The July 2006 increase in the price of electricity
repurchase has given a boost to biogas production
through methanization. This will delight farmers in
western France (Brittany, the Loire Country, and
Lower Normandy) who produce more than 50% of the
country’s livestock manure. However, in the zones
where livestock raising is the most intensive, the
priority goes to removing organic nitrogen to limit
water pollution. Yet anaerobic digestion to produce
methane does not affect the stocks of nitrogenous
matter responsible for the eutrophication of the
aquatic environment.
An ambitious project
In Rennes, within the DIGESTAERO* project, a PhD
dissertation is being conducted in collaboration
with Breton industry leaders to combine the
processes of methanization and biological nitrogen
removal by nitrification and denitrification. These
processes already exist in the food processing
industry (distilleries, fabrication of dairy
products), but they are not used in the manure
treatment context. Indeed, to limit installation
costs, the digesters should be able to be integrated
into biological nitrogen removal units that already
exist on the farm.
Moreover, the treatment unit should take into
account inputs that vary substantially in terms of
type and composition. For example, an effluent’s
rate of biodegradable material varies from 30% to
40%.
Equip livestock breeders in 2009
First, an experimental pilot made up of two
100-liter tanks was developed to study the phenomena
involved and then optimize the processes. At the
same time, a numeric model was designed first to
identify the important parameters and then to define
the optimal industry for the process. Today, the
tool provides a good response to the variations in
the liquid effluent composition. A first industrial
prototype should come out in 2009 so that it can be
adjusted to full-size operation. This will be the
last step before the industrial development of this
new process.
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Methanization: gains at all levels
With 300 million tons per year of animal
manure from livestock breeding, France
has one of the greatest potentials of
agricultural biogas production in
Europe. For example, the digestion of
1 m3 of pig liquid manure
produces approximately 25 kWh as
electricity and as much as heat. Since
July 2006, each kilowatt is bought back
up to 0.14 euros, instead of the 0.05
euros paid initially. These gains are
also important for the environment since
methanization can reduce greenhouse gas
emissions from a livestock operation.
Finally, odors are also reduced with
manure management. |
Note this on your schedule:
«What development model for the methanization of
livestock effluents is needed in France?"
This is the theme of the conference organized in
Rennes by the Cemagref, INRA, the University of
Southern Brittany, Valétec, and Odipure, to be held
on 21 November 2008. The debate will center around
the results of the DIGESTAERO project .
* DIGESTAERO, a project financed by the ANR,
associates the Cemagref, the Narbonne INRA, the
University of Southern Brittany, and two Breton
industries: Valétec and Odipure.
Some publications :