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

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Fear and caring are what's at the core of divisive wolf debate

Fear and caring are what’s at the core of divisive wolf debate. Credit: Photo by G.L. Kohuth

To hunt or not hunt wolves can't be quantified as simply as men vs. women, hunters vs. anti-hunters, Democrats vs. Republicans or city vs. rural.

What's truly fueling the divisive debate is fear of wolves or the urge to care for canis lupis. The social dynamics at play and potential options for establishing common ground between sides can be found in the current issue of the journal PLOS ONE.

"People who are for or against this issue are often cast into traditional lots, such as gender, political party or where they live," said Meredith Gore, associate professor of fisheries and wildlife and co-lead author of the study. "This issue, however, isn't playing out like this. Concerns about hunting wolves to reduce conflict are split more by social geography and less by physical geography."

It's definitely an us-versus-them debate, she added. However, it took the concept of social identity theory to better reveal the true "us" and "them." Applying principles from social psychology revealed how the two groups were interacting and offers some potential solutions to get the vying groups to work together.

The team's findings are comparable, in part, to civil uprisings in the Middle East. The region is far removed from the United States, in terms of geography. Americans, however, tend to identify with a distant, threatened identity group, said Gore, an MSU AgBioResearch scientist.

"The concept of how our identity drives our activism is quite interesting," said Gore, who co-led the research with Michelle Lute, former MSU fisheries and wildlife graduate student who's now at Indiana University. "Our findings challenge traditional assumptions about regional differences and suggest a strong role for social identity in why people support or oppose wildlife management practices."

The majority of the nearly 670 surveys were collected from Michigan stakeholders interested in wolf-hunting as a management response to wolf conflicts. However, a small percentage of the data was gathered from participants in 21 states. While the study focused on gray wolves in Michigan, its results have implications for other states' policies on wolves as well as other large carnivores such as brown bears, polar bears, mountain lions and other predators, Gore added.

Noting that there's sharp polarization in debates about wolf management is not new. However, providing empirical evidence of its existence is new and meaningful because it provides a framework for improving engagement between the fighting factions.

For example, communications may be better directed toward each identity group's concerns of fear and care for wolves. These missives could be more effective than messages simply directed toward pro-hunters or anti-hunters. Identity-specific communications may also help build trust between agencies and stakeholders.

"These types of communications may not only build trust, but they can also contribute to a sense of procedural justice," Gore said. "This, in turn, may increase support for decision-makers and processes regardless of the outcome."

Also, by shaping and discussing the issue in terms of care and fear, rather than traditional qualifiers, may help usher in a greater agreement about management strategies.

Additional researchers working on this paper include Adam Bump, Michigan Department of Natural Resources.

Source: Michigan State University

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High milk intake linked with higher fractures and mortality, research suggests

Women who drank more than three glasses of milk a day had a higher risk of death than women who drank less than one glass of milk a day. Credit: © Africa Studio / Fotolia

A high milk intake in women and men is not accompanied by a lower risk of fracture and instead may be associated with a higher rate of death, suggests observational research published in The BMJ this week.

This may be explained by the high levels of lactose and galactose (types of sugar) in milk, that have been shown to increase oxidative stress and chronic inflammation in animal studies, say the researchers.

However, they point out that their study can only show an association and cannot prove cause and effect. They say the results "should be interpreted cautiously" and further studies are needed before any firm conclusions or dietary recommendations can be made.

A diet rich in milk products is promoted to reduce the likelihood of osteoporotic fractures, but previous research looking at the importance of milk for the prevention of fractures and the influence on mortality rates show conflicting results.

So a research team in Sweden, led by Professor Karl Michaëlsson, set out to examine whether high milk intake may increase oxidative stress, which, in turn, affects the risk of mortality and fracture.

Two large groups of 61,433 women (aged 39-74 years in 1987-1990) and 45,339 men (aged 45-79 years in 1997) in Sweden completed food frequency questionnaires for 96 common foods including milk, yoghurt and cheese.

Lifestyle information, weight and height were collated and factors such as education level and marital status were also taken into account. National registers were used to track fracture and mortality rates.

Women were tracked for an average of 20 years, during which time 15,541 died and 17,252 had a fracture, of whom 4,259 had a hip fracture.

In women, no reduction in fracture risk with higher milk consumption was observed. Furthermore, women who drank more than three glasses of milk a day (average 680 ml) had a higher risk of death than women who drank less than one glass of milk a day (average 60 ml).

Men were tracked for an average of 11 years, during which time 10,112 died and 5,066 had a fracture, with 1,166 hip fracture cases. Men also had a higher risk of death with higher milk consumption, although this was less pronounced than in women.

Further analysis showed a positive association between milk intake and biomarkers of oxidative stress and inflammation.

In contrast, a high intake of fermented milk products with a low lactose content (including yoghurt and cheese) was associated with reduced rates of mortality and fracture, particularly in women.

They conclude that a higher consumption of milk in women and men is not accompanied by a lower risk of fracture and instead may be associated with a higher rate of death. 

Consequently, there may be a link between the lactose and galactose content of milk and risk, although causality needs be tested.

"Our results may question the validity of recommendations to consume high amounts of milk to prevent fragility fractures," they write. "The results should, however, be interpreted cautiously given the observational design of our study. The findings merit independent replication before they can be used for dietary recommendations."

Michaëlsson and colleagues raise a fascinating possibility about the potential harms of milk, says Professor Mary Schooling at City University of New York in an accompanying editorial. However, she stresses that diet is difficult to assess precisely and she reinforces the message that these findings should be interpreted cautiously.

"As milk consumption may rise globally with economic development and increasing consumption of animal source foods, the role of milk and mortality needs to be established definitively now," she concludes.

Source: BMJ-British Medical Journal

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