Peat, coal and coalbed methane

Multiple stratigraphic intervals in the subsurface of the Netherlands contain layers of peat and coal. These include (pre-)Holocene peat, Miocene lignite and upper Carboniferous (Westphalian) bituminous coal and anthracite, all of which have played important roles as energy sources in the country. In the Netherlands, total peat mining between the 13th and 20th centuries reached ca. 9.4 x 109 m3, while peak annual lignite production reached 1.5 Mt. Total production of bituminous coal and anthracite in the 20th century amounted to 568 Mt. Production of these energy sources ceased during the 20th century. Current resources of lignite are estimated to be at least 1700 Mt; estimates for bituminous and anthracite coal resources shallower than 1500 m below surface are between 4000 and 38000 Mt. At the turn of the 21st century, interest in coalbed methane, i.e. gas that is contained in bituminous coal started to increase. Estimates for the theoretically recoverable volumes of coalbed methane shallower than 1500 m below surface are between 7 and 107 x 109 m3. The possibility to combine the production of this gas while simultaneously storing CO2 within the coal (considered as a sink for the CO2) was investigated but is technologically challenging. While the subsurface coal and coalbed methane resources in the Netherlands are significant, there is no desire to exploit them currently, at a time when dependency on fossil fuels is diminishing in order to avoid further increase in CO2 emissions. Substantial volumes of peat are still present in the subsurface, but its organic nature and high porosity causes land subsidence and brings challenges to the built environment. Furthermore, peat oxidation induced by drainage, especially in agricultural areas, is estimated to contribute 4.246 Mt/yr or ca. 2% of the Netherlands’ annual CO2 emissions. The remaining peat has the potential to emit 2.0 Gt CO2 into the atmosphere and regardless of the energy content of the organic rich layers, this does not fit in a sustainable energy supply system. It is therefore important to increase knowledge and understanding of the characteristics and behaviour of these layers in the Dutch subsurface.