Insight into the Effects of Biochar on Manure Composting: Evidence Supporting the Relationship between N₂O Emission and Denitrifying Community

Abstract

Although nitrous oxide (N2O) emissions from composting contribute to the accelerated greenhouse effect, it is difficult to implement practical methods to mitigate these emissions. In this study, the effects of biochar amendment during pig manure composting were investigated to evaluate the inter-relationships between N2O emission and the abundance of denitrifying bacteria. Analytical results from two pilot composting treatments with (PWSB, pig manure + wood chips + sawdust + biochar) or without (PWS, pig manure + wood chips + sawdust) biochar (3% w/w) demonstrated that biochar amendment not only lowered NO2(-)-N concentrations but also lowered the total N2O emissions from pig manure composting, especially during the later stages. Quantification of functional genes involved in denitrification and Spearman rank correlations matrix revealed that the N2O emission rates correlated with the abundance of nosZ, nirK, and nirS genes. Biochar-amended pig manure had a higher pH and a lower moisture content. Biochar amendment altered the abundance of denitrifying bacteria significantly; less N2O-producing and more N2O-consuming bacteria were present in the PWSB, and this significantly lowered N2O emissions in the maturation phase. Together, the results demonstrate that biochar amendment could be a novel greenhouse gas mitigation strategy during pig manure composting.

Effect of turning frequency and season on composting materials from swine high-rise facilities

“…In these composts, concentrations of denitrifiers were similar in FT and ST composts and there were no significant differences in concentrations between samples regardless of turning frequency, compost time or season (Table 5). This is in contrast to findings of Angnes et al (2013) and Wang et al (2013) which showed that concentrations of genes for denitrification (i.e., norB, nosZ, nirK and nirS) varied over the course of composting and that the concentrations were correlated with N 2 O emissions in swine slurry composts. These HRFF materials had been accumulated/ stored and partially decomposed while under the high-rise facilities for two to three months prior to composting, likely permitting accumulation of denitrifiers and accounting for higher concentrations in the initial compost materials.…”

“…Similar criteria are necessary for amendments in HRFF; in this case woodchips were dry, maintained structure while under the production facility, and the size (average 1.9 ± 0.9 cm) was highly variable making them adequate for both liquid absorption and as bulking agent to supply structure and improve aeration. Initial nutrient levels and C/N ratios of the slurry-woodchip mix used in this study were similar to those of other swine waste composts (Tables 1 and 2; Bustamante et al, 2013;Tiquia et al, 2002;Wang et al, 2013) although initial C/N ratio and moisture content were lower than similar products from other HRFF (Table 1; Keener et al, 2001;Stowell, 2002). The initial swine slurry-woodchip mix obtained for the FT and ST differed significantly in terms of pH, N, ammonium (NH 4 + ), phosphorous (P), potassium (K), moisture and C/N ratio (P < 0.10); likely due to differences in the amount of time the material was maintained under the finishing facility, the amount of bulking material added, frequency of turning and/or seasonal conditions (temperature, moisture, humidity).…”

“…Ammonical nitrogen was high in the initial HRFF materials (3.22 g k À1 for FT and 5.24 g kg À1 for ST) used in this study, but was in the same range as those found in other livestock composts (Ros et al, 2006;Tiquia et al, 2002;Wang et al, 2013). In this case, high initial NH 4 -N suggests that, in addition to high concentrations in the manure itself, easily degradable OM was being converted to NH 4 -N through ammonification while the slurry-woodchip mix was under the HRFF.…”

Effects of aeration and internal recycle flow on nitrous oxide emissions from a modified Ludzak–Ettinger process fed with glycerol

“…S3(e)): nosZ gene clade II was 2.8-fold more abundant on day 131 than on day 228, indicating that higher abundances of N 2 O-reducing bacteria facilitated N 2 O consumption in the anoxic tank. The degree and relative rate of N 2 O consumption are potentially reflected in the abundance ratio of nosZ/(nirK+nirS) (Wang et al 2013). The abundance ratios of the genes are presented in Fig.…”

The Influence of Biochar Addition on Chicken Manure Composting and Associated Methane and Carbon Dioxide Emissions

“…Limited literature indicated that (1) biochar can be used as a bulking agent. The aeration and structure of compost materials may be improved due to the high porosity and low density of the biochar (Sonoki et al 2011); (2) biochar can hold moisture due to its large porosity and high water holding capacity (Wang et al 2013). Appropriate moisture content is critical to composting; (3) due to its large surface and porosity, biochar may alter and retain microorganisms in composting (Zhang et al 2014).…”