Impacts of climate change on cassava yield and lifecycle energy and greenhouse gas performance of cassava ethanol systems: An example from Guangxi Province, China.

Significant shock of climate change on crop yield will challenge the performance of bio-crop on substituting fossil energy to mitigate climate change. Taking cassava-to-ethanol system in Guangxi Province of South China as an example, we coupled a random forest (RF) model with 10 Global climate models (GCMs) outputs to predict the future cassava yields. Subsequently, the net energy value (NEV) and greenhouse gas (GHG) emissions of the cassava-to-ethanol system across varied topographies are assessed using a life cycle analysis. We demonstrate that the abrupt increases in temperatures are the primary contributors to declining yields. Notably, cassava yields in hilly regions decline more than those in plains and display greater variability among concentration pathway scenarios over time. Future NEV and GHG performance of cassava-to-ethanol will undergo significant decreases over time, especially within the high concentration pathway scenario (NEV decrease 28%, GHG increase 3.4% from 2006 to 2100). The performance reductions in hilly area are exacerbated by more harvest loss and labor and material inputs during the "field-to-wheel", negating its energy advantage over fossil fuels. Therefore, adopting a lower concentration pathway and favoring plantation in plains could maintain cassava-to-ethanol as a viable climate mitigation strategy. Our research also advances the methodological approach to climate change adaptation within the domain of life cycle assessment.

Cost of raising discharge standards: A plant-by-plant assessment from wastewater sector in China.

China has implemented increasingly stringent effluent standards for wastewater treatment plants (WWTPs) to protect the aquatic environment, but at the cost of more resource consumption and greenhouse gas emissions. To elaborate tradeoffs between the elevated standard and the additional burden, we compile a 10-year inventory of 6032 WWTPs across China to estimate the impacts of changes in effluent pollutant concentration on operating costs and electricity consumption. Coupled with the increasing demand for wastewater treatment, upgrading standards to the Special Discharge Limit (SDL) by 2030 would increase electricity consumption and operating costs of the wastewater treatment sector by 86.59% and 70.44% compared to the status quo in 2015. The electricity consumption-induced GHG emissions would also increase by 72.21%, which accounts for 29.16% of total emissions in the domestic wastewater treatment sector. Substantial regional differences exist in terms of upgrade-induced resource burden. Less developed regions generally suffer more stress when encountering similar standards elevation. With large-scale microdata, our findings deepen the understanding of the potential cost of raising standards and provide insights into region-customized pollutant effluent standards implementation.