When biochar undergoes pyrolysis in a woodgas gasifier and the resulting syngas is utilized as fuel in a combustion engine, how are the carbon and organic carbon-based molecules transformed? Does this process release CO2 into the atmosphere? Let’s find out.

Yes, when biochar (or any biomass) undergoes pyrolysis in a gasifier, the process releases a mixture of gases commonly referred to as “woodgas” or “syngas”. This gas primarily consists of carbon monoxide (CO), hydrogen (H2), methane (CH4), and a small amount of carbon dioxide (CO2), among other components.

When the woodgas is subsequently used as fuel in a combustion engine, the carbon monoxide (CO) and methane (CH4) in the gas react with oxygen in the air to produce energy, and this process releases carbon dioxide (CO2) and water (H2O) as byproducts. Specifically:

So, yes, burning woodgas in a combustion engine does emit CO2 into the atmosphere.

However, it’s worth noting the carbon cycle related to biochar and biomass-derived fuels. The biomass (like wood or plants) originally takes CO2 from the atmosphere during its growth via photosynthesis. When it’s subsequently gasified and combusted, the CO2 is released back into the atmosphere.

In this sense, the process can be considered “carbon neutral” because the amount of CO2 released is roughly equal to the amount the original biomass absorbed during its growth.

However, the full environmental impact is more nuanced. The pyrolysis process itself, the efficiency of the gasifier, the purity of the woodgas, and other factors can influence the exact emissions and environmental footprint of using woodgas for energy. Furthermore, the process’s carbon neutrality doesn’t consider methane (CH4) emissions, which can have a more potent greenhouse effect than CO2 – if it is not fully burned – though in smaller quantities.

Conclusion:

Woodgas-based energy production stands as a promising and environmentally responsible method of energy generation. At the heart of its appeal is its inherent carbon-neutral characteristic. The lifecycle of biomass-derived fuels, such as woodgas, completes a balanced carbon loop. Biomass, during its growth phase, absorbs and sequesters CO2 from the atmosphere through photosynthesis. Upon undergoing pyrolysis in a gasifier, the carbon captured by the biomass is then released as CO2 when the resulting woodgas is combusted. This release simply returns to the atmosphere the carbon that was originally absorbed, maintaining a balanced carbon equation.

Thus, the use of woodgas as a fuel source neither adds nor subtracts from the overall carbon levels in the atmosphere, rendering it a truly carbon-neutral energy alternative.