We develop an alternative input-output approach and apply it to the determination of key sectors in emissions. This methodology allows us to assess and classify the different productive sectors according to their greenhouse gas emissions and the role that they play in the productive structure, as well as the participation of their output in the total volume of production. In contrast with previous approaches, we do not focus on the responsibility of final demand, but on the responsibility of the total production of each sector. We apply our methodology to the 2014 input-output table for Spain provided by the World Input-Output Database (2016). The results show that the sectors that induce more emissions from other sectors are manufacture of food products, wholesale and retail trade, and construction. Those that are pulled to emit coincide with those that are relevant for their own final demand, being the most important electricity and gas provision, agriculture, and transportation. The classification obtained allows to orient the design of greenhouse gas emission mitigation policies for the different sectors. K E Y W O R D S greenhouse gas emissions, industrial ecology, input-output, key sectors, production structure, Spain 1 INTRODUCTION According to the Kyoto protocol and the internal allocation of emission objectives within the European Union, the annual average of greenhouse gas (GHG) emissions of Spain in the period 2008-2012 should have not been above a 15% increase of the 1990 emissions (taking into account the CO 2 equivalent aggregate of the six gases considered by the protocol: CO 2 , N 2 O, CH 4 , HFCs, PFCs, and SF 6 ) (Commission Decision 2006/944/EC, European Commission [EC], 2006). The emissions of Spain for the base year of the protocol were 289.7 Mt, while the average annual emissions from 2008 to 2012 amounted to 360.0 Mt, a 24.5% increase over the base year. The emissions increased well above the objective and the protocol was only fulfilled thanks to the use of the flexibility mechanisms (EEA, 2017). Moreover, if it were not for the economic crisis, the mismatch wouldhave been significantly worse.The peak in emissions occurred in 2007, while the fall in economic activity since 2008 involved quite a drastic reduction in emissions (Figure 1).Emissions fell to their minimum in 2013, when they were even below the emission level objectives of the protocol for 2008-2012. However, the economic recovery that began in 2014 led to an increase in emissions that continued in 2015, again exceeding the protocol objectives. In 2015, emissions amounted to 335,661.5 kt of CO 2 equivalent and represented an increase of 3.5% over the previous year, while GDP grew by 3.2%. The key element for this expansion of emissions was the generation of electricity in thermal power stations (Observatorio de la Sostenibilidad, 2016).The EU has proposed a plan to reduce emissions that involves a 20% reduction of 2005 levels for the year 2020. The plan shows two paths for reduction. There is a difference between the sectors sub...