From Pig to Fuel - Anaerobic digester generates energy, reduces odors

 Teng Lim is operating a small-scale anaerobic digester at the MU swine farm in Columbia. The system generates energy and can mitigate hog odor. Courtesy Jon Lamb.

The University of Missouri has unveiled a prototype small-scale anaerobic digestion system that produces biogas from pig manure. The biogas can be used to heat a farm and create electricity. The device also reduces odor from swine operations.

“What we want to do is improve and fully utilize all the biogas for energy production,” said Teng Lim, Extension Ag Systems Management associate professor.

Funded by the MU College of Agriculture, Food and Natural Resources, the anaerobic digester consists of three tanks. Manure from the hog barn pit is pumped into one tank where the manure is stored and mixed. The anaerobic digestion takes place in the other two tanks, where bacteria break down the manure in these warm and oxygen-free tanks.

The biogas from the manure can be used for electricity and hot water production. With some further treatment it can also be stored as a compressed natural gas, for heating or even vehicle fuel.

PigsLim says a larger scale digester could supply a farm’s energy needs and also be sold to the grid to provide electricity to the community.

There are other benefits to anaerobic digestion in addition to energy generation. The digested manure retains the nutrients to be good fertilizer while becoming a more consistent product. Also, the digester can reduce odor emissions.

“When the manure is treated by the digester process the odor concentration is significantly reduced,” Lim said. “There is still going to be odor, but it’s going to be much lower and less fluctuation than the raw manure.”

A Lot of Pork

The swine industry is big in the United States – there are 73,150 pork farms in America with 120 million pigs marketed each year.

Before the 1960s, most pork in the U.S. was raised in outside lots or on pasture systems. With the development of slotted floors and liquid manure handling equipment, it became possible for producers to more easily care for larger numbers of animals. Enclosed buildings overcame most weather problems and predators, and minimized the potential pollution from outside lot runoff.

Typically, pig odor is a localized air quality problem, with low concentrations of odorous gases such as p-cresol. Odor problems are often a starting point for litigation. Many farmers can go out of business just fighting a lawsuit.

An Important Part of Future Farms?

There are challenges to anaerobic digestion, the biggest being cost and management. In a commercial setting the digester would be 100 times larger than the one at MU’s swine research facility.

Lim pointed out that industry leaders and scientists believe anaerobic digesters will be an important piece of future farms, both to mitigate odor and for generating renewable energy.  The cost is a major obstacle now. The team is working closely with industry experts from Martin Machinery, a Missouri company who specializes in biogas generators and control systems.

MU researchers are using the scaled down digester to find ways to make digesters more affordable and easier to manage. They are also using it as an education tool to show producers the potentials, what it takes to process the manure, and to train people how to properly run a system like this.

Source: Cafnr

Study Yields Surprising Insights into Global Effects of Wood Fuel Burning

Courtesy of Adrian Ghilardi

The harvesting of wood to meet the heating and cooking demands for billions of people worldwide has less of an impact on global forest loss and carbon dioxide (CO2) emissions than previously believed, according to a new Yale-led study.

Writing in the journal Nature Climate Change, a team of researchers, including Prof. Robert Bailis of the Yale School of Forestry & Environmental Studies (F&ES), concludes that only about 27 to 34 percent of wood fuel harvested worldwide would be considered “unsustainable.” According to the assessment, “sustainability” is based on whether or not annual harvesting exceeds incremental re-growth.

The other authors are Rudi Drigo, an independent forestry specialist with international experience; and Adrian Ghilardi and Omar Masera of the National Autonomous University of Mexico.

According to the authors, the findings point to the need for more nuanced, local-specific policies that address forest loss, climate change, and public health. They also suggest that existing carbon offset methodologies used to reduce carbon emissions likely overstate the CO2 emission reductions that can be achieved through the promotion of more efficient cookstove technologies.

The study identifies a set of “hotspots” where the majority of wood extraction exceeds sustainable yields. These hotspot regions — located mainly in South Asia and East Africa — support about 275 million people who are reliant on wood fuel.

“If forests and woodlands would have been cut down anyway, then the projects designed to reduce wood fuel demand are not actually going to reduce deforestation.”— Robert Bailis

However, in other regions, the authors say, much of the wood used for this traditional heating and cooking is actually the byproduct of deforestation driven by other factors, such as demand for agricultural land, which would have occurred anyway.

“If forests and woodlands would have been cut down anyway, then the projects designed to reduce wood fuel demand are not actually going to reduce deforestation,” said Bailis, an associate professor at F&ES and lead author of the study. “Sure, you’re reducing wood use, but the underlying pressures driving deforestation are still out there.”

The results stand in contrast to a long-held assumption that the harvesting of wood fuels — which accounts for more than half of the wood harvested worldwide — is a major driver of deforestation and climate change.
  
Using a model originally developed by Drigo and Masera, and already applied in more than 20 countries, the researchers produce a spatially explicit snapshot of wood fuel supply and demand in 90 countries across the world’s tropical regions, where burning wood is a critical source of energy for cooking and heating.

“One of the problems with traditional bio-energy is that the situation is very locally specific, so you can’t come up with a general response for all places,” said Masera. “One of the real strengths of this paper is that it demonstrates a methodology that allows you to identify priority regions for intervention”

The study identified a set of “hotspot” regions in South Asia and Eastern Africa where the majority of wood extraction exceeds sustainable yields.

In addition to the global analysis, the researchers are using the same model to evaluate the sustainability of wood fuel resources in three case studies: Honduras, Kenya, and the Indian state of Karnataka.

“Even within a given country the situation varies a great deal,” said Drigo. “Some areas are over-exploited while others are under-exploited or totally untouched. A better understanding of the relationship between supply and demand requires this type of spatial approach to clarify what the impacts of different policies will be.”

Emissions from wood fuels account for about 1.9 to 2.3 percent of global emissions, the study says. The deployment of 100 million improved cookstoves could reduce this by 11 to 17 percent, said Bailis, who also studies the factors that influence the adoption of cleaner cookstoves in developing nations.

These reductions would be worth more than $1 billion per year in avoided greenhouse gas emissions if black carbon were integrated into carbon markets, he said.

“We need to be able to understand where these different components of non-renewability are coming from in order to get a better sense of the positive impacts of putting stoves into peoples' homes or promoting transitions to cooking with gas or electricity,” he said.

The research was funded by the Global Alliance for Clean Cookstoves, an initiative supported by the UN Foundation.

Source: Yale University

Sunlight, not microbes, key to carbon dioxide in Arctic

Terrestrial organic matter is shown spilling into a lake. Credit: Image courtesy of Oregon State University

The vast reservoir of carbon stored in Arctic permafrost is gradually being converted to carbon dioxide (CO2) after entering the freshwater system in a process thought to be controlled largely by microbial activity.

However, a new study -- funded by the National Science Foundation and published this week in the journal Science -- concludes that sunlight and not bacteria is the key to triggering the production of CO2 from material released by Arctic soils.

The finding is particularly important, scientists say, because climate change could affect when and how permafrost is thawed, which begins the process of converting the organic carbon into CO2.

"Arctic permafrost contains about half of all the organic carbon trapped in soil on the entire Earth -- and equals an amount twice of that in the atmosphere," said Byron Crump, an Oregon State University microbial ecologist and co-author on the Science study. "This represents a major change in thinking about how the carbon cycle works in the Arctic."

Converting soil carbon to carbon dioxide is a two-step process, notes Rose Cory, an assistant professor of earth and environmental sciences at the University of Michigan, and lead author on the study. First, the permafrost soil has to thaw and then bacteria must turn the carbon into greenhouse gases -- carbon dioxide or methane. While much of this conversion process takes place in the soil, a large amount of carbon is washed out of the soils and into rivers and lakes, she said.

"It turns out, that in Arctic rivers and lakes, sunlight is faster than bacteria at turning organic carbon into CO2," Cory said. "This new understanding is really critical because if we want to get the right answer about how the warming Arctic may feedback to influence the rest of the world, we have to understand the controls on carbon cycling.

"In other words, if we only consider what the bacteria are doing, we'll get the wrong answer about how much CO2 may eventually be released from Arctic soils," Cory added.

The research team measured the speed at which both bacteria and sunlight converted dissolved organic carbon into carbon dioxide in all types of rivers and lakes in the Alaskan Arctic, from glacial-fed rivers draining the Brooks Range to tannin-stained lakes on the coastal plain. Measuring these processes is important, the scientists noted, because bacteria types and activities are variable and the amount of sunlight that reaches the carbon sources can differ by body of water.

In virtually all of the freshwater systems they measured, however, sunlight was always faster than bacteria at converting the organic carbon into CO2.

"This is because most of the fresh water in the Arctic is shallow, meaning sunlight can reach the bottom of any river -- and most lakes -- so that no dissolved organic carbon is kept in the dark," said Crump, an associate professor in Oregon State's College of Earth, Ocean, and Atmospheric Sciences. "Also, there is little shading of rivers and lakes in the Arctic because there are no trees."

Another factor limiting the microbial contribution is that bacteria grow more slowly in these cold, nutrient-rich waters.

"Light, therefore, can have a tremendous effect on organic matter," University of Michigan's Cory pointed out.

The source of all of this organic carbon is primarily tundra plants -- and it has been building up for hundreds of thousands of years, but doesn't completely break down immediately because of the Arctic's cold temperatures. Once the plant material gets deep enough into the soil, the degradation stops and it becomes preserved, much like peat.

"The level of thawing only gets to be a foot deep or so, even in the summer," Crump said. "Right now, the thaw begins not long before the summer solstice. If the seasons begin to shift with climate change -- and the thaw begins earlier, exposing the organic carbon from permafrost to more sunlight -- it could potentially trigger the release of more CO2."

The science community has not yet been able to accurately calculate how much organic carbon from the permafrost is being converted into CO2, and thus it will be difficult to monitor potential changes because of climate change, they acknowledge.

"We have to assume that as more material thaws and enters Arctic lakes and rivers, more will be converted to CO2," Crump said. "The challenge is how to quantify that."

Some of the data for the study was made available through the National Science Foundation's Arctic Long-Term Ecological Research project, which has operated in the Arctic for nearly 30 years.

Source:  Oregon State University

Permafrost soil: Possible source of abrupt rise in greenhouse gases at end of last ice age

Pleistocene Ice Complex cliff: 35 meters high Pleistocene Ice Complex cliff at Sobo Sise Island (Lena Delta), Siberian Arctic. Credit: Alfred-Wegener-Institut / Thomas Opel

Scientists from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) have identified a possible source of carbon dioxide (CO2) and other greenhouse gases that were abruptly released to the atmosphere in large quantities around 14,600 years ago. According to this new interpretation, the CO2 -- released during the onset of the Bølling/Allerød warm period -- presumably had their origin in thawing Arctic permafrost soil and amplified the initial warming through positive feedback. The study now appears online in the journal Nature Communications.

One of the most abrupt rises in the carbon dioxide concentration in the atmosphere at the end of the last ice age took place about 14,600 years ago. Ice core data show that the CO2 concentration at that time increased by more than 10 ppm (parts per million, unit of measure for the composition of gases) within 200 years. This CO2 increase, i.e. approx. 0.05 ppm per year, was significantly less than the current rise in atmospheric CO2 of 2-3 ppm in the last decade caused by fossil fuels. These data describe an abrupt change in the global carbon cycle during the transition from the last ice age to the present-day warm interglacial and allow conclusions to be drawn about similar processes that could play a role in the future.

To determine the origin of the greenhouse gas, a team around by the geoscientists and climate researchers Dr. Peter Köhler and Dr. Gregor Knorr from the Alfred Wegener Institute has carried out computer simulations focusing on the new interpretation of these CO2 data. These calculations were motivated by new radiocarbon data (14C) that provide information on the age of the CO2 released to the atmosphere. The age of the carbon then allows conclusions to be drawn about the carbon source.

"The virtual lack of radiocarbon in the CO2 that was released into the atmosphere shows us that the carbon must have been very old," says Köhler. The carbon therefore cannot be originated from the deep ocean, Köhler adds: "The carbon stored in the deep ocean has been subject to exchange with the atmosphere over a period of millennia. In the atmosphere 14C has its only source. It is produced through the impact of galactic cosmic rays on molecules in the atmosphere." However, radiocarbon is unstable and decays with a half-life of around 5,700 years. The atmospheric data of CO2 and 14C can only be explained if a carbon source is assumed that contains virtually no 14C any more -- thus the greenhouse gases must have had another source than the deep ocean.

Permafrost soil contains, to some extent, very old organic material, which is released in the form of the greenhouse gases CO2 and methane when the soil thaws. Permafrost soil thus might be a possible source of old carbon. The thawing of Arctic permafrost soil might have been caused by a sudden resumption of large-scale Atlantic heat transport in the ocean that initiated the Bølling/Allerød warm period in the high northern hemisphere.

The scientists were able to estimate the amount of the carbon dioxide released to the atmosphere by applying a computer model that simulates the global carbon cycle. The simulation results indicate that the input of more than half a gigaton of carbon per year (1 gigaton = 1 petagram) over a period of two centuries is necessary to explain the observed data. This corresponds to a total amount of more than 100 gigatons of carbon. Present-day anthropogenic CO2 emissions due to fossil fuels, at approx. ten gigatons of carbon a year, are greater than the release rates of this natural process by a factor of at least ten.

According to the study, the proposed thawing of large areas of permafrost, followed by the rise in greenhouse gases, occurred at the same time as the warming in the northern hemisphere at the beginning of the Bølling warm period. The released greenhouse gases may amplify the initial warming through feedback effects.

A similar effect is also predicted for the future in the current IPCC report. Warming in Siberia, for instance, is already leading to thawing of permafrost soil: outgassing of CO2 and methane takes place. The same processes observed today -- and are expected to an even greater extent in the coming decades -- presumably occurred in a similar manner 14,600 years ago. "However, the state of the climate on Earth today has already been changed by anthropogenically emitted greenhouse gases. Future CO2 release due to the proposed thawing of permafrost will be substantially less than the input due to fossil fuels. However, these emissions from permafrost soil are additional greenhouse gas sources that further amplify the anthropogenically induced effect," says Köhler.

Source:  Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research

Put a plastic bag in your tank: Converting polyethylene waste into liquid fuel

Researchers in India have developed a relatively low-temperature process to convert certain kinds of plastic waste into liquid fuel as a way to re-use discarded plastic bags and other products.

Researchers in India have developed a relatively low-temperature process to convert certain kinds of plastic waste into liquid fuel as a way to re-use discarded plastic bags and other products. They report full details next month in the International Journal of Environment and Waste Management.

Many pundits describe the present time as the "plastic age" for good reason and as such we generate a lot plastic waste. Among that waste is the common polymer, low-density polyethylene (LDPE), which is used to make many types of container, medical and laboratory equipment, computer components and, of course, plastic bags. Recycling initiatives are in place in many parts of the world, but much of the polyethylene waste ends up in landfill, dispersed in the environment or in the sea.

Chemist Achyut Kumar Panda of Centurion University of Technology and Management Odisha, India is working with chemical engineer Raghubansh Kumar Singh of the National Institute of Technology, Orissa, India, to develop a commercially viable technology for efficiently rendering LDPE into a liquid fuel. Given that most plastics are made from petrochemicals, this solution to plastic recycling brings the life-cycle full circle allowing a second use as an oil substitute. The process could, if implemented on a large enough scale, reduce pressures on landfill as well as ameliorating the effects of dwindling oil supplies in a world with increasing demands on petrochemicals for fuel.

In their approach, the team heats the plastic waste to between 400 and 500 Celsius over a kaolin catalyst. This causes the plastic's long chain polymer chains to break apart in a process known as thermo-catalytic degradation. This releases large quantities of much smaller, carbon-rich molecules. The team used the analytical technique of gas chromatography coupled mass spectrometry to characterize these product molecules and found the components of their liquid fuel to be mainly paraffins and olefins 10 to 16 carbon atoms long. This, they explain, makes the liquid fuel very similar chemically to conventional petrochemical fuels.

In terms of the catalyst, Kaolin is a clay mineral -- containing aluminum and silicon. It acts as a catalyst by providing a large reactive surface on which the polymer molecules can sit and so be exposed to high temperature inside the batch reactor, which breaks them apart. The team optimized the reaction at 450 Celsius a temperature with the lowest amount of kaolin at which more than 70% of the liquid fuel is produced. In other words, for every kilogram of waste plastic they could produce 700 grams of liquid fuel. The byproducts were combustible gases and wax. They could boost the yield to almost 80% and minimize reaction times, but this required a lot more catalyst 1 kg of kaolin for every 2 kg of plastic.

Source: Inderscience Publishers

Acid mine drainage reduces radioactivity in fracking waste

“Fracking wastewater and acid mine drainage each pose well-documented environmental and public health risks. But in laboratory tests, we found that by blending them in the right proportions we can bind some of the fracking contaminants into solids that can be removed before the water is discharged back into streams and rivers,” said Avner Vengosh.
 Credit: Duke University

Much of the naturally occurring radioactivity in fracking wastewater might be removed by blending it with another wastewater from acid mine drainage, according to a Duke University-led study.

"Fracking wastewater and acid mine drainage each pose well-documented environmental and public health risks. But in laboratory tests, we found that by blending them in the right proportions we can bind some of the fracking contaminants into solids that can be removed before the water is discharged back into streams and rivers," said Avner Vengosh, professor of geochemistry and water quality at Duke's Nicholas School of the Environment.

"This could be an effective way to treat Marcellus Shale hydraulic fracturing wastewater, while providing a beneficial use for acid mine drainage that currently is contaminating waterways in much of the northeastern United States," Vengosh said. "It's a win-win for the industry and the environment."
Blending fracking wastewater with acid mine drainage also could help reduce the depletion of local freshwater resources by giving drillers a source of usable recycled water for the hydraulic fracturing process, he added.

"Scarcity of fresh water in dry regions or during periods of drought can severely limit shale gas development in many areas of the United States and in other regions of the world where fracking is about to begin," Vengosh said. "Using acid mine drainage or other sources of recycled or marginal water may help solve this problem and prevent freshwater depletion."

The peer-reviewed study was published in late December 2013 in the journal Environmental Science & Technology.

In hydraulic fracturing -- or fracking, as it is sometimes called -- millions of tons of water are injected at high pressure down wells to crack open shale deposits buried deep underground and extract natural gas trapped within the rock. Some of the water flows back up through the well, along with natural brines and the natural gas. This "flowback fluid" typically contains high levels of salts, naturally occurring radioactive materials such as radium, and metals such as barium and strontium.

A study last year by the Duke team showed that standard treatment processes only partially remove these potentially harmful contaminants from Marcellus Shale wastewater before it is discharged back into streams and waterways, causing radioactivity to accumulate in stream sediments near the disposal site.

Acid mine drainage flows out of abandoned coal mines into many streams in the Appalachian Basin. It can be highly toxic to animals, plants and humans, and affects the quality of hundreds of waterways in Pennsylvania and West Virginia.

Because much of the current Marcellus shale gas development is taking place in regions where large amounts of historic coal mining occurred, some experts have suggested that acid mine drainage could be used to frack shale gas wells in place of fresh water.

To test that hypothesis, Vengosh and his team blended different mixtures of Marcellus Shale fracking wastewater and acid mine drainage, all of which were collected from sites in western Pennsylvania and provided to the scientists by the industry.

After 48 hours, the scientists examined the chemical and radiological contents of 26 different mixtures. Geochemical modeling was used to simulate the chemical and physical reactions that had occurred after the blending; the results of the modeling were then verified using x-ray diffraction and by measuring the radioactivity of the newly formed solids.

"Our analysis suggested that several ions, including sulfate, iron, barium and strontium, as well as between 60 and 100 percent of the radium, had precipitated within the first 10 hours into newly formed solids composed mainly of strontium barite," Vengosh said. These radioactive solids could be removed from the mixtures and safely disposed of at licensed hazardous-waste facilities, he said. The overall salinity of the blended fluids was also reduced, making the treated water suitable for re-use at fracking sites.

"The next step is to test this in the field. While our laboratory tests show that is it technically possible to generate recycled, treated water suitable for hydraulic fracturing, field-scale tests are still necessary to confirm its feasibility under operational conditions," Vengosh said.

Source: Duke University