Agriculture Reference
In-Depth Information
Consequently, centralised biogas plants developed from solely energy
production plants into integrated energy production, waste treatment and
nutrient redistribution facilities.
Recognising that centralised biogas plants make a significant
contribution to solving a number of environmental problems in the fields of
agriculture, waste recycling and greenhouse gas reduction, the Danish
government has supported the development in different ways; an
appropriate legislative framework, research and development programmes,
investment grants and other subsidies. As a result, today 20 centralised
biogas plants are in operation in Denmark.
The overall purpose of the Danish biogas development programme
is to contribute to fulfilment of national ambitions in renewable energy
production as a tool of green house gas mitigation and organic waste
recycling.
2. THE CENTRALISED BIOGAS PLANT CONCEPT
Most of the biomass resources applicable to biogas plants in Denmark is
livestock manure, mainly slurry. Livestock production is concentrated in
the western parts of the country. Consequently, most centralised biogas
plants are placed in these areas. Slurry is transported in vehicles to the
biogas plants. Organic waste from food industries, found in the same areas,
is also applied to the biogas plant. Some plants also treat source sorted
household waste.
At the biogas plant the biomass is digested in anaerobic digestion
tanks, which include sanitation facilities that ensure pathogen kill to a
satisfactory level. After 12 - 25 days the now digested manure is
transported by vehicle to the slurry storage tanks at the farms or near the
fields where the slurry is end-used as a fertiliser. In Figure 12.1 a future
separation option is stipulated, which will presumably be implemented
when the appropriate technology is developed, as it becomes more evident
that a further distribution of nutrients is required in order to reach a higher
level of sustainability in manure handling and utilisation for agriculture as
a whole. In this respect technologically advanced separation systems are
required. If centralised biogas plants turn out to control these technologies
the way is opened for a wider adoption of biogas plants in many regions of
the world.
The biogas that emerges during the anaerobic digestion process is
converted into heat and power in a combined heat and power generation
facility. Power is sold to the electricity grid, and heat is sold through a
district heating system.
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