All about biochar

New processing equipment is making biochar a more viable solution for C&D recyclers looking to process wood.

Jessica Suarez | iStockPhoto

Recyclers of construction & demolition (C&D) material have increasingly struggled to find markets for wood. The good news, according to U.S. Biochar Initiative Director Tom Miles, is that the emergence of biochar for various applications has made recycling this feedstock more viable in some parts of the U.S.

What is biochar?

Biochars are classified by the International Biochar Initiative as being fine-grained, highly porous charcoals that help soils retain nutrients and water. While biochars are made in different forms and qualities depending on their end use, most find their way into agricultural applications through products such as compost, fertilizer and soil amendments that are used to improve the consistency and health of farmland. Specifically, the use of biochars in soils has been linked to stronger root structure, improved seed establishment, greater nutrient uptake and reduced watering requirements.

Beyond soil applications, biochars have also been used in environmental remediation for purposes such as sewage and water treatment and oilfield and land remediation. They have also been used as a non-soil carbon product in building products, animal feed and other applications.

Although biochar production isn’t new, Miles says that recent equipment developments have lessened the barrier to entry for would-be producers.

Producing biochar

akepong | Adobe Stock

To date, Miles estimates roughly 135 producers of biochar exist across the country, with 54 residing in the Pacific West, 17 in the Plains, 14 in the Southeast, 19 in the Midwest, 20 in the Northeast, and several others not designating a region, according to a recent U.S. Biochar Initiative study.

Biochar can be produced through various means. Miles says recyclers can choose to sell wood to biomass plants where industrial boilers convert wood to biochar. It can also be created via pyrolysis or gasification by burning wood with restricted airflows, or it can be produced by combustion via contractor-capacity equipment.

Miles says this contractor-capacity equipment capable of processing 8 to 15 tons per hour of material is relatively new to market. Until about a year ago, only transportable equipment that operated in stationary mode could process these volumes. However, new mobile systems that come equipped with tracks or wheels are coming online to make it easier for recyclers to process wood on-site thanks to the added mobility.

“We haven't had any systems available to make biochar at commercial rates until the last year or so,” he says. “Now, there are two mobile units that are available. Air Burners Inc. [of Palm City, Florida,] has been making transportable units using their air curtain principle since the 1990s and is now developing mobile models in collaboration with the U.S. Forest Service. ROI [Ragnar Original Innovation of Chester, New Hampshire,] recently launched a mobile carbonizer, which is now used by several recycling contractors. Those units will basically burn the material, but what you're doing is removing charcoal faster than you're consuming it. Normally, you would burn up all the charcoal and just wind up with ash, but instead of doing that, you're removing charcoal from the system before it can be completely burned, and you’re doing this on a continuous basis.”

The result is commercial-grade biochar that can be converted for various uses.

Biochar bin at Aries Clean Energy’s gasification plant in Lebanon, Tennessee.

Interest for recyclers

Miles says the production of biochar is opening up new doors for the C&D recycling community, as it provides solutions for dealing with clean wood. Biochar can be produced both by stationary carbonizers or mobile machines. Presently, Miles says many equipment vendors manufacture equipment for producing biochar, but only about a half-dozen suppliers make machines for industrial production.

“There's a lot of wood that is clean waste, [which] I'll call a fuel-quality waste, that recyclers have been traditionally supplying to biomass plants,” Miles says. “It’s a combination of both construction material and urban wood. But recyclers are having a hard time finding a place for that, or it's getting too expensive to send to landfills. That material is clean enough to convert to biochar, so you can achieve volume reduction and make a product that is worth in the order of $80 to $100 a cubic yard.

“So, the interest to a recycler would be both that they’re able to achieve volume reduction ... [and] recover a product of value. Part of the value of biochar that recyclers have told me they're interested in is that mobile units can process these materials anywhere. So, if they could use these mobile units and they can make a biochar product on-site, they wouldn't have to have the trucks to haul the wood away, and they wouldn’t have to pay to dispose of it. So, it allows for a reduction in total costs and a more efficient use of their trucks.”

Miles says because biochar is manufactured through a burning process, local regulations in various states may prohibit the use of portable machines. In other areas, the use of mobile units is welcome, as it helps negate open-burn activity. Miles says understanding regulations in one’s region can help recyclers decide whether producing biochar is a viable endeavor.

“Permitting can be an issue in general with biochar,” he says. “The federal regulation is that burning waste in an enclosed device is constituted as incineration, and an incinerator is difficult to permit, right? But local permitting agencies have still found ways of permitting these devices depending on where you go. This is true in California, Texas and Florida—all over the country. Air permitting is not something recyclers generally spend too much time thinking about, but permits are required if you’re going to produce these materials.”

The world’s largest downdraft gasifier was commissioned in October 2016 at Aries Clean Energy’s Lebanon, Tennessee, facility. The facility uses wood and sludge to create biochar.

Coming to market

The prospect of being able to create new markets from materials not typically in high demand sounds ideal, but what will it take for more recyclers to begin buying in to the idea of producing biochar?

Miles says that like anything else, barriers to entry exist in the form of time and financial investments when trying to develop biochar markets. However, for those willing to put in the effort and resources required to understand the market and make inroads in building a customer base, opportunities can abound.

“A lot of [why recyclers have hesitated to produce biochar] is it essentially requires starting a new business. It requires creating a new product, understanding who the customers are, what the product characteristics need to be, what the distribution system is. It takes three to five years to start a business,” he says. “And if you're going to get into making biochar, either you’re going to have a relationship with somebody who is already using biochar and takes in the product and gives you enough money wholesale to make it worth your while, or you have to have somebody in your staff that becomes an expert on biochar production and marketing so you can create those markets you didn’t have connections with previously.”

Miles notes that some existing products used for similar applications present another hurdle in selling biochar, but he says being able to compete is simply a matter of education and awareness regarding biochar’s benefits. Biochars are natural, renewable, low-carbon materials that can be used in place of non-renewable peat or minerals like vermiculite, which are mined abroad and processed with fossil fuels. A small addition of biochar can enhance the effectiveness of fertilizers, which can reduce the amount of fossil fuel-derived fertilizers in the market. Biochars can also help replace expensive filtration systems because they have the capacity to absorb common pollutants, such as zinc or cadmium from galvanized roofs or copper from brake linings, that leach into storm drains. When added to filters, biochars can help capture pollutants while providing growing media for green infrastructure solutions, like structured swales or bioswales. Because biochars are versatile, they can be delivered in granular or liquid forms for crops and golf course applications. They can even be used as fillers to displace plastics in carbon reinforced products. In some cases, biochars can also replace costly imported activated carbon that is typically used for methane and hydrogen storage for a number of industrial applications

Miles says researchers are currently working to find new uses for these charcoals. He notes that while studies are ongoing, researchers are looking into whether biochar and gypsum fines combined may be used for odor control and in agricultural uses. Additionally, researchers in the U.S. are looking into possible benefits of including biochar in feed to improve animal health. While this is an emerging practice in Europe, where biochar concentrates in the 1-2 percent range are added to livestock feed to reduce vet and medical costs, it has yet to be approved in the U.S. for animal feed applications.

Beyond feed, biochar has been shown to be effective in animal bedding for odor control applications and has even begun to be used for cleaning up runoff from other contaminated sites, such as abandoned mines, thanks to its ability to sequester contaminants.

Time will tell what other potential uses biochar may have. But for the time being, the prospect of being able to turn a wasted product into resources is a promising development that may open up a world of new opportunities for those recyclers willing to invest the time and effort to produce these products.

The author is the editor for Construction & Demolition Recycling magazine and can be contacted at

November December 2019
Explore the November December 2019 Issue

Check out more from this issue and find you next story to read.

Share This Content