The international sale of unused national emission quotas in relation to the Kyōto Protocol was successfully initiated in 2010. Arising from the aforementioned Protocol, the Republic of Estonia currently has the right to offer unused emission quota i.e. the assigned amount units (AAU) for sale on the international market.
The AAU sale is carried out by means of the Green Investment Scheme, pursuant to which the revenue is directed to investments ensuring a decrease in CO₂ emissions as agreed with the buyer of the quota, for example ensuring the energy efficiency of public buildings.
The organiser of the performance of investments in Estonia directed to increasing the energy efficiency of public buildings is Riigi Kinnisvara Aktsiaselts (Estonian State Real Estate Ltd).
The respective work carried out in 543 buildings with the help of Estonian State Real Estate Ltd by the end of 2013. The cost of the project was EUR 165,67 million.