• Energy Research

COVID-19 pandemic has brought tremendous environmental burden due to huge amount of medical wastes (about 54,000 t/d as of November 22, 2020), including face mask, gloves, clothes, goggles, and sanitizer/disinfectant containers. A proper waste management is urgently required to mitigate the spread of the disease, minimize the environmental impacts, and take their potential advantages for further utilization. This work provides a prospective review on the possible thermochemical treatments for those COVID-19 related medical wastes (CMW), as well as their possible conversion to fuels. The characteristics of each waste are initially analyzed and described, especially their potential as energy source. It is clear that most of CMWs are dominated by plastic polymers. Thermochemical processes, including incineration, torrefaction, pyrolysis, and gasification, are reviewed in terms of applicability for CMW. In addition, the mechanical treatment of CMW into sanitized refuse-derived fuel (SRDF) is also discussed as the preliminary stage before thermochemical conversion. In terms of material flexibility, incineration is practically applicable for all types of CMW, although it has the highest potential to emit the largest amount of CO2 and other harmful gasses. Furthermore, gasification and pyrolysis are considered promising in terms of energy conversion efficiency and environmental impacts. On the other hand, carbonization faces several technical problems following thermal degradation due to insufficient operating temperature.

Geopolymers are inorganic polymers formed from the alkaline activation of amorphous alumino-silicate materials resulting in a three-dimensional polymeric network. As a class of materials, it is seen to have the potential of replacing ordinary Portland cement (OPC), which for more than a hundred years has been the binder of choice for structural and building applications. Geopolymers have emerged as a sustainable option vis-à-vis OPC for three reasons: (1) their technical properties are comparable if not better; (2) they can be produced from industrial wastes; and (3) within reasonable constraints, their production requires less energy and emits significantly less CO2. In the Philippines, the use of coal ash, as the alumina- and silica- rich geopolymer precursor, is being considered as one of the options for sustainable management of coal ash generation from coal-fired power plants. However, most geopolymer mixes (and the prevalent blended OPC) use only coal fly ash. The coal bottom ash, having very few applications, remains relegated to dumpsites. Rice hull ash, from biomass-fired plants, is another silica-rich geopolymer precursor material from another significantly produced waste in the country with only minimal utilization. In this study, geopolymer samples were formed from the mixture of coal ash, using both coal fly ash (CFA) and coal bottom ash (CBA), and rice hull ash (RHA). The raw materials used for the geopolymerization process were characterized using X-ray fluorescence spectroscopy (XRF) for elemental and X-ray diffraction (XRD) for mineralogical composition. The raw materials’ thermal stability and loss on ignition (LOI) were determined using thermogravimetric analysis (TGA) and reactivity via dissolution tests and inductively-coupled plasma mass spectrometry (ICP) analysis. The mechanical, thermal and microstructural properties of the geopolymers formed were analyzed using compression tests, Fourier transform infra-red spectroscopy (FTIR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Using a Scheffé-based mixture design, targeting applications with low thermal conductivity, light weight and moderate strength and allowing for a maximum of five percent by mass of rice hull ash in consideration of the waste utilization of all three components, it has been determined that an 85-10-5 by weight ratio of CFA-CBA-RHA activated with 80-20 by mass ratio of 12 M NaOH and sodium silicate (55% H2O, modulus = 3) produced geopolymers with a compressive strength of 18.5 MPa, a volumetric weight of 1660 kg/m3 and a thermal conductivity of 0.457 W/m-°C at 28-day curing when pre-cured at 80 °C for 24 h. For this study, the estimates of embodied energy and CO2 were all below 1.7 MJ/kg and 0.12 kg CO2/kg, respectively.

Abstract Thermochemical waste to energy technology could efficiently tackle waste management problem, but it could emit dangerous pollutant if the quality of the feedstock is bad and standard operating condition was not met. Pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) methodology was used to assess the quality of refuse material for solid fuel by identifying the degradation behavior and produced gas in pyrolysis condition. The material used was a mineral water plastic seal (PS), laminated packaging (LP), refuse derived fuel (RDF) and mechanical biological treatment residue (SR). The results show that PS and LP have similar degradation curve since it mainly consists of polypropylene. The gas product characteristic was also similarly consisted of CO, CO2, and hydrocarbon. RDF and SR have more complex degradation curve consist of three peaks. Both are composite material consist of organics, plastics, and inert materials. CO and CO2 are still major pyrolysis gas composition. This work could be developed to build process simulation to simulate real waste to energy plant.

AbstractIndonesia, as the biggest palm oil producers and exporters in the world, is producing large amounts of low-grade oil wastessuch as palm fatty acid distillate (PFAD) from palm oil industries. Production of fatty acid methyl ester (FAME) from PFAD that having high amount of free fatty acids (FFA) was studied in this work. Low cost feedstocks such as PFADneed to be utilized to replace edible oils in order to improve the economical feasibility of biodiesel. The esterification of FFAin PFAD with methanol using a coconut shell biochar (CSB) catalyst is a promising method to convert FFA into biodiesel. In this study, the CSBcatalysts were synthesized by sulfonating the coconut shell biochar using concentrated H2SO4. The physico-characteristics and acid site densities were analyzed by Nitrogen gas adsorption, FT-IR, X-ray fluorescent (XRF), and acid-base back titration methods. The effects of the mass ratio of catalyst to oil (1-7%), the molar ratio of methanol to oil (6:1 to 12:1), and the reaction temperature (40, 50 and 60oC) were studied for the conversion of FFA to optimize the reaction conditions. The optimal conditions were an methanol/PFAD molar ratio of 12:1, the amount of catalyst of 7%wt, and reaction temperature of 60oC.

Abstract This work proposes a state-of-the art integrated system for the co-production of H 2 and power from low rank coal with high total energy efficiency. A model of this system is developed based on enhanced process integration technology, incorporating coal drying, gasification, chemical looping, power generation, and hydrogenation. In this model, heat circulation and process integration technologies are effectively combined, minimizing the exergy losses. Iron-based materials are used as oxygen carriers and are circulated in a chemical looping module consisting of three continuous processes: reduction, oxidation, and combustion. The toluene-methyl cyclohexane system is employed as a liquid organic H 2 carrier to store H 2 generated from coal. The effects of the fluidization velocity in drying, the steam-to-fuel ratio in gasification, and the chemical looping pressure are evaluated with regard to the power generation and H 2 production efficiencies as well as the overall efficiency, and the proposed integrated system exhibits very high efficiencies of approximately 12, 72, and 84%, respectively.