Jong Kim

Comparison between landfill gas and waste incineration for power generation in Astana, Kazakhstan

The city of Astana, the capital of Kazakhstan, which has a population of 804,474, and has been experiencing rapid growth over the last 15 years, generates approximately 1.39 kg capita-1 day-1 of municipal solid waste (MSW). Nearly 700 tonnes of MSW are collected daily, of which 97% is disposed of at landfills. The newest landfill was built using modern technologies, including a landfill gas (LFG) collection system. The rapid growth of Astana demands more energy on its path to development, and the viability analysis of MSW to generate electricity is imperative. This paper presents a technical–economic pre-feasibility study comparing landfill including LFG utilization and waste incineration (WI) to produce electricity. The performance of LFG with a reciprocating engine and WI with steam turbine power technologies were compared through corresponding greenhouse gases (GHG) reduction, cost of energy production (CEP), benefit–cost ratio (BCR), net present value (NPV) and internal rate of return (IRR) from the analyses. Results demonstrate that in the city of Astana, WI has the potential to reduce more than 200,000 tonnes of GHG per year, while LFG could reduce slightly less than 40,000 tonnes. LFG offers a CEP 5.7% larger than WI, while the latter presents a BCR two times higher than LFG. WI technology analysis depicts a NPV exceeding 280% of the equity, while for LFG, the NPV is less than the equity, which indicates an expected remarkable financial return for the WI technology and a marginal and risky scenario for the LFG technology. Only existing landfill facilities with a LFG collection system in place may turn LFG into a viable project.

Preliminary Experimental Investigation on the Strength and Air Permeability of Reactive Powder Concrete

A new reinforced concrete foundation system is being proposed to store renewable energy through the compressed air energy storage technology. For this application, the concrete is required to resist considerable tensile strength and to have low air permeability, which is not observed in normal concrete. Therefore, this paper is proposing to use reactive powder concrete for the suggested foundation system. Reactive powder concrete (RPC) is obtained by introducing either micro-cementitious materials like silica fume or fine powders like crushed quartz into the concrete mixture from where coarse aggregates had been removed. RPC has low water content and dense particle packing which lead to high strength and low air permeability characteristics. This paper conducts preliminary experimental investigations on the strength and air permeability of the RPC. Two important mix design parameters are studied including water-to-binder ratio ad silica fume content. Preliminary correlations between mix design parameters and strength/air permeability are developed. From the preliminary test results, it is concluded that the reactive powder concrete has potential to meet the high strength and low air permeability requirements, and is suitable for the proposed energy storage foundation system.

Numerical Investigation of Drilled Shafts near an Embankment Slope under Combined Torque-Lateral-Load Scenario

Generally, cantilevered structure-foundation systems supporting highway signs, signals, and luminaires in the areas exposed to severe wind loadings (e.g., hurricane) have been designed under coupled torsion and lateral load scenario. Especially, mast arm cantilevered structures constructed near or on an embankment slope may have more concerns on the torsional and lateral resistance of the foundation. However, most research works have merely considered drilled shaft foundations under torsion-lateral load case with an embankment in proximity. In this study, a numerical study is performed with different soil layers to: (1) understand the combined torque-lateral load behavior of drilled shafts near an embankment slope; (2) examine the effect of both the torsion and lateral resistances in the proximity of an embankment slope. It was found that torsional stiffness decreases with increase in slope angles. Finally, design criteria (e.g., minimum allowable distance from the embankment, maximum allowable point load near the embankment) of the mast arm assembly and loads are provided.

Effect of Fine Particles on Cement Treated Sand

Cement treated sand improves mechanical properties through the cementitious bonding between cohesionless particles, thus allowing several geotechnical applications such as soil stabilization against slope failure and liquefaction. Since pure sand without any fine particles is seldom available in nature, this study aims to investigate the effect of fine particles (kaolin) in a very small proportion (<5%) on cement treated sand. Two types of cements are used: (i) Ordinary Portland cement (OPC) and (ii) Calcium sulfoaluminate cement (CSA). OPC is the widely used cementitious binder whereas CSA is a rapid hardening cement that is becoming popular due to its low carbon foot print. Three different cement contents (3%, 5% and 7%) and four different fine contents (0%, 1%, 3% and 5%) for each cement content are chosen. The stiffness and strength of the cement treated sands are measured through shear wave velocity and unconfined compressive strength respectively, after 1-day and 7-day curing periods. The results show that the influence of fine particles is visible even with fine content as low as 1%. However, the effect is different between the two types of cements used and between low and high cement contents. As the fine content increases, the increase in strength and stiffness is more for OPC than CSA and more significant at low cement content (3%) than high cement content (5% and 7%).