Combined Heat and Biochar
Combined Heat and Biochar Friday, April 10, 2020
Author(s): Heather Nobert
Combined heat and biochar (CHAB) technologies are systems that optimize the combustion of wood residues. The process of combusting biomass for biochar produces not only a high carbon solid product but also thermal energy that can be used for heating and cooling.
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Production of Heat and Biochar
Biochar produced from combined heat and biochar technologies is processed under known production parameters. Temperature, residence time, and oxygen affect the final biochar product and its uses. The biochar produced in an assessment of six different units ranged from 24 – 400 dry pounds per hour. Monthly, that equates to 86 – 1500 cubic yards of biochar requiring an input of 450 – 5400 cubic yards of wood chips each month.
The heat produced by CHAB technology is substantial. The smaller units produce about 1 million British thermal units (MMBtu) each hour while the larger units can generate up to 8.5 MMBtu/hr. This heat production is significant considering the average home requires just 90MMBtu of heat annually.
Where is CHAB Most Appropriate?
Current markets for biochar are limited, but growing, especially in the Midwest. Given current markets for biochar, a combined heat and biochar production unit is most logically incorporated into operations that could benefit from both the heat and biochar. Some operations that are most suitable for biochar are:
- Compost operations
- Lumber drying kilns
- Other operations that require process heat or product drying
In addition to the CHAB unit itself, other equipment and infrastructure will be needed to handle the material and process the feedstock. Due to the seasonal nature of wood chip supply, you will need to consider how the wood chips can be stored and stockpiled for later use. Additionally, infrastructure for drying, resizing, and conveying the feedstock to the CHAB equipment will need to be purchased. This infrastructure will make up a large portion of the costs and site footprint for the overall CHAB system.
Most CHAB systems operate best with wood chips. However, many systems are capable of handling other feedstock including manure, wood pellets, sawdust, municipal solid waste, and agricultural residues.
Emissions & Regulations
Non-industrial wood energy systems, when fueled by clean wood chips, rarely require pollution controls beyond appropriate technologies to remove particulate matter from the gasses. In Nebraska, the Department of Environmental Quality regulates air quality and monitors emissions by issuing air quality operating permits.
Pricing for combined heat and biochar systems varies widely. Smaller units on the lower end of the price spectrum start around $150,000. Large systems that are designed with a specific and large purpose can cost up to $2 million. However, most systems are about $500,000 and under.