Is cattle manure a high-potential resource for biogas conversion in France?

Abstract

Agricultural biogas is a growing sector that will make use of as yet unused resources. Cattle manure is a potential resource for this sector. In this study, an inventory of French cattle manure production was undertaken by combining different databases from Agricultural Statistics (2010 French Agricultural Census, 2010 Cattle National Database Inventory) and livestock practices found on the French territory. The main results of this study show that total cattle excrement production amounts to 87 million tons per year and that farmyard manure is the main effluent with 69 million tons produced each year. Compact and very compact manure with total solids content higher than 18 %, represent a large part of the total cattle manure production (70%). Based on their physico-chemical composition, valorisation of these manures in biogas plants by solid state anaerobic digestion may be considered. However, the cattle manure resource is highly fragmented in the national territory and on the basis of current technical and economic criteria, only some farms could integrate the agricultural biogas sector. In order to better mobilize this resource it will be necessary to either pool the manure produced by several farms or to add co-substrates with higher methanogenic potential or to switch to another biogas valorisation mode.