quantified the total biomass production in Spain from 2005 to 2007. It was found that an average of 17.4 MT of crop by-products was produced yearly. Among these, 83% was cereal straw (about 14.5 MT). In this case, Ba for cereals corresponded to 50% of their Bt. Similar results were presented by IDAE (Instituto para la Diversificación y Ahorro de la Energía) in the PER11-20. In this work, crop by-products referred only to cereal straw and corn stalks and Bu was estimated to be 50% of Bt. The results were in concordance with those of Hernández and Fuertes (14.5 MT). Neither of these two works considers Bf, although it seems to be a relevant factor, especially in Spain, where more than the 50% of the soils are classified as medium-high risk of desertification.