Production of bio-char (activated charcoal from renewable and sustainable resources) and energy from waste wood


030104, 030105, 030199, 150103, 170201, 191206, 191207, 200137, 200138

Reference flow in the MFA for which is suitable the technology

Wastes from wood processing and the production of panels and furniture:

Packaging Wastes:

Construction and demolition waste:

Wastes from mechanical waste treatment (for example sorting, crushing, compacting, pelletising) not otherwise specified

Separately collected fractions from municipal wastes (household waste and similar commercial, industrial and institutional wastes):

Incoming input

The incoming waste stream is waste wood[RS1]  as listed above. Due to the different origins, waste wood can be contaminated to varying degrees with foreign substances. Therefore, the category is divided into four different qualityies (A1 to A4), of which the first three  can be used as input:

Outgoing output

As presented in table 1 the technology produces electricity and/or heat, depending on the respective demands, and about 10 % of the input is converted into bio-char. 

Table 1: Output products and their proportion of production.

Bio charcoal









Technology description

The technology encompasses a multi-staged gasification system. The core of this technology is a floating-fixed-bed reduction reactor. Due to its unique design, it allows the gasification process to happen within a tubular reactor. This prevents the backflow of gas and fuel material.

During the gasification process, the particles pass through the floating-fixed-bed. As a consequence of heterogeneous reduction reactions, the particles decrease in size until they reach the top of the bulk. Depending on the individual particles’ sinking speed, the residual bio-char particle fraction is transported by the product gas stream into a hot gas filter system. After passing a cooling unit, the produced gas is cleaned by a fuel specific water scrubber before being fed to a combustion engine (see Figure 1). 


Figure 1: Setup of floating-fixed-bed-gasification process (source:

Organizative processes to support closing the loops

The biochar produced from waste wood is classified as a waste product. To convert it into a product, strategies and concepts need to be developed and an adequate legislative setting needs to be established (e.g. end-of-waste criteria, Article 6 (1) and (2) of the Waste Framework Directive 2008/98/EC).

Practitioners opinion

The gasification of waste wood is a promising approach to transform waste wood into renewable energy and bio-char suitable as a filter medium for numerous applications. However, in order to achieve a process and to produce useable bio-char,  certain limiting factors need to be overcome.

Possible limiting factors

There are three main factors that can compromise the gasification process and the production of quality bio-char:

  1. Quality of waste wood
    Of the afore-mentioned four different quality categories of waste wood, only A1-A3 can be used. The differentiation of these categories is not always easy and at waste wood collection stations, might get mixed up when delivered by the public or by staff of construction firms.
  2. Age of waste wood
    Waste wood, even if belonging to the same quality category can have varying ages, from almost fresh to old and brittle. Partially rotten and brittle waste wood contains less energy, which compromises the stability of the gasification process.
  3. Contaminants
    Waste wood is prone to containing higher consentrations of contaminants. Aside from metal parts (nails, braces, etc.), waste wood can contain various organic or inorganic contaminants due to wood preservation agents like varnishes and stains, or by coatings. These can be emitted during the gasification process. Addressing these challenges requires a very thorough pre-processing of the incoming waste material and the installation of emission control systems, i.e. filters or other gas cleaning technologies.

In general, the more homogeneous and the better preserved the input material, the more stable is the gasification process. 

PP’s opinion of the technology

Compared to other alternative uses of waste wood, this appears to be one of the most promising technologies to expand the life cycle of waste wood and produce renewable energy.

Concept and conclusions how the technology can affect the CE effect

A prototype of this technology, using waste wood, is implemented and produces bio-char. To obtain activated bio-char, which is the ultimate aim of the CE solution, more test runs are needed and the pre-processing steps need to be refined.

Is the technology a BAT?


Charts, photo, diagrams


Huber, M., Huemer, M., Hofmann, A., Dumfort, S. (2016) Floating-fixed-bed-gasification: from vision to reality. Africa-EU Renewable Energy Research and Innovation Symposium, PERIS 2016, 8-10 March 2016, Tlemcen, Algeria
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