accepted MNRAS 2015 ; International audience ; Recent observations have revealed the existence of Complex Organic Molecules (COMs) in cold dense cores and prestellar cores. The presence of these molecules in such cold conditions is not well understood and remains a matter of debate since the previously proposed "warm- up" scenario cannot explain these observations. In this article, we study the effect of Eley- Rideal and complex induced reaction mechanisms of gas-phase carbon atoms with the main ice components of dust grains on the formation of COMs in cold and dense regions. Based on recent experiments we use a low value for the chemical desorption efficiency (which was previously invoked to explain the observed COM abundances). We show that our introduced mechanisms are efficient enough to produce a large amount of complex organic molecules in the gas-phase at temperatures as low as 10K.