We present the preliminary results of the sustainability survey carried out by the ``SEA Cero CO2'' working group among Spanish astronomers. The survey aimed at studying, within a limited scope, the carbon footprint of astronomical research carried out in Spain, as well as to collect the opinion of Spanish astronomers about possible ways to reduce it. We estimate greenhouse gas emissions correspond on average to ∼eq 0.54 tCO2eq/yr per astronomer from home-office commuting, ∼eq 1.4 tCO2eq/yr from super-computer usage and ∼eq 1.46 tCO2eq/yr from work travel. A more detailed analysis, including a comparison with pre-pandemic results is under way. We emphasize that the activities studied here represent only a fraction of the emissions caused by astronomical research. An effort at the institutional and community level is needed to quantify in detail these emissions and make plans for its immediate reduction.