Acidifying emissions

  • Acidifying emissions reduced by 71% between 1990 and 2018

    Between 1990 and 2018, potentially acidifying emissions decreased from almost 18,700 million to just under 5,500 million acid equivalents. This corresponds to a decrease of 71%. This figure is the sum of 3 types of emissions: sulphur dioxide (SO2), nitrogen oxide (NOx) and ammonia (NH3). This sum is expressed in acid equivalents, taking into account the acid-forming capacity of each substance.

    The decrease in potentially acidifying emissions between 1990 and 2018 is largely due to a significant decline in SO2 emissions (-89%). NH3 and NOx emissions dropped by respectively 56% and 59% in this period.

  • Agriculture main source of acidifying emissions

    Agriculture was in 2018 by far the most important source of potentially acidifying emissions (49%), followed by transport (19%) and industry (17%).

    In 2018, NH3 emissions made the largest contribution to the total acidifying emissions. This is largely due (95%) to agriculture. NH3 emissions did decrease between 2000 and 2018 by 28%. This was achieved by fertilisation standards, the reduction of livestock, the lower nitrogen content of animal feeds, the low-emission use of animal manure in fields and meadows, the construction of low-emission sheds and increased processing of manure. Emissions have stagnated over the last decade. A slight increase in the number of livestock and higher NH3 emissions due to the use of artificial fertilisers reduce the beneficial effect of low-emission sheds and manure processing.

    The NOx emissions made the second largest contribution to the total acidifying emissions in 2018. Emissions decrease slightly each year: compared to 2017, NOx emissions decreased by 4% in 2018. The transport sector accounted for half of these emissions (49%).

    In 1990, SO2 emissions accounted for the largest share of total acidifying emissions. In 2018 this share decreased to the smallest contribution. The largest decrease occurred between 1990 and 2010, and was largely due to consecutive EU directives concerning the restriction of sulphur in fuels. The industry and energy sectors are the main sources of SO2 emissions, with a respective share of 52% and 33%.


Flemish Environment Agency (VMM): Environmental report (MIRA), acidifying emissions 


Potentially acidifying emissions: sum of the emissions of sulphur dioxide (SO2), nitrogen oxide (NOx, expressed as NO2) and ammonia (NH3). This sum is expressed in acid equivalents (Aeq), with the acidification potential of each substance being separately factored in. The term ‘potentially’ acidifying emissions is used because the actual acidification also depends to a large extent on the processes involved between emission and deposition and on the various processes in the soil and (surface) water.

Publication date

13 January 2021

Next update

October 2021

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