


Yes, cows. Over the past decade, Voth has developed a simple yet effective process for training cows to eat weeds, including almost any type of cow and almost any type of weed. There’s no gimmick involved. Her process is based squarely on recent scientific research into how livestock choose what to eat and on well-established principles of animal behavior. Voth’s process takes only ten hours of training spread over ten days to teach a group of cattle to learn to eat weeds. It works for a simple reason: the cows never realized weeds tasted so good!

However, convincing ranchers, farmers, agency employees and academics to give cows a chance is a much more difficult job, she’s discovered.

Let’s back up for a second. Why worry about invasive weeds?

Over 90 different foreign plants are recognized as Federal Noxious Weeds. Collectively, they infest over 100 million acres across the nation, including 20 percent of our public lands, and they are expanding at a rate of 8 to 12 percent—an area the size of Delaware—every year. Weeds crowd out native plants, damage crops and forage and contribute to soil erosion. Some can poison wildlife and livestock. Taken together, they are a huge threat, not only to food production but to biodiversity and watershed health, as well.


“They just looked at me like I was insane,” she said in an interview. “Most ranchers don’t want to have goats because they require a completely different kind of fencing and the market is much more difficult to access than the beef market. These were very good reasons and they made sense to me. But I’m not the kind of person you can just say no to.”

So she turned her attention to cows instead.

She also turned to Fred Provenza and other animal scientists at Utah State University, who discovered that a food’s palatability is heavily conditioned by experience. When an animal finds a food that meets its nutritional needs it will choose this food over and over. That’s because foods that “taste good” generally have more nutrients, which our bodies need. Nutrients send positive signals to the brain. Toxins send negative signals, such as nausea, causing us to avoid foods that “taste bad.” Flavor, in other words, is the brain’s way of screening nutrients from toxins.

According to Voth, this makes weeds ideal forage for cows because most are high in nutrients and low in toxins. In fact, most weeds are at least as nutritious as grass and often higher in protein. “That means if we can get a cow to try a weed, she’ll continue eating it year after year,” Voth wrote in an essay. “As a bonus, she’ll gain weight at rates expected for an animal eating a higher protein diet. Thus, not only do we eliminate the cost of herbicides, we increase profits due to increased weight gain.”

But how do you get a cow to “like” a food it has never eaten before?

Since inexperienced animals are more likely to try new things, Voth focuses on young cows and gives them a lot of positive experience. Here’s how it works. For the first four days of the training period Voth feeds the animals unfamiliar but tasty (nutritious) food in tubs twice a day, including beet pellets, wheat bran and hay cubes. Soon the animals associate her arrival in the pasture with a tasty meal. Combined with the natural competiveness of animals at feeding time, this meaning cows will try almost anything.

On the fifth day, Voth serves weeds with some of the feeds the trainees have already tried. She repeats this for three more days, increasing the amount of weeds and reducing the other foodstuffs until the mix is 100 percent weeds by the sixth day. If the weeds are present in the pasture, the cows will start eating them once they’ve been recognized. Soon the trainees are training other animals. Voth has seen 12 cows train 120 more!

As a bonus, educated cows are open minded to trying other weeds in a pasture, even if they haven’t been trained to them.

Here’s a sample of what cows will eat: Russian, Canadian, Italian, Scotch and musk thistle; diffuse, spotted and Russian knapweed, yellow and Dalmatian toadflax, white top/hoary cress, leafy spurge, goldenrod, fringed sage, field bindweed, yellow and purple starthistle, horehound, common mullein, rabbitbrush and many others. Voth has even trained cows to chow down on brush, including wild rose, willow, even mesquite.

Weed thorns and spines don’t bother cattle. Voth has seen them eat cactus. As for toxins, her advice is to make sure the weed is safe before you start (she keeps an updated and comprehensive list on her website). Watch out for dormancy too. Her rule of thumb: if it’s green and growing, it’s nutritious!

Then there are the economic benefits. “Say you’re a typical Western rancher and you have 400-500 cows,” she wrote. “You train 50 of them and within a year they’ll have trained all the rest. The cost of training those fifty cows is about $250 and you’ll never have to do it again. On average, a gallon of herbicide costs $250 and it will treat not nearly as many acres as the cows will. It just makes sense to me.”

Me too.  A “hip-hip-hooray” for out-of-the-box thinking! Better yet, a haiku:

The War on Weeds ends
When cows begin to eat them.
Foe becomes forage
– The Tao of Cow (Kathy Voth)Copy of colorado

Black Gold

Biochar has a great press agent.

The subject of numerous books, articles, research papers, conference presentations and various top-ten-ideas-that-will-change-the-world lists, biochar enjoys a reputation that has, so far, exceeded its actual accomplishments.

I bet that’s about to change.

Biochar’s attraction is threefold. first, as a supercharged form of charcoal, it has the ability to affect many Twenty-first Century challenges simultaneously, including greenhouse gas emissions, food insecurity, waste management and renewable energy production. Second, it’s a technology, albeit a sooty one, which means it’s attractive to the scientific, entrepreneurial and techno-geek aspects of our society—which partly explains its media charm. It also appeals to the “backyard innovator” in our human nature. Third, it’s an ancient agricultural practice, which tempts the farmer in us. As the prehistoric tribes of the Amazon Basin knew, biochar can elevate soil fertility tremendously.

In fact, all of these positive attributes create a kind of identity crisis for biochar: is it a “lite” form of geoengineering, a repurposing of indigenous knowledge or a commercial opportunity for savvy businesses?

It’s all of the above—but let’s back up. What is this black gold exactly?

Biochar is produced when organic material, generally plant matter or manure, is heated to very high temperatures in a zero or near-zero oxygen environment, which bakes the carbon into a light but solid structure riddled with millions of tiny holes. The process is called pyrolysis. In nature, it occurs when trees are carbonized by intensely hot forest fires or when wood is engulfed by volcanic lava.

In human hands, it usually takes place in a specially constructed oven where temperatures can reach 500 degrees Celsius or higher. In this tightly controlled environment, between 30 and 50 percent of the original carbon is transformed into highly stable biochar. The rest becomes bio-oil and syngas, both of which are exciting to renewable energy experts as potential substitutes for petroleum.

Biochar’s appeal as a way to mitigate climate change is straightforward: by baking carbon into a substance that can last thousands of years, we interrupt the natural cycle of decomposition and respiration in which microbes digest organic material and then “burp” carbon dioxide into the atmosphere. This process is a considerable source of this important greenhouse gas, and so if we can “lock up” large amounts of carbon as biochar rather than let it decompose, then we can (potentially) make a big dent in the blanket of greenhouse gases surrounding our planet.

Johannes Lehmann, a professor at Cornell University, recently calculated that if biochar were added to the soil of only 10 percent of the world’s farms, nearly 30 billion tons of CO2 would be sequestered—approximately the total amount of humanity’s annual greenhouse gas emissions.

The waste management appeal is also straightforward: biochar can be made from a wide variety of biological or “green” waste, including lawn clippings, hedge and tree trimmings and leftover food that would otherwise end up in landfills. Ditto with dairy and horse manure. This is important because landfills and manure lagoons are major sources of methane, a potent greenhouse gas. As a bonus, diverting these sources into biochar will reduce vexing waste disposal challenges.

Of course, composting is another way to put green waste to work regeneratively, but unlike biochar, which is inert, compost is biologically active. Its microbes are busy “burping” CO2 into the atmosphere. One intriguing solution is to mix biochar into compost piles. Biochar provides structural stability and compost provides biology. Another win-win!

Biochar’s agricultural appeal is based on its almost magical ability to improve soil fertility. Since biochar can take the shape of sticks, pellets or dust, it can be easily mixed into soil. Once there, it creates a variety of important benefits.

  1. The millions of tiny holes in a piece of biochar provide “condominium” housing for micro-critters, which move in quickly and begin doing their soil-building thing.
  2. These holes also wick water from the soil into the biochar (up to six times its weight) and release it slowly, supplying the microbes and retarding evapotranspiration, both of which are very useful in a drought.
  3. Biochar’s stability and resistance to decay enables the soil to withstand flooding and other forms of erosion.
  4. Bochar is alkaline by nature which can help achieve ph balance in acidic soils.
  5. Biochar can help restore degraded land because it works best when applied to depleted soils.
  6. And biochar can help to remediate polluted air and soil.

Taken together, it’s little wonder that prehistoric peoples in South America spent 8,000 years stuffing the thin, acidic, nutrient-poor soils of the Amazon Basin with a type of biochar called terra preta. It was their homemade version of black gold!

So, given all of these impressive benefits and opportunities, why isn’t biochar in widespread use yet? One answer: biochar is more complicated than it first appears.

For starters, there are a bewildering variety of biochar types to choose from (225 and counting). There is also a confusing selection of ovens to bake them in and many (competing) schools of thought about how to produce biochar properly. Then there are technical issues involving thermal physics, feedstocks and disposal of the bio-oil and syngas produced as byproducts.

There are also practical issues involving transportation and appropriate farming practices and philosophical issues involving competition with compost projects, how to work at scale and even proper baking temperatures (higher temps produce more stable carbon storage but also use more energy and produce more waste). Finally, there are ethical issues, including the specter of ecologically destructive, industrial-scale biochar plantations.

And then there are the economic hurdles.

Biochar has not yet been produced commercially at a price that makes it competitive with conventional fertilizers or other soil amendments ($1,000 per metric ton was one price I saw). This could change with the creation of a viable carbon marketplace, where biochar could become a way for polluters to earn “credits” to offset their production of greenhouse gases. Until then, however, biochar remains mostly in a research and development phase.

It won’t last long. Biochar has too many important benefits to continue to be underutilized, especially as Twenty-first Century challenges mount. In fact, it has already come a long way in a short time—the word “biochar” didn’t even exist before 2008. Today it already has a great press agent!biocharwheel_sjp

For more on Kathy Voth see:

For a research perspective:

For more on biochar see: the U.S. Biochar Initiative

My book will be out soon! See: