AcidNews June 2015
Four Nordic projects for anaerobic digestion of manure show the potential for this methane abatement technique under varying conditions.
The Nordic Council of Ministers has published a report entitled “Nordic initiatives to abate methane emissions – A catalogue of best practices”. Five of the fourteen case studies are in the farming sector. Four of them are biogas projects.
Table: Comparison of the four projects.
Måbjerg Bioenergy plant in Denmark is one of the largest biogas facilities in the world. More than 140 suppliers provide the plant with manure slurry. Some of it is transported by pipeline, but most of the slurry gets there by road.
The biogas plant provides one heating plant and one central heating plant with gas that meets the heating needs of 5,000 homes and supplies 12,000–12,500 homes with electricity.
Lövsta is a medium-scale biogas plant run by the Swedish University of Agricultural Sciences. It is fed with a manure mix from cattle, pig and poultry, as well as potatoes from a local farm and waste flour from a mill. The biogas it produces is used for electricity production and heating.
The cost of methane abatement is basically the same for Lövsta and Måbjerg, although the scale of production differs by a factor of ten.
The third plant, Brålanda, is actually a network of several plants connected to a network and a single refining facility. The capacity is quite similar to Lövsta. The refining of biogas allows it to be used as a vehicle fuel. The methane abatement cost is only slightly higher than for the previous two plants.
Most biogas plants that digest manure are designed for processing slurry (liquid manure). However in Sweden and in many other European countries, solid manure systems are still common in farming.
Sötåsen is a full-scale trial plant for digesting solid horse manure together with cattle slurry. The results showed that the plant was more efficient than when run on cattle slurry alone. Using straw as a bedding material gave a higher methane yield, but sawdust and granulated straw caused fewer technical problems in the system. The cost of methane abatement is about three times as high as for the other, larger, biogas projects in the report, but still less than half that of some similar-sized slurry only projects.
These four case studies show that there is potential for producing biogas from manure under varying conditions, when it comes to scale, substrate and topography.
Kajsa Lindqvist
Read about other methane abatement techniques in the full report: “Nordic initiatives to abate methane emissions – A catalogue of best practices”: http://www.diva-portal.org/smash/get/diva2:764201/FULLTEXT01.pdf