Waste lube-oil based fuel characterization in real conditions. Case study: Bottom-trawl fishing vessel powered with medium speed diesel engine

Abstract

The high-fuel dependency of the shipping industry and its corresponding pollutant emissions need to be addressed within the new de-carbonisation era. Concurrently, the waste-to-energy concept arises to drive sustainable initiatives for energy production. In that sense, in the present study, the feasibility of an alternative fuel oil (AFO) based on recycled-waste lubricating oil was assessed. Tests were conducted on board a bottom-trawler fishing vessel, under real operating conditions. The fishing activity was monitored, and the engine performance, the combustion and injection properties, and the emissions characteristics were studied. The vessel performance when operating on the AFO was compared with that when operating on standard distillate diesel oil (DFO). The results showed that the AFO required preheating up to 70 degrees C owing to its higher viscosity value, which is considerably higher than the allowed by the ISO 8217 standard for distillate fuels. Therefore, a heating module was installed on board the vessel to ensure optimal performance with the AFO. The fuel consumption was slightly lower for the AFO; however, owing to its higher low-heating value, the engine efficiency was higher when using the DFO. The AFO presented lower combustion pressure than the DFO and a longer combustion period; however, its ignition process occurred earlier. The results suggested that the AFO contained light components which caused the early ignition of the fuel, as well as heavy components, which delayed the end of the combustion. The NOX emissions were considerably reduced with the AFO by 15\%; the CO2 emissions were slightly reduced as well; however, CO emissions were higher for the AFO by 15\%. By operating under the usual conditions while burning the AFO throughout a year, the vessel would consume 8 t of fuel less, and would emit 21 t of greenhouse gases less. The vessel burnt a total of 40,000 L of AFO, for approximately 300 h, without any operational issue. The results demonstrate that the distillate fuel obtained from lubricating oil is suitable for marine medium-speed engines and enables satisfactory performance.