Covid-19 has affected both the global economy and the environment. The lack of fuel demand due to lockdowns has caused a significant decline in the barrel price. Less fossil fuel burnt over the past twelve months has seen a significant improvement in global air quality. As economies ramp-up post lockdown the focus has remained on improved air quality and renewable fuel energy.


The burning of Heavy Fuel Oil (HFO) associated with power generation and maritime shipping has traditionally been the source of significant CO₂ & SO₂ emissions. The introduction of MARPOL Annex VI associated with shipping since January 2020 has reduced SO₂ emissions. Unfortunately, the processes used to reduce the sulphur content in heavy fuel oil along with subsequent blending & dilution used to create the new very low sulphur fuel oil known as Very Low Sulphur Fuel Oil (VLSFO) have not met with the “Green Spirit” of MARPOL Annex VI.


Conventional Hydrodesulphurization (HDS) is that whilst it can remove the aliphatic sulphur compounds (thiols), it finds it very difficult to remove, through its mechanism of hydrogen addition, the refractory (thiophene-derivative) S-compounds. The vast majority of desulphurisation capacity in the global refining sector today is based on HDS. The system is energy-intensive; using high temperatures and pressure to produce a modest sulphur reduction.


The HDS chemistry’s inability to remove the refractory S.compounds lies at the heart of the problem in providing low sulphur grade bunker fuel to meet the MARPOL 2020 limit of 0.5% sulphur-content. As such, we find that much of the S.content in Residuum Feeds & Off-spec Bunker is thiophenic. Blending down the Residuum requires a 1 part Residuum to 7 parts diesel ratio of dilution. High ratio blending with additives has created aromatically unstable fuel oils which have damaged ship engines and produced significant Black Carbon emissions.


Stability & Compatibility Issues

Black Carbon Emissions

Curve Marine’s patented green technology for the desulphurization of HFO will provide an economically viable solution for refiners to upgrade their plants to meet the new Sulphur limits during these difficult economic times.


Marpol Annex VI mandated by the International Marine Organisation (IMO) has been active since January 2020 improving air quality by reducing the Sulphur content in heavy fuel oil (≤3.5% to ≤0.5%) burnt by the global maritime community. The new Sulphur limits reduce Sulphur Dioxide (SO₂) emissions into the environment.


SO₂ global emissions;12% of which are attributed to maritime shipping, that leads to high concentrations of SO₂ in the air generally also lead to the formation of other sulphur oxides (SOx). SOx can react with other compounds in the atmosphere to form small particles. These particles contribute to particulate matter pollution. Particulate matter is a complex mixture of mainly black soot, i.e. virtually elemental carbon, fuel oil ash containing heavy metals such as vanadium and nickel, sulphates and associated water, nitrates, carbonates and a variety of non, or partially combusted hydrocarbon components, derived from the fuel oil and engine lubricant.

Small particles may penetrate deeply into the lungs and in sufficient quantity can contribute to health problems. Short-term exposures to SO₂ can harm the human respiratory system and make breathing difficult. Particulate matter has been linked to increased asthma attacks, heart and lung disease and respiratory problems in susceptible population groups. In addition, the concentration of sulphur dioxide in the atmosphere can influence the habitat suitability for plant communities, as well as animal life. SO₂ emissions are a precursor to Acid Rain.


Acid rain is a rain or any other form of precipitation that is unusually acidic, meaning that it has elevated levels of hydrogen ions (low pH). It can have harmful effects on plants, aquatic animals and infrastructure. Acid rain is caused by emissions of sulphur dioxide and nitrogen oxide, which react with the water molecules in the atmosphere to produce acids. Acid rain has been shown to have adverse impacts on forests, freshwaters and soils, killing insect and aquatic life-forms, causing paint to peel, corrosion of steel structures such as bridges, and weathering of stone buildings and statues as well as having impacts on human health.


The effects of acid rain deposition depend on the fragility of the materials, plants, soils and waters involved. In those instances where there is not the natural alkalinity to neutralise this acidity or alternatively the capability to withstand such attack, acid deposition has been linked with the acidification of ground and surface water, deforestation, reduction – even elimination – of aquatic life and building decay. The exposed surface of limestone (CaCO3) used for the fabric of many historical buildings turns to gypsum (CaSO4), which has a lower density and is more water-soluble, hence suffers from spalling. The impacts on the natural environment can cause further problems, for example, acidic water leeches out heavy metals. Soil no longer bound by tree roots, may be washed away, leaving a denuded landscape and potentially adding to the flood risk downstream where this soil is subsequently deposited as silt.


Sulphur removal is the only genuinely GREEN solution for MARPOL


Diluting the HFO Residuum requires a 1 part Residuum to 7 parts diesel; unstable blending, leaving 6/7ths or 86% of the residuum unsold and un-lifted from the refinery storage tanks. “Sulphur Dilution” is not the answer - Sulphur Removal is the only solution