Maize crop residues have great significance, particularly in developing countries, where the harvest of maize ears and their natural drying is widely applied. After drying and grain threshing, maize cobs are available for energetic use on farmers' yards. Shortcomings for their energetic utilization by combustion, in comparison with wood, are higher contents of potassium, chlorine, and nitrogen, and lower ash softening point. Tests in small wood chip boilers showed that the size of maize cobs should be reduced in order to facilitate better combustion and feeding with commonly used screw conveyors. Desirable length of particles should be 1-1.5 of their diameter. Within the framework of the Eureka project, a low-cost maize cobs crusher was developed and tested. It consists of a drum with six rows of knives, stationary comblike knives, and a screen situated below the drum. The test resulted with working parameters that enable appropriate size reduction. Analyses of crushed material showed that over 80% of particles were in the range of 3.15-45 mm, less than 1% smaller than 1 mm, and less than 1% larger than 63 mm. This granulation is comparable with size class P45 for wood chips in accordance with standard DIN CEN/TS 14961. Further investigations should focus on improving the combustion facilities, in order to avoid formation of ash slag, and keeping exhaust gas characteristics within values defined by legislation.

maize cobs; crushing; biofuel