A demonstration concentrating solar power plant in China: Carbon neutrality, energy renewability and policy perspectives.

Concentrating solar power (CSP) is considered as a promising renewable electricity source due to its superiority in providing dispatchable and base-load electricity. This study performs a systems process analysis to quantify the carbon emissions and nonrenewable energy costs induced by a state-of-art demonstration CSP plant located in the Tibetan plateau. Estimated to induce 111.2 g CO2 eq/kWh carbon emissions and 1.42 MJ/kWh non-renewable energy consumption, the CSP plant is considered to have extremely high carbon neutrality (88.8%) and energy renewability (86.4%). The prominent performance of carbon emissions reduction and energy conservation induced by the CSP plant shed light on its superiority of reliable power supply and environmental benefits. The plant is expected to cumulatively fulfill 3.4 million tons of carbon emissions reduction over its life cycle. In contrast to coal-based power and other renewable energy technologies, CSP technology is shown to be a promising solution to the low-carbon energy transition. Besides, a scenario analysis indicates that the incremental employment of CSP technologies will play a critical role in coping with climate change and energy security in China. Moreover, multiple policies to facilitate the development of the CSP system in China are elaborated, such as the promotion of integrated solar combined-cycle systems. The empirical finding draws a holistic picture of the carbon neutrality and energy sustainability performance of CSP technologies, and the systematic analysis in this study provides comprehensive policy perspectives for energy policy in the Tibetan region as well as in China in the context of global climate change.

Can constructed wetlands be more land efficient than centralized wastewater treatment systems? A case study based on direct and indirect land use.

Compared with centralized wastewater treatment systems, constructed wetlands are generally regarded as not suitable for wide deployment due to the comparatively larger direct land area. Much of the traditional thinking is based on an onsite perspective, while the offsite information is left out. By a comparative case study with systems accounting of both onsite and offsite land use, this study questioned the traditional picture and found that constructed wetlands can be more land use efficient than centralized wastewater treatment systems. On a unit of wastewater treated basis, the land use induced by a typical constructed wetland in China is revealed to be less than half of that by the case of a centralized wastewater treatment plant or a hybrid system. On a unit removal basis for biological oxygen demand (BOD5), chemical oxygen demand (COD), total suspended solid (TSS) and ammonia­nitrogen (NH3-N), the land use induced by a constructed wetland is only around 61%, 67%, 73% and 64% of that by a centralized wastewater treatment system, respectively. Meanwhile, the indirect effect is demonstrated to be significant for these three systems: this magnitude amounts to three times the direct land occupation for a constructed wetland, and one order of magnitude higher of that for the a centralized wastewater treatment system. By a scenario analysis for China in 2017, it is preliminarily estimated that over two billion square meters of land use could be reduced if all the centralized wastewater treatment systems are replaced by constructed wetlands. The outcome may serve a benchmark and offers a new way of thinking for management of wastewater treatment systems.