Acidifying emissions

  • Acidifying emissions significantly reduced

    Between 1990 and 2017, potentially acidifying emissions dropped by 70%.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 equivalent, taking into account the acid-forming capacity of each substance. 

     

    The decrease in potentially acidifying emissions between 1990 and 2017 is largely due to a significant decline in SO2 emissions (-89%). NH3 and NOx emissions dropped by respectively 56% and 57% in this period. 

  • Agriculture main source of acidifying emissions

    Agriculture was in 2017 by far the most important source of potentially acidifying emissions (48%), followed by transport (21%) and industry (17%). 

     
    In 2017, NH3 emissions made the largest contribution (46%) to the total acidifying emissions. This is largely due (95%) to agriculture. NH3 emissions did decrease between 2000 and 2017 by 28%. This was achieved by 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. Since 2005, these emission levels have levelled out since the slight increases in the number of livestock and manure processing and the expansion of low-emission sheds have offset each other. 

     
    The NOx emissions made the second largest contribution (39%) to the total acidifying emissions in 2017. The transport sector accounts for more than half of these emissions (52% ). The large number of diesel vehicles in the transport fleet has a negative influence on NOx emissions. Diesel cars emit more NOx than petrol cars. 56% of all cars ran on diesel in 2017. 

     
    In 1990, SO2 emissions accounted for the largest share (43%) of total acidifying emissions. In 2017, this share had decreased to 16%, 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 SO2emissions stagnated after 2011. The industry and energy sectors are the main sources of SO2 emissions (with a respective share of 51% and 34%). 

Sources

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

Definitions

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 deposit and on the various processes in the soil and (surface) water. 

Publication date

21 November 2019

Next update

November 2020

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