BIOCHAR IN RESIDUAL ASH FROM GASIFIER COOKSTOVES

摘要

Biomass based cooking with open fire is still used by more than three billion people worldwide . Open fires normally produce ash, which contains both pure ash and some unbumed carbon or biochar. The possible agricultural advantages by biochar as a soil amendment, has increasingly been discussed the last decade . There exist many different types of cookstoves suited for simultaneously cooking and biochar production. Top Lit Up Draft (TLUD) - Natural Draft stoves are tested in several countries but represent a risk for condensation of pyrolysis gases on the charcoal during the combustion phases. In the present study two different TLUD stoves were tested according to the laboratory-based Water Boiling Test (WBT) with two different fuels: wood chips of oak, Quercus petrea, and standard 6 mm wood pellets. Two of the main goals were to evaluate cooking efficiency and biochar production including suitability as a soil amendment. After the WBT, the combustion continued until the flames disappeared and the remaining biochar was then quenched, cooled and put into plastic bags and sealed for later analysis. The biochar yield and corresponding cooking efficiency are shown in figure 1. The biochar yield is lower for higher efficiencies and in general around 19-23 % based on the biomass input. The biochar was analyzed and some of the major findings are shown in table 1. PCB and heavy metal content were in all cases low.