Crop grey water footprints in China: The impact of pesticides on water pollution.

Agricultural water pollution is a significant challenge in China, a rapidly growing economy with a large agricultural sector. The grey water footprint (WF) is a tool for evaluating freshwater pollution. It expresses pollution in volumetric units identifying the pollutant that theoretically needs most water to be diluted to accepted water quality standards. Previous agricultural grey WF studies focused on nitrogen (N) and phosphorus (P), some studies included pesticides. This study assesses grey WFs based on N, P and 1513 pesticide combinations for twelve main crops and two crop categories in 31 Chinese provinces. Grey WFs, including the pesticide component, are far larger than estimated before, dominating total agricultural WFs (green, blue, and grey). The total grey WF of Chinese agriculture (4,900 109 m3 year-1) is determined by pesticides, while grey WFs related to N and P are 450 and 1,500 109 m3 year-1, differences of a factor of eleven and three respectively. The provinces Heilongjiang, Inner Mongolia, Hebei, Henan, and Shandong are hotspots contributing 37 % to the total grey WF. A limited number of pesticides used for maize, vegetables, fruits and potato (Mancozeb a fungicide, Acetochlor a herbicide and Cypermethrin an insecticide) dominate total grey WFs, contributing 80 % to the total grey WF. Eliminating the most polluting pesticides per category and redistributing the remaining ones with a similar function but lower grey WFs reduces national water pollution from agriculture by 64 %. Only five crops, i.e. maize, potato, soybean, rice and wheat, and the two crop categories, vegetables and fruits, contribute 94 % to this reduction. Probably grey WFs could reduce even further with a second elimination and redistribution effort. This study is the first national grey WF assessment related to pesticides in agriculture. It offers valuable insights to farmers and policymakers to enhance water quality in China and beyond.

Biogas feedstock potentials and related water footprints from residues in China and the European Union.

China encounters heavy air pollution caused by coal consumption. China and the EU aim to decrease greenhouse gas emissions. Shifting to biogas from residues contributes to solving both problems. This study assesses China's biogas potentials and related water footprints (WFs) and compares results with potentials and WFs for the EU. Starting from a literature review on EU biogas potentials, it analyzes information resulting in a calculation methodology, its validation and application to China. Finally, it estimates WFs and makes a comparative assessment of biogas potentials of the EU and China. In the EU, biogas from agricultural, forestry and other residues might contribute 8% (5300 PJ) to primary energy consumption, in China 10% (13,275 PJ.) In the EU, agriculture contributes 41%, forestry 26%, other residues 23%, and manure 10%. The corresponding results for China are agriculture (67%), forestry (23%), manure (7%) and other residues (3%). In the EU, biogas might contribute 45% to total gas demand; in China more biogas can be produced than consumed in 2018 (185% of demand). The EU results fall in the range of residue potentials from earlier studies. Maize, wheat, barley and rapeseed contribute 78% to the EU agricultural biogas potential. In China, dominant crops are maize (49%), rice (18%), wheat (12%) and seed cotton (6%). For water, there are large differences among WFs of specific crop residues, but also between WFs for EU and Chinese crop residues. Most Chinese crop residues have larger WFs than the EU residues. Biogas from sugar beet residues has the smallest WFs, biogas from tobacco residues the largest. Although using residues for energy does not change total national WFs, it reallocates WFs over main products and residues. The comparative assessment supports better use of biogas potentials from residues with lower WFs and is also applicable for other regions and countries.

The monthly dynamics of blue water footprints and electricity generation of four types of hydropower plants in Ecuador.

Water evaporates from reservoirs of hydropower plants (HPPs), often in significant volumes. Reservoir evaporation is a dynamic phenomenon depending on climate, varying size of open water surfaces (OWS), and electricity production. Due to a lack of data and methods to estimate the OWS's size variation, previous studies assessed HPPs water footprints (WFs) considering static OWSs acknowledging the uncertainty of this omission. This study estimates WFs of HPPs, considering dynamic OWSs for four plant types in Ecuador, Flooded lakes, and Flooded rivers, with dam heights lower or higher than their Gross Static Head (GSH). It quantifies OWSs size variation using a Digital Elevation Model and GSH data, assessing OWS evaporation, effects on electricity production and WFs. There are large differences among the evaporation of HPPs when OWS size variations are considered. HPP operation, geographical features, and climate determine temporal differences. Flooded lake HPPs have relatively large WFs. Flooded River HPPs, with dam heights below their GSH, have the smallest WFs, but water storage capacity is limited. Static area approaches underestimated annual WFs by 10% (Flooded Lake HPPs) to 80% (Flooded River HPPs). Earlier studies showed effects of HPPs on water from a water management perspective, suggesting that less water-intensive HPP technologies are favorable, or that other water-efficient electricity-generating technologies, like solar or wind, should replace HPPs. This study also included the electricity perspective, indicating that energy management and water storage are important factors for WFs. The most water-effective technology cannot fulfill current electricity production due to a lack of storage options. The system dynamics analysis indicates that aiming for small WFs is not always the best option from an energy and water perspective.

Water-electricity nexus in Ecuador: The dynamics of the electricity's blue water footprint.

Freshwater has spatial and temporal constraints, affecting possibilities to generate electricity. Previous studies approached this from a water perspective quantifying water consumption of electricity to optimize water use, or from an electricity perspective using modeling methods to optimize electricity output. However, power plants consume different water volumes per unit of electricity, depending on the applied technology, and supply systems often include a mix of different technologies with a different water footprint (WF), an indicator of water consumption, per unit of electricity. When water availability varies in time, probably the contribution of different electricity generating technologies also varies in time, resulting in WF fluctuations. Focusing on electricity generation from the water perspective, we assessed how water availability affects an electricity mix's dynamics and its blue WF using Ecuador as a case study. We studied the Amazon and Pacific basins, which have different temporal and spatial water availability fluctuations, assessing monthly water availability, electricity production, and blue WFs per plant. The Amazon basin has smaller temporal and spatial availability fluctuations than the Pacific. The difference between the largest and smallest water availability in the Amazon basin is two-fold, in the Pacific four-fold. Hydropower generation in the Amazon basin contributes more than 60% to the electricity mix. However, hydropower is directly affected by water availability, and its production decreases in water-limited periods. For biomass plants, limited water availability affects the fuel source, sugarcane bagasse. As water availability decreases, other technologies in the mix take over, causing WF variation (from 4.8 to 8.6 103 m3 per month). Usually, less water-availability means more water-efficiency, implying fossil-fueled plants in the Pacific take over from hydropower in the Amazon. It is relevant to assess the water-electricity nexus in countries with electricity mixes dominated by hydropower because energy planning needs to consider water availability and electricity mix dynamics.

Future electricity: The challenge of reducing both carbon and water footprint.

We estimate the consumptive water footprint (WF) of electricity and heat in 2035 for the four energy scenarios of the International Energy Agency (IEA) and a fifth scenario with a larger percentage of solar energy. Counter-intuitively, the 'greenest' IEA scenario (with the smallest carbon footprint) shows the largest WF increase over time: an increase by a factor four over the period 2010-2035. In 2010, electricity from solar, wind, and geothermal contributed 1.8% to the total. The increase of this contribution to 19.6% in IEA's '450 scenario' contributes significantly to the decrease of the WF of the global electricity and heat sector, but is offset by the simultaneous increase of the use of firewood and hydropower. Only substantial growth in the fractions of energy sources with small WFs - solar, wind, and geothermal energy - can contribute to a lowering of the WF of the electricity and heat sector in the coming decades. The fifth energy scenario - adapted from the IEA 450 scenario but based on a quick transition to solar, wind and geothermal energy and a minimum in bio-energy - is the only scenario that shows a strong decline in both carbon footprint (-66%) and consumptive WF (-12%) in 2035 compared to the reference year 2010.

China's rising hydropower demand challenges water sector.

Demand for hydropower is increasing, yet the water footprints (WFs) of reservoirs and hydropower, and their contributions to water scarcity, are poorly understood. Here, we calculate reservoir WFs (freshwater that evaporates from reservoirs) and hydropower WFs (the WF of hydroelectricity) in China based on data from 875 representative reservoirs (209 with power plants). In 2010, the reservoir WF totaled 27.9 × 10(9) m(3) (Gm(3)), or 22% of China's total water consumption. Ignoring the reservoir WF seriously underestimates human water appropriation. The reservoir WF associated with industrial, domestic and agricultural WFs caused water scarcity in 6 of the 10 major Chinese river basins from 2 to 12 months annually. The hydropower WF was 6.6 Gm(3) yr(-1) or 3.6 m(3) of water to produce a GJ (10(9) J) of electricity. Hydropower is a water intensive energy carrier. As a response to global climate change, the Chinese government has promoted a further increase in hydropower energy by 70% by 2020 compared to 2012. This energy policy imposes pressure on available freshwater resources and increases water scarcity. The water-energy nexus requires strategic and coordinated implementations of hydropower development among geographical regions, as well as trade-off analysis between rising energy demand and water use sustainability.

Food consumption patterns and economic growth. Increasing affluence and the use of natural resources.

This study analyzes relationships between food supply, consumption and income, taking supply, meat and dairy, and consumption composition (in macronutrients) as indicators, with annual per capita GDP as indicator for income. It compares food consumption patterns for 57 countries (2001) and gives time trends for western and southern Europe. Cross-sectional and time series relationships show similar patterns of change. For low income countries, GDP increase is accompanied by changes towards food consumption patterns with large gaps between supply and actual consumption. Total supply differs by a factor of two between low and high income countries. People in low income countries derive nutritional energy mainly from carbohydrates; the contribution of fats is small, that of protein the same as for high income countries and that of meat and dairy negligible. People in high income countries derive nutritional energy mainly from carbohydrates and fat, with substantial contribution of meat and dairy. Whenever and wherever economic growth occurs, food consumption shows similar change in direction. The European nutrition transition happened gradually, enabling agriculture and trade to keep pace with demand growth. Continuation of present economic trends might cause significant pressure on natural resources, because changes in food demand occur much faster than in the past, especially in Asia.