Use of biochar to enhance carbon sequestration in peatlands

Although peatlands are a great store of terrestrial carbon they are only a small sink compared to other nature-based or technological approaches to carbon sequestration. So as to exploit the considerable carbon storage potential of peatlands is it possible to enhance the magnitude of the peatland carbon sink with additional inputs of carbon? Biochar is refractory form of carbon that can be sourced from natural woody materials including biomass that may grow on peatlands. Biochar’s refractory nature means that it has commonly been proposed for nature-based carbon storage. The advantage of using biochar on peatlands is that natural accumulation of peat means that the growth of peat may absorb the added biochar where on mineral soils biochar may come to dominate with repeated additions of char. However, the fate and impact of biochar on the natural function of peat soils is not known – this study has aimed to fill this knowledge gap and assess whether biochar could be applied to peatlands?

This study has conducted a random-block design based upon two different application rates of biochar to a former lowland raised bog in Yorkshire. The trial consisted of triplicated plots considered within the water table frame of the peatland and plots visited at least monthly for more than a year. The plots were monitored for: gross primary productivity; net CO2 exchange; ecosystem respiration; soil water quality; albedo; and vegetation coverage alongside measurement of water table depth and weather parameters.

The study shows:

• that although biochar is alkali, and that there was an initial difference in pH due to biochar treatment, this difference did not last;
• the soil water conductivity was dominated by changes in depth to water table and not biochar treatment;
• after 10 months the DOC in soil water on treated plots was significantly higher on biochar treated plots;
• vegetation had recovered from biochar treatment within 6 months; and
• there was no significant difference in NER between treatments showing no ready decomposition of the biochar.

The limitations of biochar to enhance carbon storage in peatlands are more likely to be economic than biogeochemical.