Ying-Chu Chen

Treatment and recycling of incinerated ash using thermal plasma technology

To treat incinerated ash is an important issue in Taiwan. Incinerated ashes contain a considerable amount of hazardous materials such as dioxins and heavy metals. If these hazardous materials are improperly treated or disposed of, they shall cause detrimental secondary contamination. Thermal plasma vitrification is a robust technology to treat and recycle the ash residues. Under the high temperature plasma environment, incinerated ashes are vitrified into benign slag with large volume reduction and extreme detoxification. Several one-step heat treatment processes are carried out at four temperatures (i.e. 850, 950, 1,050 and 1,150 degrees C) to obtain various microstructure materials. The major phase to form these materials is a solid solution of gehlenite (Ca2Al2SiO7) and åkermanite (Ca2MgSi2O7) belonging to the melilite group. The physical and mechanical properties of the microstructure materials are improved by using one-step post-heat treatment process after plasma vitrification. These microstructure materials with good quality have great potential to serve as a viable alternative for construction applications.

Effects of titanate nanotubes synthesized by a microwave hydrothermal method on photocatalytic decomposition of perfluorooctanoic acid.

Titanate nanotubes (TNTs) were used to remove perfluorooctanoic acid (PFOA) from aqueous solutions in this study. Direct photolysis of PFOA by a 254-nm UV light (400 W) was found effective to decompose PFOA without presence of photocatalysts. Shorter-chain perfluorocarboxylic acids (PFCAs) and fluoride ions were formed during photodecomposition. Addition of TNTs as photocatalysts did not greatly enhance photocatalytic decomposition of PFOA. TNTs mainly act as adsorbents to adsorb PFOA and form TNT-PFOA complexes. It suggested that sodium ions and oxygen atoms on the surfaces of TNTs play important roles in PFOA adsorption. X-ray Photoelectron Spectroscopy (XPS) and Fourier Transform Infrared Spectroscopy (FTIR) analyses indicated that ion-exchange, electrostatic interaction, and hydrophobic interaction all participated in the photocatalytic reaction of PFOA by TNTs.

Constructing an effective prevention mechanism for MSW lifecycle using failure mode and effects analysis

Municipal solid waste in Taiwan is a valuable source of renewable energy. Phases of municipal solid waste lifecycle (classification, disposal, storage, collection and transportation) before incineration or landfilled face various potential failures. Applying a proper technique to eliminate or decrease potential failures is desirable and needed. Failure Modes and Effects Analysis to municipal solid waste lifecycle was found in literature. This study utilized the Failure Modes and Effects Analysis as a convenient technique for determining, classifying and analyzing common failures in the municipal solid waste lifecycle. As a result, an appropriate risk scoring of severity, occurrence, and detection of failure modes and computing the Risk Priority Number for identifying the high potential failure modes were made. Nineteen failure modes were identified, and nine of them were ranked as the priority items for improvement. Recommended actions for all failure modes were suggested. Occurrences of failures were remarkably reduced after implementing the procedure for six months. The results of this study have minimized potential failures and brought continuous improvement, thus achieving a better protection of the environment.

Potential for energy recovery and greenhouse gas mitigation from municipal solid waste using a waste-to-material approach

Energy recovery and greenhouse gas (GHG) emissions from wastes are getting noticed in recent years. This study evaluated the potential for energy recovery and GHG mitigation from municipal solid waste (MSW) with a waste-to-material (WTM) approach. Waste generated in Taiwan contains a large amount of paper, food waste, and plastics, which previously were mostly sent to waste-to-energy (WTE) plants for incineration. However, the mitigation of GHGs by the WTM approach has been especially successful in the recycling of metals (averaging 1.83×106kgCO2-eq/year) and paper (averaging 7.38×105kgCO2-eq/year). In addition, the recycling of paper (1.33×1010kWh) and plastics (1.26×1010kWh) has contributed greatly to energy saving. Both metal and glass are not suitable for incineration due to their low energy content. The volumes of paper and food waste contained in the MSW are positively related to the carbon concentration, which may contribute to increased GHGs during incineration. Therefore, the recycling of paper, metals, and food waste is beneficial for GHG mitigation. Measures to reduce GHGs were also suggested in this study. The development of the WTM approach may be helpful for the proper management of MSW with regards to GHG mitigation. The results of this study can be a successful example for other nations.

Effects of urbanization on municipal solid waste composition

The generation of municipal solid waste (MSW) is related to various features of urbanization. In this study, a linear regression model was used to evaluate the effects of several urbanization indicators on the composition of MSW. Household population (P), area of urban planning (L), tap water penetration (W), electricity sold (El), number of operating factories (I), car density (T), education level (Ed), and annual revenue (R) were chosen as important indicators of urbanization. The five major categories of MSW-paper, food waste, plastic, metal, and glass-were also chosen for specific analysis, and MSW composition was found to be closely related to household population (P) (r2u202f>u202f0.8). The volume of one category of waste, food waste, was related to the industrialization indicator (r2u202f>u202f0.9). The total volume of MSW and the total volume of metal waste were linked with household population divided by tap water penetration (P/W) (r2u202f=u202f0.9903), and with annual revenue divided by tap water penetration (R/W) (r2u202f=u202f0.9364). The volume of plastic waste and glass waste generated, respectively, was related to annual revenue divided by education level (R/Ed) (r2u202f=u202f0.9814 vs. r2u202f=u202f0.9371). In addition, a case study of Taipei City indicated that MSW disposal fees should reflect not only household population (P) but also tap water penetration (W). This study provides valuable findings quantifying the effects of urbanization on MSW composition. The results will help governments and enterprises to efficiently evaluate and predict variation in MSW composition with reference to indicators of urbanization, thereby improving the management of waste.

Effects of storage environment on the moisture content and microbial growth of food waste

Food waste (FW) has become a critical issue in sustainable development as the worlds population has increased. Direct incineration of FW remains the primary treatment option. The moisture content of FW may affect the energy efficiency of incineration. In Taiwan, FW, which includes raw (r-FW) and post-consumer (p-FW) waste, is often stored in freezers before pretreatment. This study evaluated the effects of storage environment on the moisture content and microbial growth of FW. Storage at 263u202fK was associated with the largest reduction in moisture content in both r-FW and p-FW. At 263u202fK, the moisture content of r-FW and p-FW was lowest at 96 and 72u202fh, respectively. The E.coli and total bacteria counts were steady over 120u202fh when stored at 263u202fK. Storage at 253u202fK required the greatest electricity consumption, followed by 263u202fK and 258u202fK. Based on the reduction of moisture content and increase in energy efficiency, it is suggested that FW is placed in temporary storage at 263u202fK before (pre)treatment. The results of this study will help waste-to-energy plants, incinerators, and waste management enterprises to implement proper (pre)treatment of FW for sustainable waste management.

Evaluating the operational risks of biomedical waste using failure mode and effects analysis

The potential problems and risks of biomedical waste generation have become increasingly apparent in recent years. This study applied a failure mode and effects analysis to evaluate the operational problems and risks of biomedical waste. The microbiological contamination of biomedical waste seldom receives the attention of researchers. In this study, the biomedical waste lifecycle was divided into seven processes: Production, classification, packaging, sterilisation, weighing, storage, and transportation. Twenty main failure modes were identified in these phases and risks were assessed based on their risk priority numbers. The failure modes in the production phase accounted for the highest proportion of the risk priority number score (27.7%). In the packaging phase, the failure mode ‘sharp articles not placed in solid containers’ had the highest risk priority number score, mainly owing to its high severity rating. The sterilisation process is the main difference in the treatment of infectious and non-infectious biomedical waste. The failure modes in the sterilisation phase were mainly owing to human factors (mostly related to operators). This study increases the understanding of the potential problems and risks associated with biomedical waste, thereby increasing awareness of how to improve the management of biomedical waste to better protect workers, the public, and the environment.