Organic Kitchen Waste Research Articles

Laboratory-scale membrane up-concentration and co-anaerobic digestion for energy recovery from sewage and kitchen waste.

This study assessed an alternative concept for co-treatment of sewage and organic kitchen waste in Vietnam. The goal was to apply direct membrane filtration for sewage treatment to generate a permeate that is suitable for discharge. The obtained chemical oxygen demand (COD) concentrations in the permeate of ultrafiltration tests were indeed under the limit value (50 mg/L) of the local municipal discharge standards. The COD of the concentrate was 5.4 times higher than that of the initial feed. These concentrated organics were then co-digested with organic kitchen wastes at an organic loading rate of 2.0 kg VS/m(3).d. The volumetric biogas production of the digester was 1.94 ± 0.34 m(3)/m(3).d. The recovered carbon, in terms of methane gas, accounted for 50% of the total carbon input of the integrated system. Consequently, an electrical production of 64 Wh/capita/d can be obtained when applying the proposed technology with the current wastes generated in Ho Chi Minh City. Thus, it is an approach with great potential in terms of energy recovery and waste treatment.

Co-digestion of cattle manure with organic kitchen waste to increase biogas production using rumen fluid as inoculums

Anaerobic co-digestion strategies are needed to enhance biogas production when treating certain residues such as cattle/pig manure. Co-digestion of food waste with animal manure or other feedstocks with low carbon content can improve process stability and methane production. In this study, anaerobic digestion and co-digestion of cattle manure with organic kitchen waste using rumen fluid as inoculums have been experimentally tested to determine the biogas potential. Co-digestion substantially increased the biogas yields by 24 to 47% over the control (organic kitchen waste and dairy manure only). The highest methane yield of 14,653.5 ml/g-VS was obtained with 75% organic kitchen waste (OKW) and 25% cattle manure (CM) additions. In contrast, addition of 75% cattle manure caused inhibition of the anaerobic digestion process, and its cumulative methane yield was 23% lower than that with 25% cattle manure addition. Key words: Cattle manure, co-digestion, methane, organic kitchen waste, rumen fluid.

Effects of bulking agents, load size or starter cultures in kitchen-waste composting

Abstract Background To prevent the interruption of the carbon cycle by the disposal of waste to landfills, organic kitchen waste requires proper treatment such as composting to reduce its uncontrolled degradation on disposal sites and subsequent greenhouse gases, odour emissions and nutrient losses. This study investigated the effects of bulking agent, newspaper and onion peels, composting waste load sizes of 2 and 6 kg, or the use of starter culture on kitchen-waste composting consisting of nitrogen-riched substrates, vegetable scraps and fish processing waste in an in-vessel system. The optimised formulation of kitchen waste mixture was used for a 30-day composting study, where the temperature profiles were recorded and the carbon-to-nitrogen ratios were measured as an indication of compost maturity. The kitchen-waste composting process was conducted in parallel in two fabricated kitchen waste composters. Results It was found that the onion peels were more suitable in producing matured compost where the carbon-to-nitrogen ratio reduced to 10 within 16 days of composting. A smaller kitchen waste load size of 2 kg gave a shorter composting time by half when compared to the 6 kg. The use of a microbial cocktail consisting seven types of bacteria and eight types of fungi isolated from soils as a starter culture for this kitchen-waste composting did not show advantages in accelerating the composting process. Conclusions The results suggest that the in-vessel kitchen-waste composting can be efficient with a minimal load of about 2 kg using onion peels without additional starter culture.

Microbial Consortium: A New Approach in Effective Degradation of Organic Kitchen Wastes

Present study was taken up to prepare efficient microbial consortia with concomitant enzymatic activity for the effective degradation of organic kitchen waste. Eleven different consortia were prepared and the compatibility of the bacterial strains within the consortia was checked by gram staining and enzyme production. Seven successful microbial consortia were selected in which all the bacterial strains concomitantly produced all these enzymes (amylase, protease, lipase, cellulose) in a specialized media that are responsible for the degradation of kitchen wastes. Three consortia (3, 5 and 12) were best producers of all the enzymes required for kitchen wastes degradation and it was monitored for 30 days by gradual decrease in the volume of the kitchen wastes. The maximum reduction observed was 65% in consortia no. 12 and 55% in consortia no 7 in just 21 days without any foul smell. The degradation of organic wastes by the bacterial consortia is highly significant. It reduces the time span of degradation and produces no foul odor. Pretreatment of the kitchen wastes can also be for mineralization of garbage wastes and further as biomanure which is a novel approach.

Energy- and CO2-reduction potentials by anaerobic treatment of wastewater and organic kitchen wastes in consideration of different climatic conditions

The classical municipal wastewater treatment in Germany consists of an aerobic carbon and nitrogen elimination and mostly an anaerobic sludge treatment. Organic kitchen wastes from separate waste collection as well as yard wastes are converted mostly in composting plants to soil conditioner. With these conventional types of treatment, the energy potential in waste and wastewater is lost due to aerobic material conversion. In this article three scenarios for the treatment of municipal wastewater and waste are compared on the subject of energy efficiency and useable potential: Sc1. the classical wastewater treatment and the composting of the organic waste fraction, Sc2. the anaerobic treatment of wastewater combined with deammonification and the digestion of the organic waste fraction, and Sc3. a mutual anaerobic treatment of wastewater and waste as co-digestion with deammonification. The calculation of energy and CO2-balance considers different climatic conditions. In case of using anaerobic treatment, not only the energy balance will be positive, also the CO2-balance is improved by the substitution of fossil fuels with generated biogas.

Biogas Production from Steam-Treated Municipal Solid Waste Wastewater

Biogas production from steam process wastewater carrying the organic fraction of municipal solid waste (MSW) was investigated in a bench-scale system comprised of an anaerobic completely stirred tank reactor (AnCSTR), an anaerobic filter (AnF), and an aerobic trickling filter (ATF). The AnCSTR received rinse water that contains pulp fibers that are derived from MSW. The AnF received the same rinse water from MSW process wastewater; however, the pulp fibers were not present. The ATF received effluent from the AnCSTR and AnF in fed-batch mode. Biogas production was observed at 0.02–0.29 and 0.04–0.47 kg CH4 · m−3 day−1 in the AnCSTR and AnF systems, respectively. Chemical Oxygen Demand (COD) removal efficiency was observed at 20% in the AnCSTR and up to 86% in the AnF operating at 10- to 12-day hydraulic retention time (HRT). Introduction of digester sludge in the feed at day 173 (2 days HRT) increased gas production rate in the AnCSTR from 0.13 to 0.29 kg CH4 · m−3 day−1 but did not significantly affect gas production rate in the AnF. The ATF stage removed 96% of dissolved COD. System stability was demonstrated in the AnF by full recovery of biogas production after operating the reactor under starvation conditions for 7 days. The average specific removal rate observed in the AnCSTR (kms = 0.098 day−1) was one order of magnitude lower than previously observed values using organic kitchen waste (kms = 0.27 day−1). On the other hand, organics removal rate kinetics in the AnF (kms = 0.25 day−1), were similar to the previously observed value from the organic kitchen waste. The system treated the organic portion of steam process MSW wastewater with concomitant biogas production with as low as 0.01 mg COD · L−1 in the final effluent from the ATF.