Almost nothing in your household consumes as much energy as an oven. Ovens consume from around 1000 (when already heated up) to 5000 Watts leading to ginormous amounts of carbon emissions on your average electricity mix. From an environmental perspective it’s completely crazy to bake your trash for 30 to 40 minutes (it’s like running your electric kettle at full power for 30 minutes straight). I’d rather not compost eggshells at all rather than baking them.