Biochar/Brick Co-production System

The idea is to couple the production of biochar with the production of fired bricks, analogous to the Biochar/Lime Co-Production System. The pyrolysis gas generated during biochar production is not flared off but used to fire the clay bricks. The process is thus carbon-negative. This type of production needs relatively close ('round the clock) monitoring but there is potential for automation. Heat is another co-product that could be used for space heating, greenhouses, steam, even electricity, etc.

• see: (Chinese) Vertical Shaft Brick Kiln (VSBK)

Development Proposal

• proposal: carbon-negative VSBK fired with pyrolysis gas, with biochar as a co-product
• The typical VSBK is coal-fired, mostly using low-quality coal fines: pieces of coal are scattered onto the bricks from the top. The brick kiln could be re-designed as part of a pyrolysis system to run on pyrolysis gas.
• This type of gas-fired kiln would have cleaner emissions than the coal-fired one (less soot, heavy metals, organic pollutants, etc.). The off-gas could potentially be used for CO2 enrichment in a greenhouse or garden/field. This may require a biofilter step first.
• Co-products in addition to bricks: biochar, heat (can be turned into steam), CO2-rich gas for greenhouses.

Technical challenges

Some reports suggest that high-quality biochar requires low reaction pressures, to allow all volatiles to evaporate and leave only the char behind. The simplest way to achieve this is the "open burn" approach as demonstrated by the Kon-Tiki Kiln. In contrast, if the the pyrolysis gas is captured, then this may result in higher pressures inside the pyrolysis zone, reducing the evaporation of volatiles. Potential solutions are: 1.) build higher smokestack to increase draft, 2.) an "artificial" draft system using electrical fans that pull out the exhaust, or 3.) blow CO2-rich exhaust gases into the pyrolysis zone.