Lignocellulose biomass is the most common organic raw material on earth. It’s the “glue” that gives trees and plants its strength. Lignin is the reason why fibrous waste streams like grass, wood, straw and reeds are difficult to re-use, because this glue isn’t exactly easily degradable. In the Netherlands we produce 50.000 tonnes of green fibrous waste every year within a radius of 30 km, by mowing roadsides, natural areas, dikes and maintenance of trees along public roads etc. This leads to enormous amounts of material, which we would like to re-use locally as much as possible, for instance as biofuels, new raw material and green chemicals.
The breaking down of Lignin is a tough nut to crack. Take for example paper, something we use on a daily basis. To obtain cellulose for the production of paper the use of several physical and chemical processes is required. Wood fibres are treated with various chemicals, under high pressure & temperature (hot steam, 145 degrees Celsius), are processed mechanically and treated with lots of water. This method is simply not feasible for processing local green waste flows.
Nature has developed a very effective way to break down lignin, without the necessity of extreme conditions. White rot fungi produce their own chemicals under normal temperature and atmospheric pressure. These fungi are actually like little pulping mills and are capable of pre-treating wood by producing enzymes that break down lignin. The fungus uses the cellulose that is made available for their reproductive phase by producing mushrooms.
The TKI project Bio-pulping investigated whether we can extract more bioenergy from biomass by pretreatment with white rot fungi and whether it is possible to reuse green fibrous cellulose waste streams as raw materials.
In the meantime, Bioclear Earth and the WUR have completed the project by carrying out tests on a pilot scale. Together, we have developed a blueprint for a practical and widely applicable technology. Smart use has been made of techniques that have already been developed by the mushroom cultivation sector. In addition, we have worked on a simpler, selective biological process in order to fit in better with common practices such as ensiling, composting and fermentation. To ensure that this new technology really meets the needs and possibilities of the market, various biomass suppliers, industry associations and end users have been involved in this project. They have assisted us with their expertise and provided opportunities to test the process on a larger scale.
An important step in this project was the determination of the optimal pretreatment conditions. It became apparent that, in particular, raw materials with a high lignin content benefit from this pretreatment. On lab scale, we have shown that thanks to the pretreatment, the fermentation of these fibres is faster and the production of biogas increases.
If we are able to apply the technology on a larger scale, there are many possible uses for the biopulping technology. Not only the applications for biogas production were considered, but also the possibility of applying the technology in the future for the production of paper fibre, green chemicals, second generation sugar and cattle feed from straw. During the project, successful paper prototypes have already been produced on the basis of pretreated Miscanthus.
Challenges for biopulping are a fairly long pre-treatment phase and a relatively high investment based on the 'proven technologies' from the mushroom sector. By applying an innovative step, namely the use of liquid inoculants, the costs can be reduced. Another advantage is that this technology produces considerably more biogas, up to 2 times more compared to biogas production without pretreatment. Given the current situation with natural gas prices and dependence on foreign gas, this is certainly worthwhile. We believe that more is possible with biopulping in the future by researching and developing selective growing conditions to upcycle lignin-rich waste streams and make optimal use of raw materials.
Would you like to know more about the possibilities of bio-pulping, please contact Jeroen Tideman or Eline Keuning.