Creating biohydrogen from wood waste

Thus far, wooden waste has needed to be disposed of at nice expense and, at finest, has been used to generate power in incineration vegetation. Fraunhofer researchers at the moment are utilizing this worthwhile useful resource to supply biohydrogen within the Black Forest area of Germany.

Within the joint mission H2Wood—BlackForest, fermentation processes utilizing hydrogen-producing micro organism and microalgae have been specifically developed for the biotechnological manufacturing of this inexperienced power service. A pilot plant for the manufacturing of biohydrogen is to be commissioned as early as 2025.

A research printed as a part of the mission additionally examines the potentials, obstacles and measures for regenerative hydrogen manufacturing from waste wooden and outdated wooden within the Black Forest area.

The Black Forest area is house to a lot of wooden processing corporations, together with many furnishings producers. Giant portions of wood waste are produced throughout furnishings processing, pallet disposal and constructing demolition.

Till now, this waste has been disposed of in incineration vegetation. Since outdated wooden typically incorporates wooden preservatives which have lengthy been banned as a consequence of their dangerous results on human well being, the waste fuel from the incineration course of additionally must be cleaned at nice expense. This motivated the Fraunhofer researchers to search for different makes use of for the regional wooden waste.

The concept was that waste wooden and outdated wooden may very well be used to supply regenerative hydrogen, and that biohydrogen may very well be produced from the waste utilizing biotechnological processes—completely consistent with a wood-based round financial system.

The trick is that the researchers use sugar from the wooden to supply hydrogen utilizing micro organism. The ensuing CO₂ is then used to develop microalgae that may additionally produce hydrogen.

Along with the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB and the Fraunhofer Institute for Manufacturing Engineering and Automation IPA, the College of Stuttgart, with its Institute of Industrial Manufacturing and Administration IFF, and Campus Schwarzwald are additionally concerned within the implementation of the H2Wood—BlackForest mission, which was initiated in 2021.

The manufacturing technique of biohydrogen begins with the pre-processing of outdated and waste wooden. First, the wooden waste, resembling pallets or outdated backyard fences, is pulped and damaged down into its fundamental parts.

To do that, the researchers boil the wooden underneath stress at as much as 200 °C in a combination of ethanol and water. Lignin in addition to adhesives, solvents and paints from the wooden waste dissolve within the ethanol, separating the chemical contaminants from the wooden fibers.

Within the subsequent step, the wooden fiber fraction that continues to be after boiling, the cellulose, and a part of the hemicellulose are damaged down into particular person sugar molecules (glucose and xylose), which function meals or substrate for the hydrogen-producing microorganisms.

“Separating wood into its fractions is a process that requires experience. This is where we draw on the many years of expertise that we have gained in the construction of our lignocellulose biorefinery in Leuna,” says Dr. Ursula Schliessmann, deputy institute director at Fraunhofer IGB in Stuttgart, which is answerable for the mission coordination and technology development.

To transform the produced sugar into hydrogen, the researchers at Fraunhofer IGB have established two interlinked fermentation processes utilizing hydrogen-producing micro organism and microalgae.

Carbon-based by-products produced along with hydrogen

Pre-processing produces by-products resembling lignin, and the biotechnological conversion of the wooden releases hydrogen and CO₂. The latter is then transformed into by-products resembling starch and carotenoids throughout microalgae manufacturing.

Dr. Schliessmann explains, “When the wood is fractionated, the wood fibers are freed from lignin, which, in addition to cellulose and hemicellulose, makes up 20 to 30% of the wood cell wall substance. As one of the by-products, this lignin has many uses—for example, in composite materials. One example of its use is in car panels.”

The lengthy sugar chain molecules of the cellulose are used to supply glucose, which is added to the fermentor with micro organism and serves as a carbon supply for bacterial progress. The micro organism then produce hydrogen and CO₂.

The researchers separate the CO₂ from the fuel combination and switch it to the algae reactor, a photobioreactor. The microalgae are ready to make use of CO₂ as a carbon supply and multiply. In contrast to micro organism, they don’t require sugar.

“The metabolic products of the bacteria, i.e., the apparent waste stream of CO₂are food for the microalgae and therefore do not enter the exhaust as a harmful greenhouse gas. The microalgae use this to synthesize carotenoids or pigments under the influence of light as further by-products that can be used by various industrial sectors.”

In a second step, the microalgae are transferred to a specifically designed reactor the place they launch hydrogen through direct photolysis.

Biotechnological course of with a excessive hydrogen yield

The mission companions count on a excessive yield. Initially, round 0.2 kilograms of glucose might be produced from one kilogram of outdated wooden. “We can then produce 50 liters of H₂ with this using anaerobic microorganisms,” says Dr. Schliessmann.

Throughout fermentation with anaerobic micro organism, CO₂ is produced in equal parts, i.e., 50%. As soon as the hydrogen has been separated from the fuel combination, approx. two kilograms of CO₂ within the photobioreactor can produce one kilogram of microalgae biomass.

This biomass has a starch content material of as much as 50%. It additionally incorporates the pigment lutein. The by-product algae biomass may, for instance, be used for plastic parts with the assistance of micro organism.

The modularly expandable pilot plant with three bioreactors is presently underneath building. The biorefinery is scheduled to enter operation in Campus Schwarzwald initially of 2025. Sooner or later, it is going to be attainable to mix totally different course of steps in a modular means—an excellent prerequisite for testing new applied sciences.

Hydrogen street map for the Black Forest area

On this mission, Fraunhofer IPA, along with the Institute of Industrial Manufacturing and Administration IFF, is conducting a research to find out how the native demand for inexperienced hydrogen within the industrial, transport, family and constructing sectors might be met, and what portions of waste wooden and outdated wooden can be found for its manufacturing.

On account of this hydrogen street map, suggestions have been made for the event of the hydrogen financial system within the Black Forest area.

The proposed measures embrace the promotion of analysis and growth, the enlargement of the regional hydrogen infrastructure and the strengthening of power programs integration with a view to set up hydrogen as an integral a part of the power transition.

“The study shows that the Black Forest region has a significant potential to produce hydrogen from local resources, but this potential can only be fully exploited by further developing the technologies and expanding the infrastructure,” says Vladimir Jelschow, a analysis scientist at Fraunhofer IPA and one of many authors of the hydrogen street map.