• Energy Research
• 11. Sustainability close
• CN close
• AU close
• IN close
• BE close

This study reports the transformation behavior of nitrogen during the co-hydrothermal carbonization of sewage sludge and model compounds (microcrystalline cellulose, starch, lignin, and xylan) of food waste at 220 °C, with a focus on the reaction routes between starch/xylan and NH4+. Most of the nitrogen in the raw sludge was transformed into organic-N (44.6%) and NH4+ (23.3%) in the aqueous product, and only 20.3% of nitrogen was retained in the hydrochar. The added model compounds could react with organic-N (i.e., amino acids and amines) and NH4+ in aqueous products through Maillard and Mannich reactions, generating heterocyclic-N (especially pyrrole-N) which further polymerizes to form nitrogen-containing polyaromatic hydrochar. This leads to an increase in the retention rate of nitrogen to 36.8-50.9%, especially upon the addition of starch and xylan. During the hydrothermal carbonization of starch/xylan in the NH4+ solution, the polymers are first hydrolyzed into monomers, followed by their further reaction with NH4+ to generate pyrrole-N and pyridine-N in aqueous products (especially xylan), and the pyrrole-N can then polymerize with aromatic clusters to form hydrochar-N. The results show that the model compounds of food waste substantially affect the nitrogen transformation pathways during hydrothermal carbonization, mainly because of the structures of their monomers. These findings can guide the production of sludge-based hydrochar with the targeted regulation of nitrogen content and species.

Abstract Energy utilization of crop straw is of high economic, social and ecological benefit. In this paper, based on the beneficiary pays principle, we use biogas production from crop straw as an example and analyze households' willingness to pay (WTP) for the local government-led project on energy utilization of crop straw. “Interpersonal trust” and “institutional trust” variables are introduced to improve the unified theory of acceptance and use of technology (UTAUT) model, on the basis of which, Probit and Interval Regression Models are employed to explore the determinants of households' WTP. Results show that: 1) Most households are willing to pay for biogas utilization of crop straw, and the average expected value of households' WTP is about 20.72 RMB per household monthly; 2) Crop straw program cost and benefit trade-offs, convenience of logistics and technology, and trust factors all play an important role in households’ WTP; 3) If the cultivation of trust is neglected, even if households have high expectations for the ecological performance of biogas production from crop straw, their WTP will not be improved. Conclusions are summarized to provide an important reference for the formulation of policies to improve energy utilization of crop straw in developing countries or regions.

Abstract Multi-Disciplinary Design Optimization (MDO) is a research methodology that has been applied in engineering fields to design and evaluate decisions from multiple professions using objective function. However, the application of the MDO model to the field of Urban Design is rare. This paper addresses problems of energy performance of varying Mixed Land Use structures in the context of aspatial distribution. Through the identification of objective factors, which allow for quantification of the multi-layered problem of land use distribution, MDO can be used to derive a Pareto front that can be used to limit the design decision space or choices of future designs. The data needs for the MDO process are intensive and require a high level of contextualization for the best outcomes. The MDO models test options of design decisions through constructing the relationship between the mixed-use ratio and building energy performance at the urban scale. Preliminary findings of mixed-use optimization using aspatial parameters are discussed to better understand this relationship.

Rapid urban expansion has radically transformed the city centers and the new districts of Chinese cities. Both areas have undergone unique redevelopment and development over the past decades, generating unique urban forms worthy of study. To date, few studies have investigated development patterns and land use intensities at the neighborhood level. The present study aims to fill the gap and compare the densities of different types of developments and the spatial compositions of different commercial uses at the neighborhood level. We captured the attributes of their built environment that support instrumental activities of daily living of 710 neighborhoods centered on the public elementary schools of the entire Shanghai municipality using application programming interfaces provided in Baidu Map services. The 200 m neighborhood provided the best fit to capture the variations of the built environment. Overall, city center neighborhoods had significantly higher residential densities and housed more daily routine destinations than their counterparts in the new districts. Unexpectedly, however, the total length of streets was considerably smaller in city-center neighborhoods, likely reflecting the prominence of the wide multilane vehicular roads surrounding large center city redevelopment projects. The findings point to convergence between the city center’s urban forms and that of the new districts.

AbstractRivers are basic natural resources supporting ecosystems and human societies, and the health of rivers is crucial to the Earth's sustainable development. Under the profound influence of climate change and human activities, great changes have recently occurred in the circulation and development of rivers, as well as the ways in which they are utilized. In this context, achieving an effective balance between river protection and human development is necessary. In this paper, the essential role of rivers is discussed from three aspects: the formation and evolution of rivers, the shaping of biodiversity, and the cultivation of human civilization. The paper analyzes the challenges brought to the sustainable development of rivers by climate change, human activities, and increased water demand, and proposes four dimensions of future research: scientifically balancing the relationship between river development and protection, improving the adaptability of river development and utilization in the context of climate change, improving the integrity and intelligence level of river management, and building a more fair and sustainable comprehensive river management model.

Abstract The experiment and simulation investigation of vehicle energy management (VEM) were carried out on a passenger car equipped with a turbocharged gasoline engine. The research results show that the vehicle takes on the characteristic of overcharge under urban conditions to guarantee the power by sacrificing economy. Exhaust energy after catalytic converter and the greater circulation heat transfer loss that account for more than one-third of total energy under New European Driving Cycle (NEDC) are wasted without being used, which indicates that the tested vehicle has great potential for recovering the waste heat. To solve these problems, the VEM model coupled multiple physical fields was developed and calibrated. Original turbocharger was reformed to hybrid turbocharger with the aid of simulation model, and its optimal control strategy based on equivalent consumption minimization strategy (ECMS) was designed. The one-dimensional numerical engine model was introduced into algorithms, which opens new windows for the development of VEM optimization strategies. After the transformation of hybrid turbocharger, the overcharge phenomenon under urban driving cycle has been eliminated. The main contribution to fuel saving comes from the reduction of pumping loss and alternator power consumption. The energy saving rate of hybrid turbocharger in different driving cycles ranges from 1% to 5%, which is mainly affected by the deterioration degree of overcharge on the economy of original machine and the characteristics of regeneration conditions in different driving cycles.

Abstract Using country level panel data from East Asia over the period 1998–2011, this paper examines the implications of international production fragmentation-induced intermediate goods trade on the link between energy consumption and carbon pollution. The paper focuses on the interaction effect between energy consumption and trade in intermediate goods on carbon emission. The empirical results presented suggest that international trade in intermediate goods decreases the positive impact on carbon emission of energy consumption. When compared with the trade in final goods, intermediate goods trade contributes to a greater decrease in carbon pollution resulting from energy consumption. These results confirm that the link between energy consumption and carbon pollution in East Asia is significantly affected by international production fragmentation-induced trade in intermediate goods. The results presented in this paper have some important policy implications.

Abstract The use of electric bus fleets has become a topical issue in recent years. Several companies and municipalities, either voluntarily or to comply with legal requirements, will transition to greener bus fleets in the next decades. Such transitions are often established by fleet electrification targets, which dictate the number of electric buses that should be in the fleet by a given time period. In this paper we introduce a comprehensive optimization-based decision making tool to support such transitions. More precisely, we present a fleet replacement problem which allows organizations to determine bus replacement plans that will meet their fleet electrification targets in a cost-effective way, namely considering purchase costs, salvage revenues, operating costs, charging infrastructure investments, and demand charges. We account for several charging infrastructure options, such as slow and fast plug-in stations, overhead pantograph chargers, and inductive (wireless) chargers. We refer to this problem as the electric bus fleet transition problem, and we model it as an integer linear program. We apply our model to conduct computational experiments based on several scenarios. We use real data provided by a public transit agency in order to draw insights into optimal transition plans.