ELBE–NH – Increased effectiveness of lignin-biorefineries by valorization of hydrolysates
In the framework of the ELBE-NH project (Support code BMBF 031B0091) innovative concepts for biorefineries are being researched at the TUHH, enabling more efficient use of by-products and a simultaneous product diversification. ELBE-NH builds on the results of the previous projects and is being processed by several partners in the current phase (further information).
Primary refining for the production of AS lignin from lignocellulosic biomass has been designed in the previous phases (Figure 1). For example, this AS lignin can substitute fossil components as an additive in adhesives. The biomass is decomposed / solubilized at high temperatures and pressures (liquid-hot-water hydrolysis) in a specially developed pilot plant in the technical center of the TUHH. Building on this, ELBE-NH aims to increase the effectiveness and added value through meaningful extensions and utilization of the by-products in the subsequent refining (secondary refinery).
Figure 1: Flowchart of a possible biorefinery for the production of lignin, lactic acid, propionic acid and poly- and oligosaccharides from lignocellulose.
Characterization of C5 and C6 oligomers
In order to be able to assess the success of the processes, it is necessary to establish a stable analysis for the target products at the beginning of the project. This implies the necessary hardware and software as well as suitable analytical methods. For this reason, a specific analytical method has been established for the quantification and characterization of carbohydrates such as fructans and pentosans at the IUE.
Quantification is carried out after acidic or enzymatic hydrolysis of the hydrolysates by high-performance liquid chromatography (HPLC). The HPLC with a binary pump offers a fast and precise gradient flow, and the refractive index detector (RID) enables a precise detection of the analytes. The concentrations of the saccharides contained in the analyte are determined by calibration with internal and external standards and subsequent measurement.
The chain lengths of the oligosaccharides are determined by size exclusion chromatography (SEC). The SEC is similar to the HPLC (pump, sampler, RID). By using three sequentially connected separation columns, saccharides in the analyte are separated by size and the size distribution is qualitatively determined.
Recovery of oligomers from Silphium perfoliatum
At the IUE the separation and purification of pentosanes (C5 oligomers) from multicomponent mixtures of solubilized hemicellulose, as well as the fructan recovery (C6 oligomers) from Silphium perfoliatum is forced (Figure 1). These fractions should be obtained from hydrolysate side streams of a process for the primary production of lignin from lignocellulosic biomass (straw, wood, Silphium perfoliatum, etc.).
For this purpose, suitable concepts are developed. The most effective unit operations (e.g. extraction, flocculation, precipitation, filtration, etc.) are screened on laboratory scale. For the final processing steps, chromatographic applications such as SMB (Simulated Moving Bed) are provided to achieve the highest possible product purity.
Figure 1 shows an example of a possible implementation of the biorefinery concept with as complete as possible recycling of the input materials, high added value and low waste production. The waste streams generated within the process are additionally utilized in biogas plants (not shown).
Techno-economic assessment of the concept
The parameters determined on the laboratory scale must be further scaled to the required target values. Using software-based solutions such as Aspen Plus and OpenLCA, the processes are balanced and simulated to quantify their economic and environmental impact. In the more advanced project phase, a techno-economic and ecological assessment of the overall project will be carried out on the basis of the simulated data and upscaled models.