For decades, critics have criticized McDonald’s for questionable enviromental practics. Now, the McDonald’s in Cary, NC installed a charging station for low- or zero-emission plug-in cars.

Theoretical maximum yield as a function of latitude for different cell oil contents. Weyer et al. (2009) Click to enlarge.

At team of researchers from Solix Biofuels (earlier post), Colorado State University and the National Renewable Energy Laboratory have calculated both an absolute upper limit to solar-based algal oil production as well as a feasible target range for production based on realistic efficiencies (calculated for six global sites). Algal oil can be used as a biofuel feedstock.

Based on physical laws and assumptions of perfect efficiencies, the team calculated the theoretical limit to be 38,000 gal·ac^-1·yr^-1 (354,000 L·ha^-1·yr^-1) of unrefined oil with an uncertainty of roughly 10% and with 50% cell oil content. Limits for the practical cases examined in their report ranged from 4,900 to 6,500 gal·ac^-1·yr^-1 (46,300-60,500 L·ha^-1·yr^-1) of unrefined oil.

Practical maximum yield by site, with different cell oil content. Weyer et al. (2009) Click to enlarge.

The calculated theoretical limit is lower than the 53,000 gal·ac^-1·yr^-1 figure presented by Solix’s Dr. Kristina Weyer, co-author of the paper, at the 2008 Algae Biomass Summit in Seattle, Washington. (Earlier post.)That figure, however, assumed 70% oil content in the algae, among other factors. The practical range remained the same.

The equations, calculations, and discussions in this paper have shown that, because physical laws dictate the theoretical maximum, it represents a true upper limit to production that cannot be attained regardless of new technology advances. However, if algal biofuel production systems approach even a fraction of the calculated theoretical maximum, they will be extremely productive compared to current production capability of agriculture-based biofuels.

—Weyer et al. (2009)

A number of studies have assessed the maximum theoretical efficiency of photosynthesis, but they have not specifically examined algal biofuel production or calculated maximum

instantaneous efficiency and maximum annual production yield, the authors note.

The limits calculated in the paper apply to any large-scale algal production system that relies only on solar energy input to drive growth and oil production; the authors did not consider systems that use artificial lighting or other additional energy inputs, such as sugars for heterotrophic growth (e.g., earlier post.)

The calculation for theoretical maximum yield is based on physical laws; an established value for quantum yield; solar irradiance assuming perfectly clear weather and atmospheric conditions; and assumes 100% for unknown efficiencies.

Thus, the theoretical maximum yield is a true upper limit: a value that cannot be surpassed without breaking fundamental physical laws. Due to the numerous assumptions of perfect efficiency employed in the theoretical calculation, it is an unattainable goal. A practical case is also calculated, in order to provide designers with a realistic goal, which employs solar irradiance data for several sites and reasonable but conservatively high values for some efficiencies that were assumed to be 100% in the theoretical case. The practical case therefore represents what may be possible with system optimization.

—Weyer et al. (2008)

The primary physical law that limits the production capabilities of algae is the first law of thermodynamics, which states conservation of energy for any system. For a system of

photosynthesizing algae, it is the rate of incident solar irradiance on the production area and the rate of chemical energy storage by the algae as oil and other biomass. The amount of stored chemical energy is directly limited by the amount of solar irradiance available.

For the theoretical case, total solar irradiance was calculated assuming year-round clear skies and minimal atmospheric absorption. For the practical case, total solar irradiance was calculated using weather data for six global climates, because the actual amount of irradiance is greatly reduced from the theoretical by clouds and other absorptive atmospheric conditions.

Only a portion of the solar spectrum is utilizable for photosynthesis; PAR (photosynthetically active radiation) is commonly defined as 400-700 nm.

Cell oil content is the portion of the cell that can be refined into a usable biofuel. A theoretical maximum value is not yet known, and oil content is highly specific to species and

growth conditions. Studies have cited algal lipid contents ranging from 15 to 85% (dry cell weight), although the highest values can correspond with reduced biomass

productivity.

The authors selected 50% oil content was chosen for both the theoretical and practical maximum cases, “though it is acknowledged this may be an overestimate of what will be achievable for production systems.”

While the practical case includes the estimates for efficiencies that may be improved with optimization of the growth system and chosen algal strain, the theoretical case includes no estimates and thus continues to represent an unattainable limit despite system optimization and even genetic improvements to algal strains. Any possible genetic improvements would be aimed at improvements in the efficiencies included in the practical case. These might include decreasing photoreceptor antennae to reduce photoinhibitive effects, increasing temperature tolerance, or improving resistance to predatory species. These effects are already assumed to be nonexistent in the theoretical case.

Despite any discrepancies among approaches, all estimates affirm the productive potential of algae as a biofuel feedstock. The lowest projection in this paper, is 4,900 gal·ac^-1·yr^-1, for Kuala Lumpur, is drastically higher than reported yields for corn (18 gal·ac^-1·yr^-1), canola (127 gal·ac^-1·yr^-1) or even oil palm (637 gal·ac^-1·yr^-1). Thus, the bounds on algal production presented in this paper should not be viewed as unpleasant news about physical realities, but as a realistic check that confirms its potential and will serve the industry in its pursuit of maximum algal biofuel production.

—Weyer et al. (2009)

Resources

• Kristina M. Weyer, Daniel R. Bush, Al Darzins and Bryan D. Willson (2009) Theoretical Maximum Algal Oil Production

Researchers at the University of Pittsburgh have developed a fluorescent molecular probe that can selectively detect ozone—in preference to other reactive oxygen species—in both atmospheric and biological samples.

Ground-level ozone exposure is a growing global health problem, especially in urban areas. Ground-level ozone is toxic and can damage the respiratory tract. In addition to environmental concerns about ozone, there is some debate regarding its role in biological systems.

The fluorescent molecular probes developed by Dr. Kazunori Koide and his team are able to unambiguously detect ozone in both biological and atmospheric samples.

Unlike other ozone-detection methods, in which interference from different reactive oxygen species is often a problem, these probes are ozone-specific. The researchers suggest that such probes will prove useful for the study of ozone in environmental science and biology, and so possibly provide some insight into the role of ozone in cells.

Resources

• Amanda L. Garner, Claudette M. St Croix, Bruce R. Pitt, George D. Leikauf, Shin Ando & Kazunori Koide (2009) Specific fluorogenic probes for ozone in biological and atmospheric samples. Nature Chemistry 1 (4) pp 316 - 321 doi: 10.1038/nchem.240

Xinhua. China’s motor vehicle parc has risen to more than 176.5 million units, and more than 188.8 million Chinese (>14%) of the population has learned to drive, according to the Ministry of Public Security.

Other statistics:

• The number of motor vehicles increased by 3.92% in the first half of 2009—a slightly higher rate of increase than the same period last year.

• Sales of small passenger cars and cargo vehicles increased more than 12% and more than 7.5% respectively.

• Private motor vehicles represent nearly 77% of the total, a 4.65% increase over 2008.

• More than 8 million people learned to drive in the past six months, up 9.51% over last year.

• Nearly 70% of the total drivers (more than 129 million) are motor car drivers.

The line shows the US vehicles/1,000 people for the first part of the 20th century. The data points show the vehicles/1,000 people for different countries in 1996 and 2007. Source: TEDB. Click to enlarge.

By comparison, the US vehicle parc is about 251 million units (in 2006), according to the US Bureau of Transportation Statistics. The US has about 844 vehicles per 1,000 people (in 2007), according to Edition 28 of the Transportation Energy Data Book (TEDB), published by the US Department of Energy.

In 2007, China had about 30 vehicles per 1,000 people (up from 9 per 1,000 in 1996), according to the TEDB—about the same penetration as the US had in 1916 (see chart at right).

A team of US researchers has found a significant increase in the amount of fresh water in the Arctic Ocean as well as a significant change in the distribution of fresh water, as compared with average winter values. Fresh water flowing into or out of the Arctic Ocean plays an important role in ocean circulation and may be a factor in the response of the world ocean to climate change. The study appears in the current issue of the AGU journal Geophysical Research Letters.

To study recent changes in freshwater content of the Arctic, a team from McPhee Research; Woods Hole Oceanographic Institute; the Polar Science Center at the University of Washington, Seattle; and Oregon State University analyzed data from an extensive aerial hydrographic survey carried out in March and April 2008.

In particular, the authors find that freshwater volume in the Canada and Makarov basins on the Pacific side of the Lomonosov Ridge increased by about 8,500 cubic kilometers (about 2,000 cubic miles), while the freshwater volume on the Eurasian area decreased by about 1,100 cubic kilometers (about 260 cubic miles).

The freshening of the Arctic occurred in conjunction with the recent dramatic loss of Arctic sea ice, the authors note. They find that these changes have altered Arctic Ocean circulation, with a large increase in northward transport of fresh water in the Canada Basin.

The dramatic reduction in minimum Arctic sea ice extent in recent years has been accompanied by surprising changes in the thermohaline structure of the Arctic Ocean, with potentially important impact on convection in the North Atlantic and the meridional overturning circulation of the world ocean.

—McPhee et al.

Resources

• McPhee, M. G., A. Proshutinsky, J. H. Morison, M. Steele, and M. B. Alkire (2009), Rapid change in freshwater content of the Arctic Ocean, Geophys. Res. Lett., 36, L10602, doi: 10.1029/2009GL037525

Air Products’ new AP-X liquefaction process technology, which increases single train LNG production capacity over the current generation of LNG process trains by approximately 50%, was successfully placed on-stream at the Qatargas 2 Train 4 expansion project. (Earlier post.)

The liquefaction area representing the AP-X liquefaction process technology designed for use at the Qatargas 2–Train 4 LNG facility in Ras Laffan Industrial City, Qatar. Courtesy of Qatargas. Click to enlarge.

An LNG train is the unit that transforms natural gas into liquefied natural gas by cooling its temperature to -162 °C. This single LNG process train for the Qatargas 2 facility, located in Ras Laffan Industrial City, Qatar, is rated for an annual LNG production capacity of 7.8 million tons per year (MTY), making it the first in a coming series of the world’s largest LNG process trains involving Air Products’ technology.

The AP-X process cycle is an improvement to earlier cooled mixed refrigerant processes in that the LNG is subcooled using a simple, efficient nitrogen expander loop instead of the mixed refrigerant. In addition to improving the efficiency, the use of the nitrogen expander loop makes greatly increased capacity feasible. The nitrogen expander loop is a simplified version of the cycle employed by Air Products in hundreds of its air separation plants and nitrogen liquefiers worldwide.

The feed gas for the project will come from Qatar’s North Field, the largest offshore non-associated natural gas field in the world, with proven natural gas reserves in excess of 900 trillion cubic feet.

Air Products’ new AP-X technology is also being installed for three other LNG trains under construction for Qatargas in Ras Laffan, Qatar: Qatargas 2 (Train 5), Qatargas 3 (Train 6), and Qatargas 4 (Train 7). All of these process trains have a design capacity for an annual LNG production capacity of approximately 7.8 MTY.

A majority of the total worldwide LNG is produced with Air Products’ technology. Air Products has designed, manufactured and exported more than 75 LNG heat exchangers from its Wilkes-Barre, Pa., United States facility over the last four decades.

In support of the LNG industry, Air Products provides process technology and key equipment for the heart of the natural gas liquefaction process, and also nitrogen plants for the base-load LNG facility. Upstream, Air Products provides both nitrogen and natural gas dehydration membrane systems for offshore platforms. Downstream, Air Products provides dry inert gas generators for LNG carriers, shipboard membrane nitrogen systems, land-based membrane and cryogenic nitrogen systems for LNG import terminals, and process technology and equipment for small and mid-sized LNG plants, floating LNG plants and LNG peak shavers.

Resources

• Large Capacity Single Train AP-X Hybrid LNG Process