Biochar FAQs

Biochar is produced through the thermal carbonization (pyrolysis) of biomass such as untreated wood, hedge or green clippings, as well as other residual biomasses, for example from the food industry. Due to its porous structure and massive internal surface area, it can store water and nutrients, and bind pollutants. Additionally, about half of the carbon from the original material remains locked in it long-term. These properties make it a true all-rounder, playing a crucial role in agriculture, industry, water bodies, climate protection, municipalities, and building construction.

#2 Why is biochar not yet widely used despite its many benefits?

Although the indigenous peoples of South America had been producing Terra Preta with biochar in the Amazon region around 4,000 years ago, this knowledge was long forgotten. It has only been in the last decade, driven by concerns about climate change and food security, that the potential of biochar has once again come into focus. Despite this, it remains relatively unknown in all its possible applications, and certain legal frameworks still hinder its large-scale deployment.

German Biochar is currently advocating in the agricultural sector for the approval of not only biochar made from wood with a carbon content of at least 80%, but also biochar from other types of biomass in fertilizer regulations, provided it is proven to be low in pollutants. The economic benefits of biochar, as well as its advantages for the climate, are especially pronounced when waste materials that would otherwise go unused can be put to good use.

The European Biochar Certificate (EBC) ensures that the biochar bearing this certification:
  1. Is clean and safe to use, as it meets strict limits for contaminants;
  2. Comes from an environmentally friendly production facility; and
  3. Is made from sustainably sourced biomass.
The EBC guidelines specify, among other things, which materials are allowed to be used. Additionally, the EBC certification also enables the certification of the carbon stored in the biochar as a carbon sink. For more information: https://www.european-biochar.org/en/
The term PyCCS refers to the principle of capturing carbon through pyrolysis and storing it in a way that prevents it from re-entering the atmosphere. PyCCS stands alongside terms such as BECCS (Bioenergy with Carbon Capture and Storage) and DACCS (Direct Air Capture with Carbon Storage) as a form of negative emissions technology, with the advantage that PyCCS is technically mature, currently available, and associated with low risks. In contrast, the terms Pflanzenkohle and, to some extent, Biokohle refer to the products of biomass pyrolysis. However, there is some ambiguity in the German use of the term “Biokohle,” as it encompasses not only pyrolytic carbon but also those produced by the HTC process (Hydrothermal Carbonization). HTC-based coals are highly unstable, and their production generates process water that is so contaminated that it cannot be released into wastewater treatment plants in Germany. To distinguish from HTC-based coals, the term Pflanzenkohle (plant-based biochar) has been established in German.

Biochar is produced through a process called pyrolysis. During this process, biomass is thermally treated at high temperatures, usually between 400 and 750 °C, and sometimes up to 900 °C, in an environment with little to no oxygen. This process can take place on a large scale in industrial facilities, where the gases and heat produced can also be utilized. However, biochar can also be produced on a smaller scale in methods such as a ground pit or a Kon-Tiki, which is a funnel-shaped metal container used for pyrolysis.

Yes, biochar can be made for personal use as well. One suitable method is using a Kon-Tiki, a deep, cone-shaped fire pit. In the Kon-Tiki, a small fire is first ignited, and then more biomass is gradually added. The biochar that forms in the fire is protected from combustion, which allows it to convert into charcoal rather than being burned completely.

Wooden garden waste, such as branches from trees and shrubs, are ideal for this process. Grass and leaves are usually not suitable, as they contain little wood material and are too fine to achieve uniform carbonization.

At the end of the process, water is introduced into the Kon-Tiki through a pipe with a shut-off valve. This helps to slowly extinguish the charcoal and surrounds the upper layers of coal with steam. This process improves the nutrient-storing capacity of the biochar and prevents it from burning completely once no more biomass layers can be added.

Further information can be found on the Ithaka Institute’s website. Kon-Tiki models are available in different sizes, or a cone-shaped pit can be created in the ground without the need for steel. Any pieces that are not fully carbonized should be removed and can be reused in the next carbonization cycle.

A pyrolysis plant does not only produce biochar:
  • It generates heat that can be fed into industrial processes or a local heating network, can dry wet biomass, or heat a building.
  • It can dry and dispose of waste materials using the residual heat.
  • Depending on the design, it can also generate electricity.
This creates various possibilities for developing business models around biochar production. The range extends from pyrolysis plants producing feed-grade biochar, which can be profitable mainly due to high sales prices, to plants that generate process heat from locally sourced waste materials, making their economic viability primarily based on reduced energy and disposal costs. With over 50 described applications for biochar, there are many options available. A pyrolysis plant may even be eligible for funding from the KfW (Kreditanstalt für Wiederaufbau) as a heat source.

Biochar is ideally made from dry, nutrient-poor biomass. Wet biomass can be dried using the waste heat from the pyrolysis plant and/or pre-processed in a biogas facility. Nutrient-rich and wet biomass is better composted or, if necessary, used as mulch, meaning that the plant material is directly applied to the soil.

When producing biochar, the following should be avoided:
  • Only untreated, natural biomass should be used. The use of material contaminated with chemicals must be strictly avoided – such as painted or pressure-treated wood. Special care should be taken with old wood from outdoor areas.
  • Insufficient or uneven heat: This leads to incomplete carbonization of the material.
  • Incomplete extinguishing: The material continues to smolder, and in the end, only ash remains.
  • Smoke: Every fire and pyrolysis process produces pyrolysis gases that must be completely burned so that no smoke is generated, ensuring that both the biochar and the air remain free of pollutants. With a bit of practice and sufficiently dry biomass, this can be quickly learned.
  • Pyrolysis cookers: Especially in developing countries, pyrolysis cookers are used to save wood for cooking and improve air quality. Biochar is also sometimes produced in these cookers. However, these stoves are usually not designed to produce biochar for agricultural use. Instead, the charcoal produced is often intended for further cooking or grilling. Therefore, these cookers are not typically optimized for biochar quality – there may be exceptions, but it should be assumed that the biochar produced may contain pollutants. Biochar from Kon-Tiki kilns has been repeatedly tested for pollutants and, when produced correctly, is safe for soil application.