing would be advantageous. Since the Number 4 SSDG exhaust stack abroad the T/S STATE OF MICHIGAN has been permanently modified and baseline data has been gathered, the ship makes a particularly good platform for future testing of fuels.