Abstract
In this study, the effects of apple pomace (AP) addition (0%, 5%, 10%, and 20% on a dry weight basis, named as control, AP1, AP2, and AP3) and citric acid (CA) addition on nitrogen conservation were investigated during aerobic composting of pig manure. Gaseous emissions of NH3 and N2O were inhibited by AP and CA addition, with AP’s effect greater. The inhibition improved with increasing AP addition. The AP3 treatment was the most effective on NH3 adsorption and transformation to {{bf{NH}}}_{{bf{4}}}^{{boldsymbol{+}}}-N, improved with subsequent transformation to {{bf{NO}}}_{{bf{3}}}^{{boldsymbol{-}}}-N, and inhibition of N2O and {{bf{NO}}}_{{bf{2}}}^{{boldsymbol{-}}} production. Compared with control, AP3 showed the highest inhibition of accumulated NH3 and N2O emission, by 57% and 24%, respectively, and with a 19% increase of total Kjeldahl nitrogen in the compost. The further pot experiment proved the application of the AP amendment compost could improve the yield and trace element nutrient accumulation in Chinese cabbage when planted in a typical Zn-deficient soil. This study illustrates that AP application benefits both compost nitrogen conservation and fertilizer quality.
Highlights
China is the biggest pork producing country in the world and approximately 715 million tons of pig manure (PM) were produced in 20131
The highest temperatures were obtained after 2 days with 62.6, 62.9, 61.4, 58.8, and 60.6 °C in control, and treatments of AP1, AP2, AP3, and citric acid (CA), respectively
The thermophilic phase was maintained about one week for the feedstock composition, which was necessary for obtaining a successful product[21]
Summary
China is the biggest pork producing country in the world and approximately 715 million tons of pig manure (PM) were produced in 20131. Some chemical additives such as Ca3(PO4)[2], MgCl2, FeCl3, Al2(SO4)[3], HNO3, and CaCl2, etc.[13] could be employed in composting for NH3 emission reduction through their chemical reactions with NH3 These commercial additives (mineral and biological) are effective in improving compost quality by inhibiting N loss, their usage is still restricted due to high cost and risk of excessive accompanying salt ions[4]. Recent studies showed that reducing the initial pH of the compost mixture by adding olive pomace can conserve N15 This method could lead to maximizing utilization of local resources. The aims of this study were to investigate the effect of AP addition with different amounts on the gaseous emissions of NH3 and N2O during the compost N conservation process. Concurrent treatment with citric acid (CA) was included in order to compare the effects of AP with an organic acid in composting
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