•PAHs degradation in soils increased with added B + M or B + Y, but inhibited with added B + CP.•B + M and B + Y increased concentration of DOC and abundances of PAH-degraders in soils.•B + CP ...decreased abundances of genera and functional genes related to PAHs degradation.
A incubation experiment was conducted to investigate whether combined amendment of biochar (B) and compost (CP), mushroom residue (M) and corn straw (Y) could enhance biodegradation of polycyclic aromatic hydrocarbons (PAHs) in contaminated soils. After 77 days of incubation, both B + M and B + Y significantly (p < 0.01) increased removal rate of PAHs compared with amendment of biochar alone. However, B+CP resulted in a significant (p < 0.01) decreasing of PAHs removal. Compared with no biochar and no organic substrates addition (CK) and B, both B+M and B+Y significantly (p < 0.01) enhanced concentrations of dissolved organic carbon (DOC) and were favorable for the microbial growth reflected by microbial biomass carbons (MBC) and emission of carbon dioxide. Redundancy analysis (RDA) indicated that B + CP, B + M and B + Y separated the bacterial community compared with CK and B. However, the community composition structure in B + CP was different from that of B + M and B + Y. Moreover, the abundance of some PAHs degraders and PAH degradation genes predicted by PICRUSt software was promoted by B + M or B + Y, whereas that was inhibited under B + CP. The present study suggested that both B + M and B + Y could accelerate biodegradation of PAHs mainly through increasing the concentration of DOC and the abundances of microbial PAH degraders in soils.
•Phosphogypsum increased N2O but reduced NH3 emission, thus enhancing compost TN.•Ca-Mg-P fertilizer reduced N2O emission, but enhanced NH3 & TN losses in composting.•Blending these two additives ...could mitigate NH3 & N2O emissions for N conservation.•These two additives could also improve the compost maturity and quality.
This study investigated the performance of phosphogypsum and calcium magnesium phosphate fertilizer for nitrogen conservation during pig manure composting with cornstalk as the bulking agent. Results show that phosphogypsum increased nitrous oxide (N2O) emission, but significantly reduced ammonia (NH3) emission and thus enhanced the mineral and total nitrogen (TN) contents in compost. Although N2O emission could be reduced by adding calcium magnesium phosphate fertilizer, NH3 emission was considerably increased, resulting in an increase in TN loss during composting. By blending these two additives, both NH3 and N2O emissions could be mitigated, achieving effective nitrogen conservation in composting. More importantly, with the addition of 20% TN of the mixed composting materials, these two additives could synergistically improve the compost maturity and quality.
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•Bamboo biochar aids compost pile porosity, air permeability and oxygen supply.•Biochar reduces emissions of NH3 and greenhouse gases (CO2, CH4, N2O).•Biochar provides nutrients and ...protective shelter for compost microbial growth.•10% (w/v) low-cost biochar aids organic matter degradation and compost maturation.•Particle characterization of composting matrix may well reflect the process.
The objective of the present study was to study the changes in compost particle and its relationship with other physicochemical process during aerobic composting employing 5%, 10%, 20% or 0% biochar. Changes of physicochemical and biological parameters and gases emissions indicated that appropriate biochar addition improved both degradation rate and final degree of the organic matter and simultaneously reduced CO2, CH4, N2O and NH3 emissions. Beneficial properties like stability and high porosity of biochar could optimize composting environment, accelerate the process of composting and facilitate microbial growth during the thermophilic composting stage, with increases of 1.3×1010 to 1.5×1011cfu/g. Analysis of microstructure characterization of the changes in compost particle indicated that biochar amended contributed to better degradation of compost particle with smaller sizes and a higher degree of looseness. Ultimately, 10% biochar addition optimized organic matter degradation, while reducing ammonia and greenhouse gas emissions and costs.
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•Adding amino acids promote humification process of lignocellulosic composting.•Assess the degradation and transformation of organic components during composting.•Reveal mechanism of ...organic components transformation with amino acids addition.•Propose a regulation method for improving carbon sequestration of lignocellulose.
The aim of this study is to assess the effectiveness of protein-like precursors addition on promoting humification process during lignocellulose-like biomass composting through adding amino acids to compost. The humification indexes of R1 and R2 was significantly higher than that of CK (P < 0.05). The decreasing ratio of Maillard precursor concentration of R2 and R1 was higher than CK. Amino acids addition affected the bacteria community and environmental factors during composting. Variance partitioning analysis showed that humification process was strengthened with environmental factors, bacteria community, Maillard precursors. Structural equation model (SEM) analysis showed that amino acids had substantial impact on promoting humic acid (HA) formation. The combined application of protein-like wastes and lignocellulose-like wastes was suggested to improve carbon sequestration. This study lays a foundation for economically and effectively managing different types of straws by composting.
•Succession of dominant bacteria of different C/N ratio were characterized.•Higher C/N promoted the relative abundance of nitrogen fixing bacteria.•Higher C/N compressed the denitrifying ...bacteria.•Adjustment to C/N ratio could improve compost quality.
The aim of this work was to investigate how the initial C/N ratio during composting of chicken manure/corn stover mix affected the succession of dominant bacteria in the mix which led to the reduction of the total losses of N and C in the composting process. 16S rDNA sequencing indicated that the succession of predominant bacteria was significantly affected by the temperature and the initial C/N ratio during composting. Redundancy analysis showed that higher C/N appeared to promote the relative abundance of nitrogen fixing bacteria Thermoactinomyces, Planifilum, Flavobacterium, Bacillaceae, Pseudomonas,Sphingobacterium, Paenibacillus, Bacillus and Thermobifida, while compressing the denitrifying bacteria Pusillimonas, Ignatzschineria, Alcanivorax, Cerasibacillus, Truepera and Erysipelothrix. C/N ratio of 30:1 yielded the least C/N losses in the composting process, indicating that adjustment to the initial C/N ratio could affect nitrogen transforming bacteria to reduce the total losses of N and C and improve compost quality.
•Compost supplementation contributes to enhance the nutrient content in the final bio-input.•Nitrogen-fixing and ammonia-oxidizing bacteria can increase the nitrogen content in compost.•Adding ...phosphorus- and potassium-solubilizing microorganisms improves the compost quality.•Research in nutrient-enriched compost-type bio-inputs should be intensified.
The composting is an aerobic, microorganism-mediated, solid-state fermentation process by which different organic materials are transformed into more stable compounds. The product obtained is the compost, which contributes to the improvement of physical, chemical and microbiological properties of the soil. However, the compost usage in agriculture is constrained because of its long-time action and reduced supply of nutrients to the crops. To enhance the content of nutrients assimilable by the plants in the compost, its supplementation with nutrients and inoculation with microorganisms have been proposed. The objective of this work was to review the state of the art on compost supplementation with nutrients and the role played by the microorganisms involved (or added) in their transformation during the composting process. The phases of composting are briefly compiled and different strategies for supplementation are analyzed. The utilization of nitrogenous materials and addition of microorganisms fixing nitrogen from the atmosphere or oxidizing ammonia into more assimilable for plants nitrogenous forms are analyzed. Several strategies for nitrogen conservation during composting are presented as well. The supplementation with phosphorus and utilization of microorganisms solubilizing phosphorus and potassium are also discussed. Main groups of microorganisms relevant during the composting process are described as well as most important strategies to identify them. In general, the development of this type of nutrient-enriched bio-inputs requires research and development not only in the supplementation of compost itself, but also in the isolation and identification of microorganisms and genes allowing the degradation and conversion of nitrogenous substances and materials containing potassium and phosphorus present in the feedstocks undergoing the composting process. In this sense, most important research trends and strategies to increase nutrient content in the compost are provided in this work.
Municipal solid waste in developing countries mainly consists of degradable materials (>70%), which plays a significant role in GHG (Greenhouse gas) emissions in urban localities. The increasing ...municipal solid waste generation along with the high fraction of organic waste and its unscientific disposal is leading to emission of GHG (methane, CO2, etc.) in the atmosphere. Proportion of municipal solid wastes collected by the agencies disposed at identified sites is about 60%, while the balance is disposed-off at unauthorized disposal sites leading to the environmental consequences including greenhouse gas emissions. Mitigation strategy necessitates understanding of composition of waste for its treatment and management in an environmentally sound way. The study revealed that the per capita waste generated is about 91.01± 45.5g/day with the per capita organic waste generation of 74±35g/person/day. The household per capita waste generation was positively related with income and education levels, while negatively related with family (household) size. The organic fractions constitute 82% with the strong recovery potential and conversion to energy or compost range. The total organic waste generated is about 231.01 Gg/year and due to mismanagement consequent emissions are about 604.80 Gg/year. Integrated solid waste management strategy is suggested to manage the organic fractions through technology and policy interventions, which helps in mitigating GHG emissions with potential economic benefits.
In recent years, a wide range of organizations in developed countries have embarked on efforts to address the economic, environmental and social impacts of “food waste.” Based on more than 120 ...interviews and complementary observations in the United States and France, this paper examines how recent mobilizations impact the way surplus food is actually managed with respect to sustainable production and consumption. This analysis of multiple stakeholders' interests and motives complements a growing literature on food waste prevention and management focused on technical evaluations of “solutions.” Recent frameworks on food surplus and waste establish one hierarchy of preferable categories of solutions: first, prevention (reducing surplus at the source), then recovery (reusing for human consumption) and finally recycling (feeding animals, creating energy or compost). Fieldwork results show that actors with different interests in food commodity chains actually develop competing solutions, both within and between three hierarchies based on environmental, social and economic goals. In the long term, the solutions they promote may therefore not achieve “win-win-win” benefits for all actors and at all scales. Drawing on a distinction between “weak” and “strong” sustainability, this paper argues that “strong” prevention based on holistic changes in the food system is the most sustainable solution to food surplus and waste. It suggests that academics focus on strong food surplus prevention, but also that advocates encourage government and corporate actors to differentiate between weak and strong actions to diffuse strong sustainability across organizations and countries.
•Solutions to food waste offer competing economic, environmental and social benefits.•The most promoted solutions often overlook long-term environmental and social impacts.•A switch to “strong” prevention is necessary to reduce food waste sustainably.•“Strong” prevention questions consumption patterns and food systems in a holistic way.
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•Influence of biochar addition on nutrient transformation during composting.•Biochar addition improved the water-soluble nutrient contents during composting.•Higher dosage of biochar ...addition reduced the bioavailability of heavy metals.•Higher dosage of biochar addition reduced the maturity period.•150kgha−1 TKN compost amendments increased the Chinese cabbage biomass.
The influence of biochar amended dewatered fresh sewage sludge (DFSS)-wheat straw co-composting on nutrients transformation and end products quality was investigated. This is the first study to examine the biochar applied compost quality with different kgha−1 TKN on Brassica rapa L. growth. Seven mixtures were composted over 8-weeks period in 130-L reactor using the same DFSS with different concentration of biochar (2%, 4%, 6%, 8%, 12% and 18% on dry weight basis) and without additive added treatment served as control. The results indicated that compost with 8–12% biochar became more humified within 35days of composting, and the compost maturity parameters also showed that this could be much more feasible approach to increased water-soluble nutrients including NO3, DOC, DON, PO43−, K+ and Na+, but bioavailability of Cu, Zn, Ni and Pb content reduced as compared to control. Finally, results showed that 8–12% biochar was recommended for DFSS composting and 150kgha−1 TKN of compost dosages for organic farming.
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•The Cu (II) and Pb (II) binding property of compost-derived DOM were investigated.•Alcohols, ethers and esters showed a preferential binding with Cu (II) and Pb(II).•Protein-like ...matter showed a preferential binding compared with humic-like matter.•The DOM showed higher binding affinities with Cu(II) compared with Pb(II).•The Cu(II) and Pb(II) binding ability of the DOM decreased after composting.
Three dissolved organic matter (DOM) samples were obtained from municipal solid wastes at the initial (C0), high-temperature (C7) and mature (C51) period during composting. Two-dimensional correlation spectroscopy (2D-COS) analysis on Fourier-transform infrared (FTIR), ultraviolet visible (UV–vis), and synchronous fluorescence spectra (SFS) were used to investigate the metal binding properties of compost-derived DOM. Synchronous and asynchronous maps of 2D-FTIR-COS of DOM-Cu(II) and DOM-Pb(II) were similar, however, the susceptibility and binding sequence of the corresponding spectral region was different. The N-H (amide I), phenolic OH, and C–O of alcohols, ethers, and esters were the most susceptive in the C0, C7, and C51 samples, respectively. 2D absorption COS indicated that the preferential binding with Cu(II) was shown to be at 305 nm for C0, at 236 nm for C7 and C51, and with Pb(II) at 247 nm for C0, at 233 nm for C7 and C51. 2D-SFS-COS indicated that protein-like matter showed a higher susceptibility and preferential binding with Cu(II) than humic-like substances. DOM showed a higher complexing affinity with Cu(II) than Pb(II) on the basis of the log K values. Spectral techniques combined with 2D-COS are useful to understand the binding heterogeneities of ligand sites within DOM-Cu(II) or Pb(II) during the composting.
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