Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/16/2013
Publication Date: 2/1/2014
Publication URL: http://handle.nal.usda.gov/10113/58586
Citation: Peterson, S.C., Jackson, M.A. 2014. Simplifying pyrolysis: Using gasification to produce corn stover and wheat straw biochar for sorptive and horitcultural media. Industrial Crops and Products. 53(1):228-235.
Interpretive Summary: Biochar is a renewable, affordable resource that can be made from waste crop residues such as corn stover and wheat straw. Biochar is a very porous, charcoal-like material that has excellent adsorptive properties and therefore can be used in applications currently using activated carbon, like filtration media. Another useful application for which biochar could substitute is potting substrates, especially since peat moss, a current industry favorite, is environmentally unsound since its growth/replacement rate is extremely slow. To make biochar requires pyrolysis, which means you must heat biomass to high temperatures while simultaneously omitting oxygen. This is typically done using batch methods where the feedstock is sealed in some type of oven and the air is evacuated and replaced with nitrogen or some other inert gas, then heated so that pyrolysis takes place and biochar is formed. In this work, we start with corn stover and wheat straw feedstocks, and compare biochar produced by traditional pyrolysis methods vs gasification via a cookstove. In the gasification method, there are several significant processing advantages, such as 1) it can be run in normal air atmosphere and does not require any nitrogen or other inert gas; 2) it's an exothermic process for which the heat generated can be captured and used to offset production costs; and 3) its throughput is higher, because you can configure a continuous-feed setup as opposed to being limited to batch processing. In this work we produce and characterize biochars made from both methods, and illustrate how biochar made from gasification, although having lower carbon content and surface area, may still be advantageous from a production standpoint when considered for sorptive media and potting substrate applications.
Technical Abstract: Biochar is a renewable, useful material that can be utilized in many different applications. Biochar is commonly produced via pyrolysis methods using a retort-style oven with inert gas. Gasification is another method that can utilize pyrolysis to produce biochar, but with the advantage of not requiring inert gas; this method can be carried out in normal atmospheric conditions. Gasification is also more amenable to scale up and provides heat that can be used to generate power and/or help recoup processing costs. In this work three different feedstocks, corn stover, wheat straw, and wheat straw treated with glycerin were tested in two types of biochar production; one using an atmospherically-controlled retort oven for conventional pyrolysis, and the second using a gasification cookstove. The resulting biochar samples were characterized in terms of their physical and chemical properties. Gasification of glycerin-modified wheat straw shows good potential to produce useful biochar for sorptive and horticultural applications.