Work Package 2

Pre-treatment methods for recycled Wood mixtures

Ethanol based organosolv and alkaline oxidation will be studied as pre-treatment methods for recycled waste wood aiming to produce well hydrolysable cellulosic fibres, as well as polymeric lignin and hemicellulose side streams with distinct structural features that could be utilized in biobased products in WP3. Performance of those will be compared with Steam Explosion.

Workpackage Leader

Detlef Schmiedl

Fraunhofer ICT 

Work Package 2.1

Steam explosion pre-treatment

Steam explosion is generally considered the most practical and so far best established pre-treatment technology for the 2nd generation bioethanol production from LC feedstocks. However, the remaining lignin retards the enzymatic hydrolysability of the fibers, and the utilisation of lignin after simultaneous saccharification and fermentation (SSF) is more difficult due to the remaining carbohydrate and protein impurities. There are still many practical reasons (simple process, available industrial equipment, and minor use of added chemicals) favouring steam explosion, and it will be considered here as a reference treatment for the organosolv cooking and modified alkaline oxidation.

Work Package 2.2

Ethanol/water organosolv pulping

Ethanol-water organosolv pulping is an autocatalytic pulping process with water/ethanol-mixtures. During the process catalytic amounts of carboxylic acid (acetic acid) will be liberated from hemicellulose. This process allows the complete fractionation of LC biomass in its main components without aggressive chemicals. The presence of acidic catalyst during the pulping further increases the purity of cellulose, enhances lignin dissolution, and increases the amount of oligomeric hemicellulose. Removing of ethanol from the pulping liqueur readily leads to a lignin precipitation. The hemicelluloses are mainly dissolved in the first pulp washing stage after the removal of the lignin containing cooking liquor, and relatively pure hemicellulose fraction for WP3 can be obtained. Further separation techniques can be used to generate a concentrated hemicellulose fraction. Resin like components (resin acids, glues) might disturb the pulping process. Thus, a pre-extraction stage with organic solvents before the pulping is necessary in the case of resinous-rich wood species.

Work Package 2.3

Alkaline oxidation pulping

LC raw materials can be effectively fractionated also by alkaline oxidation. Carbonate based alkaline oxidation with elemental oxygen has been shown to produce well hydrolysable pulp generally suitable for fermentation processes with fresh wood even without any additional catalysts. The optimal cooking conditions (time, temperature, alkalinity, O2 charge, and need for mechanical defibering) will be screened for recycled wood mixtures to reach the sufficient kappa level providing the highest enzymatic hydrolysability (to be determined in WP3).

Work Package 2.4

Super critical water oxidation of pulping water phases

Supercritical Water Oxidation (SCWO), is a high-efficiency, thermal oxidation process capable of treating a wide variety of hazardous and non-hazardous wastes. The SCWO reaction takes place at elevated temperature and pressure above the critical point of water (Pc= 220.55 bar, Tc=373.976 C). SCWO is ideally suited for treating waste streams containing high concentrations of water. SCWO processing systems are fully enclosed and do not produce hazardous air pollutants (HAPS) or NOx. SCWO processing is not limited to disposal of organic compounds and complex organic wastes. Chemical reactions in SCWO processing systems obey the laws of mass, charge, energy and elemental conservation.

Work Package 2.5

Thermochemical process to convert contaminated wood waste into biofuels and chemicals (ENERKEMprocess©)

Enerkem converts mixed waste and residues into a pure synthesis gas (or syngas) which is suitable for the production of biofuels and chemicals using proven, well-established and commercially available catalysts. With its proprietary technology platform, the company is able to chemically recycle the carbon molecules from non recyclable waste into a number of products. Enerkem has validated its technology over 10 years using solid waste from several municipalities, as well as a broad range of residues. Enerkem’s process uses relatively low temperatures and pressures, which reduces energy requirements and costs. Feedstock analysis and a pilot trial is foreseen within ReWoBioRef that shall provide a general feasiblity study and a proof-of-concept for the utilisation of contaminated wood of A IV, D and lower grades from European waste wood sources.