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Methyl and ethyl alcohol fuels, also referred to as methanol and ethanol, can be alternatives to comply with emission limits. A study for the European Maritime Safety Agency (EMSA) investigated if operational profiles and the fuel prices make them attractive
Now that fuel prices are low, using marine gas oil (MGO) is the easiest compliance strategy for ship operation in[ds_preview] emission control areas (ECA). The installation of scrubbers for use with heavy fuel oil (HFO) is considered costly regarding regulatory uncertainties. Liquefied natural gas (LNG) requires high investment and at the same time lacks necessary infrastructure as well as regulatory standards. Sulphur-free fuels, methanol and ethanol, can ensure compliance with the European Commission Sulphur Directive. In anticipation of future environmental regulations, that might put limitations to particulate matter emissions at sea, they could also be a solution.

To evaluate the potential of methyl and ethyl alcohol fuels for the shipping industry, Swedish consultancy SSPA together with subcontractor Lloyd’s Register conducted a study for the European Maritime Safety Agency (EMSA). Besides environmental properties, also technical and economical aspects were investigated.

Methanol (CH3OH) is widely used in the chemical industry. It can be produced from fossil and renewable feedstocks. The majority is produced from natural gas, renewable sources can be pulp mill residue, waste or CO2. Ethanol (C2H5OH) is mainly produced from biomass, with the majority on the world market produced from corn and sugar cane. It is the most widely used bio-fuel and used as a blending component for gasoline.

For these alternative fuels there are a few technical factors to be considered for both newbuild and retrofit projects, the researchers pointed out. Both alcohols contain hydrogen and carbon as do HFO, MGO and LNG, but their molecules also contain oxygen (in a hydroxyl group OH). This leads to a different behaviour regarding ignition, combustion energy density by mass as well as particulate and NOx emissions.

Methanol and Ethanol both have a lower density than MGO and HFO, an important factor for the required storage volume. It also defines, how much fuel can be injected into the cylinder for combustion. Both alcohols do have a lower heating value (LHV) of 20MJ/kg which is about half that of HFO and MGO. This means that twice as much fuel is needed to obtain the same amount of energy. Thus, onboard fuel storage requires more space. However, the Researchers compared the space requirements of MGO and methanol on a ro-ro vessel and found, that cargo capacity would reduce by only 4%. An alternative would be to bunker fuel more often.

Since methanol and ethanol both are conductive polar solvents, they can cause galvanic and dissimilar metal corrosion. Components in contact with the fuel, e.g. coatings, piping or seals, have to be compatible to prevent this. Low viscosity and poor lubricity make adaptions to the injection system of diesel engines necessary. Also lubrication oil has to be selected carefully, since the alcohols are not miscible with any oil. However, according to the study Caterpillar in long-term trials has used the same crankcase lube oil for diesel and methanol and found the results to be acceptable.

Besides the technical side, there is also an economical side to a fuel change – especially important for owners that have to deal with a difficult market. Thus, the researchers also carried out a cost and economics analysis to compare HFO, MGO and LNG to Methanol and Ethanol. While historical bunker price data for conventional fuels is available, this is not the case for the alcohol fuels. Also for LNG there are no data series available yet. The study looked at the period from July 2009 to March 2015 and calculated bunker prices for LNG from gas prices in Europe adding import, storing and bunkering charges. Official list prices for methanol are set in open contract negotiations between producers and purchasers. For ethanol there is more reliable price information, due to its use as gasoline additive.

More interesting than price per tonne of fuel are the respective prices calculated on an energy basis (per MWh). The price spread between MGO and HFO remained relatively consistent over the period. Until early 2013 there also was a consistent spread between methanol and MGO. Then global demand increased and methanol prices grew relative to conventional fuels. But the price for natural gas, the primary feedstock of methanol, is falling and new production capacities are being built in the USA. The study suggests, that methanol prices may potentially revert to 2011/2012 levels in the future. Ethanol competes with liquid petroleum transport fuels and shows a more erratic price curve. The price is usually higher on an energy basis and, because its primary feedstock is crops, ethanol prices are influenced by crop prices.

Case studies

To calculate payback times for investments in fuel compliance strategies, the researchers identified three exemplary fuel price points between 2009 and 2015 to get a low, an average and a high price scenario. Then they analysed cases for a ferry, a chemical tanker and a cruise ship operating fully or partly in ECAs, taking into consideration installation costs and fuel prices. For the payback time calculation, MGO was taken as base line scenario against which comparisons were made. In an average fuel price scenario, both methanol and HFO with scrubber and SCR resulted in payback times between 1.5 to 3.1 years for all case study ships operating 100% within an ECA. According to the study also LNG resulted in a reasonable payback time for operation within ECAs, with slightly longer payback times, depending on ship type. Fuel and operational costs for methanol and LNG were found similar, but investment costs for LNG were higher for both retrofit and newbuild solutions.

For vessels operating outside ECAs for longer periods the results show longer payback times. For a ferry operating 100% outside an ECA, the investment in methanol, ethanol or LNG did not pay back, because annual fuel expenses were above those for HFO. Ethanol in the case studies only paid back in high oil price scenarios, where all ship types showed short payback times for alcohol fuels.

The researchers concluded that methanol could be competitive with other emissions compliance strategies, depending on fuel price differentials. Due to higher fuel costs, ethanol is currently not a financially attractive option. Investment costs for alcohol fuel retrofits are estimated similar to those of installing exhaust gas treatment solutions with HFO systems and below investments into LNG technology. While LNG and methanol fuel costs were estimated similar in this study, the lower installation costs made methanol attractive. As more experience with the technology will be gathered, investment cost for alcohol fuel solutions is anticipated to decrease. According to the researchers costs for the alternative fuels must be below MGO fuel costs on an energy basis to show competitive payback times (more information at http://www.emsa.europa.eu/).


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