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Graphical abstract Highlights • Amendment of biochar to composting significantly prolonged thermophilic stage duration. • Biochar increased organic matter degradation derived heat and water vaporization heat. • Heat exchange was found a two-fold reduction in response to biochar addition. • Biochar displays potential to ameliorate composting at low ambient temperature. Abstract In this study, the effects of biochar amendment on swine manure composting performance at temperatures in the −5 °C–15 °C range was investigated. Monitoring result showed biochar addition significantly prolonged thermophilic stage duration to meet harmless standards of livestock manure compost at 5 °C, assisting a seemingly difficult composting to succeed. Additionally, from viewpoint of thermal balance, biochar increased organic matter degradation derived heat from 50.4% to 86.5% and water vaporization heat from 29.6% to 73.5% while decreasing heat exchange by two-fold. Overall, the results presented herein indicated that biochar has potential to play a positive role in amelioration of animal manure composting at relatively low ambient temperature and provide insight into how biochar influences heat generation and flow during composting. [ABSTRACT FROM AUTHOR]

A comprehensive model of thermal balance and degradation kinetics was developed to determine the optimal reactor volume and insulation material. Biological heat production and five channels of heat loss were considered in the thermal balance model for a representative reactor. Degradation kinetics was developed to make the model applicable to different types of substrates. Simulation of the model showed that the internal energy accumulation of compost was the significant heat loss channel, following by heat loss through reactor wall, and latent heat of water evaporation. Lower proportion of heat loss occurred through the reactor wall when the reactor volume was larger. Insulating materials with low densities and low conductive coefficients were more desirable for building small reactor systems. Model developed could be used to determine the optimal reactor volume and insulation material needed before the fabrication of a lab-scale composting system. [ABSTRACT FROM AUTHOR]

Biodrying was firstly used for post-treatment of anaerobically digested sludge (ADS) with wheat residues (WR) as bulking agents to improve its quality and reduce its amount. After 18days of biodrying, water was removed at a rate of 664.4gkg(-1) initial water at the typical ratio of ADS/WR. A separate aerobic incubation test showed that 8.11-14.84% of volatile solid (VS) was degraded in the ADS. The degradation of C- and H-containing materials (e.g., carboxylic acid) accounted for oxygen consumption and VS loss. The WR also showed strong biodegradability, and contributed approximately 86.01% of biogenerated heat during the process. Thermal balance analysis showed that the produced heat was primarily consumed through water evaporation and conductive transfer. 454 pyrosequencing implied the obvious succession from the anaerobic to aerobic microorganisms during the process. Some dominant Firmicutes, such as Clostridium and Bacillales, seemed to relate with organic matter degradation of the substrates., (Copyright © 2014 Elsevier Ltd. All rights reserved.)