1. Abstract
Biogas Upgrading is a young market in France. It has been regulated since the end of 2011. The benefits
of green gas in term of circular economy, sustainable development and environment assure that this
sector will have an important part in the energy transition of our XXIst
century. Since the sector is
subsidized, biogas upgrading market is developing very fast in France. At the beginning of the summer
of 2016, nineteen plants inject green gas on the natural gas grid and a hundred are in construction or in
the end of funding.
Biogas upgrading consists in removing hydrogen sulphide, water,carbon dioxide and unwanted traces
compounds from biogas to allow biomethane injection in gas grids.
There are several methods to eliminate hydrogen sulphide but the final one to reach very low
concentration is always by using carbon molecular sieves. All processes involve compression and
cooling system to eliminate water. The difference between upgrading processes is the technology used
to eliminate carbon dioxide. Water scrubbing, chemical scrubbing, pressure swing adsorption and
membranes are sharing the market. Cryogenic upgrading is also a developing technology.
Tens of companies develop the whole process to upgrade biogas. Mature process guarantee an effective
time of work superior to 8500 hours per year. A trend is seen on the methane loss of the process. From
the lower to the bigger, there is cryogenic upgrading, amine scrubbing, membranes,waterscrubbing and
pressure swing adsorption (PSA).There are other important parametersfor the choice of the technology.
For example, PSAis the only one able to eliminate oxygen and nitrogen. Waterscrubbing does not allow
the valorization of the carbon dioxide in the offgas. Some PSA allow to produce heat by burning the
offgas in a burner low power. Some processes produce more or less heat whereas others consume it and
the choice depends on the heat requirement of each project.
Business plans, made for each estimate, give the economic criteria associated with an upgrading biogas
project. This economic study show the upgrading cost for projects of different capacity. The price of
biogas is calculated to have a profitable investment in biogas upgrading, for a company buying biogas
and selling biomethane. A modelisation of these costs shows the limit of the profitability for a small
capacity upgrading project.