Polytechnik

You might ask, what is Green Carbon and why visit? From the name you might conclude that it has something to do with vegetable carbon, the thermal treatment of biomass, or biochar, right? With the current market and industry trends, it was worthwhile to investigate and describe a hidden gem in the POLYTECHNIK portfolio, located in the north of Germany. Yes, Green Carbon is the name of POLYTECHNIKs’ industrial process for carbonizing biomass. With so many technology companies vying for a space under the sun in this sector, pushing CDRs, energy and the multiple benefits of something called biochar it can be a confusing landscape to navigate. Biochar, charcoal, char, carbonized biomass, vegetable carbon…All of it boils down to either getting a clean, sustainable and stable natural carbon or a coal like fuel substitute. You will hear terms such as slow pyrolysis, flash pyrolysis, steam explosion, torrefaction, carbonisation and HTC (hydrothermal carbonization) to name a few… See what we mean. Challenging, for sure.

Green Carbon and the process behind it

Photo 1: Green Carbon aerial view

Green Carbon is based on a proven concept. The R&D team settled on this design after about a 15-year development period. It is a high temperature slow pyrolysis. High temperature means we go up to 650 – 700 ºC in the process and slow pyrolysis means that the pyrolysis takes around 2-4 hours. Now these are very important factors because they ensure that carbonization is taking place with a high-quality product as an outcome. Essentially it is a continuous process based on a retort – batch concept. POLYTECHNIK has secured it’s Know How and development with a patent on the so-called Green Carbon Process.

Photo 2: Green Carbon retort

Feedstock

The plant is conveniently located in the countryside, around two hours to the west of Hamburg, surrounded by trees and wind turbines. The entrance to the site, right off the highway, opens through the truck access road and a weigh bridge where each delivery of feedstock is weighed. Furthermore, depending on the quality of the biomass delivered, the truck is unloaded in a certain designated area of the feedstock yard. You will find green biomass residues from garden, park and roadside maintenance, hog fuel and some round wood.

Photo 3: Round wood and hog fuel

The large amount of green material (leaves, needles and other herbaceous materials) can be a reliable source for the composting process in the feedstock yard. This is a seasonal by-product of the feedstock handling. However, this is not a prerequisite for Green Carbon, just a convenient project specific case for this location.

In one of the future texts, we will deal with the Green Carbon pyrolysis process itself, stay tuned.

Viktor Radic, dipl. ing.