Founding member of ARTi and CEO, Dr. Bernardo del Campo together with Professors Thomas Brumm, and Nir Keren from the Department of Agricultural and Biosystems Engineering at Iowa State University published the study Fast Pyrolysis Biochar Flammability Behaviour for Handling and Storage
Biochar is becoming a popular product in agriculture, gardening, and other soil-related activities. It is made from biomass residues and is put into the ground to improve soils, reduce runoff, and sequester carbon. However, there has been a lack of information on its flammability which would have a substantial impact on how biochar can be handled. Given that flammability may vary substantially depending on how and from what biochar is created, it can have a variety of qualities. Founding member of ARTi and CEO, Dr. Bernardo del Campo together with Professors Thomas Brumm, and Nir Keren from the Department of Agricultural and Biosystems Engineering at Iowa State University published the study Fast Pyrolysis Biochar Flammability Behaviour for Handling and Storage in the journal ACI Avances en Ciencias e Ingenierías (ACI Advances in Science and Engineering). ACI is published by the University of San Francisco de Quito, Ecuador (Link)
The work here is important not just for ARTi but for the entire biochar industry. Biochar is a product where scale really matters. The more the better. This means more sequestered carbon, larger tracts of improved soils, and greatly reduced levels of unwanted biomass residues. However, biochar is produced at very high temperatures and this always means safety precautions must be taken.
Safety aspects of biochar related to transportation, storage, disposal or field applications have to be understood as best as possible. The goal of the research conducted by Dr. del Campo and colleagues was to examine the flammability characteristics of fast pyrolysis biochar. Pyrolysis is how biochar is made. ARTi builds and designs world-class pyrolysis reactors. We welcome you to see the article on Dr. del Campo’s pyrolysis patent design at this (Link). Pyrolysis is the heating of organic material like biomass in a very low-oxygen environment. Because there is low oxygen, the material does not just burn. Instead, it thermally decomposes into combustible gasses and biochar. Pyrolysis is a high-temperature process operating at about 500 degrees Celsius or higher. When you are handling, storing, or transporting a material made at such high temperatures and in large volumes then it is a must to understand the flammability traits and risks involved. Plus, there are regulations to deal with as well.
The test methods used were EPA 1030 and ASTM D4982. EPA 1030: Ignitability of Solids is from the US Environmental Protection Agency and it “outlines method suitable for the determination of the ignitability of solids and is appropriate for pastes, granular materials, solids that can be cut into strips, and powdery substances” (Link) ASTM, one of the world’s largest international standards developing organizations created D4982 which is Standard Test Methods for Flammability Potential Screening Analysis of Waste (Link). These test methods provide a consistent and reliable way to evaluate the flammability of biochar.
Findings of the Study
According to the results of the EPA 1030 Ignitability of Solids test, biochar is not flammable. But when put to the test using the quick screening method ASTM D4982, biochars revealed potential flammability issues. Nevertheless, any flammability concerns were lessened by the addition of 20–50% moisture.
Pyrolysis gets the biomass hot but it’s not burning.
Compared to the slow pyrolysis biochar and conventional charcoal examined in this study, fast pyrolysis biochar was more flammable. However, the flammability was less than what it would be with the same biomass feedstock having not been pyrolyzed. The tendency towards flammability when measured with the EPA 1030 correlated with higher oxygen content and biochar surface area. The underlying key finding of the study is that recurring tests on Fast Pyrolysis Biochar Flammability should be done as the material can vary widely due to the numerous methods of production and types of feedstock.
How the Study Was Considered and Conducted: Material Presence, Pyrolysis Method, and Feedstock Type
Carbon content is one aspect but some contaminants can be found mixed in with the feedstock like dirt or soil. Sand and re-condensed bio-oil vapors can be present from the process itself. All of these can affect flammability. Bio-oil that re-condenses in the biochar is more likely to ignite or create conditions that trigger ignition than biochar. Re-condensed bio-oil can possibly trigger oxidation reactions at lower temperatures. Foreign sand in the biochar sample resulted in high “ash” contents, which may influence flammability potential.
The presence of materials besides the key feedstock is the one set of factors that can determine flammability. The type of pyrolysis method is another and central to this study. Previous research comparing different thermochemical production methods showed fast pyrolysis as more likely to be flammable (Zhao, M., et al., 2014). The study conducted by Dr. del Campo and colleagues is meant to help address a lack of research on fast pyrolysis biochar flammability. The study was not definitive and more as well as recurring examinations are recommended.
The third and fourth sets of factors that can influence biochar flammability are feedstock and then reactor types. Under a variety of circumstances, a number of fast pyrolysis biochars were made from agricultural and forestry feedstock. Fast pyrolysis biochars were produced using a variety of reactors, biomass feedstocks, and processing variables, and they had a wide range of chemical compositions. The feedstock included red oak, corn stover, loblolly pine, and switchgrass. These are feedstock types with similar properties to those used for making fast pyrolysis biochars. You are invited to have a look at a previous blog article on the many materials ARTi has successfully pyrolyzed (Link). The three reactor types used in this study were auger, fluidized bed, and free fall reactors. The residence time for the fluidized bed was between 2 and 10 seconds, the free fall was under 5 seconds, and the auger reactor was between 20 and 60 seconds. The temperatures ranged from 400 to 600°C. As before, the test methods used were EPA 1030 and ASTM D4982.
The findings from this study were then evaluated with information on other carbonaceous materials produced using various reactor types, such as gasification, slow pyrolysis, and conventional charcoal, from industrial production facilities or other research institutes.
Oat hull-derived biochar
EPA 1030 addresses the Ignitability of Solids.
A preliminary EPA 1030 screening was performed to determine whether biochars fall within the category of Flammable Solids. Materials were ignited on a test strip. Distilled water was added at times to show the presence of moisture in some cases. To determine whether there was a relationship between flammability and chemical and physical features, the Pearson correlation coefficient, a measure of linear correlation between two sets of data, was used. Flammability is on one side and it varies. On the other side are the chemical and physical features which also vary. From this test method, it was seen that none of the materials were considered intrinsically flammable.
The ASTM D4982-95 is the Flammability Potential Screening Analysis of Wastes.
Through this test method, it is possible to not only gain information about the biochars’ flammability with a fast screening test but also to examine the effect of moisture on this trait. The test includes two tests. The first is exposure of the material to heat and flame and the second is to the source of a spark. It is important that the samples to be measured were not altered in any way. The analysis of the biochar’s chemical and physical properties was highly thorough and made use of Iowa State University’s extensive array of tools.
It was found that biochars, biomasses, and coal samples are flammable using this test, despite the fact that it is impossible to tell if the material is burned or not with decaying embers. The authors of the paper emphasize that their initial biomass had a far larger potential for flammability than the biochars that were produced from them, necessitating the extinguishment of the sample when the test was completed. No differences were seen in the flammability potential between the dried samples and the samples with their original moisture content.
When tested using ASTM D4982, the four biochars with the addition of 20–50% moisture by weight significantly reduced the risk for ignition. A quick and easy way to ensure safer transit and storage, as well as to further improve safety in processing or storage facilities, is to increase moisture content.
Outcomes and Review of the Study
Under the guidelines of the EPA 1030 screening fast pyrolysis biochars are not considered flammable materials. Under the ASTM D4982-95 methods, red oak, corn stover, loblolly pine, and switchgrass fast pyrolysis biochars might all be categorized as “flammable.” The operator must visually assess whether the material is lighted or not, which is shown by fading embers meaning that it is crucial to remember that this test may be subjective.
- The addition of moisture to the biochar to 20 to 50% w.b. completely suppressed the flammability potential when tested according to ASTM D4982.
- Dr. Bernardo del Campo et al. recommend recurring tests on fast pyrolysis biochar flammability due to the wide range of possible biomass feedstocks and production methods.