Periodic injection of liquefied kitchen and food waste in municipal solid waste: Effects on leachate and gas generation

With continuous advancements in the zero-waste strategy in China, transportation of fresh municipal solid waste to landfills has ceased in most first-tier cities. Consequently, the production of landfill gas has sharply declined because the supply of organic matter has decreased, rendering power generation facilities idle. However, by incorporating liquefied kitchen and food waste (LKFW), sustainable methane production can be achieved while consuming organic wastewater. In this study, LKFW and water (as a control group) were periodically injected into high and low organic wastes, respectively. The biochemical characteristics of the resulting gas and leachate were analyzed. LKFW used in this research generated 19.5-37.6 L of methane per liter in the post-methane production phase, highlighting the effectiveness of LKFW injection in enhancing the methane-producing capacity of the system. The release of H2S was prominent during both the rapid and post-methane production phases, whereas that of NH3 was prominent in the post-methane production phase. As injection continued, the concentrations of chemical oxygen demand, 5-d biological oxygen demand, total organic carbon, ammonia nitrogen, total nitrogen, and oil in the output leachate decreased and eventually reached levels comparable to those in the water injection cases. After nine rounds of injections, the biologically degradable matter of the two LKFW-injected wastes decreased by 8.2 % and 15.1 %, respectively. This study sheds light on determining the organic load, controlling odor, and assessing the biochemical characteristics of leachate during LKFW injection.

Conceptualization of Bioreactor Landfill Approach for Sustainable Waste Management in Karachi, Pakistan

Finding a sustainable approach for municipal solid waste (MSW) management is becoming paramount. However, as with many urban areas in developing countries, the approach applied to MSW management in Karachi is neither environmentally sustainable nor suitable for public health. Due to adoption of an inefficient waste management system, society is paying intangible costs such as damage to public health and environment quality. In order to minimize the environmental impacts and health issues associated with waste management practices, a sustainable waste management and disposal strategy is required. The aim of this paper is to present a concept for the development of new bioreactor landfills for sustainable waste management in Karachi. Furthermore, this paper contributes to estimation of methane (CH4) emissions from waste disposal sites by employing the First Order Decay (FOD) Tier 2 model of the Intergovernmental Panel on Climate Change (IPCC) and determining of the biodegradation rate constant (k) value. The design and operational concept of bioreactor landfills is formulated for the study area, including estimation of land requirement, methane production, power generation, and liquid required for recirculation, along with a preliminary sketch of the proposed bioreactor landfill. This study will be helpful for stockholders, policy makers, and researchers in planning, development, and further research for establishment of bioreactor landfill facilities, particularly in the study area as well as more generally in regions with a similar climate and MSW composition.

Influence of moisture content and leachate recirculation on oxygen consumption and waste stabilization in post aeration phase of landfill operation

Sustainable completion of municipal solid waste landfills requires post-closure care after a time when utilization of landfill gas produced from biodecomposition of organic waste be not possible/or economically feasible. Research proved that in-situ aeration is a promising approach employed for landfill aftercare. The application of post aeration operation is targeted to achieve accelerated waste stabilization to avoid long term environmental and public health impacts from landfills. In in-situ aeration operation, consumption of supplied oxygen has significant influence on biological stabilization of solid waste placed in the landfills. The consumption of oxygen is regulated by operation parameters of landfill - one of the important is presence of moisture in landfill ecosystem. This research aims to assess the influence of moisture content and leachate recirculation on the oxygen consumption during post aeration phase of landfill operation. The effect of oxygen consumption on the extent of waste stabilization achieved after experiment was also assessed. Three lab-scale landfill simulation reactors (LSRs) were used - in two of three reactors (LSR-1 and LSR-3) operation was carried out in two phases: Anaerobic and post-aeration. One reactor (LSR-2) was operated under anaerobic condition throughout the experiment and used as control. To compare the oxygen consumption, conventional landfill (CLF) conditions without excess water addition and leachate recirculation were simulated in LSR-1 and the bioreactor landfill conditions (BRLF) with excess water injection and leachate recirculation were simulated in LSR-3. In CLF 46.4% of supplied oxygen was consumed during post aeration phase while in BRLF only 0.96% of oxygen consumption was noticed. In result of higher oxygen consumption, biostabilization rate of waste in CLF was 7% higher than BRLF at the end of experiment. This study demonstrated that, in presence of low moisture in landfill ecosystem optimal air distribution can be realized which results in enhanced waste oxidization and stabilization.