Energy Plant Species: Their Use and Impact on Environment and Development

If so, technical solutions for removing waterborne toxicants would be needed to prevent occupational and ecological exposures. Mercury is removed from flue gas in some configurations of coal-fired electric-generating units EPA, However, mercury removal is ineffective for certain types of coal and plant configurations NETL, Contaminants in flue gas could place another constraint on the type of coal-fired electricity facilities that would be suitable for providing CO 2 for algae cultivation see sections Estimated Land Requirements and Estimated Nutrient Requirements in Chapter 4.

Open ponds may not be suitable for many soil types without using lining, and a thorough review of potential effects on surface water and groundwater quality would have to be conducted if clay-lined ponds are to be used. If outdoor ponds are poorly lined or the lining fails as a result of wear, then seepage of the pond water into the local groundwater system could occur. Clays that are compacted and graded have structural integrity that can be comparable to synthetic liners Boyd, However, integrity can be compromised by poor construction. Nitrate leaching has been observed below structured clay soils White et al.

Local terrestrial vegetation might take up some of the culture media released through seepage. In some areas, if open ponds contain high concentrations of dissolved inorganic nitrate, seepage may contribute to concerns related to nitrate poisoning if the groundwater is used for drinking by livestock or humans. Withdrawal of freshwater adjacent to briny aquifers or injection of saline wastewater into the ground could result in salinization of groundwater if fresh water and briny aquifers are not well separated. Salinization of groundwater is a potential problem for some agricultural lands where irrigation is prevalent Schoups et al.

However, one of the key advantages of algal biofuel is that the feedstock could be produced on nonarable land Ryan, ; Assmann et al. Using sealed algal cultivation systems would practically eliminate the potential for leakage, barring catastrophic breaches. Where open systems are used, technologies such as the development of impermeable, long-lived liner systems and regional solutions for minimizing nutrient leakage could be deployed, and regulations to minimize leakage could be developed.

For example, Phyco BioSciences uses a trough system that has a lightweight, fabricated liner. The liner is expected to eliminate leakage or minimize percolation to less than 0. Potential preventive measures might include specifications for soil type, combined with defined values for the minimum depth from the pond bottom to groundwater.

Moreover, local regulations likely require lined ponds, which would reduce the probability of leakage of waters but contribute to capital costs and lead to temporary system closures when the liners are replaced because of wear or failure. Measures to prevent inadvertent discharge of water for example, overflow corridors or basins during extreme weather events would be helpful in preventing water pollution.

Wastewaters derived from municipal, agricultural, and industrial activities potentially could be used for cultivating algal feedstocks either in open ponds or in photobioreactors for algal biofuels and could provide an environmental benefit. Microalgae have been used in wastewater treatment for a long time Oswald et al.

Microalgae have been shown to be effective for wastewater treatment in diverse systems including oxidation stabilization ponds and shallow raceway systems and using both phytoplankton and periphyton Green et al. High rate algal ponds HRAPs , which are shallow, open raceway ponds used for treating municipal, industrial, and agricultural wastewater, combine heterotrophic bacterial and photosynthetic algal processes Park et al.

The ponds allow the growth of high-standing crops of algae, which remove nitrogen and phosphorus from the wastewater Sturm et al. The concept of adapting HRAPs for the purpose of biofuel production was proposed more than five decades ago Oswald and Golueke, The feasibility and scale of such systems will be determined by the amount of wastewater, the availability of land near the facilities generating the wastewater and produced water, and the climatic conditions of the region.

See also Chapter 4. If wastewater is used, the wastewater treatment rate and the harvesting schedule would determine the maximum volume of ponds or photobioreactors. A major goal of wastewater treatment is removal of nitrogen and phosphorus Pittman et al. In conventional treatment systems, phosphorus is especially difficult to remove Pittman et al. In advanced wastewater treatment, phosphorus typically is either chemically precipitated using aluminum- or iron-based coagulants to form an insoluble solid, or it is stripped from the water by microbial activity EPA, The recovered phosphorus is then buried in a landfill or treated to create sludge fertilizer Pittman et al.

Given that readily available supplies of phosphorus may begin running out by the end of the 21st century Vaccari, , conservation and stewardship of U. Recycling nutrients from wastewater and using them for further algae production could be an attractive option for using otherwise discarded nutrients Exhibit 9. Algae-based treatments have been found to be as efficient as chemical treatment in removing phosphorus from wastewater Hoffmann, Moreover, because harvested algal biomass contains the nutrients that were absorbed during cellular growth, wastewater-integrated systems can perform an important nutrient removal service.

In laboratory-scale experiments, more than 90 percent of nitrogen and 80 percent of phosphorus were removed from primary treated sewage by the green alga Chlorella vulgaris Lau et al. Similarly, laboratory cultures of Chlorella and Scenedesmus removed 80 to percent of NH 3 , nitrate, and total phosphorus from wastewater that already had undergone secondary treatment Martinez et al.

They reported only a 19 percent removal of dissolved nitrogen and a 43 percent removal of dissolved phosphorus from this treated effluent. These differences in nutrient removal observed may be related, in part, to the different scales of the studies. The ultimate level of nutrient removal benefit may depend on the level of wastewater treatment that occurs prior to nutrient uptake in the algal cultivation systems and on the chemical and ecological conditions that exist in the wastewater-fed production system.

Algae have the potential to remove nutrients from agricultural or industrial wastewater. Some studies have found high efficiencies of removal of nitrogen and phosphorus from wastewater containing manure Gonzalez et al. Algal biofuel systems have the potential to increase water quality and to promote municipal or agricultural wastewater treatment systems with improved sustainability.

However, the maintenance of lipid-rich strains and the manipulation of growth conditions to promote high lipid production have yet to be demonstrated consistently for outdoor pond systems, including wastewater treatment ponds DOE, b. Industrial wastewaters have lower nutrient concentrations and higher toxicant concentrations, and thus are less likely to be used to generate the algal biomass necessary for commercial-scale production of biofuels Pittman et al.

Integrated algal biofuel production systems can remove many other pollutants, such as metals and organic contaminants, including endocrine disruptors Mallick, ; Munoz and Guieysse, ; Ahluwalia and Goyal, ; DOE, b. Whether pollutant uptake by algae is desirable depends on whether coproducts are to be produced with algal biofuels or whether the lipid-extracted algae are to be used for nutrient recycling. Pollutant removal by these systems would improve water quality, but it also could pose a potential risk if organisms such as migrating waterfowl directly or incidentally consumed high metal content algae during the cultivation process, or if humans or wildlife were exposed chronically to the dried algae during biomass processing.

Uptake of pollutants by algae is not desirable if residual biomass is to be used for human cosmetic products or animal feed. The pathways described in Chapter 3 affect the types, probabilities, and magnitudes of water-quality effects Table For example, slow releases of nutrients to natural environments and increased potential for eutrophication and groundwater pollution are common for open systems but not for closed systems. Herbicides likely would be used only in open systems. The water quality benefit for wastewater treatment is achieved only if wastewaters are used as nutrient sources, but the scenarios in Chapter 3 do not specify this.

Open-pond, salt water, producing FAME a , recycling nutrients and water. Open-pond, salt water, producing biomass, pyrolysis, recycling some nutrients and water. Slow releases from seepage, overtopping likely, catastrophic breaches rare. Herbicides, heavy metals may be present and pose occupational or ecological exposures and risks. Proposed sustainability indicators for water quality include aqueous concentrations and loadings of nutrients, herbicides, metals, and salinity of groundwater GBEP, These indicators are standard measures for quality of water and wastewater Eaton et al.

Concentrations of nutrients are included because they relate to benefits or potentially adverse effects on water quality for example, eutrophication. These usually are measured quantities, and baseline levels and natural variability also can be measured. Loadings are field measures or simulation results representing the contribution of released algal biofuel culture media to receiving waters. These may be compared to other loadings to those waters. Good design and engineering would minimize the potential for releases of water and nutrients from open-pond systems to surface water and to ground water.

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Toxicant concentrations for example, metals need to be characterized, particularly if wastewater or produced water is used as culture medium. Information on the nutrient removal efficiencies of commercial-scale facilities would be needed if algal biofuel production is to be combined with wastewater treatment. Land-use change is a change in anthropogenic activities on land, which often is characterized in part by a change in land cover, including the dominant vegetation.

Land-use changes play a role in the sustainability of algal biofuel development because of associated environmental effects, such as net GHG emissions, changes in biodiversity, and changes in ecosystem services such as food production. Moreover, there is growing societal concern about the spatial and temporal scales of some types of conversions, such as deforestation and urbanization. The impacts of algal biofuel development will depend in part on the type of land conversion, the extent area of land use that has changed, the intensity of land disturbance and management, and the duration of the change for example, whether it is reversible.

Commercial-scale production of algal biofuels will require substantial land area for each facility see Chapter 4 , and the large-scale deployment of algal biofuels will lead to conversion of lands from other existing uses. Land conversion for ponds, processing facilities, and refineries for most products will be localized, and potential land conversion for related infrastructure, such as roads and power lines to the facilities, will be more diffuse and will involve linear features. This section focuses on land-use change LUC associated with algae cultivation, because change associated with feedstock processing or refining facilities is not different in kind from that of other liquid fuel sources.

High-value lands used by agriculture, by other commodity industries, and for residential purposes are unlikely to be used for algae cultivation because algae cultivation does not require fertile soils and because capital and operating costs would have to be kept low for algal biofuel companies to operate close to the profit margin Table Similarly, the conversion of forestland is unlikely because of the high costs of clearing and site preparation and the high value for residential or recreational use.

Land-use change for algal biofuels is. On coasts, dredge spoil islands might be additional options for use. For example, Phycal, an algal biofuel company, is using fallow land in Hawaii that was previously a pineapple plantation but is no longer economically viable for that use. Sapphire, another company operating in the Southwest, plans to develop nonagricultural land for algae cultivation.

Siting requirements are described in Chapter 4. Competing land demands could change over time and may influence the landscape of algal biofuels. For example, some of the same lands that are attractive for algal biofuel development are also attractive for large-scale solar power development BLM and DOE, Direct land-use change generally is defined as a direct cause-and-effect link between biofuel development and land conversion in the absence of strong external mediating factors. Direct land-use change occurs within the biofuel production pathway when land for one use is dedicated for biofuel production.

However, in practice, direct land-use change from biofuel production generally is assumed to include lands used for feedstock production, processing, storage, and refining areas. Indirect land-use change occurs when biofuel production causes new land-use changes elsewhere domestically or in another country through market-mediated effects NRC, Direct land-use change can result in carbon sequestration or net GHG emissions, depending on the type of land conversion and prior land use.

For example, converting from annual-crop production to perennial-crop production can enhance carbon storage on that piece of land Fargione et al. Conversely, clearing native ecosystems to produce row-crops would result in a one-time release of a large quantity of GHGs into the atmosphere Fargione et al. Perennial pasture is effective in sequestering carbon in soil Franzluebbers, ; Gurian-Sherman, Removal of such vegetation would result in a one-time loss of carbon and the elimination of any potential for further carbon sequestration if the land is to be left as a pasture.

In contrast, if the algae cultivation ponds are installed on degraded land that is not storing much carbon, immediate emissions from the conversion will be minimal. Indirect land-use change could occur if the use of land to cultivate biofuel feedstocks replaces and ultimately reduces the production levels of crops destined for a commodity market. The lowered production of those commodities could drive up market prices, which in turn could trigger agricultural growers to clear land elsewhere to grow the displaced crops in response to market signals Babcock, ; Zilberman et al.

However, as stated above, because algal feedstock cultivation does not require fertile cropland, arable land likely will not be used for algal biofuels Sheehan et al. In addition, protein from lipid-extracted algae potentially can replace soybean or other terrestrial crops as feedstuff Wijffels and Barbosa, and reduce the demand for land by terrestrial crops.

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The nutritional compatibility of algal feedstuff and the animal diet would have to be examined. Pasture and rangeland could be converted to algae cultivation, and displacement of these land uses by algae also may or may not result in other indirect effects. If the pasture or rangeland is surplus and not in use, then repurposing the land will not incur indirect land-use change ILUC.

In contrast, if algae cultivation displaces grass-fed cattle production, producers might decide to change to corn-fed cattle production. Changing from grass-fed to corn-fed cattle production also would exert pressure on the corn-grain market. Alternatively, if existing pasture and rangeland is limiting beef production, such that removing some of this land would decrease production, then grass-fed cattle production might be replaced elsewhere.

The indirect land-use changes not only affect ecosystem services, but result in changes in GHG emissions that have to be considered in life-cycle GHG assessments for algal biofuels. If the indirect effects of algal biofuel production are to be quantified, then the potential biodiversity, water quality, and water balance impacts would include those associated with indirect land conversions. Previous quantification of indirect effects of biofuels generally has been limited to GHG effects and food security effects.

As in the case of terrestrial-crop biofuels, market-mediated indirect land-use changes are difficult to ascertain, and estimates of associated GHG emissions are highly uncertain NRC, Although complex models have been used to project the extent of indirect land-use changes as a result of terrestrial-crop biofuels, the committee is not aware of similar projections for algal biofuels.

Algae cultivation is less likely to incur indirect land-use changes because it does not require prime agricultural land. Converting crop lands to new crops algal biofuels also will require new ownership or a willingness on the part of farmers to grow a new commodity. Growing algal biofuels will require differing work schedules than row crop farming. Even if cropland is not to be converted to algal ponds, the above discussion of potential pasture conversion illustrates a potential for indirect land-use change.

With respect to land-use change, the primary relevant difference among the pathways in Chapter 3 is the difference between the land required for open-pond and photobioreactor systems see Chapter 4. The spatial and temporal scales of land-use change would be commensurate with those of land use.

In general, algal biofuel development will avoid forestland and land with agricultural value. Avoiding pastureland and areas of high biodiversity or recreational value also would eliminate some of the sustainability concerns associated with commercial development of algal biofuels. Land-use change is not consistently proposed as a criterion for sustainability, even though it often is considered a factor influencing aspects of the sustainability of biofuel for example, GHG emissions, biodiversity, water quality, and soil quality.

Therefore, some compilations of sustainability indicators do not include indicators of sustainable land use for example, McBride et al. However, there are aspects of land use, such as infrastructure, impervious surfaces, and some disturbances, that may be long lasting or irreversible and may not be adequately considered using indicators of other categories of sustainability. Potential indicators of sustainable land use include percent impervious surface Sutton et al.

Changes in impervious surface area affect the water cycle and watershed dynamics, as well as terrestrial and aquatic habitats. The area of land disturbed can be considered a measure of sustainability. Land disturbance areas can be normalized based on a land-condition factor Eq. Table shows examples of land condition factors that can be multiplied by disturbed area to give a currency of disturbance. Reprinted with permission from Elsevier. Land condition factors are multiplied by disturbance area to allow comparison of disturbed areas of different intensities and scales.

Trends in land-use change related to algal biofuel production are important to quantify. However, until there is a history of commercial development of algal biofuel production facilities, probable land-use changes and trends will need to be projected based on economic and social drivers and environmental contributing factors. Where important or rare ecosystem services are provided by the baseline land use, a measure of those services could serve as a sustainability indicator for algal biofuels.

The services of pastures, rangelands, and coastal waters that might be displaced by feedstock production facilities would be important to quantify. Relevant metrics would be:. A less direct indicator of livestock numbers or biomass would be area covered by grassland and shrubland West, ; The H.

Additional sustainability indicators have been suggested for brownfield redevelopment efforts. Some of these are summarized in Wedding and Crawford-Brown and would be appropriate where algal biofuel production is sited on brownfields. The potential to mitigate GHG emissions is one of the motivations to develop biofuels. The basis of mitigation is that carbon emissions from combusting a biofuel are cancelled by the corresponding capture in photosynthesis.

This said, the net GHG emissions of producing biofuels and coproducts are not zero because of carbon and other GHGs emitted in processing. Primary GHG emissions from algal biofuels are expected to be connected to the use of energy in the processing chain see section Energy in Chapter 4. The translation of energy use to GHG emissions is complicated by variability in the carbon overhead of different forms of energy, in particular electricity.

Environmental Impacts of Renewable Energy Technologies

Depending on the mix of fossil fuels, hydropower, nuclear, wind, and other sources providing power to the grid, emissions vary by state from 13 to 1, grams CO 2 equivalent per kilowatt hour EIA, The approach taken by many analysts is to use a national average emission factor Liu et al. LCA results for net GHG emissions for algae biofuel production vary from a net negative value that is, a carbon sink to positive values substantially higher than petroleum gasoline Table As with the case for energy use see Chapter 4 , drivers of variability in CO 2 emissions are nutrient source, productivity and process performance, and the credit associated with coproducts.

For example, Sander and Murthy assumed that residual algal biomass substitutes for corn in ethanol plants. Corn is energy intensive to produce; the. The direct carbon emissions of driving an average gasoline automobile is about 0. GHG credit from replacing corn with oil-extracted algae as a feedstock for ethanol results in a negative carbon balance. For reference, the direct carbon emission of combusting gasoline is about 2. The vast differences in results in Table , ranging from a net carbon credit to emissions far larger than those from petroleum-based diesel, present a challenge for interpretation.

Differences in nutrient sourcing and coproducts are treated via four scenarios: The common coproduct system used is generation of bioelectricity from gas generated by anaerobic digestion with the electricity generated substituting for carbon emissions from the U. Table shows the ranges in results from the six treated studies, after normalization, for the four scenarios.

These meta-analysis results suggest that the CO 2 source and coproducts are critical factors in the GHG balance. It is, however, premature to conclude that algal biofuels based on recycling CO 2 and producing biogas has net negative GHG emissions. The variability in Table is based on differences in energy data and assumptions in the six existing studies. It is not yet clear if current LCA analyses of algal biofuel production systems will accurately reflect the energy use of a real-world, scaled-up system. None of the studies above addresses the potential issue of indirect land-use change from biofuels.

As stated earlier, it is possible that conversion of pastureland to algae cultivation facilities would necessitate conversions to pastureland elsewhere. However, uncertainties are too great to quantify this probability or to calculate net GHG emissions under these assumptions. See section Land-Use Change in this chapter. While many agricultural processes emit non-carbon GHGs such as nitrous oxide N 2 O and methane Weber and Matthews, , these emissions have not been established empirically as significant for algae cultivation.

N 2 O could be emitted from cultivation systems, and these emissions would need to be quantified in the future for cultivation conditions that might promote N 2 O or methane emission. One study of a single species quantified N 2 O emissions from algal culture under laboratory conditions Fagerstone et al. In this study of Nannochloropsis salina with nitrate as a nitrogen source, elevated N 2 O emissions were observed under a nitrogen headspace photobioreactor simulation during dark periods, but N 2 O emissions were low during light periods.

In contrast, when the headspace consisted of air open-pond simulation , N 2 O emissions were negligible. Denitrifying bacteria were present. Denitrification is the microbial reduction of nitrate and nitrite with generation of N 2 O and, ultimately, gaseous nitrogen. Anaerobic environments are required for the transformation, but high rates of denitrification occur where oxygen is available alternately, then unavailable Kleiner, In rivers, ponds, lakes, and estuaries, the production of N 2 O is correlated with nitrate concentrations in the water Stadmark and Leonardson, Whether anaerobic denitrification is the only potential pathway for N 2 O generation in algal cultivation systems is unclear.

Weathers has shown that certain Chlorophyceae in axenic culture evolve N 2 O when using nitrite as a nitrogen source. They speculated that oxidation of ammonium NH 4 by bacteria was the likeliest N 2 O-generation pathway under the observed aerobic conditions. Proper management of the algal cultivation systems, which would prevent senescence of algae and maintain aerobic conditions in ponds, likely would keep N 2 O emissions to low levels.

Methanogenesis can occur in freshwater and marine sediments, waterlogged soils, marshes, and swamps where oxygen is low. These conditions might prevail in some ponds with substantial biomass or other organic matter in the sediment. Methane is released when organic acids, alcohols, celluloses, hemicelluloses, and proteins are degraded. Methane production is related to water temperature Stadmark and Leonardson, and is maximized at neutral pH Alexander, Methanogenesis is suppressed by nitrogen compounds that bacteria can use as electron acceptors, including nitrate and nitrite Bollag and Czlonkowski, , but these compounds may be reduced easily in oxygen-depleted environments.

Methanogenesis and denitrification might be enhanced if the culture fails. During catastrophic failure of the culture, the dense algal cultures in algal biofuel ponds can become anaerobic and emit a variety of volatile nitrous or sulfur compounds as well as methane. However, culture failures would be expected to be short-term and rare occurrences if algal biofuel companies are to maintain a profit margin. The opportunities for mitigating energy use discussed in the section Energy in Chapter 4 apply to reduction of GHG emissions.

There is additional potential to mitigate GHGs by using low-carbon energy sources for processing and by substituting for carbon-intensive coproducts. For example, the carbon benefit of generating bioelectricity is larger in areas where the grid relies on fossil fuels. The yields for producing and properties of different coproduct options are poorly understood. The potential for N 2 O and methane emissions could be reduced through thorough mixing and proper management of algae cultivation Fagerstone et al.

The data gaps for estimating energy use and the method gaps in reducing energy use discussed in the section Energy Chapter 4 apply to reduction of GHG emissions. An appropriate sustainability indicator for GHG emissions is the amount of CO 2 equivalent emitted per unit energy produced, which has been selected as an indicator for GHG emissions of biodiesel and commonly has been used in discussing energy-related GHG emissions GBEP, ; Mata et al.

The introduction of large bodies of water in arid or semi-arid environments could alter the local climate of the area by increasing humidity and reducing temperature extremes. Similarly, the introduction of large-scale, open-pond algal cultivation systems in arid or semi-arid environments, where much of algae production in the United States is projected to take place see Chapter 4 , could affect local climate and ecosystems.

The use of photobioreactors would not likely alter local climate. Studies of reservoirs provide some useful ecological information. Reservoirs created by the damming of rivers could affect evaporation rates of the surrounding landscape, leading to changes in vegetation cover and terrestrial species diversity Huntley et al. Large dams can affect surrounding climate and precipitation, particularly in Mediterranean and semi-arid climates Degu et al.

The sustainability indicators for potential changes in local climate are trends in relative humidity and trends in temperature distribution statistics. While parallels can be drawn from the introduction of large reservoirs in arid regions, the variability in size, geography, and production methods that will emerge as the algae industry grows will necessitate additional research to fully understand and address the impacts associated with local climate alteration.

The air quality impacts of algal biofuel production will depend on system design. Different air quality issues arise in conjunction with the different steps of the algal biofuel supply chain. Thus, this section is organized by the steps along the production pathways. The wide range of potential organisms for producing algal biofuels and the wide range of final fuel products result in a broad range of possible air emissions. This section focuses on the air quality emissions unique to algal biofuel production and does not consider emissions of fossil fuels used to power processing equipment or emissions of fossil fuels that may be used in manufacturing fertilizer or pesticides.

The purpose of the chapter is to consider emissions unique to algal biofuel production so that appropriate indicators are identified. However, emissions from fossil fuels used along the production pathway of algal biofuel would need to be considered in any LCA of the airquality impacts of different algal biofuel designs. Further, how algal biofuels will be scaled up and how air quality might change with increasing scale is uncertain. The committee is not aware of any measured emissions of atmospheric pollutants from algal biofuel feedstock ponds published in the literature.

Under normal running conditions in open ponds, the cultures are aerobic, and low emissions of volatile organic compounds VOCs are expected Rasmussen, ; A. However, macroalgae and microalgae growing in natural marine environments are known to be important sources of VOCs, including isoprene and monoterpenes Giese et al. Three of the species tested are being grown for biofuels in open raceways, open ponds, and closed photobioreactors, with test samples derived from cultures being grown in treated wastewater with CO 2 enrichment.

In preliminary findings, 45 VOCs have been identified P. Other emissions expected are aerosols that may be emitted directly or created in the atmosphere through reactions of gaseous emissions of precursor gases of sulfur dioxide SO 2 , nitrogen oxides NOx , NH 3 , and VOCs. Aerosols could include algae and nutrients, as well as a wide range of compounds that are produced by microalgae, including toxins. See section Pathogens and Toxins later in this chapter.

Microalgae in the natural marine environment are known sources of sulfate aerosols for example, Liss et al. A large number of algae produce odorous secondary metabolites reviewed in Smith et al. The odors are produced during aerobic growth as secondary metabolites. Other odorous compounds are associated with the decay of algae under anaerobic conditions where bacteria break down the organic material and produce hydrogen sulfide and NH 3 , both of which have a strong odor.

In open ponds intended for algae cultivation, anaerobic conditions are minimized. Emissions from photobioreactors would be lower than those from open ponds if undesirable gaseous products and odorous chemicals are scrubbed before gas exchange with the outside environment is permitted.

Drying processes may produce coarse and fine particulates, including algae and lysed algae. The concentrations of particulates in air will depend on the technologies used; for example, belt dryers and convective systems will lead to greater local emissions than passive solar drying. Whether emissions move beyond the facility will depend on the level of containment.

Particulates could be an occupational hazard even in closed facilities. In confined areas, dust could be an explosion hazard. Poor drying methods also can give rise to decomposition of biomass and release of VOCs, amines, methane, and other compounds. Most proposed algal biofuel processing methods involve extraction of lipids or other compounds from cells using organic solvents.

Extraction with organic chemicals, by necessity, results in some solvent emissions, and the quantities emitted depend on the technology applied. The most common solvent that is openly discussed by manufacturers is hexane Demirbas, ; Lardon et al. In an environmental assessment, Sapphire Energy, Inc. Desirable properties of these solvents are low cost, recoverability, low toxicity, nonpolar structure, and poor extractor of non-lipid cell components Rawat et al. Hexane is used as an extractant of vegetable oils in biodiesel production with fugitive hexane emissions Hess et al.

Compliance with regulatory standards likely would minimize release of solvents. Technologies to convert total biomass to drop-in liquid fuels are being tested. These processes may have additional feed inputs and will have different air emissions from those from production of esterified or green diesels. Pyrolysis of biomass yields three energy products—solids char , liquids bio-oils , and gases—in various proportions depending on the temperature, pressure, residence time, and other factors.

The gases are recycled to provide energy for the system and thus do not contribute directly to air emissions except for any fugitive emissions that might escape the system. The heating of the pyrolysis units might contribute a small amount of NOx and carbon monoxide CO.

Environmental impact of electricity generation

Additional energy, likely supplied by natural gas may be required to sufficiently dry the algal biomass prior to pyrolysis. Particulate emissions, acid gases, and hydrocarbon emissions from pyrolysis are not characterized in the literature. The bio-oil produced from whole-cell pyrolysis will require additional upgrading to produce transportation fuels.

The upgrading can be done with a separate hydrotreating step or a process similar to the Integrated Hydropyrolysis and Hydroconversion process. In either case, input of hydrogen is required.

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The production of hydrogen produces low levels of NOx Spath and Mann, and makes a CO 2 stream that could be used to supply the algae cultivation. Anaerobic digestion for processing wastewater from algal biofuel production facilities is described in Chapter 2. NH 3 has been observed to be present in biogas from anaerobic digestion at concentrations up to ppm Schomaker, The concentration of NH 3 in biogas would depend on the nitrogen content of the particular feed material.

Early work by Golueke et al. NH 3 would not be released to air around the facility because of the desire to recycle nutrients required for cultivation. The primary categories of environmental effects associated with the end use of biofuels in vehicles are evaporative emissions and tailpipe emissions from fuel combustion. Fischer-Tropsch F-T synthesis converts a mixture of CO and hydrogen which may be derived from biomass into liquid hydrocarbons. Generally, the type and quantities of emissions vary depending on fuel characteristics for example, chemical properties and blends , age of the vehicle or other equipment, power output of engine, operating condition of engine, how the vehicle or other equipment is operated, and ambient temperature Graham et al.

Using biofuels in place of petroleum-based fuels decreases emissions of some air pollutants while increasing others Table ; NRC, EPA established emission standards for tailpipe emissions of CO, hydrocarbons, NOx, and particulate matter to which vehicle manufacturers and refiners have to comply EPA, a. Emissions of air pollutants need to be assessed over the life cycle of algal biofuels and compared to petroleum-based fuels and other alternatives.

The Hill et al. They found that although the uses of gasoline and terrestrial-plant biofuels corn-grain ethanol and cellulosic ethanol release similar amounts of VOC, PM, NO x , SO x , and NH 3 , emissions from the production stages are significantly different between petroleum-based fuels and biofuels. The committee is not aware of any LCA of such air pollutants for algal biofuels. Such analysis is critical in assessing whether biofuel production and use result in air quality improvement compared to fossil fuel and it provides information on stages in the supply chain that are key contributors to air pollutants.

Particulate emissions, hydrocarbon slip, and acid gases all possible from combustion of off-gas. With respect to air quality, the differences in expected effects among the pathways in Chapter 3 depend on the type of culture system open versus closed , the drying process, and whether or not extraction and pyrolysis steps are present in the pathway Table Algae produce a number of aerosols and secondary metabolites, some of which may be noxious for example, malodorous or harmful to humans. Similarly, some supply-chain processes, such as extraction and drying, may emit solvents or particulates that could affect local air quality if not contained.

If an algal biofuel facility is located near human populations, measures likely will be taken to contain or limit the release of any products that negatively affect local air quality or are perceived to be a risk to public health. The health costs of some types of air emissions were discussed in Hill et al. Depending on the quantity of these outputs, and the proximity of population centers to a production facility, the reduction in air quality and perceived health and quality-of-life risks may impact the.

If the public is not made aware of these potential effects prior to the siting and permitting of a facility, there is a risk that the production of undesirable compounds will be viewed as unacceptable after the construction of the facility has been completed.

If this is the case, litigation or protests may slow or shut down operations, resulting in financial losses for the developer and negative attention for the industry at large. The more contained a process is, whether it is the biomass cultivation process, drying, solvent extraction, pyrolysis, or digestion, the lower the emissions to air will be. Therefore, photobioreactors could have reduced air-quality impacts compared to open-pond systems. However, full LCA of the air pollutant emissions associated with the production of the bioreactor materials and system operation also would be needed to assess whether photobioreactors represent a small or negligible impact on air quality.

Although passive processes for example, solar drying reduce air quality impacts compared to active processes that generate dust or increase volatilization rates, they are not practical solutions at large scale. Siting facilities at a distance from human population centers and ecological species of concern would mitigate potential adverse effects of air pollution on humans.

Appropriate sustainability metrics for air quality would depend on the processes used in algal biofuel production. Concentrations would have to be measured or modeled at scales appropriate to bound regulatory levels or potential human health or annoyance effects. Measuring air emissions from large open ponds can provide information for occupational and other environmental exposure estimates that can be compared to thresholds for human health or environmental effects. Information and data gaps include the relationship between particular drying technologies and the types and concentrations of particulates released, releases of solvents during extraction, likely concentrations of NH 3 in air during anaerobic digestion, and chemicals potentially released during pyrolysis.

That information would be submitted when the biorefineries seek air-quality permits. Species invasiveness is a concern unique to biofuels produced from algae and vascular plants. In addition, changing land use or altering landscapes to produce algal biofuel feedstocks can affect biodiversity.

Environmental Impacts of Renewable Energy Technologies | Union of Concerned Scientists

Effects of many biofuel feedstocks on biodiversity and mechanisms leading to those effects are beginning to be understood. However, existing studies Fargione et al. Many cyanobacteria and eukaryotic microalgae are cosmopolitan in their spatial biogeographical distributions and therefore could not be invasive if released in regions included in their broad habitat range. However, they are not necessarily found in every location where their habitat requirements for example, pH, salinity, temperature, moisture, and climate are met, so their distribution is often mosaic-like Hoffmann, Other algae may be endemic to particular regions, for example, some cyanobacteria in Swedish lakes Rott and Hernandez-Marine, and particular marine species Hoffman, Endemic species could become invasive if transported elsewhere, but these species could also exist in low numbers in other locations even though they have not been recorded there.

Algae may have broader distributions than what has been recorded because of the lack of sampling on some continents especially of benthic habitats and because of the lack of detection of organisms at low densities Hoffmann, Coastal marine macroalgae tend to be less cosmopolitan in their spatial distribution than phytoplanktonic cyanobacteria and microalgae. Macroalgae have narrower temperature, light, substratum, and nutrient preferences. The wide range of processes that could transport microalgae away from open water also could contribute to their dispersal and consequentially to a broad distribution.

Vectors of algae include aquatic insects Stewart et al. The most important vectors of algae are birds Atkinson, ; Kristiansen, In one study of 16 species of waterfowl, 86 species of algae were found on the feet, 25 species on the feathers, and 25 species on the bills. Most algae survived out of surface waters for four hours, but most did not survive for more than eight hours Schlichting, Some species of algae may appear to be rare. Whitford explains that species of freshwater algae may appear to be rare for several reasons for example, infrequent historical collections, species with long-lived spores that do not easily germinate, and species that are highly specific in their habitat requirements , but that very few freshwater species are actually rare.

This suggests that few rare species of algae could be displaced by invasive algae used to produce biofuel feedstocks. Releases of improved nongenetically engineered or genetically engineered strains of algae from biofuel production cultures to natural environments can be expected to be common, especially from open ponds. Releases may occur during the feedstock production stage or possibly during the harvesting or drying stages. Releases probably will occur most often through aerosolization, although leakages from ponds or weather-related spillage for example, high tides and heavy storms also are possible.

The probability of release from an open pond would be related to pond area and freeboard space that is, the distance between normal water level and the top of the cultivation pond , the direction and speed of prevailing winds, the frequency and quantity of. Humidity affects the survival of unicellular algae Ehresmann and Hatch, Survival rates differ among algal groups. In one study climatic characteristics such as temperature, relative humidity, rainfall, wind velocity, and hours of sunshine affected the release and vertical transport of algae Sharma and Singh, Atmospheric density of algae is affected by aerosolization rate Sharma and Singh, , wind speed, and rainfall, as well as survival rate.

The abundance of algae in the atmosphere also depends on taxonomy of the algae. In one study, cyanobacteria had the highest density, whereas chlorophytes and diatoms were much less common Sharma and Singh, ; Wilkinson et al. Dissemination to distant sites can occur through the air, through water, and by boats Alexander, or animal vectors.

The wide range of vectors that could remove algae from open ponds include aquatic insects Stewart et al. Closed photobioreactor systems would have a much lower risk of release and transport of algae. Harvesting operations from open or closed systems could be a major potential route for loss of microalgae to the surrounding environment. If algae require culture media with characteristics substantially different from the surrounding natural environment especially if the algae have narrow tolerance limits to nutrients concentrations, pH, or salinity , then releases to the local landscape likely would result in low survival rates.

Survival rate would be further reduced if the cultured species is not tolerant of desiccation Hoffmann, Environmental concerns associated with releasing algae from biofuel facilities into natural waters include the potential for species invasiveness, alteration of nutrient recycling and trophic relationships, and the displacement of rare algal species. Although some researchers and producers are considering the use of regionally native species that are adapted to the local climate Odlare et al.

Some of the nonnative or improved species may be invasive in some environments. Invasive algae can compete with native species for light, space, or nutrients, and have different tolerances for stressors, compared to native species White and Shurin, Thus, invasive species can affect community composition and ecosystem processes Strayer et al. Successful invasions are characterized by the invasive potential of the invader and the invasibility of the native community Lonsdale, Species that are not invasive in one environment may be invasive when introduced to a different habitat Raghu et al.

For example, an algal species that thrives in saline waters may not survive or may invade freshwater ecosystems, even if released in a large quantity. Whether the ecological niches of invaders and the invaded community overlap is a predictor of success as well Mehnert et al. Whether a particular cultured algal species poses a threat as an invasive species to the surrounding aquatic environments needs to be considered.

Some of the same characteristics that can make a species desirable as a biofuel feedstock, for example, rapid growth, vegetative propagation, pest resistance, and robustness in culture, also are those associated with invasiveness.

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Possible but unlikely with appropriate controls Possible for nontarget species in cultures; low likelihood of blooms of nontarget species released to natural environments. Impossible unless accidental breach of photobioreactor Impossible unless accidental breach of photobioreactor. Releases of some exotic algal species, particularly from open-pond cultures, could threaten the integrity of local and regional ecosystems Ryan, Blooms of exotic species could displace native species, with adverse impacts on organisms that feed on those species propagating through aquatic food webs.

An example is the diatom Didymosphenia geminata also known as Didymo or Rock Snot that can cause dense algal blooms. The blooms block sunlight and cause a local decline in native plant and animal life.

The primary variable that is different among the pathways in Chapter 3 and would influence the likelihood of species invasions and changes in biodiversity is whether the pond system is open or closed Table Algal species known to be noninvasive or unlikely to cause harmful blooms could be selected for large-scale cultivation for fuels. Invasiveness varies in different natural environments, and site-specific assessments might be necessary to reduce risks of invasion.

Moreover, species that are intolerant of conditions in natural waters for example, salinity in the vicinity of the biofuel facility may be selected to minimize the risk of invasion if released. Landscape design also may be considered to limit any potential impacts of releases of algae from pond systems. Placing systems well away from waterways and wetlands where pond algae may thrive could reduce or minimize the likelihood of blooms of released species. When considering the factors that affect the probability of release and the abundance of released organisms above, then mitigation measures might include shields from wind and mechanisms to discourage vectors.

Indicators of sustainable ecological communities include metrics of aquatic diversity and invasiveness of algae. One category of such metrics would be diagnostic traits for invasiveness. Unlike coal and natural gas , they can generate electricity and fuels without releasing significant quantities of CO2 and other greenhouse gases that contribute to climate change, however the greenhouse gas savings from a number of biofuels have been found to be much less than originally anticipated, as discussed in the article Indirect land use change impacts of biofuels.

Both solar and wind have been criticized from an aesthetic point of view. The major advantage of conventional hydroelectric dams with reservoirs is their ability to store potential power for later electrical production. The combination of a natural supply of energy and production on demand has made hydro power the largest source of renewable energy by far. Other advantages include longer life than fuel-fired generation, low operating costs, and the provision of facilities for water sports.

Some dams also operate as pumped-storage plants balancing supply and demand in the generation system. Overall, hydroelectric power can be less expensive than electricity generated from fossil fuels or nuclear energy, and areas with abundant hydroelectric power attract industry. However, in addition to the advantages above, there are several disadvantages to dams that create large reservoirs. Without power turbines, the downstream river environment would improve in several ways, however dam and reservoir concerns would remain unchanged.

Small hydro and run-of-the-river are two low impact alternatives to hydroelectric reservoirs, although they may produce intermittent power due to a lack of stored water. Land constrictions such as straits or inlets can create high velocities at specific sites, which can be captured with the use of turbines. These turbines can be horizontal, vertical, open, or ducted and are typically placed near the bottom of the water column. The main environmental concern with tidal energy is associated with blade strike and entanglement of marine organisms as high speed water increases the risk of organisms being pushed near or through these devices.

As with all offshore renewable energies, there is also a concern about how the creation of EMF and acoustic outputs may affect marine organisms. Because these devices are in the water, the acoustic output can be greater than those created with offshore wind energy. Depending on the frequency and amplitude of sound generated by the tidal energy devices, this acoustic output can have varying effects on marine mammals particularly those who echolocate to communicate and navigate in the marine environment such as dolphins and whales.

Tidal energy removal can also cause environmental concerns such as degrading farfield water quality and disrupting sediment processes. Depending on the size of the project, these effects can range from small traces of sediment build up near the tidal device to severely affecting nearshore ecosystems and processes. Tidal barrages are dams built across the entrance to a bay or estuary that captures potential tidal energy with turbines similar to a conventional hydrokinetic dam. Energy is collected while the height difference on either side of the dam is greatest, at low or high tide.

A minimum height fluctuation of 5 meters is required to justify the construction, so only 40 locations worldwide have been identified as feasible. Installing a barrage may change the shoreline within the bay or estuary , affecting a large ecosystem that depends on tidal flats. Inhibiting the flow of water in and out of the bay, there may also be less flushing of the bay or estuary, causing additional turbidity suspended solids and less saltwater, which may result in the death of fish that act as a vital food source to birds and mammals.

Migrating fish may also be unable to access breeding streams, and may attempt to pass through the turbines. The same acoustic concerns apply to tidal barrages. Decreasing shipping accessibility can become a socio-economic issue, though locks can be added to allow slow passage. However, the barrage may improve the local economy by increasing land access as a bridge. Calmer waters may also allow better recreation in the bay or estuary.

Electrical power can be generated by burning anything which will combust. Some electrical power is generated by burning crops which are grown specifically for the purpose. Usually this is done by fermenting plant matter to produce ethanol , which is then burned. This may also be done by allowing organic matter to decay, producing biogas , which is then burned.

Also, when burned, wood is a form of biomass fuel. Burning biomass produces many of the same emissions as burning fossil fuels. However, growing biomass captures carbon dioxide out of the air, so that the net contribution to global atmospheric carbon dioxide levels is small. The process of growing biomass is subject to the same environmental concerns as any kind of agriculture. It uses a large amount of land, and fertilizers and pesticides may be necessary for cost-effective growth. Biomass that is produced as a by-product of agriculture shows some promise, but most such biomass is currently being used, for plowing back into the soil as fertilizer if nothing else.

Wind power harnesses mechanical energy from the constant flow of air over the surface of the earth. Wind power stations generally consist of wind farms , fields of wind turbines in locations with relatively high winds. A primary publicity issue regarding wind turbines are their older predecessors, such as the Altamont Pass Wind Farm in California. These older, smaller, wind turbines are rather noisy and densely located, making them very unattractive to the local population.

The downwind side of the turbine does disrupt local low-level winds. Modern large wind turbines have mitigated these concerns, and have become a commercially important energy source. Many homeowners in areas with high winds and expensive electricity set up small wind turbines to reduce their electric bills.

A modern wind farm, when installed on agricultural land, has one of the lowest environmental impacts of all energy sources: Landscape and heritage issues may be a significant issue for certain wind farms. However, when appropriate planning procedures are followed, the heritage and landscape risks should be minimal. Some people may still object to wind farms, perhaps on the grounds of aesthetics, but there is still the supportive opinions of the broader community and the need to address the threats posed by climate change.

Offshore wind is similar to terrestrial wind technologies, as a large windmill -like turbine located in a fresh or saltwater environment. Wind causes the blades to rotate, which is then turned into electricity and connected to the grid with cables. The advantages of offshore wind are that winds are stronger and more consistent, allowing turbines of much larger size to be erected by vessels. The disadvantages are the difficulties of placing a structure in a dynamic ocean environment.

The turbines are often scaled-up versions of existing land technologies. However, the foundations are unique to offshore wind and are listed below:. Monopile foundations are used in shallow depth applications 0—30 m and consist of a pile being driven to varying depths into the seabed 10—40 m depending on the soil conditions. The pile-driving construction process is an environmental concern as the noise produced is incredibly loud and propagates far in the water, even after mitigation strategies such as bubble shields, slow start, and acoustic cladding.

The footprint is relatively small, but may still cause scouring or artificial reefs. Transmission lines also produce an electromagnetic field that may be harmful to some marine organisms. Tripod fixed bottom foundations are used in transitional depth applications 20—80 m and consist of three legs connecting to a central shaft that supports the turbine base. Each leg has a pile driven into the seabed, though less depth is necessary because of the wide foundation. The environmental effects are a combination of those for monopile and gravity foundations. Gravity foundations are used in shallow depth applications 0—30 m and consist of a large and heavy base constructed of steel or concrete to rest on the seabed.

The footprint is relatively large and may cause scouring, artificial reefs, or physical destruction of habitat upon introduction. Gravity tripod foundations are used in transitional depth applications 10—40 m and consist of two heavy concrete structures connected by three legs, one structure sitting on the seabed while the other is above the water. As of , no offshore windfarms are currently using this foundation. The environmental concerns are identical to those of gravity foundations, though the scouring effect may be less significant depending on the design.

Floating structure foundations are used in deep depth applications 40— m and consist of a balanced floating structure moored to the seabed with fixed cables. The floating structure may be stabilized using buoyancy, the mooring lines, or a ballast. The mooring lines may cause minor scouring or a potential for collision. Geothermal energy is the heat of the Earth, which can be tapped into to produce electricity in power plants. Warm water produced from geothermal sources can be used for industry, agriculture, bathing and cleansing.

Where underground steam sources can be tapped, the steam is used to run a steam turbine. Geothermal steam sources have a finite life as underground water is depleted. Arrangements that circulate surface water through rock formations to produce hot water or steam are, on a human-relevant time scale, renewable. While a geothermal power plant does not burn any fuel, it will still have emissions due to substances other than steam which come up from the geothermal wells.

These may include hydrogen sulfide , and carbon dioxide. Some geothermal steam sources entrain non-soluble minerals that must be removed from the steam before it is used for generation; this material must be properly disposed. Any closed cycle steam power plant requires cooling water for condensers ; diversion of cooling water from natural sources, and its increased temperature when returned to streams or lakes, may have a significant impact on local ecosystems. Removal of ground water and accelerated cooling of rock formations can cause earth tremors.

Enhanced geothermal systems EGS fracture underground rock to produce more steam; such projects can cause earthquakes. Certain geothermal projects such as one near Basel, Switzerland in have been suspended or canceled owing to objectionable seismicity induced by geothermal recovery.

Currently solar photovoltaic power is used primarily in Germany and Spain where the governments offer financial incentives. Photovoltaic power is also more common, as one might expect, in areas where sunlight is abundant. It works by converting the sun's radiation into direct current DC power by use of photovoltaic cells.

This power can then be converted into the more common AC power and fed to the power grid. Solar photovoltaic power offers a viable alternative to fossils fuels for its cleanliness and supply, although at a high production cost. Future technology improvements are expected to bring this cost down to a more competitive range. Its negative impact on the environment lies in the creation of the solar cells which are made primarily of silica from sand and the extraction of silicon from silica may require the use of fossil fuels, although newer manufacturing processes have eliminated CO 2 production.

Solar power carries an upfront cost to the environment via production, but offers clean energy throughout the lifespan of the solar cell. Large scale electricity generation using photovoltaic power requires a large amount of land, due to the low power density of photovoltaic power. Land use can be reduced by installing on buildings and other built up areas, though this reduces efficiency. Also known as solar thermal , this technology uses various types of mirrors to concentrate sunlight and produce heat.

This heat is used to generate electricity in a standard Rankine cycle turbine. Like most thermoelectric power generation, this consumes water. This can be a problem, as solar powerplants are most commonly located in a desert environment due to the need for sunlight and large amounts of land. Many concentrated solar systems also use exotic fluids to absorb and collect heat while remaining at low pressure. These fluids could be dangerous if spilled.

Negawatt power refers to investment to reduce electricity consumption rather than investing to increase supply capacity. In this way investing in Negawatts can be considered as an alternative to a new power station and the costs and environmental concerns can be compared. Note that time shifting does not reduce total energy consumed or system efficiency; however, it can be used to avoid the need to build a new power station to cope with a peak load.

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