France develops 'super maize' for biogas

We are actively following the developments on the front of biogas technology (here, here and here) because the green gas has many advantages over liquid biofuels (earlier post). In Europe, a lot of work is going on, with Scandinavian countries investing in a biogas infrastructure for cars, whereas in Central Europe (mainly Germany and France), the gaseous biofuel is becoming a prime feedstock for the generation of CO2-neutral electricity.

Biogas (biomethane) can be made from the anaerobic digestion of agricultural, household and municipal waste, or from organic industrial residues such as abbatoir waste. More and more, though, dedicated biomass crops are being used as a biogas feedstock (research info below). In Germany, energy crops for the production of biogas already make up 10% of the entire energy crop hectarage. In France, a special 'giant maize' variety [*.french] has now been developed solely for methanisation, by the Arvalis Institut du Végétal, near Rennes.

The maize is a cross between Peruvian highland varieties and continental European varieties. The Peruvian maize is adapted to the harsh climatic conditions of the Andes mountains, but when crossed with his European counterpart, and cultivated in the mild climate of the continent, the maize turns out to grow extremely fast ("in Europe, they literally explode" as one researcher has it). The hybrid produces very high levels of biomass, with a dry matter yield of around 30 tonnes per hectare.

The maize, is not suitable as a fodder, because, as researcher Joël Thierry explains "forage maize has a high cellulose content, whereas the biogas maize is starch-rich. This maize is dedicated to the production of biomethane only". The grain yield of the Euro-Peruvian super hybrid isn't exceptional, but its stalks and leaves are all the more so.

Arvalis is now working on reviving a maize variety with low lignin contents which it developed earlier (lignin is the 'woddy' and 'fibrous' part of plants, which are least degradable.) Unsuitable as a forage crop, it finds a new life as a dedicated energy crop. As Joël Thierry says, "the new maize varieties are also highly efficient in recycling and fixing nitrogen, which decreases fertilizer requirements and which ups their energy balance."

The enthusiasm for biogas in France is due to active government support, with a regime allowing producers to feed the electricity they generate into the national grid:
biomass :: bioenergy :: biofuels :: energy :: sustainability :: biogas :: methane :: maize :: France ::


They get a good compensation for it, because the CO2-emission reductions value of the green gas is taken into account. The national electricity company, Electricité de France, has set the price for this green electricity twice as high as that of regular electricity. Farmers are obviously jumping on the opportunity.

This price regime allows farmers to difversify their revenue sources. Biogas installations are fairly simple and not too capital intensive. A digester is basically a big pit where the maize (and other substrates) are mixed, heated and then left to degrade by bacteria. Compare it to a simple artificial stomach of a cow, with an electricity generator attached to it at the end. After 20 days of fermentation, the producer obtains biogas with a methane content of around 60-70%, CO2 and a solid matter rich in organic matter which makes for a green fertilizer. A liquid with a high ammoniac content (feedstock for N-fertilizer) is also obtained as a byproduct.


More information:

Le magazine agricole des grandes cultures: Un maïs géant pour faire du méthane - Oct. 1, 2006

Arvalis Institut du Végétal: Institut du Végétal prépare le maïs du futur: faisons confiance à l'innovation - Sept. 21, 2006

Thomas Amon, Vitaliy Kryvoruchko, Barbara Amon, Werner Zollitsch, Erich Pötsch: Biogas production from maize and clover grass estimated with the methane energy value system - [*.pdf] Department of Sustainable Agricultural Systems, Division of Agricultural Engineering, University of Natural Resources and Applied Life Sciences, University of Vienna.

Pia Mähnert, Monika Heiermann, and Bernd Linke: Batch- and Semi-continuous Biogas Production from Different Grass Species,[*.pdf] Leibniz-Institute of Agricultural Engineering Potsdam-Bornim, Agricultural Engineering International: the CIGR Ejournal. Manuscript EE 05 010. Vol. VII. December, 2005.

Annimari Lehtomaki: Biogas production from energy crops and crop residues [*.pdf], Dissertation, Jyvaskyla Studies in Biological and Environmental Science (163), Faculty of Mathematics and Science, University of Jyvaskyla, 2006.