Solar Powered Desalination for using Electrodialysis

by Maithili Joshi

A major problem across the world in developing and underdeveloped nations is the lack of access to clean drinking water. This has detrimental effects on general health, and also the ability to keep these rural communities going. This article was particularly interesting to me because issues of water in countries like India are so important for the health of people, and the health of the environment. Additionally, the use of solar power to reduce environmental effects was of particular interest to me because of its innovative use for other pressing environmental issues. Continue reading

‘Shade Balls’ Roll their Way into the Spotlight

by Samantha Englert

This past summer you may have noted that social media has been flooded with pictures and videos of black balls blanketing several California reservoirs, somewhat reminiscent of a massive playground pit filled with black plastic balls. You were probably wondering, what exactly am I looking at? These floating objects have been referred to in the news as bird balls, conservation balls, reservoir balls and floating ball blankets, yet the biologist from the Los Angeles Department of Water and Power who developed this technology named them “Shade Balls.” So what are these Shade Balls? Continue reading

The Syrian Civil War: A Result of Climate Change

by Chloe Rodman

Kelley et al. (2015) writing in The Proceedings of the National Academy of Sciences linked the Syrian Civil War to climate change. The Fertile Crescent, more specifically Syria, has experienced a severe prolonged drought since 2006. In a country dominated by agriculture, the drought killed enormous amounts of livestock and crops. To make matters worse, before this dry spell began, former Syrian President Hafez al-Assad implemented policies to increase agricultural production, despite a shortage in water. These policies made Syria particularly defenseless when the drought began. Continue reading

Effects of Utility Scale Solar Energy on Aquatic Ecosystems in the Southwest

 

by Melanie Paty

In a recent Environmental Management article, Grippo, Hayse, and O’Connor (2015) speculate on the potential detriments solar farm development imposes on temporary bodies of water and the wildlife that depend on them. The authors’ locational focus is the Southwestern United States, where there are more than 40 pending or approved solar development permits. Temporary bodies of water, either intermittent, “seasonally dry stream, especially during times of low rainfall or high heat,” or ephemeral, “defined as those that do not receive groundwater inputs and contain water only briefly and in direct response to precipitation,” play an important role in desert ecosystems: they connect the landscape, transport water and nutrients downstream, serve as the short-term habitat for animals with aquatic life stages and the reproductive site for various animals, and give rise to riparian corridors that provide a variety of benefits to local animal species. However, unlike permanent bodies of water, temporary water is not protected under the Clean Water Act, unless it is significantly connected to a permanent body of water. Continue reading

Dams and Agriculture in Idaho

by Adin Bonapart

Water storage and distribution infrastructure (dams) allow large areas of land that wouldn’t otherwise have access to water (i.e. away from riparian areas) to be farmed and settled. Furthermore, dams give farmers security against variations in climatic conditions and water supply (i.e. droughts), ­­­which, allows farmers to grow higher-valued, more water intensive crops. Hansen et al. (2014) find that the presence of dams has a “small, positive, but non-significant effect” on farmland values. For these reasons, the construction of dams tends to lead to improved crop yields and planted acreage. Continue reading

Nuclear Power Generation: High Demands for Cooling Water Use

by Cameron Bernhardt

Nuclear power is often praised for its potential to replace carbon-intensive energy sources and reduce greenhouse gas emissions from electricity and power generation. Although nuclear power may offer a promising future in this regard, it is likely to place stresses on the environment in other ways, namely through increased demands on water for cooling and space for waste disposal. Byers et al. (2014) tested six decarbonization pathways to estimate current water use in the UK electricity sector and project water use to 2050 in the UK. The study observed the water use associated with cooling for all varieties of thermoelectric power plants, but nuclear power accounts for over 20 percent of the UK’s electricity mix and is likely to share a large stake in the future of the UK’s power mix. Byers et al. concluded that the pathways with the highest projected proportion of nuclear generation resulted in tidal and coastal water abstraction that exceeded current levels by up to six times. This finding suggests that nuclear power may not be as viable a future energy source as previously thought, especially in areas where water resources are relatively scarce. It seems that the UK should extend its investigations into the merits of nuclear power, and similar studies may be warranted to assess the impacts of nuclear generation in other countries. Continue reading

Shale Gas Produces Half the GHG Emissions and Consumes Half the Freshwater of Coal

by Shannon Julius

The long term environmental concerns having to do with shale gas development are primarily greenhouse gas (GHG) emissions and freshwater consumption, as other forms of environmental degradation can be remediated over time. Ian Laurenzi and Jersey Gilbert (2013) of the ExxonMobile Research and Engineering Company performed a life cycle assessment (LCA) of both GHG emissions and freshwater consumption of Marcellus shale gas. The life cycle begins with well drilling and ends with burning the fuel for power generation. Using their elaborated system boundaries, the researchers found that a Marcellus shale gas well releases 466 kg of carbon equivalent units per megawatt hour of power produced (kg CO2eq/MWh) and consumes 224 gallons of freshwater per megawatt hour of power produced (gal/MWh) over the course of its lifetime. The biggest contributor to both GHG emissions and freshwater consumption is power generation. The result of this study are highly dependent on the variables chosen to represent the shale gas well life cycle, especially the expected ultimate recovery of natural gas. Despite the potential for variability of results, the result of 466 CO2eq/MWh is consistent with other published life cycle assessments for conventional and shale gas, and almost all of the 14 other studies fall within the 10%–90% range of 450–567 CO2eq/MWh. Even considering factors that can increase total results, this study shows that average GHG emissions from shale gas are 53% lower and freshwater consumption is 50% lower than what is required for an average coal life cycle. Continue reading

Heat-absorbing Materials Useful for Increased Solar Still Efficiency

The solar still is the simplest form of solar-powered desalination. It uses the mechanisms of evaporation and condensation—the same processes used other forms of distillation—to purify the water. In a solar still, water is kept in an airtight container. As the water heats up, it evaporates and becomes water vapor. The lid of the still serves as the condenser to transform the purified water vapor back into water and the water slides down the slope of the lid to a collection point. Murugavel et al. (2010) built and tested a solar still with a roof-like glass lid, shallow basin, and insulation. They investigated the effects of various insulating and heat-absorbing materials on the efficiency of the still, since operation of the still depends on the amount of water evaporated, which depends on the amount of heat added to the water, among other things. The materials tested here included rocks, brick, metal, and cloth. The results of their testing showed that a ¾ inch layer of quartzite rock on the bed of the still performed the best. Murugavel et al. also performed theoretical calculations using energy balances and heat transfer equations to determine the theoretical efficiency possible for the chosen parameters. While the quartzite rock performed the best in tests, the actual efficiency was still nowhere near the theoretically possible one.—Erin Partlan
 
Murugavel, K., Sivakumar, S., Ahamed, J., Chockalingam, K., Srithar, K., 2010. Single basin double slope solar still with minimum basin depth and energy storing materials. Applied Energy, 87, 2, 514–523.
 
Murugavel et al. built and tested a solar still in Kovilpatti, India. They crafted a basin from mild steel plate, created a glass cover with a north and south slope, and insulated it with glass wool. In testing, a minimal water depth of 0.5 cm was used. Measurements were taken of the influx and outflux of water and of the temperature of the body of water and the water vapor. Also, atmospheric conditions were monitored to ensure that factors were controlled between test days. From incident solar radiation and ambient temperature data, the authors conclude that this is a valid assumption. The materials used to collect extra heat on the basin were ¼ inch quartzite rock, ¾ inch quartzite rock, ¼ inch washed stones, 1½ inch cement concrete pieces, 1¼ inch brick pieces, mild steel trimmings, and a light black cotton cloth. Multiple trials were run with each material, and while the overall productions hovered around 3.5 L/day of water, the ¾ inch quartzite material performed slightly better than the rest at 3.66 L/day of water.
 

In the theoretical testing, the authors use thermodynamic equations to model the heat influxes and outfluxes of the system. They note that they are novel in their approach as they use a variable term for the transmittance of solar energy through the glass cover, a term usually assumed to be constant. The resulting equations in their modeling are expressions for the instantaneous and overall water production of the solar still. However, when the parameters from the test of the ¾ inch quartzite rock are used, it was found that four-fold increase in the production rates was theoretically possible. While the authors note several areas of discrepancy—the change in water volume and depth over time, a higher proportion of water vapor inside the still, and differences in the absorptivity of the different testing materials—these results imply that the heat-absorbing material used has a minimal impact on improved efficiency, and that instead, focuses should be made on improving the design of the solar still itself to better utilize the incident energy. 

Revised Approach to Water Footprinting

A revised water footprint method devised by Ridoutt and Pfister takes into consideration the type of water source and different usages during stages of production to determine how much Dolmio® pasta sauce and Peanut M&M’s® contribute to water scarcity (2009).  Existing water footprint calculations use the volumetric summation of all water content in the product at all stage of production and consumption. Under the existing method, the products Dolmio® pasta sauce and Peanut M&M’s® have water footprints of 202 and 1153, but the revised water footprints offer a drastically different relationship. The stress-weighted water footprints of Dolmio® pasta sauce and Peanut M&M’s® are 141 and 131. Winnie Wong

Ridoutt, B., Pfister, S., 2010. A revised approach to water footprinting to make transparent the impacts of consumption and production on global freshwater scarcity. Global Environmental Change 20, 113-120.

Bradley G. Ridoutt of the Australian Commonwealth Scientific and Research Organization and Stephan Pfister of the Swiss Federal Institute of Technology Zurich demonstrated a revised water footprint calculation method using brand products, Dolmio® pasta sauce and Peanut M&M’s®. Ridoutt disaggregates water according to the different sources: blue water which is surface and groundwater sources, and green water which is rainwater that is consumed through crop evapotranspiration. Because some places have a higher degree of water scarcity than others, location and level of stress imposed by different activities are considered in calculating a product’s water footprint. Therefore, the water consumption at specific locations at each point in the product life cycle and the water stress index (WSI) by Pfister (2009) were used to determine the level of contribution to water scarcity of both products.

In both cases of Dolmio® pasta sauce and Peanut M&M’s®, the agricultural stage of production contributed the greatest, followed by operations, ingredients processing and packaging. The study found that blue water sources are typically directly consumed at rates exceeding short-term replacement therefore processes heavily using blue water sources contributes significantly to stress-weighted water footprints. A main ingredient of Dolmio® pasta sauce is tomato. Due to the stress-heavy consumption of blue water in agriculture, tomatoes contributed more than 95% of stress-weighted water footprint. Therefore, efforts to reduce water footprint should focus on stress-heavy processes and not necessarily processes that use more water.

The study argues that the simplistic existing volumetric method is unequipped to accurately depict how production impacts water scarcity. This method is misleading and confusing as these water footprints do not accurately reflect a product’s impact on the water supply. A revised water footprint method would allow quantitative comparisons between products in terms of potential to contribute to water scarcity. Water footprint assessment methods need to accurately reflect the impact of consumption and this requires a revised approach that considers the incorporation of water stress characterization factors. The revised method will help corporations direct optimal actions to reduce negative impact of water supply and help consumers to make more informed purchases. 

Ecosystem model predicted water availability

Species distribution models typically use four common proxies for water in order to predict how water availability will impact future species distribution. However,  the affects of changes in vegetation structure and functioning on the water balance of terrestrial ecosystems are not accounted for. Hickler sought to assess whether the water availability measure commonly used in species distribution models properly account for hydrological effects of changes in vegetation structure and functioning (2009). In his study, ecosystem models LPJ- GUESS and LPF- DGVM which took into account soil water content along with variables based on climate. The projections for future water availability from four common proxies for water and the soil water content predicted by ecosystem models differ substantially. Winnie Wong
Hickler, T., Stepan F., Miguel B. A., Oliver S., Wilfried T., and Martin T. S., 2009. An ecosystem model-based estimate of changes in water availability differs from water proxies that are commonly used in species distribution models. Global Ecology and Biogeography 18, 304-313.

The paper focused on water availability in Europe. The LPJ-GUESS model includes a number of factors that influence water availability not account for in common proxies for water. LPJ- DGVM is a simplified ecosystem model that was also assessed. The four commonly used proxies for water availability used were total annual precipitation, total precipitation during water scarce periods (June, July and August), annual water deficit, sum of actual evapotranspiration divided by equilibrium evapotranspiration. Water stress experienced by plants are a function of water availability and both soil after and atmospheric variables are biologically meaningful. For tree species, the water content of soil is a more direct measure of water availability than variables purely based on climate.
The changes projected by the four proxies correlated with each other white these variable showed no or very weak correlations with the two ecosystem models. Projected changes in the four proxies for water availability indicate a net effect of increasing temperate  and annual rainfall in many areas will be drying over most of Europe. In contrast the ecosystem models the sign of change (positive or negative) differs in 32% of the total study area. These significant differences in results are important because results from species distribution models has been used for guiding policies for adaptation to climate change.