2.1.5.1. Environmental Impacts

The computation of the environmental impacts of cogeneration considered two types of impacts: (a) the GHG emissions resulting from the fuel burned in each cogeneration plant, and (b) the avoided GHG emissions resulting from the possible replacement of large thermal power plants in the country (that use fossil-derived fuels for electricity production) by cogeneration plants in the industry. It is expected that the availability of cogeneration plants could remove the necessity of installing a thermal power plant (that uses oil-derived fuels to run) with capacity equal to that corresponding to the total cogeneration potential. Both results were added to obtain the net GHG emissions.

#### (a) Emissions in cogeneration plants

The fuels required for cogeneration depend on the prime mover selected. Cogeneration in Ecuador will use diesel, biogas, and lignocellulosic biomass, which are the fuels available currently in the country (See Section 3.2). The GHG emissions were estimated for each type of fuel. The computations followed the concept of conservation of carbon, from the fuel combusted into CO2, according to the guidelines from the International Energy Agency [81]. For biogas, GHG emissions also considered

the release of methane to the environment that can be avoided by using effluents in palm oil mills to produce biogas via anaerobic digestion [28].

(b) Emissions avoided by replacing thermal power plants

This computation consisted of determining how much fossil-derived fuels could save the country due to the substitution of existing or expected thermal power plants for electricity production (which could be a necessity to offset hydropower generation capacity in the country, especially during the dry season of the year) by cogeneration in industrial plants. To make easier the computations, it was assumed that the efficiency of large thermal power plants is ~35% [80] (although the efficiency of some existing thermal power plants in Ecuador is lower). The expected efficiency of the cogeneration plants taken as a reference was calculated in five representative companies (including a hospital and a hotel, where trigeneration is possible). Results showed efficiencies >70% in all cases. Thus, the difference in efficiency in a scenario without cogeneration and a scenario with cogeneration was conservatively taken as 30%.
