Plans to give manure digestion a new boost on the Dairy Campus in Leeuwarden have been afoot for many years. The international collaborative partnership Biogas-Leeuwarden BV is now receiving investment from the FSFE, and its partner the Nationaal Groenfonds, for the realisation of an innovative manure digester on the Dairy Campus.

The Biogas-Leeuwarden project is taking place on the grounds of the Wageningen University & Research Centre (WUR) in Leeuwarden. The ambitious Dairy Campus project was started on this site in 2007 by the WUR together with, amongst others, the province of Friesland and the district of Leeuwarden. At the end of 2015, there will have to be 520 dairy cows walking around that are part of a trend-setting investigation into dairy products and production. Manure processing is an increasingly important part of this process. In 2007, the WUR invested in a co-digester to resolve the bottleneck in manure waste. This project was suspended in 2013 due to the high costs of co-digestion material.

A consortium of parties from Friesland and America (comprising Universal Energy Solutions BV, Clark Technology LLT, Evergreen LLT) have developed a new technology that makes it possible to use waste such as roadside grass and wood as co-digestion material.

The materials are much cheaper and sometimes even represent a source of revenue (so-called gate fees). This gives rise to a healthy business case.

Breakthrough with ‘Hogen’ technology
Normal co-digesters mainly convert glucose (sugars) and fats. A co-digester must use at least 50% manure. The other substrates are generally corn silage, glycerine, vegetable fat and grain waste. However, the costs for these co-substrates have risen sharply in recent years, making things difficult for co-digesters in financial terms.

The technology used at the WUR focusses upon breaking down (hard) cellulose and lignite (the most important components in manure, grasses and wood). These biomass flows are much cheaper, which makes the business case very interesting.
The planned process with the ‘Hogen’ technology can be compared to the way a cow digests grass.
The first step in the process is the milling (chewing) of the foodstuff into short fibres (enlarging of the surface area) with the ‘hydropulper’.
After this, it goes into the ‘hydrolysis tank’ (an acid environment comparable to a stomach) to break open the cellulose cell membranes; all extra oxygen is also removed in this process.
It then goes into the plug-flow reactor (the bowels); instead of the traditional 1 tank bio-digester, the digestate now goes through 4 separate zones containing special bacteria that effectively convert the biomass into biogas.
The end result is pressed in a screw, with the water going back into the system. Because the input is relatively dry material such as grass and wood, there is hardly any waste water. The solid fraction is odourless and can be used as chemical fertiliser.

The WUR biogas project could represent a breakthrough in the processing of manure, grasses and wood into biogas, whilst delivering a healthy financial profit. The project as a whole will cost 6M, which is broken down into two phases of 3.5M and 2.5M respectively, financed by the consortium, the Nationaal Groenfonds and the FSFE.

Piet van der Hoop, founder of Biogas-Leeuwarden
“We have put together a strong consortium to realise this project. I am very happy that we can now really get down to work.”

Michel Hendriks, FSFE foundation management
“In recent years many digesters have struggled financially. A technology that gets more biogas out of biomass flows, such as manure and roadside grass, would give a strong stimulus to this sector. The Dairy Campus serves as a clear example, both nationally and internationally. This is also an excellent location to realise the Biogas-Leeuwarden project.