Jinglan Hong

Environmental and economic life cycle assessment for sewage sludge treatment processes in Japan

Life cycle assessment for sewage sludge treatment was carried out by estimating the environmental and economic impacts of the six alternative scenarios most often used in Japan: dewatering, composting, drying, incineration, incinerated ash melting and dewatered sludge melting, each with or without digestion. Three end-of-life treatments were also studied: landfilling, agricultural application and building material application. The results demonstrate that sewage sludge digestion can reduce the environmental load and cost through reduced dry matter volume. The global warming potential (GWP) generated from incineration and melting processes can be significantly reduced through the reuse of waste heat for electricity and/or heat generation. Equipment production in scenarios except dewatering has an important effect on GWP, whereas the contribution of construction is negligible. In addition, the results show that the dewatering scenario has the highest impact on land use and cost, the drying scenario has the highest impact on GWP and acidification, and the incinerated ash melting scenario has the highest impact on human toxicity due to re-emissions of heavy metals from incinerated ash in the melting unit process. On the contrary, the dewatering, composting and incineration scenarios generate the lowest impact on human toxicity, land use and acidification, respectively, and the incinerated ash melting scenario has the lowest impact on GWP and cost. Heavy metals released from atmospheric effluents generated the highest human toxicity impact, with the effect of dioxin emissions being significantly lower. This study proved that the dewatered sludge melting scenario is an environmentally optimal and economically affordable method.

Life cycle assessment of four municipal solid waste management scenarios in China.

A life cycle assessment was carried out to estimate the environmental impact of municipal solid waste. Four scenarios mostly used in China were compared to assess the influence of various technologies on environment: (1) landfill, (2) incineration, (3) composting plus landfill, and (4) composting plus incineration. In all scenarios, the technologies significantly contribute to global warming and increase the adverse impact of non-carcinogens on the environment. The technologies played only a small role in the impact of carcinogens, respiratory inorganics, terrestrial ecotoxicity, and non-renewable energy. Similarly, the influence of the technologies on the way other elements affect the environment was ignorable. Specifically, the direct emissions from the operation processes involved played an important role in most scenarios except for incineration, while potential impact generated from transport, infrastructure and energy consumption were quite small. In addition, in the global warming category, highest potential impact was observed in landfill because of the direct methane gas emissions. Electricity recovery from methane gas was the key factor for reducing the potential impact of global warming. Therefore, increasing the use of methane gas to recover electricity is highly recommended to reduce the adverse impact of landfills on the environment.

Environmental assessment of sewage sludge as secondary raw material in cement production--a case study in China.

A life cycle assessment was carried out to estimate the environmental impact of sewage sludge as secondary raw material in cement production. To confirm and add credibility to the study, uncertainty analysis was conducted. Results showed the impact generated from respiratory inorganics, terrestrial ecotoxicity, global warming, and non-renewable energy categories had an important contribution to overall environmental impact, due to energy, clinker, and limestone production stages. Also, uncertainty analysis results showed the technology of sewage sludge as secondary raw material in cement production had little or no effect on changing the overall environmental potential impact generated from general cement production. Accordingly, using the technology of sewage sludge as secondary raw material in cement production is a good choice for reducing the pressure on the environment from dramatically increased sludge disposal. In addition, increasing electricity recovery rate, choosing natural gas fired electricity generation technology, and optimizing the raw material consumption in clinker production are highly recommended to reduce the adverse effects on the environment.

Life cycle assessment of sewage sludge co-incineration in a coal-based power station

A life cycle assessment was conducted to evaluate the environmental and economic effects of sewage sludge co-incineration in a coal-fired power plant. The general approach employed by a coal-fired power plant was also assessed as control. Sewage sludge co-incineration technology causes greater environmental burden than does coal-based energy production technology because of the additional electricity consumption and wastewater treatment required for the pretreatment of sewage sludge, direct emissions from sludge incineration, and incinerated ash disposal processes. However, sewage sludge co-incineration presents higher economic benefits because of electricity subsidies and the income generating potential of sludge. Environmental assessment results indicate that sewage sludge co-incineration is unsuitable for mitigating the increasing pressure brought on by sewage sludge pollution. Reducing the overall environmental effect of sludge co-incineration power stations necessitates increasing net coal consumption efficiency, incinerated ash reuse rate, dedust system efficiency, and sludge water content rate.

Life cycle assessment of electronic waste treatment

Life cycle assessment was conducted to estimate the environmental impact of electronic waste (e-waste) treatment. E-waste recycling with an end-life disposal scenario is environmentally beneficial because of the low environmental burden generated from human toxicity, terrestrial ecotoxicity, freshwater ecotoxicity, and marine ecotoxicity categories. Landfill and incineration technologies have a lower and higher environmental burden than the e-waste recycling with an end-life disposal scenario, respectively. The key factors in reducing the overall environmental impact of e-waste recycling are optimizing energy consumption efficiency, reducing wastewater and solid waste effluent, increasing proper e-waste treatment amount, avoiding e-waste disposal to landfill and incineration sites, and clearly defining the duties of all stakeholders (e.g., manufacturers, retailers, recycling companies, and consumers).

Uncertainty propagation in life cycle assessment of biodiesel versus diesel: global warming and non-renewable energy.

Uncertainty information is essential for the proper use of life cycle assessment and environmental assessments in decision making. To investigate the uncertainties of biodiesel and determine the level of confidence in the assertion that biodiesel is more environmentally friendly than diesel, an explicit analytical approach based on the Taylor series expansion for lognormal distribution was applied in the present study. A biodiesel case study demonstrates the probability that biodiesel has a lower global warming and non-renewable energy score than diesel, that is 92.3% and 93.1%, respectively. The results indicate the level of confidence in the assertion that biodiesel is more environmentally friendly than diesel based on the global warming and non-renewable energy scores.

Environmental assessment of recycled printing and writing paper: A case study in China

A life cycle assessment was conducted using IMPACT2002+ to estimate the environmental impact of producing printing and writing paper, which is entirely made with wastepaper. To confirm and add credibility to the study, uncertainty analysis was conducted using Taylor series expansion. Printing and writing paper produced from wood pulp was assessed for comparison. Compared with the wood pulp contained scenario, printing and writing paper made from wastepaper represented environmental benefit on non-carcinogens, respiratory inorganics, global warming, and non-renewable energy categories. In both scenarios, the technologies significantly contribute to the potential impacts of non-carcinogens, respiratory inorganics, terrestrial ecotoxicity, global warming, and non-renewable energy. The influence of the technologies on the way other categories affect the environment was negligible. Improved efficiency in electricity consumption, decreased transport distance from raw material buyers to suppliers, and change in the end-life treatment of solid waste from landfill to incineration are the key factors in reducing the overall environmental impact.

Environmental and economic impact of furfuralcohol production using corncob as a raw material

PurposeCorncob as agricultural waste has dramatically increased in recent years. Some corncobs are recycled and reused as bioproducts, whereas a large amount remains unused and burned in the fields. Currently, furfural production technology is one of the most commonly used technologies for corncob valorization because furfural is one of the most promising chemicals for sustainable chemical production. However, very few studies have analyzed the impact of furfural and furfuralcohol production on the environment and economy via life cycle assessment (LCA) and life cycle costing (LCC). This study aims to quantify the environmental and economic impacts of furfural and furfuralcohol production, identify the main pollution processes and substances, improve potentials, and build a database on the furfural industry.MethodsLife cycle assessment and life cycle costing were carried out to estimate the environmental and economic impact of corncob-based furfural and furfuralcohol production.Results and discussionThe corncob production, transport, and electricity consumption stages had the greatest impact on the environment because of direct heavy metal, phosphate, and phosphorus emissions. The overall economic impact was mainly attributed to tax, corncob, transport, electricity, and infrastructure investment. Optimizing corncob transport, raw materials and consumption efficiency, and waste disposal is highly important in reducing both environmental and economic burden.ConclusionsThe key factors that contribute to reducing the overall environmental and economic impacts are increasing electricity consumption efficiency and furfural product yield, decreasing transport distance from corncob buyers to suppliers, choosing the appropriate corncob compression technology, and optimizing the wastewater reuse system.

Effects of electron donors on the microbial reductive dechlorination of hexachlorocyclohexane and on the environment.

The reductive biotransformation of α-, β-, γ-, and δ-hexachlorocyclohexane isomers was investigated using five alternative electron donors (i.e., glucose plus methanol, glucose only, methanol only, acetate, and ethanol) in a batch assay of an HCH-dechlorinating anaerobic culture. In addition, a life cycle assessment was conducted using the IMPACT2002+ method to evaluate the environmental effects of HCH bioremediation with the aforementioned electron donors. Results showed that the electron donors methanol plus glucose, ethanol, glucose, and methanol can significantly enhance the biotransformation of each HCH isomer. However, the amended electron donors and the byproduct of the anoxic/anaerobic systems may negatively affect the environment (e.g., respiratory inorganic, land occupation, global warming, and non-renewable energy categories). These effects are attributed to the electron donor production processes. To avoid secondary pollutants, a linear relationship between the upper bound electron donor applications and HCH concentration was observed from an environmental perspective. Results indicated that the methanol scenario was the most suitable option for the current research.

Life cycle assessment comparison of substrates for the bioremediation of pentachloroaniline under acidogenic/methanogenic conditions

PurposeIn general, pentachloroaniline (PCA) biodechlorination is specific to the conditions of a system; such conditions include the type and concentration of electron donors and oxidizing agents as well as nutrient availability, pH, and temperature. In the bioremediation of contaminated sediments and soil, most researchers have focused on the ability of various electron donors to remove target compounds. However, the amended electron donors and the byproduct of the anoxic/anaerobic systems may cause more environmental impact. Therefore, methods for consistently evaluating the environmental effects of such electron donors and byproducts are highly needed. Accordingly, life cycle assessment (LCA) was carried out to estimate the environmental effect of PCA biodechlorination under acidogenic/methanogenic conditions through laboratory-scale experiments. Four scenarios, intended to assess the influence of electron donors on the environment and develop laboratory experimental research, were compared. In these scenarios, four compounds were used: acetate, lactate, methanol, and glucose + methanol.Materials and methodsThe LCA was carried out using IMPACT2002+ to estimate the environmental impact of PCA biodechlorination under acidogenic/methanogenic conditions. To add credibility to the study, sensitivity analysis was also conducted.Results and discussionIn all scenarios, the technologies significantly contributed to respiratory inorganics, global warming, as well as increased the adverse impact of nonrenewable energy on the environment. Specifically, the emissions from the electron donor production processes played an important role in the scenarios. PCA dechlorination and methanogenic processes substantially contributed to the aquatic/terrestrial ecotoxicity and global warming, respectively.Optimizing the concentration of amended electron donors and increasing the population size of dechlorinating microorganisms are highly important in reducing the environmental burden by PCA bioremediation.ConclusionsResults showed that the methanol scenario was the most suitable option determined in this research. In addition, results indicate amended electron donors can cause fewer environmental impacts in carcinogens and noncarcinogens categories. By contrast, the amended electron donors can significantly increase environmental impacts in respiratory inorganics, global warming, and nonrenewable energy categories. Increasing the population size of dechlorinating microorganisms and optimizing the concentration of amended electron donors are highly recommended to reduce adverse environmental impacts.