Maximising greenhouse gas sequestration in the UK uplands

Biogeochemical Cycles

IAP2-20-043

Overview

The most efficient carbon (C) store in the terrestrial biosphere are our peatlands – UK peatlands store more carbon than the forests of UK and France combined, and furthermore, unlike forests, peatlands can be perpetual greenhouse gas (GHG) sinks. Analysis for the UK’s National Emissions Inventory indicates that the UK’s peatlands currently emit at least 23 Mt CO2eq /yr (4% of reported UK GHG emissions for 2018), but if properly managed they could be a net sink of 2 Mt CO2eq /yr. Thus there is already an opportunity to manage peatlands to provide both an avoided loss of GHG and a perpetual sink. But are these National Emissions Inventory values the best we can do for peatlands?
The current approaches to bringing peatlands back to being GHG sinks has focused on raising water tables and revegetating with peat-forming species (eg. sphagnum mosses) but could that be improved and increased? There are approx. 18000 km2 of deep peat in the UK with up to 7000 km2 of that peat is under burn management of heather (Calluna vulgaris) and the total area of heather in the UK is nearer 30000 km2. Two GHG management opportunities arise from the occurrence of heather and its rotational burn management. Firstly, this supervisor has estimated that current burn management in the UK releases 821 PJ/yr (26 GW) which is more than the current UK biomass energy target – could that heather be harvested for biomass energy? Second, if heather biomass could not be burnt for energy could it go for local biochar production and re-applied to peatland, i.e. adding to carbon sequestration? This project will address these two possibilities, and specifically, address the following questions:
• What is the impact of cutting, rather than burning heather on peatland functions and services (e.g. GHG regulation, biomass, water quality) ?
• Can biochar enhance peatland function without affecting other ecosystem services?
• How much biochar can be applied to peat without detrimental impact?
• How much heather can be harvested from the UK?
The project will address these questions using a combination of field experiments and modelling studies based upon sites in the Peak District and the North Pennines. The output from the project is to provide novel choices for the sustainable management of UK upland peatlands in light of the government’s commitment to achieving net zero GHG emissions by 2050.

Methodology

At upland sites we will establish 20 x 20 m replicated plot. These plots will follow an experimental design that allows for pre- and parallel controls as well as replicated treatments. In year 1 all plots will be monitored for a baseline with treatment intervention at end of year 1. Treatments would include: cutting of heather; cutting of heather with addition of biochar and a control. Each plot will be instrumented to consider the range of Carbon and GHG fluxes in the context of the prevailing soil and hydro-climatic conditions. Triplicated fixed collars will be used for CO2 and CH4 flux measurement; surface runoff traps will collect particulate organic carbon (POC), and dipwells will give access to soil water and enable water table measurement. Soil water will be analysed for DOC but also their pH and redox conditions. One automatic weather station will be used for the entire experimental design. At the start of the experiment the plots will be characterised for their biomass composition and stock and peat cores analysed (especial attention to presence of biochar), It would be expected that plots would be visited and monitored on at least a monthly basis. Annual GHG, water and solute fluxes will be constructed using standard protocols developed for previous peatland research and along with soil and biomass measurements used to calculate C/GHG budgets for each site and treatment. In addition a series of mesocosms will be established at Durham University to test specific question arising from the observations from the field trials.

Project Timeline

Year 1

1. Literature review
2. Establish field trial plots
3. Training in field and laboratory techniques
4. Characterise field trial plots
5. Run field trial plots for control year

Year 2

1. Carry out treatment interventions
2. Run field trials for first treatment year
3. Establish mesocosm experiments

Year 3

1. Run field trials for second treatment year
2. Conduct mesocosm experiments
3. Present results at international conference (eg. EGU in Vienna)
4. Analyse data for writing up

Year 3.5

1. Complete thesis
2. Write up papers

Training
& Skills

he studentship will involve full training in the necessary field, laboratory and data analysis techniques needed. The field techniques include: formal experimental design; the use of gas analysers; systematic sampling; and total greenhouse gas budgeting. Laboratory analysis will include: gas calibration; water quality analysis and mesocosm experiments.

References & further reading

1. Evans CD et al (2017) Peatland Inventory Report to BEIS; https://ukair.defra.gov.uk/assets/documents/reports/cat07/1904111135_UK_peatland_GHG_emissions.pdf
2. Royal Society (2019) Greenhouse gas removal; https://royalsociety.org/topics-policy/projects/greenhouse-gas-removal/
3. Worrall F, Clay GD (2014) The potential use of heather, Calluna vulgaris, as a bioenergy crop. Biomass & Bioenergy 64, 140-151.

Further Information

Prof. Fred Worrall, Dept of Earth Sciences, University of Durham, Tel. no. 0191 334 2295, Fred.Worrall@durham.ac.uk

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