Feasibility Study On Artificial Soils Made Of Solid Wastes

A large number of organic and inorganic solid wastes emerge owing to human life and production in modern society. The ways to treat wastes relate to people’s living environment and recycling of resources. So it is a very meaningful and promising work to exploit the wastes scientifically and reasonably on the basis of grasping the nature of them. In this study, the work was carried out on the focus of the local’s representative, large output organic and inorganic wastes. Explored the possibility to use them making artificial soils, finding out changes of some important parameters during the process and provided references for the further application of this technology to the actual production.According to the principles of economy and obtaining materials from local sources, this experiment chose organic and inorganic wastes of large amounts in the region. The organic wastes were sewage sludge, cow dung, vermicompost and mushroom residue. The inorganic wastes were fly ash, gypsum, steel slag and coal gangue. The organic wastes mainly relied on sewage sludge, cow dung and vermicompost, while take mushroom residue as secondary reliance. The inorganic wastes mainly relied on fly ash, while take gypsum, steel slag and coal gangue as secondary reliance. Nine treatments were set, and the ratio of organic and inorganic wastes were 1:1,1:2,1:3.The physicochemical and biological properties of artificial soils cultured through the constant temperature and humidity were measured. The results obtained as follows:(1) The nine artificial soils were made of different materials and different proportions. Of them, content of most water-stable aggregates have reached that of water-stable aggregates in the natural soil. The types of solid wastes、mixing ratio and culturing method were confirmed in this experiment. And these can give the artificial soils basic physical properties similar to the natural soil.(2)The pH will be effected by the transformation of the organic solid wastes during the cultivation process. Therefore, the pH value predicted by the method of the pH value of the critical ratio has a large difference with the measured pH value. Considering one kind of organic solid wastes in the same organic fractions(sewage sludge, cow dung, vermicompost) and pH value of fly ash of inorganic solid wastes, and then calculated by the method of the theory of pH, the pH value predicted is similar to the measured pH. After culturing, the pH value of artificial soils accord with the plant growth needs.(3)In the process of artificial soil preparation, organic matter will degrade, resulting in the content of organic matter reducing greatly. So in the preparation, organic components should be accounted for a large proportion. The result showed that, when the organic solid wastes and inorganic solid wastes ratio of 1:3, residual of organic matter has fallen below 6% in the artificial soils made of sewage sludge and earthworm manure and closed to the organic matter in fertile and natural soil. Therefore, mainly use the two kinds of organic solid wastes preparing artificial soils should no longer increasing the proportion of inorganic materials.(4) Nitrogen is the most important nutrient in the soil. Of the three kinds of organic solid waste treatments, carbon/nitrogen of the sludge and earthworm manure treatments is less, so the mineralization of organic nitrogen is strong during cultivation. Inorganic nitrogen increased and ammonium nitrogen transform into nitrate nitrogen significantly. Carbon/nitrogen of the cow manure treatment is larger. Although the mineralization of organic nitrogen is also very strong, ammonium nitrogen released was oxidized to nitrate nitrogen and being used by microbial extensive, therefore in the preparation of artificial soils with cow manure, the content of total inorganic nitrogen was significantly lower.(5)Heavy metals of solid wastes used in the experiment did not exceed the standards of agriculture permitted by the state. So it can be used for the preparation of artificial soil. Nine kinds of artificial soils were tested bio-toxicity and they were not biological toxic. So the materials and methods using for making artificial soil in this experiment have the environment safety and biological safety.(6) On the basis of the above results, it was feasible using the existing solid wastes in the local to make artificial soil. Taking the method of the experiment to treat solid wastes not only reduce the pollution to the environment caused by the solid wastes’random stacking, but also solve the problem of some nursery industry parks being short of soil resources. At the same time it can obtain certain economic benefits and promote the sustainable development of society.