Kitchen Waste Digestion and Odor Removal by Biological Method

High-rate iron-rich activated sludge as stabilizing agent for the anaerobic digestion of kitchen waste

ABSTRACTThe aim of this study was to evaluate the effects of autoclave and microwave irradiation (MW) pretreatments on the solubilization, biogas and methane yields of kitchen waste (KW). Autoclave (for 30 min @ 120, 1 bar) and MW (for 400 s @ 80, 700 W) pretreatments were used to enhance anaerobic digestion of KW. The anaerobic digestion of KW in autoclave and MW pretreatments were compared with a control in a batch leach bed reactor with down flow (LBR DF). During autoclave and MW pretreatments, the biogas yields were respectively 25.41 and 41.43% higher than the control test and for methane were respectively 22.73 and 38.91% higher than the control test. The highest solubilization efficiency was obtained after MW pretreatment (89.21%), followed by after autoclave pretreatment (85.73%), and the lowest value was obtained with control (61.37%). Mathematical models fitted experimental data with R2>0.9798. The present study shows that autoclave and MW pretreatments can be used to improve biogas and methane yields and solubilization efficiency. Schnute and modified Gompertz models gave a good fit of the first stage of fermentation as well as the asymptotic phase.

Evaluation of single vs. staged mesophilic anaerobic digestion of kitchen waste with and without microwave pretreatment

This study reviews the available and most commonly used methods of gas deodorization. Comparing various methods of odor removal, undoubtedly biological methods of pollution degradation have an advantage over others—chemical and physical. This advantage is manifestedmainly in ecological and economic terms. The possibility of using biological methods to remove H2S and NH3, as the most common emitted by the municipal sector companies, was analyzed in terms of their removal efficiency. The method of bio-purification of air in biotrickling filters is more advantageous than the others, due to the high effectiveness of VOCs and odors degradation, lack of secondary pollutants, and economic aspects—it is a method competitive to the commonly used air purification method in biofilters.

Effects of biochars derived from different feedstocks and pyrolysis temperatures on the anaerobic digestion of kitchen waste

Stabilization of anaerobic digestion of kitchen wastes using protein-rich additives: Study of process performance, kinetic modelling and energy balance

With the development of urbanization, industry, agriculture and aquaculture, malodorous pollution has become increasingly serious. Odour pollutants can be produced by non-biological or biological pathways, which not only have a great negative impact on the regional ecological environment, but also cause great harm to the health of local people and animals. Compared with physical method, chemical method and adsorption method, biological deodorization method has the characteristics of high odour removal rate, environmental friendliness and low cost. Biological method is gradually becoming the preferred technique for odour removal in some odour producing areas. In this paper, the mechanism, the patent application status and the application prospect of biological deodorization are summarized and analysed, so that we can have a deeper understanding of biological deodorization.

Effects of thermal pretreatment on the biomethane yield and hydrolysis rate of kitchen waste

The aim of this work was to investigate the acid inhibition during the anaerobic digestion of kitchen waste. Four biodegradable substrates of soybean, fat meat, rice, and celery cane were considered in this paper. A series of anaerobic co-digestion tests were performed on the four substrates at the load of 1.0 gVS/(l·day) and anaerobic granular sludge. The results show that the acid inhibition was occurred at the load of 1.0 gVS/(l·day) for the soybean and rice; the corresponding pH values at the lowest acidification points were 5.03 and 3.73, respectively. There was no acid inhibition during the whole digestion period for the celery cane substrate. And the results also reveal that the order of the cumulative gas yields for different substrates from highest to lowest is: celery cane > soybean > fat meat > rice; while the order of the average methane (CH4) percentage from highest to lowest is: celery cane > fat meat > soybean > rice. Finally, the method to calculate the lowest acidification points of the four substrates was provided by the least squares method, and it is verified by the measured data, and good agreement is found.

Synergy of multi-enzyme pretreatment and Paraclostridium benzoelyticum bioaugmentation: A dual strategy for enhancing methane production in dry anaerobic digestion of kitchen waste.

Anaerobic digestion is widely used for biodegradable solid organic wastes in order to recover bio-energy in the form of biogas. Some previous studies presented that co-digestion of various substrates can improve biogas yields as well as enhanceperformance of organic wastes digestion, in comparison with digestion of sole solid waste. This study aimed to evaluate the performance of anaerobic mono-digestion and anaerobic co-digestion of the following mixtures: (a) sole kitchen waste (KW), (b) KW and sewage (SW), (c) sole sludge (SL)and (d) KW and SL. This study was conductedby four lab-scale anaerobic complete mixing reactors (numbered MH1 – MH4) in 4,5 liters working volume atorganic loading rate (OLR) 2,0 g(VS).L-1.d-1. The KW was collected from canteen B4 and SW was collected from effluent from septic tank C6 Building in Ho Chi Minh University of Technology (HCMUT). The results show that the reactor of sole KW obtained average total chemical oxygen demand (tCOD), soluble chemical oxygen demand (sCOD), total solid (TS), volatile solid (VS), total phosphorus (TP) and total Kjeldahl nitrogen (TKN) of 62 %, 62 %, 71 %, 72 %, 73 % and 45 %, respectively, whereas reactor of KW and SW co-digestion had were tCOD, sCOD, TS, VS, TP and TKN removal of 73 %, 78 %, 75 %, 79 %, 59 % and 57 %, respectively. Thus co-digestion of KW and SW revealed an efficient enhancement of digestion, instead of sole KW digestion. Similarly, TS (74 %) and VS removals (75 %) of co-digesting mixtures of SL and KW were higher than those of sole SL digestion (67 %). Furthermore, co-digestion of SL and KW obtained better performance in tCOD and sCOD removals (70 % and 76 %, respectively).

Anaerobic co-digestion of kitchen waste and cattle manure was carried out in laboratory scale in batch and semi-continuous modes under mesophilic temperature. Five feedstocks of R1, R2, R3, R4, and R5 were tested, which were made by mixing kitchen waste with cow manure at different mixing ratios of 0:1, 1:1, 2:1, 3:1, and 1:0, respectively. The results showed that 61.0–85.2% of specific methane potential of R2–R4 were contributed by the addition of kitchen waste, which exhibited the highest specific methane potential and biodegradability in batch test. In semi-continuous operation, the methane yield in the digestion of kitchen waste as sole feedstock was 8.8–37.8% less than that of R2–R4. The highest methane yield of 233 ml/g volatile solid was obtained at the mixing ratio of 3:1; therefore, the mixing ratio of 3:1 is recommended as the optimal one for the co-digestion of kitchen waste and cow manure.

The anaerobic digestion of kitchen waste was studied in both batch and continuous modes. The effect of increasing loading rates on pollutant removal and biogas production was investigated for single-phase digestion and two-phase digestion systems. The anaerobic biodegradability of the kitchen waste obtained from the batch study was 83.5%. Single-stage digestion of kitchen waste was subjected to varying organic loading rates (OLR) ranging from 1.5 kg volatile solids (VS) m–3 d–1 to 5.5 kg VS m–3d–1, with a common hydraulic retention time (HRT) of 15 d. The optimum performance of the system was observed at an OLR of 4.5 kg VS m–3 d–1 in terms of pollutant removal efficiency and biogas production. The removal rates for chemical oxygen demand (COD) and VS at this optimal OLR were 81% and 79%, respectively. Maximum production of the methane was 0.288 m3/kg of VS added. Beyond the optimal OLR, the volatile fatty acids concentration increased and reached its maximum value (9.2 g/L) at the higher loading rate tested (5.5 kg VS m–3 d–1). Anaerobic digestion of the kitchen waste was carried out in a two-stage reactor with different loading rates of 4, 6, and 8 kg VS m–3 d–1. The retention time given to both hydrolysis and methanogenesis phases was 5 d, for a total HRT of 10 d. Best performances were observed in the third run with the OLR of 8 kg VS m–3 d–1. High removal efficiencies for COD and VS were found as 92% and 94%, respectively. A total of 0.22 m3 of methane was produced by 1 kg of VS added. Responses to the fluctuations in the loading rates were sudden and many times unfavourable in the single-stage system, while the fluctuations were suppressed or overcome at a faster rate in the two-stage reactor, without creating too many problems. Comparison of the overall performance showed that phase-separated digesters or the two-stage digesters may offer the best choice for high efficiency, concerning pollutant removal.

Optimization of hydrolysis conditions for minimizing ammonia accumulation in two-stage biogas production process using kitchen waste for sustainable process development

Synergetic degradation of waste oil by constructed bacterial consortium for rapid in-situ reduction of kitchen waste