Centuries ago, Amazonian farmers created some of the world’s most fertile farmland by converting biomass to charcoal in their fields. Much of the carbon they buried hundreds of years ago remains sequestered there today. Today, researchers seek to use a similar method to create a “carbon-negative” energy source with the potential to make a huge difference in the fight against global warming.
The most promising approach utilizes a process called pyrolysis, in which biomass from forests, agricultural waste, or animal waste is heated at 350-450 degrees C in an oxygen depleted chamber. This produces three outputs: syngas, a liquid fuel called bio-oil, and biochar (a charcoal-like solid). Most frequently, biochar has been viewed as a mere byproduct of the creation of bio-oil, which can be utilized in a variety of industrial applications and has been successfully converted into both diesel fuel and petroleum. Syngas, another byproduct of bio-oil production, is generally burned to provide heat for the process.
New research, however, is showing biochar to have practical applications of its own. Not only is it excellent at sequestering carbon, but it has also been found to improve soil quality when used as a soil amendment. Biochar reduces soil pH, increases water retention, and makes it easier for plants to take up nutrients from the soil (by increasing cation exchange), which significantly increases crop yields. In addition, a study by Johannes Lehmann of Cornell University has shown that biochar can reduce nitrous oxide emissions by 50% and methane emissions by nearly 100% on affected cropland. Lehmann believes that biochar, along with associated biofuel programs, has the potential to sequester up to 9.5 billion tons of carbon a year—more than the sum of all global carbon emissions from fossil fuels today.
While little doubt exists about the potential of pyrolysis for providing a renewable energy source or about biochar’s ability to effectively sequester carbon, research into its effects on soil is still at an early stage. According to an analysis by Almuth Ernsting and Deepak Rughani, there is some uncertainty over how effective biochar is at improving cation retention capacity in the short run, and there have been few studies testing its effectiveness outside of the laboratory. Pyrolysis may also release dangerous carcinogens (including very small amounts of benzo(a)pyrine) with clear implications for public health, although early work indicates that these chemicals are not produced in large enough quantities to be hazardous. More work is also needed to determine the mixture of biochar and fertilizer that will best improve crop yield (biochar requires some fertilizer present before it is effective). And there is little current knowledge on how to produce and distribute the material on a global scale. Still, biochar has already garnered enough support that a consortium of African governments has pushed for the inclusion of biochar in the December UNFCCC talks in Copenhagen.
Private companies have begun to demonstrate interest in the field, and are examining ways to make the process cost-competitive. The largest barrier to producing biochar and bio-oil cost-effectively has always been the high price of transporting biomass, which is bulky and not very energy-dense, to a central production facility. To overcome this, many are considering creating a network of small-scale, local pyrolysis plants where biochar and bio-oil could be produced. Companies could then transport the concentrated bio-oil to a central refinery, and the biochar could be applied to the soils closer to where the biomass was collected. This approach would not only help overcome the challenging logistics of a large-scale operation, but could provide a simple, practical biochar production model adaptable for use in local communities and developing nations. UOP, an arm of industry giant Honeywell International, Inc, is one company getting involved in creating such a locally-based distributed production model, although with more of a focus on liquid fuels than biochar. The company announced in fall 2008 a letter of intent with Ensyn Corp to form a joint venture to research and produce biofuels from pyrolysis. According to UOP Director of Renewable Energy and Chemicals Jennifer Holmgren, the partnership expects to be producing commercially viable products within three years.
Private investment is also helping to rapidly close the gaps in scientific knowledge. In a just-released study, industry leaders Dynomotive Energy Systems Corp. and BlueLeaf Inc. found that application of their biochar could improve crop yields by up to 17%. The study, which can be found on the Dynamotive website, also provides evidence that biochar reduces nutrient depletion in soil, increases the number of plants per area, and increases plant root length.
Dynomotive is currently in talks with the El Dorado Chamber of Commerce in Arkansas to construct a new, $40 million plant designed to produce both bio-oil and biochar. After putting the bio-oil through a two-stage refining process, the company believes it can produce ethanol-equivalent fuel at a cost of under $2 per gallon. The company has already signed a contract with Springhill Land and Timber for the delivery of 220,000 tons per year of sawdust, and expects to start production by 2011.
The implications of bio-oil and biochar range from improving energy security to dramatically reducing and storing billions of tons of harmful carbon emissions. While current production incentives are small, a campaign is underway to give it recognition as a viable carbon offset in trading schemes. “Reducing emissions isn’t enough,” said chairman of the Copenhagen Climate Council Tim Flannery in a recent Time article, “we have to draw down the carbon stock in the atmosphere. And for that, slow pyrolysis biochar is a superior solution to anything else that’s been proposed.”