The complexity of the rule system in relation to the low price of tCERs and ICERs is a main barrier for sink projects in CDM. In addition, the awkward temporary crediting and a competing voluntary market with higher price and lower transaction costs can be mentioned as causes of the lack of sink projects within CDM. Another main reason for the absence of sink projects in CDM is that the demand was significantly reduced when the EU decided not to include these projects in the EU ETS. The incentives for the private sector to engage in sinks in CDM have been very low and the main actor on this market has been the Community Carbon Development Fund and the BioCarbon Fund of the World Bank29.