Biochar and other properties resulting from the gasification and combustion of biomass with different components

Gasification is a process in which fuel such as wood is burned at high temperatures with a small amount of air. It results in three main byproducts: syngas, heat, and char. The syngas, which is primarily composed of hydrogen and carbon monoxide, can be inserted into a boiler to produce energy, while the char can be used to enhance soil fertility. The goal of this thesis is to understand how better syngas and biochar quality can be produced and how the gasification process influences its production. This thesis explores the characteristics of biochar from a downdraft gasifier at the University of Iowa from corn, soybeans, wood pellets, and refuse derived fuel (RDF). Several tests were carried out on the different resulting biochars. The analysis included analyzing their carbon, hydrogen and moisture contents and studying their surface areas. Through SEM X-ray analysis, minerals such as potassium, chlorine, and iron were located and examined. It was found that wood biochar was the most porous char with a high amount of carbon content, while RDF char had the lowest porosity with the lowest carbon content. Some studies have shown that more porous char may hold more nutrients in the soil. Three of the four biochar’s, excluding RDF, also showed significant phosphorus and potassium content which is known be found in fertilizers. The RDF biochar showed a high concentration of aluminum. This thesis also explores in detail where these minerals are located on the char surface and their relationship with porosity. The syngas content from different biomass components was also tested. Biomass, such as wood or paper, is known to be made up of three major components: hemicellulose, cellulose, and lignin. It was found that, in agreement with previous studies, biomass with a high amount of cellulose led to high amounts of CO production, while fuel with high lignin content led to high amounts of hydrogen production. Finally, this thesis also explores the syngas, char, and tar content from burning miscanthus briquettes in a downdraft gasifier with two air inlets. The optimum condition at which miscanthus briquettes can be burned was found to be 20.29% CO and 18.68% H₂, which yielded the maximum syngas heating value content of 5.5 MJ/Nm³.