Influences Of Catalysts On Properties Of Carbonization Reaction Products

Biochar is a newly emerged technology to cope with the greenhouse effect. It is also a new method to improve soil fertility. Both of the above are one of the hot-topics in today’s scientific research. Most of these researches were focused on acid soil, laboratory incubation experiment, or field experiment of a single growing-season. At the same time, catalysts were widely used in bio-energy production. Based on these facts, two researches were conducted in this study. The first one was the long-term impact of ordinary biochar on soil properties and crop yields in a field experiment running on a calcareous soil, and the second one was a laboratory experiment, focusing on the effect of catalysts on the properties of products of the hydrothermal carbonization of sewage sludge and the pyrolysis of crop straw. The main aim of this study was to provide an experimental basis for the further agricultural application of these catalysts-contained biochar. The main results are listed as followed:The catalysts shortened the heating time of sludge hydrothermal carbonization process from9to23%, meaning saving energy somewhat. The catalysts significantly reduced the content of C and N in the hydrochar, and CaO significantly increased the acid buffer capability and pH of the hydrochar. The catalysts reduced the carbonization degree of the hydrochar. The catalyst significantly reduced the concentration of C in the hydro-liquid, and significantly improved the biochemical degradability of the hydro-liquid. The dispersed heavy metals in original sludge were concentrated in the hydrochar, the hydro-liquid and the tar. The impact of CaO on content and activity of heavy metals in the hydrochar was greater than that of FeCl3. CaO increased the proportion of acid-soluble heavy metals in hydrochar while FeCl3had little effect on the activity of the heavy metals activity.K2CO3or K2CO3/CaO mixture reduced the concentration of total C and N in the biochar, and increased the ratio of DOC, easily mineralized N, exchangeable P and K in the biochar, meaning catalysts could increase the nutrients availability of the biochar. The K2CO3or K2CO3/CaO mixture increased pH and CEC of the biochar, but reduced iodine adsorption of the biochar. K2CO3or K2CO3/CaO mixture reduced the carbonization degree of the biochar, indicating catalysts could reduce the stability of the biochar, improving the degradability of the biochar, thereby improving the bio-driving power of the biochar.Application of biochar to calcareous soil had no significant effect on the average annual yield of winter wheat and summer maize. The most appropriate dosage of biochar was60t ha-1. Biochar applying had little effects on soil available nutrient, but improved the soil bulk density and water holding capacity in this calcareous sandy soil.The above results shows two facts, one is that application of ordinary biochar to calcareous soil has no negative effects both on soil properties and crop yield, and the second is that the agronomic properties of the catalyst-contained biochar is better that that of the ordinary biochar. Of course, the agronomic effects of the catalyst-contained biochar need to be tested by the field experiment.