Samsø chasing a Bio-LNG solution
A delegation from Samsø travelled for inspiration on liquefaction of biogas in Northern Ireland. GO-LNG supports this planned green revolution at Samsø to deliver Bio-LNG for the ferry, and the liquefaction technology is the key to the business plan. The study visit has been financed by Go-LNG.
New ways ahead
For most biogas enthusiasts the injection of biomethane to the gas grid is usually the way to go in Denmark, but when a ferry has been constructed for liquefied gas, the liquefaction is indispensable. However, the trip opened the eyes for an interesting liquefaction solution, which may also be applicable for other areas with biogas potential and no gas grid.
Biomethane is in some cases today transported in compressed form for transport usage over longer distances in expensive trailers as compressed gas at 220 bar. However, this liquefaction technology may become a competitive alternative in areas without a gas grid under certain conditions. A trailer with Bio-LNG can move 7 times the amount of energy compared to compressed biomethane. This can expand the use of Bio-LNG for heavy transport to more cases.
Greenville Energy had a biogas plant and used the gas to traditional CHP to produce heat and power. An increase in production and new potential customers could only be reached via liquefaction and Cryo Pur from France was contacted. Cryo Pur has designed a new technology for this exact purpose in small-scale, corresponding to a farm-scale biogas – or the planned Samsø biogas size. Very few biogas liquefaction plants of this size exist worldwide.
Greenville is now selling Bio-LNG to a dairy some 50 km away and the business case is good under these conditions. Return on Investment was calculated to be 4 years for Greenville Energy and the plant was installed and inaugurated in January 2018.
Denis Clodic, the founder of Cryo Pur, explained with enthusiasm about the technology for biogas liquefaction (see Box). The plant was assembled in Paris and installed in Omagh during 5 weeks and inaugurated in January 2018.
Basically, there are 4 steps in the process from raw biogas to liquefied biomethane – or Bio-LNG. The plant treats 300 m3 raw biogas hourly
1. The raw gas is cleaned of Sulphur in a filter of activated carbon which is standard at many biogas plants.
2. The gas is cooled down to minus 70 degrees C where water and other impurities from the gas are frozen. In a double line, this process can continue and alternate between freezing and thawing, removing the water from the gas.
3. The remaining CH4 and CO2 is cooled further to minus 120 degrees C, where CO2 will freeze and is released as liquefied CO2 and stored in cryogenic storage
These first steps are carried out at atmospheric pressure
4. The methane is cooled further and under a pressure of 14 barg the methane is liquefied and stored in cryogenic storage
The daily production is around 5 tons liquid CO2 and around 3 tons of liquid CH4.
The process uses a unique knowledge of temperature and pressure controls but technology bricks are kept simple as it uses conventional refrigeration systems..
The Samsø Business case
At Samsø, the ferry at present buys LNG on the world market in Rotterdam with low taxes challenging the biogas and liquefaction business plan. It may not be economically feasible to deliver Bio-LNG at this price, and if the local politicians are not willing to pay extra and increase the ferry ticket price, it may not be realized.
However, this visit has inspired Samsø to think of new alternatives. If a biogas plant with liquefaction can be established and delivering the Bio-LNG to more lucrative markets than the ferry this could be a start. The Island will get the same benefits in terms of recycling of societal wastes into nutrients, the associated jobs and circular economy.
Søren Stensgaard, head of Technical Department at Samsø Municipality see new opportunities with this technology. – We can see several new options for us to open up for Bio-LNG. We can potentially reach new customers, we can create the circular economy on the island and potentially the liquid CO2 is another product for new customers or for future methanation to produce more biomethane. It is not our first choice to by-pass the ferry, but the liquefaction technology could pave the way for interesting bio-LNG alternatives.