Bio-energy with carbon capture and storage

Methane

Composite number

Engineering

Ecology

Biology

Materials science

Climate change mitigation

Carbon fibers

Carbon neutrality

Diesel fuel

Geology

Current (fluid)

Oceanography

Waste management

Renewable fuels

Environmental engineering

Diesel exhaust

Greenhouse gas

Organic chemistry

Particulates

Renewable energy

Mathematics

Biofuel

Combustion

Environmental science

Geometry

Composite material

Chemistry

Reduction (mathematics)

Electrical engineering

Progress in Energy and Combustion Science

The impact of ship emission reductions can be maximised by considering climate, health and environmental effects simultaneously and using solutions fitting into existing marine engines and infrastructure. Several options available enable selecting optimum solutions for different ships, routes and regions. Carbon-neutral fuels, including low-carbon and carbon-negative fuels, from biogenic or non-biogenic origin (biomass, waste, renewable hydrogen) could resemble current marine fuels (diesel-type, methane and methanol). The carbon-neutrality of fuels depends on their Well-to-Wake (WtW) emissions of greenhouse gases (GHG) including carbon dioxide (CO2), methane (CH4), and nitrous oxide emissions (N2O). Additionally, non-gaseous black carbon (BC) emissions have high global warming potential (GWP). Exhaust emissions which are harmful to health or the environment need to be equally removed using emission control achieved by fuel, engine or exhaust aftertreatment technologies. Harmful emission species include nitrogen oxides (NOx), sulphur oxides (SOx), ammonia (NH3), formaldehyde, particle mass (PM) and number emissions (PN). Particles may carry polyaromatic hydrocarbons (PAHs) and heavy metals, which cause serious adverse health issues. Carbon-neutral fuels are typically sulphur-free enabling negligible SOx emissions and efficient exhaust aftertreatment technologies, such as particle filtration. The combinations of carbon-neutral drop-in fuels and efficient emission control technologies would enable (near-)zero-emission shipping and these could be adaptable in the short- to mid-term. Substantial savings in external costs on society caused by ship emissions give arguments for regulations, policies and investments needed to support this development.

Reduction in greenhouse gas and other emissions from ship engines: Current trends and future options