How is biomass actually converted to plastic cups, chemicals or biofuels? We often hear that there are alternatives to petroleum-based products, but how do they work in practice? How is a pile of grass, stems or leaves processed into all kinds of useful products? At Wageningen UR Food & Biobased Research, scientists work on these topics on a day-to-day basis. Two of them give us a peek into the kitchen of the Biobased Economy.
“Often, we get literally a few cubic metres of green stuff, such as sugar beet, roadside grass or tomato stems,” says Edwin Keijsers, a specialist in extracting fibres from biomass. “This is sometimes first left to brew and steam outside for a while. However, if you need fresh material, you need to get started quickly or the composition will change and important functional properties will be lost. While the fibres have a longer shelf-life, for an economically viable process you need to fully utilise all the ingredients, including, for example, proteins and sugars.”
Paper containers made of tomato leaves
Processing tomato stems into cardboard, for example, and making leaves suitable as raw material for paper containers, requires mechanical, enzymatic and chemical processes. “It’s a complex procedure,” Keijsers says. “The leaves and stems are separated, shredded and cleaned. Next, the sap is extracted using a belt filter press. This is done not just to remove excess water, but also to extract any ingredients from the biomass that are not required to make paper, yet can still have value for other materials or chemicals. This includes raw materials for plastics or biocides. The process is designed so that tomato leaves are ultimately transformed into a material that can easily be converted into containers in a paper mill using existing machines.”
Keijsers and his colleagues have a toolbox full of techniques and knowledge on the used biomass. “The fibres in the tomato stems retain moisture too well,” he says. “This makes the machine in the mill runs somewhat slower. Other components, which we still want to remove, cause an unpleasant odour during production. A tailored solution is required for each issue.”
Testing refining processes in the technology hall
The equipment in the technology hall of Food & Biobased Research allows Wageningen scientists to search for the most efficient and feasible way to get value from crops and residues. “This allows us to investigate and show what the costs and benefits are,” explains Robert Bakker, another scientist at Food & Biobased Research. “Processes that have been developed in the lab are scaled up to a level that makes the process relevant to the industry. This helps companies to decide whether they wish to invest in a given process.”
“Biomass residues and byproducts don’t always have the same composition, so we are working on processes which can deal with this variety in a flexible way,” continues Bakker, who specialises in extracting proteins and sugars from biomass waste streams. “If residues contain a lot of high-quality proteins which can be processed in, e.g., compound feed or human food, we want to get those out first. If there are few or no proteins, then the process focuses primarily on extracting cellulose and lignin.”
What Bakker and his colleagues then do with the cellulose depends on its structure. For this purpose, samples of the biomass are first analysed in the lab. Depending on the composition of the lignocellulose, the scientists determine which enzymes are best used to get the most value from the sugars via fermentation – as enzymes can break down sugar chains in controlled conditions in bioreactors.
Temperature, acidity and mixing methods in the conical reactors are adjusted so that the enzymes can do their work optimally. The viscous paste-like mass slowly changes into a liquid. Once the process is completed, it can be clearly seen what impact the enzymes have had – the resulting liquid consists of several layers, and soluble components (such as sugars) are separated from undissolved components (such as lignin).
Micro-organisms can subsequently be used to transform the sugars into various chemical compounds. The typeof the micro-organisms added to the liquid depends on the product desired – (poly)lactic acid, ethanol, butanol or hydrogen. This allows products and fuels to be derived from biomass which could, until recently, only be made by refining petroleum.
Wageningen scientists work on a daily basis to make biorefinery processes better, more efficient and cheaper, laying the foundation for a Biobased Economy.