Charcoal addition to soils in NE England: A carbon sink with environmental co-benefits?

Interest in the application of biochar (charcoal produced during the pyrolysis of biomass) to agricultural land is increasing across the world, recognised as a potential way to capture and store atmospheric carbon. Its interest is heightened by its potential co-benefits for soil quality and fertility. The majority of research has however been undertaken in tropical rather than temperate regions. This study assessed the potential for lump-wood charcoal addition (as a substitute for biochar) to soil types which are typically under arable and forest land-use in North East England. The study was undertaken over a 28 week period and found:i)No significant difference in net ecosystem respiration (NER) between soils containing charcoal and those without, other than in week 1 of the trial.ii)A significantly higher dissolved organic carbon (DOC) flux from soils containing large amounts of charcoal than from those untreated, when planted with ryegrass.iii)That when increased respiration or DOC loss did occur, neither was sufficiently large to alter the carbon sink benefits of charcoal application.iv)That charcoal incorporation resulted in a significantly lower nitrate flux in soil leachate from mineral soils.v)That charcoal incorporation caused significant increases in soil pH, from 6.98 to 7.22 on bare arable soils when 87,500 kg charcoal/ha was applied.Consideration of both the carbon sink and environmental benefits observed here suggests that charcoal application to temperate soils typical of North East England should be considered as a method of carbon sequestration. Before large scale land application is encouraged, further large scale trials should be undertaken to confirm the positive results of this research.

Research Highlights
► Charcoal was incorporated into mineral and organo-mineral soils in NE England.
► No significant difference in NER was observed other than in week 1 of the trial.
► Higher DOC was lost from vegetated soils containing large amounts of charcoal.
► Charcoal incorporation resulted in a significantly lower nitrate flux in soil leachate.
► Increased NER and DOC did not offset the C sink benefits of charcoal application.