KFW40EE house - fireplace fire but it should not get too hot

that does not exist - unused rotting in the forest. There it is decomposed by microorganisms and brings added value to the soil and the ecosystem. So your argument is not only wrong but also completely impossible. I would prefer that wood rots rather than being burned. If it’s about benefit, then the natural cycle is a greater benefit than the fireplace as a show and fun object.

My argument referred exclusively to CO2 emissions. And there it is not wrong. During this decomposition exactly the amount of CO2 is released that the tree once absorbed and which is also released when burning it.
I hope you also never drive anywhere with the car where you just have fun.

During this decomposition, exactly the amount of CO2 is released that the tree once absorbed and that is also released when burning it

This is only theoretically correct. Practically, this is somewhat offset by a few details that should not be neglected. Humus/soil also binds CO2. If you remove nutrients and substance from the soil by burning the wood, the soil can bind less CO2. The rotting tree does release CO2, but the ecosystem also binds some again.

Furthermore, it is highly foolish to focus on only one aspect and sugarcoat it. Even if the amount of CO2 should be the same in both cases, it would be negligent to ignore the rest of the facts and comfortably sit back in front of the fireplace with the good conscience that you are watching a CO2-neutral fire. This does injustice to the rest of the ecological footprint. And it helps no one.

I don’t exactly know what this topic has to do with my driving behavior, but yes, I very rarely drive just for fun. Because I don’t have a car at all. Under these circumstances, driving is rather difficult. Let alone just driving for fun. Before you ask: I have flown only once in my entire life. I use the bicycle for 100–200 km a week, I walk little, I have never boarded a helicopter, I haven’t ridden a horse since my girlhood, go-karting, stilts, and roller skating are also history. I cannot walk on my hands, and I have a subscription for public transport. I avoid Flixbus, but I do take trains. I have more than enough fun, satisfaction, and exercise. I don’t have a fireplace to watch. Any more questions?

That is only theoretically true. In practice, this is a bit undermined by a few not insignificant details. Humus/soil also binds CO2. If you remove nutrients and substance from the soil, it can bind less CO2. The rotting tree does release CO2, but the ecosystem also binds some again.

I don't exactly know what that has to do with my driving behavior, but yes, I rarely drive just for fun. I actually don't have a car at all. Under these circumstances, driving a car is rather difficult. Not to mention that I would then simply drive for fun.

If you drive somewhere with your car just for fun, you are also releasing CO2 just for fun. It’s the same as if someone heats a fireplace with wood for their own pleasure. If you "demonize" that, you shouldn't do things just for fun that harm the environment either.

If you "demonize" that, you should also not do things for fun that harm the environment.

Honestly, yes, I do quite few things that are fun and harm the environment. I have a guitar made from tropical woods. It can be burned CO2-neutrally until my death. Until then, however, that one guitar provides many hours of fun. None of us are super ecological. And the "if you say something, then I'll point out other things you probably don't do well either" does not help the discussion. It's nonsense, even bigger than the fireplace itself. I do not per se "demonize" things that are fun and harm the environment. I at most "demonize" the incomplete arguments with which people sugarcoat the things and I point strongly to the issue: can't adults sometimes just do without or show that they make carefully weighed decisions. But that is not the case here. The care is mainly about the concern that it should not get too warm in the house. How else should anything ever change if one does not stick to the whole truth? I just don't understand that fun as a supreme purpose is sufficient to acquire absurd things. The thread title already shows the complete absurdity: fireplace, but not too hot. Then you know already that it might not be quite a grown-up idea. You can still do it if fun is that important to you. But then also with full knowledge that it's nonsense and at the expense of others. Not with "it's CO2 neutral, so not so bad." Because that is wrong, with or without CO2.

1kg wood, residual moisture 12-15% already brings about 4kWh of heat energy into the house at an efficiency of a basic stove of 85-90%. I haven't even turned on the heating in February. How much % of electricity is generated by coal in winter (Dec-Feb), 40%? Rather 45% and the balance is probably not nice.

The numbers all lie somewhere between wrong, theoretical optimum, and physically impossible. But even with these numbers, the gap to the heat pump would still be enormous. I don't condemn anyone who burns something. Most do, and I still occasionally do. But please stop sugarcoating it for yourselves!