I see now that you live on the 2nd floor... the toilet (on our right) with a lttle window, the bedroom (on our left) with large window and the lounge and dining room (in the middle) with a door that opens to the balcony...somewhere in a post-war area outside the CBD of Hamburg... (howzat for for a detective work?)

Anyway, I popped in to show you this -- it's about transforming 'earth'

Wikipedia says: ...The concrete industry is one of two largest producers of carbon dioxide (CO2), creating up to 5% of worldwide man-made emissions of this gas, of which 50% is from the chemical process and 40% from burning fuel. The carbon dioxide CO2 produced for the manufacture of one tonne of structural concrete (using ~14% cement) is estimated at 410 kg/m3 (~180 kg/tonne @ density of 2.3 g/cm3) (reduced to 290 kg/m3 with 30% fly ash replacement of cement). The CO2 emission from the concrete production is directly proportional to the cement content used in the concrete mix; 900 kg of CO2 are emitted for the fabrication of every ton of cement. Cement manufacture contributes greenhouse gases both directly through the production of carbon dioxide when calcium carbonate is thermally decomposed, producing lime and carbon dioxide, and also through the use of energy, particularly from the combustion of fossil fuels...

And www.americanforests.org says: A tree can absorb as much as 48 pounds of carbon dioxide per year, ... One large tree can provide a supply of oxygen for two people...

Roughly speaking, we need 8-10 large trees for every ton of concrete. That is we must Grow more trees! Even little flowers on a balcony. ;-)