Energy Switch on PBS brings in experts to discuss the adoption of cleaner energy.
These last two weeks they have discussed ocean shipping. (Shipping pt 1 and pt 2) Ocean shipping delivers close to 90% of our goods and generates 3% of carbon emissions mostly as diesel. Most are now diesel electric.
The UN has mandated reductions in carbon emissions. 30% by 2030; 80% by 2040; 100% by 2050. The goals are very ambitious.
Alternatives to diesel are 1) LNG, 2) methanol, 3) ammonia, 4) hydrogen.
LNG is easiest but still produces carbon dioxide. Cleaner than diesel but not the best solution.
Cost is a major concern. Also availability at ports around the globe. Many ports now are population centers with land occupied by buildings. Location for new fuel tanks is a problem.
Both methanol and ammonia are hydrogen derivatives, usually made from natural gas. Green hydrogen by electrolysis of water with inexpensive green electricity would be one way.
They did not discuss the presence of hydrogen in some natural gas. If geological hydrogen is available, that could be a good solution. Abundance needs to be explored.
Methanol is usually made from the carbon in natural gas, but could be made from reaction of captured carbon dioxide with green hydrogen. That effectively recycles carbon dioxide.
Methanol and ammonia are alternatives to hydrogen. Liquid hydrogen is possible but requires extreme cold. Compressed hydrogen requires heavy cylinders. Methanol is a flammable liquid and toxic if you drink it but easy to ship and store. Low fuel value compared to diesel means larger tanks required for equivalent energy. Ammonia can be burned or converted back to hydrogen. Its much like propane. Liquifies under modest pressure. Toxic if fumes escape.
Nuclear fueled ships was discussed but is too costly. An incident at sea would probably mean stricken ship cannot dock at any port. Use of on shore nuclear plants to make green hydrogen was mentioned. Might be practical.
They did not mention fermentation alcohol as a green fuel. Almost any carbohydrate can be used. Green. But likely not inexpensive.
They discussed other issues. Bilge water used to weight down an under-loaded vessel for stability can be a problem when discharged far from home. It can spread non-native species.
Powering vessel in port while loading and unloading can be a problem. Diesels produce smoke. On shore electric hook-up or small generator can be used to reduce emissions.
All of these are under discussion. Experimental vessels are under construction to see how they perform, identify problems, and get economics. Major infrastructure investments are needed to implement a plan. Time is short.
Methanol and ammonia are large volume commercial products available most places around the globe. That means green product can be swapped to make them available at most ports. Once the right choice is identified, investment to build capacity can fill the void as the demand increases.
Energy Switch is an excellent program series. Highly recommended.