Largest nitrogen flows in chemical industry, energy and agro-food sectors
In 2009, the nitrogen flows in 11 nodes of the Flemish economy and households varied between 25 and 546 ktonnes N. The largest flow passes through the chemical and other industries (546 ktonnes N). These include the fertiliser industry and the paper industry, with the fertiliser industry processing 98 % of the nitrogen in the ammonia synthesis from inert nitrogen gas (N2).
The energy sector has a large nitrogen flow (462 ktonnes N) due to the nitrogen content of natural gas (14 %), which is neutral to the environment because it is inert nitrogen gas (N2). Emissions from the energy sector consist for 99 % of nitrogen gas (N2).
The agro-food sectors (cattle feed industry, agriculture split up into animal production and crop production, and food industry) form the main block within which intense exchange of nitrogen between the nodes takes place. Imports of nitrogen in the form of crops for cattle feed have been allocated to the cattle feed sector. The processing of manure has been allocated to the node 'biomass processing'. This also includes the composting of organic biological waste (fruit, vegetable and garden refuse, green compost and other organic waste) and industrial digestion with power generation. This relatively small flow (31 ktonnes N) is in full expansion and has therefore been included as a separate node.
The transport sector comprises all goods and passenger traffic in Flanders. Imports pertain to the nitrogen content of fossil fuels. Emissions to air are not regarded as exports, but constitute a substance flow to air in the amount of 65 ktonnes N.
Households and trade & service include residential nitrogen flows through food consumption (51 ktonnes N). Waste processing and public wastewater treatment process final production and consumption flows in Flanders. Public wastewater treatment comprises the interconnected sewer system (including sewer overflows) and sludge treatment.
Potential for reuse and recycling
Total imports across all nodes are estimated at 1,017 ktonnes N, or 1 million kg N. Exports amount to 656 ktonnes N. The difference, 362 ktonnes N, indicates the order of magnitude of the accumulation in the environment in Flanders in 2009, including inert N2 gas. A precise estimation of this accumulation or emissions is included in the MIRA core set 'environmental data'.
It shows that Flanders has a surplus of nitrogen available in waste and residual flows such as household waste water, organic biological waste and animal manure. This provides a large potential for reuse and recycling. Environmental gains can be achieved in the agro-food sectors in particular. Nitrogen can be reused and emissions to water, air and soil can be reduced.