Synergistic effects of chemical additives and mature compost on reducing H2S emission during kitchen waste composting.

Additives could improve composting performance and reduce gaseous emission, but few studies have explored the synergistic of additives on H2S emission and compost maturity. This research aims to make an investigation about the effects of chemical additives and mature compost on H2S emission and compost maturity of kitchen waste composting. The results showed that additives increased the germination index value and H2S emission reduction over 15 days and the treatment with both chemical additives and mature compost achieved highest germination index value and H2S emission reduction (85%). Except for the treatment with only chemical additives, the total sulfur content increased during the kitchen waste composting. The proportion of effective sulfur was higher with the addition of chemical additives, compared with other groups. The relative abundance of H2S-formation bacterial (Desulfovibrio) was reduced and the relative abundance of bacterial (Pseudomonas and Paracoccus), which could convert sulfur-containing substances and H2S to sulfate was improved with additives. In the composting process with both chemical additives and mature compost, the relative abundance of Desulfovibrio was lowest, while the relative abundance of Pseudomonas and Paracoccus was highest. Taken together, the chemical additives and mature compost achieved H2S emission reduction by regulating the dynamics of microbial community.

Asynchronous Event-Triggered Output-Feedback Control of Singular Markov Jump Systems.

This study focused on the asynchronous event-triggered output-feedback controller design problem for discrete-time singular Markov jump systems (MJSs). A hidden Markov model (HMM) was employed to estimate the system mode, which cannot always be ideally detected in practice. Because the full state is also difficult to obtain in practical scenarios, an output-feedback control scheme was used. In addition, an HMM-based event-triggered mechanism was also employed in the design of the controller to reduce the communication burden of the networked system. Sufficient conditions for the stochastic admissibility of a closed-loop singular MJS with a prescribed H∞ performance index were established using the Lyapunov functional technique. Finally, design procedures for an asynchronous event-triggered controller were summarized as a linear-matrix-inequality-based optimization algorithm. Two examples were considered to verify the effectiveness of the asynchronous event-triggered output-feedback controller design method.

Asynchronous H∞ Control for Continuous-Time Hidden Markov Jump Systems With Actuator Saturation.

In this article, we address the asynchronous H∞ control problem of a class of hidden Markov jump systems (HMJSs) subject to actuator saturation in the continuous-time domain. A bunch of convex hulls is utilized to represent the saturated nonlinearity. Considering that there is an asynchronous mode mismatch between the system and the controller, we establish a hidden Markov model (HMM) to simulate the situation. By means of the Lyapunov theory, sufficient conditions are presented to ensure that the resultant closed-loop HMJS is stochastically mean square stable within the domain of attraction with a prescribed H∞ performance index. Furthermore, the state feedback gain matrix and the estimation of the domain of attraction are given by solving an optimization problem, which is constructed via linear matrix inequality (LMI) techniques. Finally, the reliability and validity of the derived results are examined by a numerical example.

Insight into the dynamic microbial community and core bacteria in composting from different sources by advanced bioinformatics methods.

Microbial communities are important for high composting efficiency and good quality composts. This study was conducted to compare the changes of physicochemical and bacterial characteristics in composting from different raw materials, including chicken manure (CM), duck manure (DM), sheep manure (SM), food waste (FW), and vegetable waste (VW). The role and interactions of core bacteria and their contribution to maturity in diverse composts were analyzed by advanced bioinformatics methods combined sequencing with co-occurrence network and structural equation modeling (SEM). Results indicated that there were obviously different bacterial composition and diversity in composting from diverse sources. FW had a low pH and different physiochemical characteristics compared to other composts but they all achieved similar maturity products. Redundancy analysis suggested total organic carbon, phosphorus, and temperature governed the composition of microbial species but key factors were different in diverse composts. Network analysis showed completely different interactions of core bacterial community from diverse composts but Thermobifida was the ubiquitous core bacteria in composting bacterial network. Sphaerobacter and Lactobacillus as core genus were presented in the starting mesophilic and thermophilic phases of composting from manure (CM, DM, SM) and municipal solid waste (FW, VW), respectively. SEM indicated core bacteria had the positive, direct, and the biggest (> 80%) effects on composting maturity. Therefore, this study presents theoretical basis to identify and enhance the core bacteria for improving full-scale composting efficiency facing more and more organic wastes.

Impact of aeration rate on phosphorus conversion and bacterial community dynamics in phosphorus-enriched composting.

This study was to investigate the effects of different aeration rates on phosphorus (P) conversion and bacterial community dynamics in P-enriched composting by 16S rRNA gene sequencing, sequential P fractionation, network analysis and structural equation model (SEM). Results indicated that Olsen P content increased by 138 %, 150 %, 121 % after composting with aeration rate (L kg-1 DM min-1) at 0.2 (AR0.2), 0.4 (AR0.4) and 0.6 (AR0.6). AR0.4 was more conducive to enhance P solubilization efficacy and available P accumulation. Redundancy analysis indicated Lactobacillus, Spartobacteria and Pseudomonas were key bacteria associated with HCl-Pi especially in AR0.2 and AR0.4. Network analysis showed that increased aeration rate enhanced the connection and function homoplasy among modules and AR0.4 had more orderly community organization for key bacteria to solubilize P in directly and indirectly biotic way. SEM suggested indirectly biotic P-solubilization had more contribution than directly biotic way mainly by phosphate-solubilizing bacteria.

Effect of superphosphate addition on heavy metals speciation and microbial communities during composting.

Superphosphate fertilizer (SSP) as an additive can reduce the nitrogen loss and increase available phosphorus in composting but few studies investigated the effect of SSP addition on heavy metal and microbial communities. In this study, different ratios (10%, 18%, 26%) of SSP were added into pig manure composting to assess the changes of heavy metal (Cu, Mn, As, Zn, and Fe) fractions, bacterial and fungal communities as well as their interactions. SSP addition at 18% had lower ecological risk but still increased the bioavailability of Cu, Mn, and Fe in composts compared to control. Adding 18% SSP into compost decreased bacterial number and increased the fungal diversity compared to CK. Redundancy analysis indicated heavy metal fractions correlated significantly with bacterial and fungal community compositions in composting with 18% SSP. Network analysis showed adding 18% SSP increased microbial interaction and positive cooperation especially enhanced the proportion of Proteobacteria and Ascomycota.

Two-Dimensional Asynchronous Sliding-Mode Control of Markov Jump Roesser Systems.

In this article, asynchronous sliding-mode control (SMC) is investigated for 2-D discrete-time Markov jump systems. As the system modes are not always accessible to the controller, the hidden Markov model is employed to describe the asynchronization between the system modes and controller. A new 2-D sliding surface is constructed and the corresponding asynchronous SMC law is designed under the framework of the hidden Markov model. By Lyapunov function and linear matrix inequality (LMI) approaches, the reachability of system dynamics to the predefined sliding surface is investigated, and sufficient conditions are established to guarantee that the underlying 2-D system is asymptotically mean-square stable (AMSS) with an H∞ disturbance attenuation performance. Then, an algorithm is provided to derive the asynchronous 2D-SMC law. Finally, an example is given to verify the validity and effectiveness of the new SMC law design algorithm.

Asynchronous Guaranteed Cost Control of 2-D Markov Jump Roesser Systems.

This article is concerned with the problem of guaranteed cost control for 2-D Markov jump Roesser systems with mismatched modes. The hidden Markov model is introduced to describe the asynchronous phenomenon caused by mismatched modes, and an asynchronous linear state-feedback control law is designed based on this model. With the help of the 2-D Lyapunov function and linear matrix inequality (LMI) techniques, sufficient conditions are established to ensure the asymptotic stability of the concerned system with a bound of the predefined guaranteed cost under three different boundary conditions, respectively. Finally, an algorithm that concludes the design processes of the optimal asynchronous guaranteed cost control law is proposed, and a numerical example is provided to verify its effectiveness.