The above unit can be used for a variety of feedstocks, it has a pre-dryer, incorporates the ability to closely control process parameters of temperature and residence time. It will a) produce biochar from nearly any feedstock b) condense wood vinegar from the raw syngas stream, c) crack and filter the raw syngas remaining after the condensation step to produce a clean mixture of hydrogen and carbon monoxide, known as syngas, and d) optionally burn the syngas to generate electricity. Syngas can also be used as a replacement for natural gas or propane for heating purposes.
The challenge we are attempting to address with this system is to maximize the potential for profitability, in particular by monetizing the gas stream in the most economical way possible. In this regard, we have developed a very inexpensive catalyst to crack the syngas for this device. We estimate that the revenue from the combined products of biochar, wood vinegar and electricity should recoup the investment cost for this unit within approximately 4 - 6 months of operation.
This biochar kiln is manufactured in a modular fashion, in 3 main sections, and its throughput capacity can be easily increased by adding units to the mid-section to make it longer. Its functional capacity can be enhanced by adding sections to fractionate the condensate yield, producing essential oils or chemicals like terpenes for instance. A section can also be added to the end to convert the char to activated char. The feedstock stream required for the lowest capacity unit would be about 16 tonnes of wood chip (@ 20% moisture content) per day. The unit is intended to run 24/7. Once started, this kiln is self-sufficient in terms of energy. Startup is accomplished with either natural or bottled gas.
The lowest capacity plant will produce, per day, about 4 tonnes of biochar, 2500 liters of wood vinegar, and (optionally) 8400 kWh of electricity. We conservatively estimate revenue per day to be $150 x 4 for the biochar, $1 x 2500 for the wood vinegar, and $ 0.05 x 8400 for the electricity, 600 + 2500 + 420 = $3520 per day. Note that the rate paid for electricity is often at least double the above estimate. The kiln will cost approximately $400,000, and the optional motor genset designed to run on cracked syngas will cost approximately $450,000 - $550,000.
Heat energy to dry and pyrolyse the feedstock is provided by flaring a portion of the syngas produced and/or recycling waste heat from the reactor and genset. The unit requires a relatively small amount of electricity to run the blowers, feed mechanisms and control electronics. Hence once it reaches operating conditions, it is entirely self-sufficient in terms of energy.