PacPyro, in developing its technology, has steered away from condensing any bio-oil product from the process as it believes that safe and sustainable markets for bio-oil still require significant research and development. The PacPyro kiln is therefore optimised for minimal production of bio-oils, and any bio-oils that are produced are cracked down into more syngas in the proprietary gas-cleaning arrangement.
The solid remaining after the de-volatilisation of the biomass is called ‘char’.
The processing results in a dense carbon structure of conjugated aromatic rings, which has a highly developed surface area. When this char product is utilised as a soil amendment it is referred to as biochar. The greenhouse gas balances across slow-pyrolysis projects have garnered a lot of interest because they have the potential to be carbon negative, that is, to remove carbon from the atmosphere. Plants have evolved over millions of years to efficiently take up CO2 from the atmosphere. When plants die, however, they decompose, releasing the carbon stored in the biomass back into the atmosphere. Under some conditions, such as in landfills, a portion of the carbon in the biomass can be released as the potent greenhouse gas, methane. However, if biomass is directed into a slow-pyrolysis process, about half of the carbon stored will be made into syngas.
When syngas is combusted for energy the carbon is released as CO2 back into the atmosphere, with this energy providing a renewable alternative to fossil fuels. The other half of the carbon is stabilised in the biochar. Biochar has been shown to be very recalcitrant in soils, as it is not susceptible to degradation in the environment by biological (soil microbes) or chemical pathways. Therefore, across the life of the project, more carbon is taken up by the plants than is released back into the atmosphere – hence a net removal is achieved.
The biochar rollout