Assessing the multifunctional role of anaerobic digestion in England

360 Pages·2015·4.12 MB·English

by  Robert Tickner

Assessing the
multifunctional role of
anaerobic digestion
in England

Robert Charles Dominic Tickner
September 2014

A thesis submitted to the School of Environmental Sciences at the University of East Anglia in
fulfilment of the requirements for the degree of Doctor of Philosophy

© This copy of the thesis has been supplied on condition that anyone who consults it is
understood to recognise that its copyright rests with the author and that use of any
information derived there from must be in accordance with current UK Copyright Law. In
addition, any quotation or extract must include full attribution.

To the Edwards Tickner

To Edward George Tickner (1939–1997), whose memory I cherish,
who provided me with so many opportunities in life, including completing this thesis;
I aspire to do as much for my family.

To Edward Louis Tickner (2012–), who brings so much joy and laughter to our lives;
I hope to provide as many opportunities for him as my father did for me.

Abstract
The main drivers behind today’s energy policy dialogue relate to the impacts of energy
generation on the environment; the finite resources used to generate energy; and the nation’s
desire to provide an affordable and secure source of energy. Bioenergy is recognised as
playing a significant role in helping the UK to meet its low-carbon objectives by 2050. Thornley
et al. (2009) emphasised the importance of accurate information regarding the relevant
impacts on entire bioenergy systems when making choices relating to the development of
new bioenergy capacity.
Motivated by the environmental and economic challenges provoked by the impact of
increasing energy demands and resource competition on the biosphere, this thesis assesses a
single bioenergy conversion technology – anaerobic digestion (AD). By examining the
technology’s capacity to generate energy, mitigate GHGs and manage biowaste materials, this
research aims to establish the role that AD might play in England.
Adopting a novel approach to assessment, this research combines life-cycle and economic
measures in a single computer model, which is used to assess four different potential methods
for the deployment of AD in England, including the hub-and-pod concept, not used in this
country to date.
The energy-generating, agricultural and waste management sectors of the UK collectively
emitted approximately 259.4 MtCO .a-1 in 2011 (DEFRA, 2013b). In 2013, the UK generated
2eq
359 TWh electricity (DECC, 2013a: Chapter 5). This research demonstrates that in the three
regions of England investigated, using the hub-and-pod method explored by this thesis, AD
could mitigate 4.072 MtCO .a-1 (1.6 per cent) of these UK annual GHG emissions, and could
2eq
generate 5.45 TWh (1.5 per cent) of electricity generated annually by the UK. These figures
represent 10 per cent of the government’s renewable energy target for 2020 (EU, 2009).

Acknowledgements
The author is enormously grateful for the support offered throughout this research from both
Professor Andrew Lovett and Dr Jane Powell, who jointly supervised this work. Both provided
endless advice, guidance and support, from which I have learnt an enormous amount. A
special thank you to you both for your patience, particularly when reading my work. Thanks
must also go to Dave Knott, who showed me that MS Excel can do far more than add and
subtract; Andrea Finegan, who provided an insight to the world of energy finance; and Dr Neill
Mackay, who sang to us all in the office during our dark days of research, and enlightened me
in some mathematics.
A number of people have been extremely kind and generous with their time and advice,
enabling this research to be completed with a high degree of accuracy. Thanks go to Russell
Mulliner (Marches Biogas), for his advice on the building specifications of AD facilities; Lois
Griffin and Dr William Mezzullo (Future Biogas); Stephen Finch (Royal Agricultural College),
David Moreton (Easton College) and Richard Davies (DairyCo), who all provided invaluable
advice on different aspects of farming practices across the country; and many other people
across the AD industry, including Lucy Hopwood (NNFCC), Rosaline Hulse and Matt Hindle.
A special thank you to all those who agreed to participate in the questionnaires and interviews
completed at the start of this research, and who provided such a colourful insight into the
world of AD. They remain anonymous, as agreed at the outset. However, in particular, a big
scoop of ice-cream gratitude goes to Gary Jones, who, with ebullient enthusiasm, provided an
insight into all aspects of AD, and is never one to shy away from offering an opinion or a little
anecdote of the quirks of the industry.
Last, but not least, to my friends and family, who have provided support and encouragement
over the last few years. To my son, Edward, who allowed me to miss book and bedtime far too
often; and to my wife, Alison, for her love, support and encouragement over the last four
years, and in particular for reading this thesis more times than she would have desired.
This research has been an enlightening experience and has been made possible by all those
who have helped. It has been extremely rewarding to have had the opportunity to work with a
lovely bunch of people across academia, agriculture, engineering, finance and government.
Thank you all.

TABLE OF CONTENTS
List of figures ............................................................................................................................. xvii
List of tables ................................................................................................................................ xxi
Abbreviations and notations ..................................................................................................... xxv
Chapter 1: Introduction ................................................................................................................ 1
1.1 introduction ................................................................................................................... 1
1.2 Background .................................................................................................................... 1
1.3 Energy and the environment ........................................................................................ 5
1.4 Bioenergy....................................................................................................................... 7
1.4.1 Sustainability .......................................................................................................... 8
1.4.2 Biowaste management ........................................................................................ 10
1.5 Anaerobic Digestion .................................................................................................... 13
1.5.1 Generating energy with anaerobic digestion ...................................................... 14
1.5.2 Mitigating greenhouse gases with anaerobic digestion ...................................... 15
1.6 Anaerobic Digestion Strategy and Action Plan (2011) ................................................ 17
1.6.1 Anaerobic digestion facilities in the UK ............................................................... 17
1.6.2 The Strategy and Action Plan ............................................................................... 18
1.6.3 Incentives ............................................................................................................. 19
1.7 Summary and thesis outline ........................................................................................ 20
Chapter 2: Literature review ...................................................................................................... 22
2.1 Introduction ................................................................................................................. 22
2.1.1 Evaluation of anaerobic digestion ....................................................................... 24
2.2 Life-cycle assessment of anaerobic digestion ............................................................. 25
2.3 Economic assessment of anaerobic digestion ............................................................ 30
2.3.1 UK support mechanisms for anaerobic digestion ............................................... 31
2.3.2 Economic and regional scenario-based research ................................................ 32
2.3.3 Summary .............................................................................................................. 40
2.4 Feedstock .................................................................................................................... 41
2.4.1 On-farm feedstock ............................................................................................... 41
2.4.2 Off-farm feedstock: biowaste materials .............................................................. 43
2.4.3 Waste reporting ................................................................................................... 45
2.4.4 Processing methods for biowaste ........................................................................ 49
2.4.5 Hub-and-pod anaerobic digestion ....................................................................... 50
2.5 Feedstock characteristics impacting on the assessment of Anaerobic Digestion ....... 52
2.5.1 Emissions from manures, slurries and digestate ................................................. 52
2.5.2 Agricultural greenhouse gas reduction indicator framework .............................. 54
2.5.3 Feedstock pre-treatment and ensiling ................................................................. 55
2.5.4 Co-digestion of feedstock..................................................................................... 56
2.6 Digestate ...................................................................................................................... 57
2.6.1 Delivery of digestate to land ................................................................................ 59
2.7 Biogas treatment options ............................................................................................ 60
2.7.1 Potential biogas pathways ................................................................................... 61
2.8 Conclusions .................................................................................................................. 62
Chapter 3: Methodology ............................................................................................................. 64
3.1 Introduction ................................................................................................................. 64
3.2 Questionnaire and case studies ................................................................................... 64
3.3 Life-cycle assessment and anaerobic digestion ........................................................... 65
3.3.1 Background ........................................................................................................... 65
3.3.2 Life-cycle assessment methodology .................................................................... 66
3.3.3 System boundaries ............................................................................................... 67
3.3.4 Three English regions ........................................................................................... 68
3.3.5 Life-cycle goal and scope definition ..................................................................... 71
3.3.6 Life-cycle inventory analysis ................................................................................. 84
3.3.7 Life-cycle impact assessment ............................................................................... 85
3.3.8 Life-cycle interpretation ....................................................................................... 85
3.4 Economic assessment using Financial Investment methods ....................................... 85
3.4.1 Financial parameters ............................................................................................ 87