Utilization of medical stone to improve the composition and quality of dissolved organic matter in composted pig manure

https://doi.org/10.1016/j.jclepro.2018.06.230Get rights and content

Highlights

  • Medical stone improve the biodegradation of alcohol, proteins and aliphatics.

  • Medical stone enhanced the aromaticity, molecular weight and humificationof compost.

  • Medical stone increased the humic-like matter while decreased the fulvic-like matter.

  • 10% medical stone addition best promote the composting process and efficiency.

Abstract

This research was conducted to evaluate the effect of medical stone (MS) on the dissolved organic matter (DOM) extracted from composted pig manure (PM). Five treatments with different MS amounts (0%, 2.5%, 5%, 7.5% and 10% of PM by dry weight) were mixed with the initial feedstock and composted for 60 days. DOM was extracted from the composted materials and characterized using spectroscopic techniques, including UV–visible, Fourier transform infrared (FTIR) and fluorescence spectroscopy. The results showed that the addition of MS improved the biodegradation of protein-like materials, ether, alcohols, and polysaccharides. Compared to the control, the ratios of FTIR spectra peaks (1645 cm−1/1407 cm−1, 1645 cm−1/2930 cm−1, and 1645 cm−1/1003 cm−1) in treatments in which MS was added were higher, and the peak ratio (1645 cm−1/1103 cm−1) was increased by 4.54%–10.22%. Adding MS could also increase the SUVA254 and SUVA280 values while decreasing the E250/E365 ratio, which indicates that the addition of MS increases aromaticity and molecular weight of the compost as well as humic-like compounds. Furthermore, the addition of MS improved the efficiency of the composting process and the rate of humification. The Pi,n of region V in the MS amended treatments (53.86%–56.66%) was higher than in the control (52.17%), and 10% MS addition yielded the highest value. Overall, the results show that the addition of 10% MS to PM is beneficial to the composting process.

Introduction

Composting is widely accepted as an appropriate management technique for disposing of and recycling organic waste, such as sewage sludge, animal manure, food waste and municipal solid waste (Li et al., 2012, Zhang and Sun, 2015, Chan et al., 2016, Awasthi et al., 2017). Composting technology can reduce the volume and weight of the organic waste, and generate a stable and harmless product (compost), which can be used as a soil amendment or fertilizer (Bernal et al., 2009). However, conventional composting still presents several drawbacks, such as nitrogen loss, low composting efficiency and undesirable final product quality (Wang et al., 2016a). The use of unstabilized or immature compost will poison crops, inhibit seed germination and adversely affect the ecology (Huang et al., 2006). Therefore, improvement in composting technology and compost maturity are both essential for enhancing the use of compost.

In recent years, the incorporation of mineral additives (e.g., biochar, zeolite, lime and medical stone) to improve the composting process, promote compost maturity, and accelerate the organic matter degradation, has been widely reported (Dias et al., 2010, Gabhane et al., 2012, Awasthi et al., 2016a, Wang et al., 2017). Turan (2008) and Villasenor et al. (2011) discovered that adding zeolite could reduce the salinity levels of compost and improve the quality of the final product. Dias et al. (2010) stated that co-composted poultry manure with wood biochar could promote the degradation of organic materials and the maturation of compost, which was in agreement with the results of Khan et al. (2014), who studied chicken manure composting. Moreover, some researchers found that adding a mixture of additives could also improve composting efficiency and promote OM humification (Zhang and Sun, 2015, Awasthi et al., 2016b). Overall, the addition of mineral additives could improve the porosity and microbial activity during composting, facilitate the organic matter transformation, and enhance the quality of the end product (Li et al., 2012, Chan et al., 2016, Awasthi et al., 2017).

Most of the biological activity in the composting process occurs in a water-soluble phase, and the variation of dissolved organic matter (DOM) could reflect the biochemical transformation of organic materials and the stabilization of compost products (He et al., 2013a, Wei et al., 2014). Additionally, DOM contains various kinds of oxygen-containing and aromatic functional compounds, which could interact with a number of inorganic and organic contaminants (Plaza et al., 2009). Thus, knowledge of the composition and structural characterization of DOM extracted from compost is very important for evaluating the quality and maturation of the final compost. Meanwhile, improving the composition and quality of dissolved organic matter is beneficial for the successful utilization of compost. To date, different type of spectroscopic techniques such as UV–visible, Fourier transform infrared (FTIR), and fluorescence spectroscopy, have been utilized to assess the composition, chemical structure and spectroscopic features of organic substances that extracted from the compost, such as humic acid, fulvic acid and DOM (Shao et al., 2009, He et al., 2011, Xi et al., 2012, Song et al., 2015). Furthermore, substantial previous research has indicated that integrating various spectroscopic methods (FTIR, UV–visible, and fluorescence) to characterize OM is better than using a single spectroscopic technique (Xi et al., 2012, Wei et al., 2014, Song et al., 2015). With the help of the spectroscopic techniques, some research has been conducted to explore the effect of biogas residue and microbial agent on chemical structure and molecular weight variations of DOM and fulvic acid (Xi et al., 2012, Song et al., 2015).

The use of medical stone, a novel mineral additive, has been applied to pig manure and sewage sludge composting to improve nitrogen conservation and OM degradation as well as enhancing the composting process (Wang et al., 2016b, Awasthi et al., 2018). However, the effect of adding MS on the variation of DOM generation during PM composting has not previously been reported. Therefore, the aims of this research are to investigate the structure and composition of DOM during PM composting when different amounts of MS are added. This research may supply important information regarding the application of mineral additives for organic waste composting.

Section snippets

Materials and the composting process

The PM and sawdust used in this study were gathered from a local hoggery and wood–processing plant in Yangling township, Shaanxi, China. The mineral additive (medical stone) was obtained from Shijiazhuang Jiacheng Building Materials Co. Ltd., China. Fresh PM and sawdust were mixed at a ratio of 2:1 (dry weight), and different dosages (0%, 2.5%, 5.0%, 7.5% and 10%) of MS were added into the initial feedstock on a dry weight of PM basis, and denoted as the control, T1, T2, T3 and T4,

FTIR spectra

The FTIR spectra of all samples contained similar peak locations (Fig. 1). The major absorption bands were characterized by (i) Osingle bondH stretching of phenols, carboxylic, and alcohols at ∼3400 cm−1; (ii) Csingle bondH stretching vibrations of aliphatic structure at ∼2930 cm−1; (iii) mainly Cdouble bondC skeletal vibrations of aromatic rings at∼ 1645 cm−1; (iv) Nsingle bondH deformation and Cdouble bondN stretching of amides at ∼ 1570 cm−1; (v) Csingle bondO asymmetrical stretching of carboxyl and symmetric stretching of the COOat ∼1407 cm−1, (vi) Csingle bondO

Conclusions

FTIR spectra of DOM show that the easily degradable organic matter such as protein-like material, polysaccharides, alcohols and aliphatics decrease after composting, and by increasing the amount medical stone, the degradation rate of organic matter with sample structures is elevated. The UV–visible spectra of DOM indicates that the addition of medical stone could enhance humification, molecular weight and aromatic polycondensation. Fluorescence spectra suggest that the content of fulvic- and

Acknowledgment

The authors are grateful for the financial support from a Research Fund for International Young Scientists from National Natural Science Foundation of China (Grant No. 31750110469), and The National Key Research and Development Program of China (2016YFD0800606). We are also thanks to our all laboratory colleagues and research staff members for their help.

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