Atmospheric Pollution –Shipping Plays Catch-up.

ByJohn Humphery,

CEng, FIMarEST, etc.

Introduction.• Estimate: >90% of the world’s goods are carried at sea

at some stage in their lifetimes (ores, plastics, manufactured goods or delivery to final user, etc.)

• Fifteen large, unmodified ships can generate as much atmospheric pollution per year as all the world’s cars in the same year (a study). CO2, SOx, NOx, particles.

• IMO (UN-based) regulations require marine fuel sulphur-content to be reduced from 3.5% (pre 2016) to 0.5% by 2020, with corresponding reductions in flue-gas emissions. (Known as the sulphur cap.)

• This will mean major modifications to most of the world’s ships and changes to available fuels.

Pollution-reduction and increasing fuel-costs necessitate increased fuel-efficiency.

Reducing pollution per tonne of fuel.

• Traditional: Heavy fuel oil (HFO.) Refinery-dregs, black sludge. Cheap, causing particulates, sulphur dioxide, oxides of nitrogen: generally smokey (see last picture).

• Diesel: Usually burns more cleanly (steady running), but fuel can still contain high sulphur content (note new IMO regs).

• LPG: (Liquified Petroleum Gas). Mixed propane (C3H8) and butane (C4H10). Needs a high-pressure storage system –explosion? A refined fuel and fairly clean.

• LNG: (Liquified Natural Gas). Mixed methane (CH4) and ethane (C2H6). 60% of energy of diesel. Needs only a low-pressure storage system with insulation. Recovered from gas-wells, eg, North Sea. Increasingly popular with shipping companies. Evaporation of cargo can fuel tankers. Fairly cheap and clean.

Other, less-conventional fuels:

• Hydrogen. The cleanest-burning fuel of all, producing only water. Used in conjunction with fuel-cells which produce electricity. But, can only be stored in liquid form under high-pressure and at very low temperature. Explosive. Many engineering problems yet to be solved.

• Alcohols. May be developed in the longer term (2030 and longer). Produced from biomass.

• Wind power. See below.

Sideways-thinking:• Electricity (not diesel-electric). Small battery-

powered ships are now feasible (cf. cars), with short, regular trips, eg, within ports or as ferries. Easily extended to autonomous ships (cf. cars!) Battery-technology will improve, eg, graphene, fast-charging (but needs high-capacity supply).

• Nuclear. No atmos. pollution, huge power output and endurance, but problems with spent-fuel disposal and ships not acceptable in many ports. May become necessary as other options become unavailable (cf. power-generation on land).

A battery-powered tanker delivering fuel-oil (!) to conventional ships

The “Lenin” the world’s most powerful ice-breaker (Russian, old, nuclear).

The “Savannah” (USA), 1960s. Nuclear. Passengers, cargo. Mothballed.

Reduce chemical fuel required to complete a trading- trip.It’s been done before! Use the wind! Last commercial sailing ship sailed in mid 1950s. But slow or v. slow, high maintenance (sails rigging, etc.) large crew (expensive). So, update, add sail to power.

A conventional motor ship fitted with a computer-controlled wing-sail.Can be retro-fitted to conventional ships and deployed when conditions (wind-strength and direction) are suitable. This ship is probably under sail and motor power together.Fuel-cost savings to 30% are anticipated with reduced engine-wear.

Use of twin sails and motor (no white-caps, little wind!). Computer control.

Anton Flettner (mid 1920s) used spinning rotors for propulsion.Wind blowing past rotating cylinders sets up pressure difference -draws ship forward, (Magnus effect – see Google etc.) Rotors spun electrically. E.G., Maersktanker, 240m long, 2 light rotors, each 30m tall x 5m dia: each produces 3MW power using 50kW electricity. Fuel reduction up to 10%. Similar rotors on ferries, Finland - Sweden

Making fuel-burning ships cleaner.• Modern ships’ engines are probably approaching

the limit in terms of fuel-burning efficiency. But, until recently, little attention has been given to treating flue-gases to reduce CO2, SOx, NOx and particulates.

• Due to sulphur-cap, shippers are scrambling to fit “scrubbers” between ships engines and funnels to clean up flue-gases.

• So far, fitted mainly to cruise-ships and ferries for use in environmentally-sensitive areas.

Scrubbers.• Exhaust gases are passed up through scrubbers

which are large cylinders containing water “shower” systems. SOx gases are dissolved out and some particulates are washed out. Washing water is recovered, cleaned and re-used, and cleaner flue gases exit the ship via the funnel.

• This is a simplification and there are variations on the theme, but many ships are currently being fitted with scrubbers to comply with tightening international regulations.

Conclusions.

• The IMO is legislating to reduce noxious emissions by ships.

• Ship-operators are responding by using less-polluting fuels or by using technology to clean up exhaust gases to the atmosphere, or both.

• There may not be enough time to modify all ships or supply enough cleaner fuel before new legislation becomes effective.

Conclusions (continued).

• Technology is advancing rapidly to increase fuel efficiency, fuel-variety and availability, and reduce ship-induced pollution. Better paints and bubblers (to reduce fouling and hydrodynamic friction), methanol and hydrogen fuels, and nuclear propulsion are all being investigated.

• Many older ships may become non-viable over the next ten years or so. Resulting scrapping of hulks may lead to more pollution-risks.