Beyond the Hype
Market development has been inching along for years, but with no price on carbon there are no incentives for regions with decent-quality soil to use biochar as a soil amendment or for carbon sequestration. In addition, the capital costs of building production facilities are high and often unattainable.
However, new research is confirming biochar's climate mitigation potential and discovering additional applications. A recently published research paper authored by some of the world's leading soil scientists shows that biochar has the potential to mitigate up to one-tenth of current greenhouse gas (GHG) emissions. The study takes into account the utilization of biomass resources untapped today and does not propose converting any additional acreage into cropland.
Study co-author James Amonette says he hopes the paper, "Sustainable Biochar to Mitigate Global Climate Change," will influence members of the scientific community and policy makers to accept biochar as a valid climate change mitigation technique. He doesn't view biochar is the final or only solution, but believes it is one of several key players.
Building a Solid Case
Amonette, a soil scientist at the U.S. DOE's Pacific Northwest National Laboratory, says for the past several years he has wanted to produce a solid biochar study and finally got started in 2009 after discussions with study co-author Dominic Woolf of Swansea University in Wales. "We are extremely concerned about climate change and ways to mitigate it, and independently arrived at the conclusion that nobody has done a real thorough study on biochar," he says.
Amonette and fellow researchers calculated that when taking into consideration all biomass resources presently available, biochar has the potential to sequester 1 to 2 gigatons of carbon per year. "We really need about 15 gigatons per year carbon equivalent, so it's not the panacea," he says. "At the same time, it's a significant player, and the goal of this paper is to make a solid case for biochar that the scientific community can understand and accept because a lot of people are really turned off by the hype."
The most difficult component of the study, according to Amonette, was determining the availability of a sustainable supply of biomass. "We relied heavily on some work done earlier," he says. "Basically, we had to sort out how much biomass is already being used for various purposes, how much is being left and how much we can take off the soil/land without causing soil erosion."
In rice paddies, Amonette says, it was relatively simple to determine soil impacts because the land is flat so there's no concern about erosion. "You can pretty much take all the residue from a rice paddy and convert it to biochar at some point," he says. "You may want to use the rice straw for animal bedding, but rice husks could be used at any time because there is no good use for them."
Wheat and corn are grown on land that slopes, and removing too much residue can cause major soil erosion problems. "You have to leave a certain amount on the surface or you'll be exacerbating that part of the problem," Amonette points out. "So we had to, depending on the crop, look at soil fertility classifications around the world-there are seven different classes of soil that we used-and a major component of that is how steep are the slopes and how rocky is the soil. We looked at those things to determine how much residue could be taken off."
Following their sustainable biomass assessment, the researchers compared the tradeoffs of using the available material as a soil additive such as biochar as opposed to using it to generate bioenergy. Initially, they found that, on average, biochar is 20 percent more effective than bioenergy at mitigating climate change, Amonette says. "We then did a second analysis that proved, depending on the fertility of the soil to which the biochar was applied and on the power source or type of fossil energy being offset, in some instances, bioenergy was a better climate mitigation option."
What is the better use for the biomass varies greatly from one scenario to the next. "Instead of competing though, they can work together," Amonette says. "Bioenergy is still a very good way to go, but it's not going to solve the problem by itself. It has the same limitations that biochar does."
Carbon Prices and Soil
From Amonette's perspective, the bioenergy route will continue to be chosen over climate mitigation because there is still no value for carbon. "Looking at the Midwest, it has fertile soils but uses a lot of coal, so that would be where you want to produce bioenergy," he says. "Biochar doesn't make sense there, because if you add it to the soil you won't get a response. In the Southeast or the tropics where you've got these poor soils, it's a whole different matter and biochar makes a lot of sense."
Biochar probably won't be used for climate mitigation until it becomes economical to do so, Amonette says. "That's when carbon storage becomes valuable," he adds.
Johannes Lehmann, associate professor of soil fertility management and soil biogeochemistry at Cornell University, echoes Amonette's views on carbon pricing prompting the use of biochar to combat climate change. "We don't really know what the value of biochar is right now," he says. "We're just beginning to be able to put together accurate data on that-carbon prices that would make this economically feasible."
Lehmann, who contributed to Amonette's research paper, says that production efforts are currently focused on producing bioenergy from pyrolysis where biochar is simply a byproduct, but most have not yet been successful. This situation is common in bioenergy production, he says. "For example, methane generation is fairly successful in Europe, especially in Germany, where you have guaranteed feed-in rates. In the U.S. it's not very successful. Situations like that may change as energy prices change, and maybe there will be a carbon price at some point and then everything will change. At the moment, however, it seems in many countries, including the U.S., making ends meet by just producing bioenergy is difficult."
As far as using biochar as a soil improver, Lehmann says that depends on the location and the crop being produced, which is no different than when considering the use of nitrogen fertilizer. "You put different amounts of it on different crops, in different soils and at different times of the year," he says. "You really can't say what the value of nitrogen is across the world, and you can't say what the value of biochar is across the world. Biochar has shown tremendous yield increases in some situations with some crops and soils, but for others the soils are good enough and the biochar doesn't improve it."
At the moment, the perception is that biochar can miraculously enhance soil quality and magically improve crop growth, but that is not always the case, Lehmann says. "It is more effective than compost," he says. "It has a greater surface area, has a greater ability to hold onto nutrients to make them available to the plants, and it is also one to two magnitudes more stable than compost."
Those characteristics alone make it more attractive than compost, he adds, if the objective is to improve the soil and enhance its nutrient holding capacity. "You need to know what you're managing your soils for."
That is the purpose of a research project conducted by the USDA-Agricultural Research Service in Prosser, Wash.,-to further enhance the value of biochar by sequestering nutrients from dairy manure lagoons. Hal Collins, soil scientist/microbiologist and project leader, says the concept was successfully proved, but the one hurdle he has encountered is finding someone to provide a system to produce mass amounts of biochar.
Adding More Value
Using waste material from a nearby dairy with an anaerobic digester, Collins and his team were originally taking the liquid waste material from lagoons and applying it to soils as a nutrient source, as well as applying the fiber material as compost. The problem with using the liquid dairy manure is mainly the cost of transporting it to the field. "It's such a huge cost to move liquid from one location to the other, so if you can concentrate nutrients much like the fertilizer industry does, you're moving much less bulk," Collins says.
In the past, Collins has worked on applying biochar to soils, and discovered its cost to be high as well. "Entrepreneurs want about $200 per ton of biochar, and our studies don't show much of an improvement in soil until about 10 tons of biochar is applied on an acre, so that's about $2,000 an acre," Collins says. "Our thought was we have this source of material, and also a problem with the high amount of nutrients in a small location like a dairy. We could take this material, pelletize it, pyrolyze it and obtain energy from that, and then put the biochar back into the lagoon with a filtering system in order to sequester the nutrients."
About 40 grams of biochar per liter of effluent was added to the 378-liter test lagoon and was then left for 15 days. Test results demonstrated the removal of 68 percent of the phosphorous and 14 percent of the nitrogen from the effluent. Mineralization experiments showed that 85 pounds of phosphorous per acre would be available to crops after the addition of 5 tons of enriched biochar per acre.
According to Collins, dairies in Washington could produce 230,000 tons of nutrient-enriched biochar a year from manure, reducing leaching and runoff. He envisions the entire process occurring at a dairy or hog farm, where they would also be able to generate their own power via the pyrolysis process.
So what's next? Collins is still trying to find a pyrolysis unit that is able to make enough material to allow widespread field application. "We have had no luck," he says. "There are a lot of promises to build these units, but I haven't seen any. I don't fault them for not getting up and running, though, as it is all about money and the investors just aren't there."
Collins says he built his own pyrolysis unit to make biochar, but what he really wants to do test is the quality of the biochar that the future industry will produce, rather than biochar produced under highly controlled conditions. "I understand there should be some companies in Oregon bringing units on line fairly soon, some of whom I've been speaking with," he says. One of those belongs to Halfway, Ore.-based Biochar Products Inc., which is working with Advanced Biorefinery Inc. in Canada to bring a mobile, 1-ton per day fast pyrolysis unit on line. Owner Eric Twombly says the machine has already been demonstrated in the forest, and after fixing a few engineering problems, a multi-stop demo trip in California is planned for next spring.
Twombly says a lot of people have claimed that they are able to build a biochar plant, but few have-partially because of a lack of capital, but also because many systems just aren't viable. "As much noise as there is about it, the problem is that it isn't as simple as it seems," he says. "It's easy to take a couple barrels with wood in it and make biochar out of it. Almost all slow pyrolysis systems require a batch process. When that batch process gets bigger, it needs a longer residence time. Once you scale it up, you can't produce very much, and that's the real limit."
Although researchers are currently willing to pay $1,000 to $2,000 per ton for biochar, in the long term it will probably be worth about $100 per ton, Twombly says. "If you're making 2 or 3 tons a day, that doesn't pay the bills, especially for biochar-only machines that don't belong to a farmer or those that aren't integrated with some other project where there's a need to get rid of waste."
While the price of carbon, the absolute impact of using biochar as a climate mitigation tool, and the production, transportation and storage economics of biochar remain uncertain, Lehmann says there will be tradeoffs that will even out. "When applying it to soil, even if only 1 teragram (1 million metric tons) or 50 teragrams of carbon is offset globally with biochar, we will have improved soil quality and happy farmers," he says. "It still withdraws some carbon from the atmosphere, and that is a good way to go because it is a no lose."
Twenty-five years from now, the idea of what is sustainable may change, Amonette adds. "The global crisis may have deepened, and we could be looking at total disaster verses a small disaster, in which case there may have to be some tradeoffs that people make."
Anna Austin is a Biomass Magazine associate editor. Reach her email@example.com or (701) 738-4968.