Changes in Phosphorus Fractions and Nitrogen Forms During Composting of Pig Manure with Rice Straw

The study was conducted to reveal P fractions and N forms changing characters during composting of pig manure with rice straw.During composting,the NH 4 ＋-N concentration decreased and reached at a relatively low value（〈400 mg kg-1） in the final compost,while the NO 3--N concentration increased.Total N losses mainly occurred during thermophilic phase due to the high temperature,the high NH 4 ＋-N concentration and the increase of pH value.Labile inorganic P was dominated in the pig manure and initial compost mixture.During composting,the proportion of labile inorganic P of total extracted P decreased,while the proportion of Fe＋Al-bound P,Ca＋Mg-bound P and residual P increased.The evolutions of the proportion of labile inorganic P,Fe＋Al-bound P and Ca＋Mg-bound P were well correlated with the changes of pH value,organic matter and C/N ratio.Therefore,composting could increase the concentration of N and P and decrease the presence of NH 4 ＋-N and labile P fractions which might cause environmental issues following land application.

A pilot field-scale study on biotrickling filter treatment of NH_3-containing odorous gases from organic waste composting plants

The use of a biotrickling filter was investigated for a pilot field-scale elimination of NH3 gas and other odorous gases from a composting plant in Tongzhou District, Beijing. The inlet gas flow rate was 3500 m3/h and NH3 concentration fluctuated between 2.76–27.84 mg/m3, while the average outlet concentration was 1.06 mg/m3 with an average of 94.9% removal. Critical volumetric loading (removal efficiency=100%) was 11.22 g-N/(m3·h). The odor concentration removal was 86.7%. NH3 removal efficiency decreased as the free ammonia (FA) in the trickling liquid increased. The pressure drop was maintained at about 50 Pa/m and was never more than 55 Pa/m. During the experiment, there was neither backflushing required nor any indication of clogging. Overall, the biotrickling filter was highly efficient and cost-effective for the simultaneous biodegradation of NH3 and other odorous gases from composting, suggesting the possibility of treating odorous gases at the industrial level.

Comparative effects of composted organic waste and inorganic fertilizer on nitrate leachate from the farm soils of northern Guam

The purpose of this study was to quantify the release of nitrate into vadose zone as well as the nitrogen-holding capacity of compost applied on calcareous soils of northern Guam amended with both inorganic fertilizer and composted organic waste,to examine potentially adverse effect of these nutrient materials to groundwater quality.Three different nitrogen levels each of the composted organic waste and the inorganic fertilizer were applied to corn(maize)(farmland)study plots for three consecutive seasons,two dry and one rainy season.During each season,soil organic matter(SOM,w/w%)content and carbon-nitrogen ratio(C/N,w/w%),were determined for analysis of the nitrogen-holding capacity of these calcareous soils.Nitrate levels in soil pore water were also determined for study of potential groundwater contamination.For three seasons,compost plots showed higher SOM%contents and lower C/N%than fertilizer plots.That is,compost-treated soils showed higher SOM content and adsorbed more nitrogen under normalized soil mass than did fertilizer-treated soils.Nitrate levels in pore water were generally higher on compost plots during early stages of corn but were generally higher on fertilizer plots during active leaf,tasseling,and maturity stages.During the rainy season,nitrate leachate seemed to increase,but this trend could not be confirmed because rainfall amounts were not measured.Overall,composted organic waste proved to be a good amendment for soil productivity and agricultural sustainability while reducing nitrate leachate from northern Guam farmland.

Humification characterization of biochar and its potential as a composting amendment

Biochar has received increasing attention due to its applications as a soil amendment. Here, the chemical properties of solid and water-extractable fractions of four biochar samples were investigated. The results showed that wood biochar and bamboo biochar samples were 60%-80% more hydrophobic than those of rice husk biochar and rice husk ash. In addition, the acidity was 3.88 mmol/g from the total functional groups and 1.03 mmol/g from the carboxyl groups/lactones/phenols found in the wood biochar sample, which were about 1.5 times greater than those of the bamboo biochar sample. These functional groups could be used to determine the sorptive capacity of biochar for ionic solutes and water content and to increase the degradation of compost organics. The wood biochar sample was found to have the most humification materials （fulvic acid-like material ＋ humic acid-like material） in the water-extractable fraction, which was 3-10 times higher than that in the rice husk biochar and rice husk ash; humified materials were not detected in the bamboo biochar sample. Humification materials in biochar may be involved in increasing the proportion of humic acid-like materials in humic-like substances within the compost product. Wood biochar had better hydrophobic, sorptive, aromatic, and humification properties compared to other biochars, suggesting that it may be used in composting in order to exert its effect as both a bulking agent and a composting amendment during the solid waste composting process.