The carbon budget implications of establishing Miscanthus plantations

Andy Robertson (PhD candidate at CEH Lancaster)

Supervised by Dr. N. McNamara, Dr. C. Davies and Prof. P. Smith with help from Dr. E. Bottoms, Dr. A. Stott and H. Grant

Problems and solutions

• National governments are committed to reducing CO2 emissions

• But as energy demands increase so too do CO2 emissions from fossil fuel derived energy

• Renewable sources of energy are likely to be part of the solution

• Bioenergy has great potential but uncertain just how beneficial it can be - data is lacking!

Viability of bioenergy

• Sustainability criteria required before implementation • Ecosystem services, carbon budgets, biodiversity...

• This research focuses on C budgets and C cycling

• Benefits are very location dependent but measuring everywhere is impossible – therefore, modelling is required

• Several components of C cycling models are poorly quantified and this research aims to ‘fill the gaps’

Miscanthus as a bioenergy crop

• Very different to other crops currently grown in the UK

• Miscanthus is a C4 crop species that can grow up to 4 meters tall and produce >10 t · ha-1 · yr-1

• Ideal life cycle for annual biomass production

Miscanthus life cycle

April

June August

March December

October

February

Miscanthus as a bioenergy crop

• Each year a lot of litter is left on site after the plantation is harvested. How much C does this add to the soil?

Carbon cycling in Miscanthus

• Carbon moves continuously through the ecosystem • Two C inputs to soil below a bioenergy crop – litter and roots

Input manipulation experiment

• Trenches dug to exclude roots • Plant litter managed monthly • All plots sampled for:

Efflux of CO2

Soil C/N and NH4+/NO3

- contents

Results to date – CO2 emissions

0

100

200

300

400

500

600

700

800

Single Litter Double Litter No Litter No Roots No Roots or Litter

Cum

ulat

ive

CO2 e

mis

sion

s (m

g CO

2-C

∙ m-2

)

Treatment

Miscanthus as a bioenergy crop

• Miscanthus C has a different isotopic signature to the soil allowing belowground respiration to be partitioned

• This also allows the C from the plant to be traced into the C in the soil

• Working with SIF upstairs to use 13CO2 values to track how much CO2 is Miscanthus-derived.

Results to date – CO2 emissions by source

0

100

200

300

400

500

600

700

Single Litter Double Litter No Litter No Roots No Roots or Litter

Cum

ulat

ive

CO2 e

mis

sion

s (m

g CO

2-C

∙ m-2

)

Treatment

C4 - Miscanthus Carbon

C3 - Original carbon

Future research

• Continued investigation and more detailed analysis of current experiment

• Study the amount of Miscanthus C in soil from different treatments

• Remove treatment effects on abiotic factors and determine if differences in C efflux are still significant

• Going to Aberdeen in October to work with modellers who can help apply the data to a C cycling model

Acknowledgements

Supervisors Niall McNamara (CEH Lancaster) Pete Smith (University of Aberdeen) Christian Davies (Shell Global Solutions) Jon Finch (CEH Wallingford)

Other acknowledgements Emily Bottoms Andy Stott Helen Grant Sean Case Mike Whitfield Simon Oakley Harriet Rea Photo credits to Emily Bottoms and www.SimplyNetworking.com