[Analysis on the target product from sewage sludge pyrolysis and experiments on using the char for enhancing plant...

Characteristics of sewage sludge pyrolysis under low temperatures were studied and the influences of reaction temperature and moisture content on products distribution and their properties were also investigated with a purpose to select a proper target product. After a dissective comparison, char produced from the pyrolysis process was chosen as the target product and then its effect on plant cultivation was checked by using it to plant garlic when blended into normal soil; also its heavy metals contents and their transfer to the garlic were investigated. The primary research results showed that with the moisture content reduced to a certain level, char production was above 40% of sewage sludge when the pyrolysis process took place under 550 degrees C; ash content of the char is around 60% - 65%, but it is rich with nitrogen, phosphorus and potassium contents. The heavy metal contents in the char meet up with the limitations for land use, and the garlic stems planted in the soil blended with the char grew much faster than those planted in normal soil with their averaged height being 3-4 cm higher; however the heavy metal contents in the fast-growing garlic stems were a little higher than that in the normal ones, which was not suitable for edible plants. The results obtained suggested that char produced from sewage sludge pyrolysis process could be a target product arranged for land use especially for non-edible plant cultivation.