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[AgriLife Today] Closed-loop concept could be the future of sustainable animal farms

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By: Adam Russell

STEPHENVILLE – Dr. Eunsung Kan sees his concept of a closed-loop dairy farm, which reuses wastewater, emits zero waste and powers itself on manure, as the future of sustainable animal farming.

Kan, a Texas A&M AgriLife Research chemical and environmental engineer in Stephenville, said his concept could change the way dairies, swine and poultry farms deal with manure, wastewater and greenhouse gasses while utilizing the waste to generate electricity.

Animal waste is a blessing and curse for dairies.

Manure is sold to local farmers who need to infuse nutrients into the soil for crops and forage. However, tons of manure can also be logistically taxing as facilities keep up with the treatment and distribution of large quantities of environmentally problematic materials monitored by state and federal environmental regulators.

Farm operations have been implicated in higher-than-normal levels of nitrogen and phosphorous, antibiotics, heavy metals and hormones in surface and groundwater downstream from facilities. Manure is also a known contributor to greenhouse gas emissions, such as methane and carbon dioxide.

The U.S. Department of Agriculture Natural Resources Conservation Service estimates manure from a dairy milking 200 cows can produce as much nitrogen as is in the sewage from a community of 5,000-10,000 people.

Kan’s research would utilize existing technology – biochar, a carbon material similar to charcoal, created from animal manure and agricultural waste, such as corn stubble or rice straw – that would be used to filter solid waste and effluent. The biochar could be used as a slow-release fertilizer or converted, via pyrolysis, which is the decomposition of organic material by heat, into energy to power the farm.

The closed-loop dairy concept focuses on three main goals – wastewater treatment using dairy manure-derived biochar, producing bioenergy using dairy manure and capturing greenhouse gasses via adsorption onto dairy manure-derived biochar, Kan said.

Biochar has proven to provide a beneficial surface chemistry that can filter a wide range of contaminants, including nitrogen and phosphorous, he said. When the surface of biochar is modified with several methods in a lab, it has shown an ability to capture antibiotics, pesticides, hormones, heavy metals and other possible contaminants.

“The mission is the treatment and reuse of dairy wastewater and the conversion of dairy waste into energy to power the facility,” he said. “It focuses on providing a model for sustainable farming.”

Last year, Kan received a $1 million grant from the Texas A&M University Chancellor’s Research Initiative Fund to research the viability of the closed-loop dairy system. Before joining AgriLife Research, he also received about $400,000 in research grants from the Environmental Protection Agency, U.S. Department of Agriculture and U.S. Geologic Survey to research the concept’s potential to treat animal waste, control greenhouse gas emissions and convert manure to energy.

CONCEPTUAL SYSTEM

The closed-loop dairy is a relatively simple concept, Kan said.

Cows produce manure, which when mixed with remnants of local crops, can become a seemingly endless supply of filtering material, fertilizer and energy.

Columns filled with biochar would act as a water purification system that filters nitrogen, phosphorous and other contaminants from liquid as it passes through, Kan said.

“The affluent from the column would then be very low in nitrogen and phosphorous,” he said. “If we filter to low levels of nitrogen and phosphorus it wouldn’t cause any environmental problem.”

The biochar used to filter nitrogen and phosphorous could then be used as slow-release fertilizer that provides needed nutrients to plants and would not wash away as runoff from heavy rains. In addition, biochar immobilized with photocatalysts would decompose toxic contaminants to harmless products when irradiated by exposure to ultraviolet light.

For instance, Kan’s study has shown that a biochar immobilized with photocatalysts completely degraded antibiotic and hormone compounds while effectively controlling pathogens. The potential for biochar’s use to filter wastewater goes beyond agriculture and could be applied at any wastewater treatment plant, or even to filter contaminants in injection water used in the petroleum industry for fracking.

For energy, dairy manure would be fed into a pyrolysis reactor on site that would use relatively low heat, 500-1,000 degrees Fahrenheit, to create compressed hydrogen and carbon monoxide syngas that can be used to create electric power, Kan said. Excess electricity could be sold to local utility companies. The byproduct from pyrolysis of dairy manure is biochar.

“The principle is very simple,” Kan said. “The dairy would just need a different size reactor to meet its scale of manure output and energy needs.”

Dr. Sergio Capareda, an AgriLife Research agricultural engineer in College Station, proved the pyrolytic conversion of dairy manure to syngas and biochar from his USDA-funded project, Kan said. Kan plans to advance this concept by biologically converting syngas to butanol and bio-jet fuel as alternative transportation fuels, and developing biochar-based processes for wastewater treatment and greenhouse gas control.

Several other researchers and engineers within the Texas A&M system are collaborating with Kan, and interest in the concept is growing among public institutions and private companies.

CONCEPT TO REALITY

Kan will produce a lab-scale version of the closed-loop dairy to determine the necessary scale for application and experimentation at the neighboring Southwest Regional Dairy Center in Stephenville, a privately owned working dairy operated by Tarleton State University used for educational purposes. He hopes to have a system, including the pyrolysis reactor, operating at the dairy within three to four years.

“Having the dairy farm here provides a good opportunity for field data,” he said. “The field demonstrations will help us work out any problems that might arise at the various scales that might be applied by commercial animal farms.”

The dairy produces milk that is processed for consumption and into products such as cheese and yogurt and sold in local grocery stores.

Clay Dameron, the dairy’s waste manager, said between 300-400 cows are milked daily. Those cows produce manure and effluent that is treated via a conventional lagoon system. Around 90-130 tons of solids are moved to nearby croplands and pastures every three weeks where it’s used as fertilizer. Treated liquids from the lagoon are dispersed via sprinklers in nearby fields.

Kan said he believes the closed-loop system will prove to be a logistically and financially viable model for dairy producers to implement in the future. He expects his pilot project at the regional dairy to produce data that will draw more interest and investment from public institutions and private companies.

“It is very exciting,” he said. “I look forward to working with my collaborators and colleagues to make this concept a reality that could change the way dairies operate by providing a self-sustaining, environmentally friendly model.”

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Farm & Ranch

Tracks in the Sand

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This morning, I walked out into my arena and noticed something that gave me pause. The roping steers had been in there the day before, and even though the ground was wide and level, the sand carried their story. Hoofprints crossed every direction, but in several spots, the same trail was pressed deeper than the rest. Twelve steers had been turned out, yet more than a few chose the exact same path, wearing it down until it stood out from all the other tracks.

Cattle are creatures of habit. Anyone who has spent time around them knows this. They like routine: the same feed, the same water trough, the same shade tree in the pasture. When they are turned loose, they rarely wander without purpose. More often than not, they move together, following the same course as the steer in front of them. There are reasons for this: efficiency, safety, instinct. Walking a beaten path conserves energy, and following the herd is their natural defense. Even in an arena with no real destination, those instincts come through. By the end of a short turnout, you will see the evidence, lines where they have chosen the easiest way to travel and stuck with it.

Out on the range, those lines last longer. Before fences and highways, cattle drives cut deep paths across the land. The Chisholm Trail, which carried herds north from Texas through Oklahoma into Kansas, was walked by millions of cattle in the late 1800s. More than a century later, faint traces of those trails remain, worn so deep by hooves and wagon wheels that the land still carries the mark. On ranches today, you can see the same effect in pastures where cattle walk the same lines between water and grazing. From the ground those trails might look like nothing more than dusty ruts, but from the air, they sometimes stand out as sharp lines winding through otherwise open fields. Cattle do not simply pass over the land; they shape it. Every step adds up.

That simple truth extends beyond livestock. We all make tracks. Our habits and routines are our trails, worn in by repetition, sometimes efficient, sometimes limiting. Like the cow paths, they can serve a purpose, keeping us steady and helping us move forward. But when repeated without thought, they risk becoming ruts, keeping us from stepping into new ground. History offers perspective here too. The old cattle trails built towns and economies, but once railroads and fences changed the landscape, those paths were no longer useful. Sticking to them would have meant going in circles. Progress required something new.


The Tracks We Leave

Standing in the arena, I thought about the kind of tracks I leave behind. Most of mine are not visible in the dirt. They are pressed into my daily life, how I work, the way I handle challenges, the example I set. Some are helpful and worth keeping. Others may have outlived their purpose. The difference comes in knowing when to stay in the track and when to step out of it.

Tomorrow I will drag the arena and smooth it all clean again. The next time the steers are turned in, they will make the same trails. That is their nature. But unlike them, I have a choice. I can decide which paths are worth walking, which ones to change, and what kind of tracks I want to leave for others who might follow.

Tracks tell a story. Sometimes they are only temporary, fading with the next rain. Other times they last for generations, reminders of where herds and people once walked. This morning, the cattle showed me again that even the smallest things on the ranch carry meaning. Their tracks in the arena were not just marks in the sand. They were a lesson: every step matters, and the paths we choose shape more than just the ground beneath our feet.

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Farm & Ranch

Grazing North Texas – American Lotus

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Farmers and ranchers are in a very close partnership with Mother Nature. If we really pay attention, she presents us some interesting scenarios.

For example, though they are totally different types of plants, water lilies and prickly pear have a lot in common. They both have strikingly beautiful flowers, both plants are edible, both of them are invaders into their respective habitats, and too much of either one can be an obstacle that we have to deal with.

Many north Texas ranches rely on excavated ponds for livestock water. Any time a pond contains a significant amount of shallow water so that sunlight reaches the bottom, some type of pond weed will develop. The plant family that includes water lilies and lotuses is a common invader in our livestock water.

Water lilies and lotuses are in the same plant family but they are two separate genera. There are easy ways to tell them apart:
• A primary difference is that water lily leaves commonly float on the surface, but lotus leaves can grow above the water line.
• Water lily leaves and flowers are thick and waxy, while lotus leaves and flowers are thin and papery.
• Water lily leaves have a distinct notch in the leaf, while lotus leaves are more rounded.
• Water lily flower petals are pointed, and lotus petals are more rounded.

The photos attached to this writing are from Clay County, and this plant is common across north Texas. American lotus is adapted to a wide area, from Honduras north through Mexico and across the eastern US and into Canada.

American lotus is a perennial, and it is cold tolerant and heat tolerant. It can grow in any pond or slow moving stream that contains shallow water areas. It prefers water with a depth of about 12 inches. Germination can occur from the large lotus seeds. Tubers, or roots, are established in the mud, and long slender stems extend upward. Leaves and flowers are both emergent in that they grow above the water line.

Lotus flowers are fragrant, and yellowish white with rich gold centers. They open in the morning and close by late afternoon, then open again the next day.

Lotus is an edible plant and has a history as a food source. The large tuberous roots, the size of a human arm, were baked like sweet potatoes. The leaves were eaten like spinach, and the large seeds were ground into flour. Stems taste somewhat like beets and were usually peeled before being eaten.

There is a large world-wide industry of cultivating lilies and lotuses in water gardens. According to Dr. Jerry Parsons, Professor and Extension Horticulturist with Texas A&M AgriLife Extension, cultivation of these plants dates back as early as ancient Egypt. Today, anyone with determination and a little money can have a water garden.

In 2011, the 82nd Texas Legislature designated the water lily “Texas Dawn” as the official Texas State Water Lily. Texas Dawn is a hybrid developed by Texas resident Kenneth Landon, a world-renowned expert in the field of water lilies and the director of the International Water Lily collection in San Angelo.

Ducks and other wildlife utilize the large acorn like seeds of American lotus, and submerged portions of all aquatic plants provide some form of wetland habitat. Many of us have tried to pull a bass out of a group of water lilies or lotuses, and I’m sure others have had better luck than I did. Although there can certainly be benefits to lilies, lotuses, and other aquatic plants, they can also infest ponds to the extent that the pond is not functioning correctly.

So, while the rest of the world works hard to grow these plants, ranchers sometimes need to control populations in their stock ponds. Once it gets a foot hold, American lotus can spread aggressively in wetland areas.

The primary issue that encourages American lotus, and most other water weeds, is shallow water. Look closely at a good livestock pond and you will find that the deeper water is basically free of infestation. Any pond will have a certain amount of shallow water that encourages water weed growth, depending upon the terrain at the pond site and how the pond was constructed. Some ranchers who enjoy and utilize wetland habitat may prefer to have ponds with significant shallow water area.

Almost all livestock ponds have a certain life expectancy. Siltation, or movement of soil into the pond bottom through rainfall runoff, is a natural occurrence. How fast siltation occurs into each pond, and how deep the pond was to start with, determines the length of time that the pond will contain adequate depth for dependable water for livestock.

Ponds that develop infestations of water weeds over a large percent of the surface may not have adequate depth to remain a viable water source for livestock during drought periods, especially in western north Texas where evaporation rates are higher.

Mud, or silt, from the pond bottom, can be removed to deepen the water, but this is a very expensive process. It is often more economical to construct a new pond rather than try to remove the silt from an old one. Most of us do not have the funds to continually construct deep water livestock ponds, so we must try to keep existing structures functioning and providing good drinking water for livestock, for as long as we can. Control of pond weeds like American lotus may be necessary, and it can be accomplished.

There is currently no feasible biological control. American lotus can be cut and removed, but this process us usually temporary because lotus can reestablish from seeds and roots.

American lotus can be safely controlled by chemicals. This must be done carefully. If a pond containing a large amount of any pond weeds is treated to remove all of the vegetation, a fish die-off could occur. When the dying weeds decompose, they use up the oxygen in the water and fish can suffocate. If possible, treat only a portion of the area, wait about two weeks, and treat another portion.

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Farm & Ranch

The Many Benefits of Rabbit Manure

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By Landon Moore

Rabbits offer a lot to the home gardener, and perhaps the most useful of all is their waste. Rabbit manure is likely the single most versatile and valuable fertilizer of any animal manure. It’s a “cold” manure, meaning it can be applied directly to plants in any form without the risk of burning them. In contrast, manure from sheep, horses, cows, and especially poultry must be aged before it’s applied, or it may damage plants. Because rabbit manure doesn’t need to be aged, it retains more of its nutrients and is therefore twice as rich as chicken manure and four times more potent than horse or cow manure. Rabbit manure is safe to apply to soil growing edible crops, has virtually no smell, and contains no harmful seeds. It can be used immediately, or be dried, powdered, made into tea, or turned into worm castings. A single trio of rabbits and their offspring can produce up to two cubic yards of fertilizer per year, along with 100 to 200 pounds of meat.

Rabbit manure is in such high demand as a fertilizer, particularly for roses, that it’s often sold online at a premium price. Some rabbitry owners even charge people to come scoop the manure themselves, paying by the bag. Larger rabbitries might sell by the truckload, but many owners keep it all for their own gardens. You may wonder what makes this little mammal’s excrement so uniquely useful. To understand, we first need to look at the qualities that make it special and then explore its various applications.

To begin with, let’s take a closer look at a rabbit’s biology. Contrary to popular belief, rabbits are not rodents but belong to the order Lagomorpha and family Leporidae, along with hares. All domestic rabbits are domesticated European rabbits (Oryctolagus cuniculus) and are unable to produce fertile offspring with American cottontails. Rabbits are considered “pseudo-ruminants” because they have a single-chambered stomach, but they also have an organ called the cecum, which functions similarly to a rumen and makes up about 40% of their digestive tract. They are crepuscular, meaning they are most active at dawn and dusk, typically feeding in the evening.

Rabbits actually produce two kinds of manure. The familiar dry pellets make up most of their waste, while the other type, known as “cecotropes,” is a moist and smelly substance resembling tiny bunches of grapes. Cecotropes are not fully digested, and because rabbits cannot chew their cud, they reingest the cecotropes as they are excreted. This fermented substance allows the rabbit to absorb more nutrients than it would through initial digestion. While cecotropes are occasionally found in cage trays, the feeding behavior that leads to them is usually only witnessed by the rabbit owner.

The dry pellets are the true manure that most people are familiar with. These small, round, dry pellets have almost no smell when kept dry. When crushed, they break down into a powder resembling tiny grass fragments because, in essence, that’s what they are. Some people crush the pellets before applying them to speed up their absorption into the soil, while others appreciate their “slow-release” feature. Additionally, the manure’s water solubility can be exploited in several ways. Soaking a wheelbarrow full of manure creates a potent sludge that can be easily applied to flat surfaces. If the odor is not an issue, the smell will dissipate once the manure is either dissolved by moisture or dried by the sun. Another method is to make manure tea: fill a cloth bag with manure, seal it, and submerge it in a barrel of water for a few weeks. A simpler method involves placing damp manure at the bottom of a barrel, filling it with water, and letting it sit in the sun for a couple of weeks. Stir occasionally, and you’ll have a powerful liquid fertilizer ready for use.

Domestic rabbits should be fed a modern, pelleted feed, which provides all the nutrients they require. This diet eliminates the risk of noxious seeds being present in the manure, making it safe to apply directly to the lawn, especially during winter. Winter and spring rains will break it down, and by late spring, you’ll have a healthy carpet of turf.

Rabbit manure’s nutrient content varies depending on factors like storage, age, and diet, but it generally contains around 2% nitrogen (N), 1.3% phosphorus (P), and 1.2% potassium (K). The Oregon Extension Service gives a range of 3-4.8% nitrogen, 1.5-2.8% phosphorus, and 1-1.3% potassium. Even at the lower end of the scale, rabbit manure has higher nitrogen content than poultry manure and twice the nitrogen content of cattle manure. One reason rabbit manure doesn’t burn plants is due to the biology of birds, which lack bladders and produce more ammonia in their waste. In contrast, rabbits release ammonia in their urine, which is why their manure may have a stronger odor.

Because of its balanced nitrogen-to-phosphorus ratio, rabbit manure promotes a wider variety of species in the same application area. Applying it directly to heavy clay soils will improve them quickly, especially when combined with other organic matter. It can also improve sandy soils by adding texture and helping them retain moisture. Anyone raising rabbits will have a steady supply of manure, as they are efficient producers. A small herd of 17 animals, including their litters, can produce about one ton of manure annually.

Beyond fertilizing, rabbit manure has several other uses. It is considered the best food for earthworms and can be combined with moisture-holding bedding like peat moss, shredded paper, or hay taken from used nestboxes. Many rabbitries (including my own) keep worm beds right under the cages. The resulting castings are rich in nutrients and can be used as-is or incorporated into soil amendments. A couple of feet of manure under a foot of soil in a hotbox can generate enough warmth to start and grow seeds, even in cold climates like Vermont.

In Europe and Asia, the rabbit meat industry is a billion-dollar market. While the Czech Republic leads in per capita consumption (over 8 pounds per person annually), China is the leading producer of rabbit meat. A recent study in China examined the effects of replacing peat moss in seed-starting soil with rabbit manure. The study found no significant difference in germination rates and noted that the manure provided increased nutrients for seedlings. The ideal ratios for seed-starting soil were found to be one-third manure, one-third perlite, and one-third vermiculite, or half manure and half perlite.

Rabbit manure is often overlooked as a nuisance, but as we can see, it’s an incredibly versatile soil conditioner, excellent fertilizer, ideal food for earthworms, and a superior seed-starting medium. Anyone raising rabbits should consider this another benefit, in addition to having a home meat supply, exhibition livestock, or pets.

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