The role of biochar in English agriculture : agronomy, biodiversity, economics and climate change
File(s)
Author(s)
Gathorne-Hardy, Alfred
Type
Thesis
Abstract
This thesis explores the impact of biochar on the sustainability of English agriculture. It takes an integrated approach by looking at a range of agronomic, economic, biodiversity and climate change conditions that affect the total sustainability of biochar. Central to biochar use is its impact on yield. Laboratory and field trials were established to investigate the agronomic properties of biochar in both arable and grassland situations. Biochar strongly increased arable yields when associated with higher nitrogen fertiliser levels, showing an increase in Nitrogen Use Efficiency (NUE). Biochar had no apparent impact on grass yield. Central to biochar sustainability is the sustainability of its feedstocks. Four feedstocks were identified whose use could potentially increase local biodiversity, and whose use is potentially sustainable - coppiced hedgerows, undermanaged small farm woodlands, short rotation coppice willow and straw. The impacts of harvesting these on biodiversity were assessed through a combination of experiments and desk based review. The management of small farm woodlands is likely to increase sustainability. The sustainability of hedgerow coppicing depending on species groups - beetle numbers increased, but small mammal numbers were not affected. There is little evidence about the impact of removing straw on soil biodiversity, but if biochar replaces straw, straw can be harvested sustainably. The yield results from the arable trials were fed into three spreadsheet models. The first explored the net greenhouse gas (GHG) balance of biochar use. To better understand the impact of emission timing on biochar use a novel accounting method - Net Present Carbon -was developed. Biochar use can mitigate or exacerbate climate change, depending on the feedstock used and the boundaries of the model. The second model looked at the net economic balance of biochar use. Depending on feedstocks, biochar can be economical to produce without carbon payments through yield gains. Including a C price makes the economic return highly dependent on the C balance. A final model was then developed to investigate the trade-offs of biochar use between five different sustainability objectives: fixed carbon (C), all GHG emissions, economic return, local biodiversity and global biodiversity. Overall sustainability of biochar use depends greatly on what measure is used to assess sustainability-there is no scenario where it is possible to optimise all sustainability indices, instead trade-offs always occur.
Version
Imperial Users only
Date Awarded
2012
Advisor
Knight, Jon
Woods, Jeremy
Heaton, Becky
Cowie, Annette
Sponsor
UKERC through the SPARKS network.
Publisher Department
Centre for Environmental Policy
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)
Author Permission
Permission not granted