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Biochar


Biochar paper

Biochar is becoming a valuable product usable for a variety of purposes, ranging from use as a soils supplement to filtration ("activated charcoal") and more. 

A common use for biochar is as a soil supplement, where it is often compared with compost.  While both align well with "cradle to cradle" recycling, biochar is generally likely to be a better option than compost because: biochar retains more moisture; loses less nutrients less quickly; is sterile; and has a higher mineral content.  A main notable difference however is in how these two products support GHG reduction and Climate Change.  This is because compost has a low "fixed" carbon ratio, so it emits GHGs more readily than biochar.  This means that biochar is more efficient at sequestering carbon than compost but also, has appreciably higher sequestration ratio for any given weight or material - either as feedstock or as a soil supplement product.

Key to sequestration is the broader array of materials that can produce biochar compared compost.  With municipal solid waste for example, as much as 88% of MSW is atmospheric carbon suitable for Advanced Gasification.  With compost, only organic materials are usable, which may be as low as 11% of the typical total (dry) waste volume.  This means that optimized biochar production has the potential to be carbon negative: in effect, MSW's atmospheric carbon means Advanced Gasification extracts carbon from the atmosphere and under most uses, buries or "sequesters" it.  This means our IRM approach is one of the few proven and viable options to economically sequester GHGs.

Biochar can also be obtained from other systems such as pyrolysis-type units.  These usually operate at lower temperatures than gasifiers, with shorter latency, resulting in challenges with biochar quality compared to output from a high quality gasification process.  This is because pyrolysis typically leaves more residual contaminants, which may in turn limit use and value.  West Biofuels' biochar summary provides further comment, with extended information available to clients on request.

Example

A 44-tonne RotoGasifier operating since 2014 in White Cross, Louisiana produces biochar from bagasse, a residual bi-product from sugar cane processing.  This sticky residue is difficult to process with other technologies, however the RotoGasifier succeeded.  This is a testament to its flexibility in handling difficult feedstocks.  In this example the RotoGasifier's heat is captured and used to dry the sugar cane, thus reducing demand for natural gas and also, reducing GHGs. The biochar is sold by American Biocarbon.

 

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