Does soil carbon loss in biomass production systems negate the greenhouse benefits of bioenergy?

Annette L. Cowie*, Pete Smith, Dale Johnson

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

72 Citations (Scopus)

Abstract

Interest in bioenergy is growing across the Western world in response to mounting concerns about climate change. There is a risk of depletion of soil carbon stocks in biomass production systems, because a higher proportion of the organic matter and nutrients are removed from the site, compared with conventional agricultural and forestry systems. This paper reviews the factors that influence soil carbon dynamics in bioenergy systems, and utilises the model FullCAM to investigate the likely magnitude of soil carbon change where bioenergy systems replace conventional land uses. Environmental and management factors govern the magnitude and direction of change. Soil C losses are most likely where soil C is initially high, such as where improved pasture is converted to biomass production. Bioenergy systems are likely to enhance soil C where these replace conventional cropping, as intensively cropped soils are generally depleted in soil C. Measures that enhance soil C include maintenance of productivity through application of fertilisers, inclusion of legumes, and retention of nutrient-rich foliage on-site. Modelling results demonstrate that loss of soil carbon in bioenergy systems is associated with declines in the resistant plant matter and humified soil C pools. However, published experimental data and modelling results indicate that total soil C loss in bioenergy systems is generally small. Thus, although there may be some decline in soil carbon associated with biomass production, this is negligible in comparison with the contribution of bioenergy systems towards greenhouse mitigation through avoided fossil fuel emissions.

Original languageEnglish
Pages (from-to)979-1002
Number of pages24
JournalMitigation and Adaptation Strategies for Global Change
Volume11
Issue number5-6
Early online date24 Aug 2006
DOIs
Publication statusPublished - 30 Sept 2006

Bibliographical note

We acknowledge the support for this project provided by International Energy
Agency Task 38, and particularly thank Robert Matthews for helpful discussions
on structure and content. We thank Gary Richards for making FullCAM available
for this project, and Keryn Paul for advice on FullCAM, and for supplying the
FullCAM parameterisation data.

Keywords

  • Bioenergy system
  • Greenhouse gas balance
  • Land use change
  • Soil carbon

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