Effect Of Adding Biochar On Cyanobacteria And Swine Manure Composting

Aerobic composting is an important way of disposing and recycling organic waste. A lot of manure produced by intensive farming are usually made of high quality organic fertilizer through aerobic composting. In recent years, aerobic composting is also used to deal with a lot of cyanobacteria produced by lake eutrophication. Currently organic waste composting exists some defects, including backward process, long composting cycle, large amount of nitrogen lossing and lot’s of greenhouse gas emissions. Because of cyanobacteria and poultry manure both have the characteristic of high water content, it will easily result in the loss of nitrogen in the process of composting. Biochar is a product which can be made by crop straw and other biomass waste under the conditions of limited oxygen and low temperature. Biochar has loose structure, large specific surface area,and strong adsorption, adding to the composting, it will maybe play a role in adjusting composting structure, promoting maturity extent and reducing greenhouse gases emissions. In this paper, wheat straw and rice shell biochar (two different proportions) were added to the compost of cyanobacteria, studying the effect of adding different kinds of biochar on nutrient content and maturity extent. At the same time, the effects of wheat straw biochar on maturity extent and greenhouse gases emissions during swine manure thermophilic aerobic composting were also investigated.The main conclusions are as follows:(1) At the end of composting, adding wheat straw biochar and a lower proportion of rice shell biochar were significantly reduced the content of NH4+-N, NO3--N and total nitrogen. Adding a higher proportion of rice shell biochar has no significantly difference in the content of NH4+-N and total nitrogen, but significantly increased 56.09% of NO3-N content compared to the pre-composting.(2) At the end of composting, adding wheat straw biochar and a higher proportion of rice shell biochar significantly increased seed germination index each by 95.14% and 47.49%, however, adding a lower proportion of rice shell biochar has no significantly difference on seed germination index.(3) The compost at the rate of 5:1 and 2.3:1 reached thermophilic composting stage 2 days ahead, and the period of maturation was shortened by 5 days as compared to treatment at the rate of 12:1. EC value of biochar compost were significantly reduced except the compost at a ratio of 2.3:1, which EC value has beyond the security scope of application.(4) The concentration of NH4+-N in biochar compost reached a steady state in 11 days ahead over the control. At the end of composting, NO3--N concentration in the biochar compost at the ratio of 12:1,5:1 and 2.3:1 were increased by 53.70%,148.36% and 27.61%, respectively. The losses of total nitrogen of compost was decreased by 32.07%for 12:1, 60.78% for 5:1 and 50.18% for 2.3:1 compared to the control.(5) Compared to the control, adding wheat straw biochar significantly decreased CH4 emission by between 82.03% and 96.93%. CO2 emission was decreased by 20.21%(5:1) and 41.10%(2.3:1). Whereas, NO2 emission of compost was increased by 66.61%for 12:1, 50.11%for 5:1, and reduced by 40.87% for 2.3:1.