How can we cut the carbon cost of aviation? There are several possibilities. It is unfortunately unlikely that battery power is ever going to be able to replace fossil fuels on long haul fights (I hope to be proved wrong). Easyjet is aiming to be flying a single isle battery powered plane on 80% of its routes by 2040, and is hoping to be flying routes under 500km on battery planes by 2027 (they are well on the way to this target).
The plane they are intending to use would have one isle and seat 80 passengers or so.
However, there is another possibility.
Algae is a very exciting possibility for biofuel. It is very fast growing and holds much energy. More importantly, it wont need large areas to grow, partly as it grows down in water as much as 10m. The algae that is being researched (Brucks algae) can grow in sea water, unlike most. We could therefore create vast biofuel growing areas a few miles off the coast. Out here it will not interfere with the coastal ecosystem, and this stretch of see is little used by wildlife. It grows 12 times faster than any plant grown in soil and has a higher fat content as well.
There is another big advantage. Currently the majority of our fossil fuels have to be imported from the middle east. This import alone has a high carbon footprint. Therefore if Biofuels had the same carbon footprint as fossil fuels we would already be at a significant advantage. However, as biofuels absorb the carbon from the air in growth, even if they emit all of it when burnt, they are essentially carbon neutral.
In summary, in the long run hopefully electric planes can be built to transport hundreds of people to the other side of the earth. However, if biofuels can be developed that use no or almost no land to grow, and dont have adverse impacts on other ecosystems this could also be a largely carbon neutral way to transport people around the world.
There is of course the possibility that people stop flying, however there are many problems with this. In terms of this website, it would make the business model of conservation around the world collapse. This is because if people cant travel, then you cant protect mega fauna by showing it to rich visitors.