From grass to gas

Every year about one million tons of grass is harvested during maintenance of the roadsides and national parks in the Netherlands. Since this grass is unsuitable for animal consumption the municipalities have to dispatch it as waste at their own costs.

For a project anaerobic digestion 2.0 researchers of Bioclear earth and TNO developed a method to reuse the harvested grass as a resource of raw sugars. Sugars from plant waste are highly suitable as feedstock for the production of green chemicals and biofuels.

Energy rich, but hard to break down

Grasses contain a lot of lignocellulose. They owe their rigid structure to this fibrous and hard to break down material. However, lignocellulose is very energy rich which makes it an attractive feedstock for the production of bio-energy. However it’s a challenge to make this energy available. Due to the poor degradability of lignocellulose anaerobic digestion is difficult, making it economically less profitable.

Super-Heated Steam and enzymes unlock fibres for faster fermentation

During the project anaerobic digestion 2.0 two different pre-treatments were combined to enhance the degradability of lignocellulose. First the grass was treated with Super-Heated Steam (TNO) and subsequently with on-site produced enzymes (Bioclear earth). This separates the fibrous material and produces sugar water. The generated sugar water is converted into biogas via anaerobic digestion. By applying these pre-treatments on fibrous materials, which are hard to degrade, up to 30x faster and 2x more biogas can be produced.