Obituary in Remembrance of Tony Allan

It is with great sadness that we received the news that Tony Allan has passed away on the 15 April 2021 [...

Water footprint of bio-energy and other primary energy carriers

Freshwater is essential for life on earth, not only for basic human needs such as food, fibre and drinking water, but also for a healthy environment. In the near future, important challenges are to meet basic needs and to ensure that the extraction of water does not affect freshwater ecosystems. At present, humanity already uses 26 percent of the total terrestrial evapotranspiration and 54 percent of accessible runoff. If the world population increases further, there is concern in several regions and countries with limited water resources if food and fibre needs of future generations can be met. In general, global change is often considered in relation to climate change caused by emissions of greenhouse gasses, such as CO2 from fossil energy carriers. A shift towards CO2-neutral energy carriers, such as biomass, is heavily promoted. Nowadays, the production of biomass for food and fibre in agriculture requires about 86% of the worldwide freshwater use often competing with other uses such as urban supply and industrial activities. A shift from fossil energy towards energy from biomass puts additional pressure on freshwater resources. This report assesses the water footprint (WF) of bio-energy and other primary energy carriers. It focuses on primary energy carriers and expresses the WF as the amount of water consumed to produce a unit of energy (m3/GJ). The report observes large differences among the WF’s for specific types of primary energy carriers. For the fossil energy carriers, the WF increases in the following order: uranium (0.09 m3/GJ), natural gas (0.11 m3/GJ), coal (0.16 m3/GJ), and finally crude oil (1.06 m3/GJ). Renewable energy carriers show large differences in their WF. The WF for wind energy is negligible, for solar thermal energy 0.30 m3/GJ, but for hydropower 22.3 m3/GJ. For biomass, the WF depends on crop type, agricultural production system and climate. The WF of average biomass grown in the Netherlands is 24 m3/GJ, in the US 58 m3/GJ, in Brazil 61 m3/GJ, and in Zimbabwe 143 m3/GJ. Based on the average per capita energy use in western societies (100 GJ/capita/year), a mix from coal, crude oil, natural gas and uranium requires about 35 m3/capita/year. If the same amount of energy is generated through the growth of biomass in a high productive agricultural system, as applied in the Netherlands, the WF is 2420 m3. The WF of biomass is 70 to 400 times larger than the WF of the other primary energy carriers (excluding hydropower). The trend towards larger energy use in combination with increasing contribution of energy from biomass to supply will bring with it a need for more water. This causes competition with other claims, such as water for food crops

Without water no energy, significant trade-offs between carbon and water footprints important for global energy and water policy

Water and energy are strongly related. Water supply needs energy and energy supply needs water. The focus of the pre-2009 water for energy studies was mainly on the quantification of cooling water use in thermoelectric generation and on water use for transport fuel production. Most of the studies were based on grey literature using data from industry, often from the USA. Water footprint (WF) studies have made it possible to quantify water for bioenergy and hydropower, because the assessments were made based on publically available data, e.g. weather data. WF studies provided new information on the amount of water needed for specific renewable energy types. Energy that originates from photosynthesis (e.g. crops, trees or algae) has relatively large water footprints compared to fossil energy sources. Energy that originates from hydropower also has large average WFs, but variation is large. This paper gives an overview of the contribution of water footprint studies on water for energy relationships. It first explains why water is needed for energy, gives an overview of important water-energy studies until 2009, shows the contribution of WF studies, and indicates how this contribution has supported new research. Finally, it provides knowledge gaps that are relevant for future studies. Energy source categories are: 1. biofuels from sugar, starch and oil crops (food crops); 2. cellulosic feedstocks (residues and energy crops); 3. biofuels from algae; 4. firewood; 5. hydropower and 6. various sources of energy including electricity, heat and transport fuels. Especially category 1, 3, 4, 5 and to a lesser extent 2 have relatively large WFs. This is because the energy source derives from agriculture or forestry, which has a large water use (1,2,4), or has large water use due to evaporation from open water surfaces (3,5). WFs for these categories can be calculated using the WF tool. Category 6 includes fossil fuels and renewables, such as photovoltaics and wind energy and has relatively small WFs. However, information needs to be derived from industry. The policy to decrease carbondioxide emissions has consequences for water. Energy policies need to account for significant trade-offs between carbon, land and water footprints

The water footprint of global food production

Agricultural production is the main consumer of water. Future population growth, income growth, and dietary shifts are expected to increase demand for water. The paper presents a brief review of the water footprint of crop production and the sustainability of the blue water footprint. The estimated global consumptive (green plus blue) water footprint ranges from 5938 to 8508 km3/year. The water footprint is projected to increase by as much as 22% due to climate change and land use change by 2090. Approximately 57% of the global blue water footprint is shown to violate the environmental flow requirements. This calls for action to improve the sustainability of water and protect ecosystems that depend on it. Some of the measures include increasing water productivity, setting benchmarks, setting caps on the water footprint per river basin, shifting the diets to food items with low water requirements, and reducing food waste

Consequences of Transport Low-Carbon Transitions and the Carbon, Land and Water Footprints of Different Fuel Options in The Netherlands

Transport greenhouse gas emissions are mainly caused by the use of fossil fuels, e.g., gasoline and diesel. This case study for the Netherlands calculates how alternative fuels, e.g., electricity, hydrogen or biofuels, contribute to policy aims to decarbonize transport. Alternative fuels, produced in various ways, have different carbon (CF), land (LFs) and water footprints (WFs). This study assesses CFs, LFs and WFs for fuels (kgCO2e/m2/m3 per GJ), showing differences among fuels dependent on primary energy sources. It calculates CFs, LFs and WFs for four scenarios with different fuels. The biofuel scenario is not attractive. CFs slightly decrease, while LFs and WFs increase enormously. The electricity scenario has small CFs and the smallest LFs and WFs, but this is only when using wind or solar energy. If storage is needed and hydrogen is produced using wind energy, CFs double from 3055 to 7074 kg CO2e, LFs increase from 15 106 to 43 106 m2 and WFs from 3 106 to 37 106 m3 compared to the electricity scenario. The case study shows that wise fuel choices contribute to policy aims to decarbonize transport, although LFs and WFs are also important to consider. These case study results are relevant for sustainable transportation transitions worldwide

The water–energy nexus in irrigated agriculture in South Asia::Critical hotspots of irrigation water use, related energy application, and greenhouse gas emissions for wheat, rice, sugarcane, and cotton in Pakistan

Asia has a large water scarcity problem, especially in countries depending on irrigation, limiting agricultural production, and increasing food insecurity. When water becomes scarce, it needs conveyance over longer distances or pumping from deeper groundwater stocks, requiring pumping energy, often fossil energy, emitting greenhouse gasses. This causes a trade-off between irrigation water supply and fossil energy use contributing to global warming. This research focuses on the water–energy–food nexus in irrigated agriculture to improve resource management. It uses Pakistan as its case study area and assesses water consumption, energy (EFs), and carbon footprints (CFs) associated with irrigation water supply for the major crops (wheat, rice, sugarcane, and cotton) per district. The method first assesses irrigation water volumes (surface and groundwater) per crop per district and next the energy and CO2 emissions to provide this water. Data on allocated water volumes, crop areas and pumping types were taken from governmental reports. Groundwater tables and energy data were taken from scientific publication based also on actual measurements. The research identifies unfavorable hotspots and favorable areas from a water and energy perspective. Drivers determining water consumption, EFs, and CFs related to irrigation water supply show spatial and temporal differences and include crop types, temporal crop water requirements, fractions of gravity-fed and pumped water, groundwater tables, and energy sources (diesel, electric, and solar). In Pakistan, annual irrigation supply requires 103 PJ of energy generating a CF of 11 109 kg CO2 (6% of the national CF). Diesel pumps, pumping shallow groundwater, contribute most (73%), followed by electric pumps pumping deep groundwater. Energy for surface water pumping is negligible. Wheat contributes 31% to the EF, cotton 27%, and sugarcane and rice 21% each. CFs, caused by fossil energy use to pump irrigation water, are also dominated by wheat (32%) and cotton (31%), followed by rice and sugarcane (19% each). Ten hotspot districts contribute 42% to the EF of the major crops and increased by 21% in fourteen years. Wheat and cotton in Punjab and rice and cotton in Sindh are the most energy-intensive. EFs range between 3,500 and 5,000 TJ per district, with some districts in Punjab, the most important agricultural province, using even more. Large differences occur among EFs per unit of irrigation water, ranging between 7 and 2,260 KJ/m3, CFs between 1 and 444 g CO2/m3. The identification of hotspots may contribute to measures to minimize water consumption, EFs and CFs for agriculture in Pakistan. Other countries that also rely on irrigation could apply methods applied here to identify hotspots