Does it make sense for a tropical middle income country to burn rice straw at the coal power plants? This note documents an empirical model of the rice straw cofiring sector. It is an implementation of the theoretical equations described in the manuscript Economics of co-firing rice straw in coal power plants in Vietnam. Blending biomass with fossil fuels is a relatively low-cost technology to use renewable energy in the electricity generation sector. Most coal power plants can co-fire a small fraction (<10% energy) of biomass without major retrofit. In high income countries, over a hundred of power plants cofire biomass, often because governments forced utilities to deliver a minimum fraction of their electricity from renewable sources. ...