So you want to use plants to reduce CO₂

The useful part of the conversation was not the arithmetic. It was the cleanup of what problem is actually being solved. For indoor air, people kept coming back to the same conclusion: you want outside air exchange, not biological tricks. Several readers pointed to CO2 monitors that made the problem obvious in bedrooms and home offices, and the practical recommendation was an ERV or HRV if you cannot just open a window. A few people also noted that the “brain fog” blamed on CO2 may partly be VOC buildup, which ventilation fixes too. A lot of comments tried to turn the post into a climate debate. The sharper framing there was that plants only help if the carbon stays out of circulation. Living forests and grasslands matter enormously, but mostly as existing carbon stocks and ecosystem stabilizers, not as a magic sink that can offset fossil emissions forever. Once plant matter burns or rots, the carbon comes back. That is why the more serious plant-based sequestration ideas in the comments all ended with pyrolysis, biochar, burial, or other ways to keep biomass from decomposing. Several readers also pushed attention toward the ocean, both because it already absorbs a large share of human emissions and because ocean acidification, deoxygenation, and warming are doing damage that gets less public attention than forests do.