Manures collected from animals such as cattle and pigs during periods of the year when they are housed, typically contain 6-10% dry matter and so are not appropriate for combustion or gasification without energetically and financially costly drying.
They are also inefficient to transport any distance or store owing to the high proportion of water.
However some energy technologies make use of biomass in an aqueous slurry, and these can make efficient use of such 'wet' materials. The high water, and low dry matter content means that the most appropriate energy technology for making use of animal slurries is anaerobic digestion for the production of biogas.
Dairy cattle typically produce between 42 kg and 64 kg (depending on body weight) of manure per day, so if they are housed for 50% of the year that corresponds to 7.6-11.6 tonnes pa per cow. Between them the UK herd of 2 million dairy cows produces around 20 million tonnes of slurry, equivalent to around 2 million tonnes of dry matter (at 10%).
The resource from the UK beef herd of 1.8 million will be less, as they typically spend less time housed, though may still be in excess of 5 million tonnes (wet) pa.
Pigs and sheep
There are also 4.9 million pigs in the UK and 20 million sheep. However, as sheep are kept almost entirely outdoors collecting their manure may not be practical.
Other uses for animal slurry
Animal slurry is widely used as a fertilizer and there are a number of methods to spread it on the land, though recent concerns about loss of ammonia to the air means that Defra now advises against broadcast spreading.