Submitted to: Journal of the Science of Food and Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/27/2011
Publication Date: 1/5/2012
Citation: Cantrell, K.B., Martin, J.H. 2012. Stochastic state-space temperature regulation of biochar production Part I: Theoretical development. Journal of the Science of Food and Agriculture. 92:481-489. Interpretive Summary: Future biochar production systems will need to consistently generate high quality biochars targeted for a specific soil improvement use. In order to do this, the biochar production system will need to take into account changes in processing temperatures as well as be able to handle a variety feedstock types like manures and other agricultural residues. A state-of-the-art control system was designed for a non-continuous, laboratory-scale biochar production unit. In this work, the methods and mathematical expressions are presented. This control system surpassed traditional control systems by controlling an indirect heat source and utilizing difficult to measure temperature-dependent process parameters. By measuring different variables describing the process response, this new control system was able to accurately match the biochar production to a defined temperature input schedule.
Technical Abstract: The concept of a designer biochar that targets the improvement of a specific soil property imposes the need for production processes to generate biochars with both high consistency and quality. These important production parameters can be affected by variations in process temperature that must be taken into account when controlling the pyrolysis of agricultural residues like manures and other feedstocks. A novel stochastic state-space temperature regulator was developed to accurately match biochar batch production to a defined temperature input schedule. This regulator surpassed traditional PID (proportional-integral-derivative) controls since the state-space regulator simultaneously controlled the indirect heat source and sample temperature by employing difficult to measure variables such as change in temperature (i.e., stability) in the description of the pyrolysis system’s state-space.