A third route, known as
pyrolysis, heats dried and ground biomass to about 550 ˚C in an oxygen - depleted
chamber (so the biomass doesn't burn), producing a mixture of gases, liquids, and a gray, carbon - rich solid called coke.
In GDI engines, fuel is sprayed directly into the combustion
chamber, which leads to incomplete fuel evaporation due to the limited time available for fuel and air mixing, resulting in pockets with high temperatures but insufficient oxygen, leading to
pyrolysis reactions and soot formation.