Home » Build Soil » Soil Inputs » Fertilizers » Bone Char Benefits

Bone Char Benefits

By Maria Dimengo
From the October 2018 issue of Acres U.S.A. magazine

Farmers have been experimenting with animal waste for centuries, using it as a fertilizer or as a way to recycle healthy nutrients back into the soil: While some focused on traditional forms of waste, others directed their attention to the benefits of “bone black,” bone char or animal char.

Many see its benefits as a soil amendment. If the soil was dry, it could help retain water. If the soil was wet like a sponge, it could be crushed and sprinkled in to retain nutrients.

Bone char is derived from carbonizing crushed animal bones using a high-heat process known as pyrolysis. When processed through an energy-efficient airtight burner, charcoaled materials can be cleanly burned, finely ground and added to compost.

Primarily rich in calcium phosphate, calcium carbonate and micronutrients, bone char is granular and useful as an adsorbent. Since prehistoric times, it has been used to create bone black pigment used notable painters and artists. Modern uses centered on sugar whitening and defluoridating water.

bone char

Scott Bagley, owner of Exeterra, LLC in Athens, Ohio, discovered the benefits of bone char while experimenting with biomass and other organic materials. While doing forest restoration work, Bagley became interested in developing natural lump BBQ charcoal as a value-added product. He thought it might be a way to create additional revenue from some of the low-value wood he found.

He began looking around for a self-contained unit to make his hardwood cooking charcoal and came across a company out of England that designs cast-iron vessels, or “retorts,” used for burning. Bagley purchased a unit for himself and later partnered with the Carbon Compost Company of Exeter, Devon, England, to sell the Exeter Charcoal Retort exclusively in the Unites States, Canada, Mexico and the Caribbean.

While he was working on getting his business off the ground, a livestock producer from Kansas reached out to Bagley and wanted to know if the unit could be used to burn bones. Bagley wondered if the end product would behave like wood, so he came up with his own do-it-yourself process and started experimenting.

Trial and Error

A lot of people might build a fire, cut a few holes in old metal drums and place a cylinder inside. A crude design might be helpful for burning yard waste, twigs and tree branches, but a bigger burner is needed for a more productive yield.

Bagley also knew it would take a lot of bones before he would begin to see noticeable yield. He worked with a deer processor to run a few test batches but discovered that fresh bones didn’t offer the ideal solution. The Exeter unit processes feedstocks up to 6 inches in diameter and 6 feet in length, which proved to be the ideal setup.

A customer figured out a way to burn the bones successfully, and now the Callicrate Cattle Co. is making bone char and selling it online. The company makes bone broth and sells their specialty product along with biochar produced from pyrolyzed recycled wood. “It’s a story of soil to soil,” said Mike Callicrate. “There’s not a more complete story out there.”

Callicrate sells bone char primarily to gardeners. Since it’s a fairly expensive product, he says the product is best used on higher value crops.

Bagley believes dried bones are a locally available wasted resource and potential moneymaker for a lot of farmers, especially livestock producers. “Some clients are importing their bone char from Brazil or Sweden when they could be making it on their own,” he said.

making bone char
Teegan Callicrate checks the first batch of bone char at Callicrate Cattle Company.

During the Industrial Age, entrepreneurs created their own enterprise, collecting dead carcasses and harvesting bones for the booming sugar refinery business. Bagley has been building a bone char sideline himself for nearly four years now and believes there is potential for building a co-op model around it.

“It could be similar to a dairy farm cooperative,” said Bagley. “What if there was a similar cooperative where farmers share the equipment and a brand?”

Since a lot of deer bones make their way into landfills during hunting season, a deer hunter might consider a way to harvest and burn them. There are lots of opportunities, and Bagley hopes to conduct future workshops on bone char so other farmers can learn about the benefits.

Bone Black: A Scientific Perspective

Like Bagley, bone char has been somewhat of a fascination for Johannes Lehmann, professor of soil sciences at Cornell University and a fellow for the university’s Atkinson Center for a Sustainable Future. Lehmann studies soil organic matter and nutrients in managed and natural ecosystems. Part of his work involves the study of soil degradation and sustainable agriculture in the tropics.

Over the next few years, Lehmann and his team plan to expand collaborative studies with Jimma and Injibara Universities in Ethiopia to test batches of bone char for pilot studies. His team has been working with experts at government blending facilities to experiment with sample trials and formulations. These experiments are not yet being done on a large-scale here in the United States, but hold promise for countries like Ethiopia.

Because it is a land-locked country, Ethiopia has to import all of the phosphorus being used for agriculture. High prices and a reduction in supply means there is not enough fertilizer available to satisfy demand. Meat consumption is part of the culture in Ethiopia, so bones are plentiful and high in calcium and phosphorus. “It’s a country with many pastoralist communities, so we see the greatest opportunity,” said Lehmann.

Researchers also see an opportunity to study biochar, using sewage sludge, food and animal waste. Cornell recently invested in a new pyrolysis kiln — the largest of its kind — at a university in the United States. The kiln has the ability to transform more than 100 pounds of waste in an hour. During an open house in late spring, scientists spoke about the potential for studying energy production from gases and making new biomaterials.

industrial bone char machine

Researchers will study new ways to market pyrolysis technology and convert “trash” into treasure for businesses, farmers and municipalities. “It also means working with poultry farmers and dairy manure and transforming that waste into fertilizer,” said Lehmann. “We’re also looking at sewage sludge here in the U.S. and in developing countries. As an example, we’re finding new value for wastes from separating toilets in the slums of Nairobi.”

Lehmann spoke about how ground-up bones can be used for feed, which essentially creates another unique product stream. He shares the same outlook as Bagley, reiterating the soil fertility qualities of bone char that have been touted since the early 1800s.

“Once they discovered how ground bones in the soil really helps, it was being advertised for all husbands and wives ‘who want to succeed in life’ and have a great garden,” said Lehmann.

Source of Phosphorus

Phosphorus is an essential plant nutrient and because of the global demand, it faces depletion as a finite resource. Lehmann said the situation is so dire that conflicts over phosphorus may occur between countries that are desperate for it.

“It’s something you dig out of the ground, therefore it’s finite,” said Lehmann. “Similar to oil, it’s never clear where it is and how much is there. We don’t know when it will run out. No one knows. I have talked with people who want to use bone meal for their poultry mix, but they have a hard time finding it. It’s not easy to get to.”

According to Callicrate, bone char consists of about 37 percent phosphorus and 33 percent calcium.

Researchers from the Massachusetts Institute of Technology (MIT) address the decline in phosphorous production on its Mission 2016 website. They estimate that the world’s phosphate production will peak before the year 2040, then enter a long, slow decline. The world’s consumption levels will continue to increase, however, and create a gap between supply and demand.

Lehmann believes that bone char and other organic products can help mitigate the loss of phosphorus through the years. However, it has become somewhat of a moving target because phosphorous is not distributed like oil. Although Morocco, the western Sahara, Iraq and Algeria hold most of the world’s reserves, many developing countries have little chance of gaining market share.

An overabundance of phosphorus can also lead to issues. As Lehmann explains, phosphorus found in lakes can cause eutrophication, spurring excessive growth of plants and toxic algae because of too many minerals and nutrients.

“There are lots of reasons why we should re-think our broken nutrient cycle,” he said. “We are generating excess nutrients along the food chain and have a hard time feeding it back through the supply chain. We consider this a disposal issue.”

When asked about further experimentation and perhaps the disposal of human bones, Lehmann provides historical reference. Consider all of the horse and human bones left behind after 4 or 5 million people died during the Napoleonic Wars in the early 1800s. Historians claim that companies were hired to collect the bones months after battle to burn them or grind them up for fertilizer.

This poses a new moral and ethical question. Would we ever consider using human bones in the production of bone char?

According to Lehmann, “That is a bridge I am not ready to cross.”

Watch a video about bone char featuring Mike Callicrate. For more information about Callicrate Cattle Co., call 785-332-3344. Mike Callicrate presented “Building a Healthy, Humane and Fair Food System” at the 2018 Acres U.S.A. Eco-Ag Conference & Trade Show in Louisville, Kentucky.

Editor’s Note: This article appeared in the October 2018 issue of Acres U.S.A. magazine.