Case Story Netherlands

GREEN GAS HUB

Provision of biogas by farmers by pipe to a Green Gas Hub with a centralised upgrading process

April 2017

Mission and Vision

The waste treatment company Attero was the first green gas producer in the Netherlands and supplies energy to 350,000 households. The company operates a green gas hub at Wijster. Local farmers deliver their biogas from their own facilities, after it is dried and desulphurised, via a biogas pipeline to the Green Gas Hub at Wjister. The farmers do not have to invest in a refining installation to achieve natural gas quality as this is now carried out at the Green Gas Hub.

The Green Gas Hub Concept

The Wjister Green Gas Hub is in a rural sparsely populated area. According to Attero’s Lars Huigen the hub’s goal was to collect local biogas and to combine the refining and injection steps for a number of digesters. Mr Huigen points out “At Wijster, we started with just a single supplier to the collective biogas pipeline, a farm that digests residual plant products.“ Lars Huigen notes that “We started generating biogas from our landfill 25 years ago to overcome fugitive methane release. Dumping of household refuse in landfills is now prohibited in the Netherlands, but the digestion process is set to continue here for many years yet.”

Lessons learned

Separation of different feedstocks in different digesters

At Wijster, Attero has a digester for the organic liquid fraction. This is organic household refuse that has ended up in grey wheelie bins and may not be used in compost as a result. Mr Huigen notes that “Organic household refuse is separated from the ‘grey’ waste stream and is digested separately; in this way, it’s still sustainable. In addition to that, we have a digester for green organic household refuse, which is separated at source. We use the component that is easily degradable and convert it to biogas. What’s left of the digested materials is mixed in with bulky organic household refuse and turned into compost.”

Affordability of biomass

One of the most important success factors in the development of biogas projects is the availability of affordable biomass and the corresponding logistics required to deliver it and to transport the products away. The Wijster plant has years of experience in this area. Lars Huigen notes that “We have been working on an energy infrastructure that facilitates biogas production from a regional centre: the green gas hub.”

Refining to natural gas quality

The most valuable part of the process is refining biogas to natural gas quality. “Any CO2, contaminants, and moisture that are present have to be removed. For this reason we have three installations at Wijster, each of which works in a different way. The first one to become operational, a Pressure Swing Absorbtion (PSA) system, pressurises the gas to remove CO2 and any contaminants. The second one is a water scrubber that uses water to refine biogas to green gas. Since 2014, we have been operating a membrane installation that, in addition to green gas, produces pure liquid CO2 for use in horticulture. All residual products are thus put to good use.”