Migration And Transformation Of Nitrogen And Phosphorus During Liquefaction Of Pig Manure And Cattle Manure

Nowadays,China's livestock and poultry breeding industry is becoming more and more intensive,resulting in the accumulation of a large number of livestock and poultry manure.As a unique kind of biomass,livestock manure is rich in nutrients.It is a necessary measure to develop rational manure to prevent nutrient loss and pollution to the environment.As a highly efficient thermochemical technology,liquefaction has been started to be applied in livestock manure treatment.This study compares the morphological structure of nitrogen and phosphorus in livestock manure before and after liquefaction.In order to explore the migration and transformation of nitrogen and phosphorus in the liquefaction process,the following work has been carried out:First,the biomass components in the manure were tested.The raw materials are pig manure,cow manure and biogas residue,and then four different liquefaction temperatures were set.They are 180?,220?,260 ? and 300?,respectively.Nitrogen and phosphorus in liquefied products were studied at different liquefaction temperatures.The recovery and extraction experiments of inorganic phosphorus showed that after liquefaction,phosphorus is mainly concentrated in biochar,and the residual rate reached over 90%.Most of the more active phosphorus is converted into more stable inorganic phosphorus,wherein the recovery ratio of Ca-P in the pig manure liquefaction product exceeds 50.65%.In addition,the content of available phosphorus has also been greatly reduced,and the effective phosphorus in pig manure has even decreased by 71.95%.X-ray diffraction(XRD)analysis shows that the proportion of phosphorus with higher active state in biochar is significantly lower at high temperature,and phosphorus tends to combine with heavy metals to form pyrophosphate,orthophosphate and phosphate minerals.Elemental analysis of the liquefied product shows that the nitrogen content in the biochar exceeds 60%.With the increase of liquefaction temperature,the proportion of nitrogen in biochar decreases,and most of the nitrogen gradually tends to be enriched in bio-oil.A small amount of inorganic nitrogen is dissolved in the liquid phase,but not detected in the gas phase.Nitrogen-containing compounds.X-ray photoelectron spectroscopy(XPS)and gas chromatography-mass spectrometry(GC-MS)results show that the decomposition of protein nitrogen with the increase of liquefaction temperature will produce a series of nitrogen-containing pollutants.Amine nitrogen is an important precursor for the production of nitrogenous contaminants.Exploring the migration and transformation of nitrogen and phosphorus in the process of liquefaction.It not only can recover a large amount of phosphorus from livestock waste to reduce environmental pollution,but also produce very little nitrogen-containing pollutants after liquefaction treatment,which proves that liquefaction technology is very reliable and environmentally friendly.