BSX-3070 Progress Check 1 (15th December 2023)

Name: Enzo Dufayard

Student ID number: 500565442

Title of dissertation: How can anaerobic digestion be implemented and benefit the UK

Supervisor’s name: Koley Freeman

Date: 14/12/2023

Please answer the following questions:

1. When was your last meeting with your supervisor? 21/11/2023

2. How many meetings have you had in semester 1? 3
3. What written work have you sent to your supervisor in advance of this
progress check? I showed a draft in person
4. How did you send this written work in? If it’s been submitted separately to
this form, please also note the date and subject line of any email
submissions here: I have not sent it
5. How much do you agree with the statement “I feel confident that I have
made enough progress on my dissertation so far”? Make a mark on the
scale or write a number beside it.

I feel between 3 and 4

6. How much do you agree with the statement “I have the skills I need to
complete my dissertation to a standard I will be happy with, and/or have
concrete plans to learn any skills I don’t yet have”? Make a mark on the
scale or write a number beside it.
I feel between 4 and 5

7. Which skills or areas of knowledge do you still want/need to develop? (I

may use this answer to add or tailor teaching sessions!)

How can anaerobic digestion be implemented and benefit

the UK
 Enzo Dufayard

A dissertation submitted in partial fulfilment of the requirements for the degree

of BSc/MZool in animal behaviour

School of Natural Sciences, Bangor University

Academic year 2023-24

Supervised by Koley Freeman

Declaration

By submitting this dissertation, I confirm that I am familiar with Bangor University’s rules about unfair
academic practice, including plagiarism, self-plagiarism, and collusion, and have had a chance to discuss any
concerns with my supervisor. I confirm that this assignment is all my own work and that I did not use AI to
produce any of the text. I also confirm that no part of this text has been submitted for academic credit before
(including for BSX-2021).

Student name: Enzo Dufayard Date: 14/12/2023

Signature: DUFAYARD

Abstract
 - Single paragraph >300 words

Keywords

Anaerobic Digestion, Renewable Energy, Waste Management, Sustainable Development,

Biogas Production, Climate Change Mitigation

Introduction

The United Kingdom must face two urgent environmental imperatives:

managing ever-growing volumes of organic waste in a sustainable manner
while reducing dependence on fossil fuels by transitioning to renewable
energy sources.

Landfills across the country are stretched beyond maximum capacities as

diverse organic waste streams including household food scraps,
agricultural residues and industrial by-products accumulate faster than
decomposition rates can offset (GOV.UK, 2023). This aggravates
greenhouse gas emissions (GHG), primarily in the form of methane, as the
anaerobic decomposition of landfilled organics is uncontrolled (Mohan et
al., 2006). Simultaneously, the need to mitigate climate change compels
the UK to accelerate the deployment of renewable, low-carbon energy
alternatives to displace carbon-intensive systems (GOV.UK, 2021).

Anaerobic digestion (AD) presents a strategic opportunity to

simultaneously tackle the challenges of organic waste diversion and
renewable energy production by utilizing microbial metabolic pathways to
convert organic materials into biogas. The resulting methane-rich biogas
can address energy needs while nutrient-concentrated digestate serves as
an organic fertilizer, enabling circular second-life applications (Rehman
et al., 2019). Although small-scale anaerobic digesters have been
employed in the UK for over a century in wastewater treatment contexts,
recent decades have witnessed growing interest in scaling AD
infrastructure to unlock waste management and energy synergies.
Government incentives, evolving regulation, and technological
advancements have facilitated increased adoption of AD processes using
diverse organic feedstocks across agricultural, industrial, and municipal
environments (The Anaerobic Digestion & Bioresources
Association, 2023).

This literature review critically assesses the current state and potential of
AD in the UK. The analysis integrates peer-reviewed literature,
governmental data, and industry perspectives to explore environmental,
economic, and social implications. Focusing on historical roots,
technological intricacies, and societal and environmental implications, the
research probes how AD can improve the UK's waste management
practices. It emphasizes the synergies between microbial consortia and
organic substrates while unravelling the symbiotic relationship between
AD and renewable energy production

Definition and principles of anaerobic digestion

Anaerobic digestion refers to the sequential, oxygen-free breakdown of

organic materials through microbial activity, resulting in the generation of
biogas (a mixture of methane and carbon dioxide) as well as digestate (a
nutrient-concentrated residue) as end products. Maintaining optimal
conditions including temperature, pH and nutrient levels is vital to support
the microbial community through each sequential phase of AD so that
waste organics can ultimately be recycled into energy.

Four biological processes facilitate this conversion of complex organic

compounds into methane via specialist microbial communities in the
absence of oxygen (Speece, 1983):

1. Hydrolysis
 2. Acidogenesis
3. Acetogenesis
4. Methanogenesis

AD begins with Hydrolysis, where complex organic matter is broken

down into simpler forms accessible for further microbial processing.
Specialized hydrolytic bacteria secrete extracellular enzymes, including
cellulases, proteases, and lipases, initiating the deconstruction of larger
molecules into sugars, amino acids, and fatty acids. This sets the stage by
transforming complex organic molecules into simpler and more accessible
building blocks, kickstarting the cascading AD process (Menzel et al.,
2020).

Acidogenesis follows, involving the fermentation of simpler organic

compounds generated via hydrolysis. Acidogenic bacteria facilitate this
conversion process, breaking down compounds like amino acids, sugars,
and long-chain fatty acids into intermediates such as ethanol, acetate,
lactate, carbon dioxide, and hydrogen. This phase creates mixed
intermediate products, releasing hydrogen and paving the way for
subsequent phases towards methane generation (Chakraborty et al.,
2022).

Acetogenesis, performed by acetogenic bacteria, converts compounds

from acidogenesis into acetic acid, carbon dioxide, and hydrogen.
Acetogens play a crucial role in reshaping intermediates and supplying
acetate, hydrogen, and carbon dioxide—essential precursors for methane
generation. This phase bridges the gap between acidogenesis and
methanogenesis, redirecting electron flows to set the stage for the
terminal conversion of carbon dioxide to methane (Oh et al., 2018).

In the final phase, Methanogenesis leads to the conversion of simple

one-carbon compounds into methane gas. Thriving in oxygen-free
conditions, methanogenic archaea leverage substrates generated in
earlier stages, particularly acetic acid, and hydrogen, to catalyse the
conclusive conversion of one-carbon compounds into methane (CH4). This
culminates in the production of a methane-rich biogas, marking the
critical endpoint of the intricate anaerobic digestion process (Jadhav et
al., 2022).

Figure 1: Diagram showing how an Anaerobic Digestion plant configured to produce

energy and biofertilizer from biowaste feedstock works (Department for Environment Food
and Rural Affairs, 2011)

Historical development and status of anaerobic digestion

The roots of AD in the UK extend back to the late 19th century when
small-scale anaerobic digesters were first employed for sewage
treatment. However, it wasn't until the late 20th century that AD emerged
as a technology with significant environmental and energy benefits. The
UK government, recognizing its potential, catalysed this transition by
providing crucial financial incentives, including the Renewables Obligation
(RO), Feed-in Tariffs (FiTs) Scheme, Renewable Heat Incentive (RHI), and
Renewable Transport Fuel Obligation (RTFO) (Department for
Environment Food and Rural Affairs, 2011).
Over the past decade, AD has experienced substantial growth in the UK,
expanding its scope from sewage treatment to encompass organic waste
from various sectors such as agriculture, food production, and municipal
solid waste. Governmental support, including initiatives by the Anaerobic
Digestion and Bioresources Association (ADBA), has played a pivotal role
in facilitating this expansion and addressing regulatory challenges (The
Anaerobic Digestion & Bioresources Association, 2023).
Technological advancements, including improved reactor designs,
enhanced monitoring systems, and innovations in feedstock processing,
have increased the efficiency and reliability of AD systems. The
integration of combined heat and power (CHP) systems has further
enhanced the economic viability of AD projects by enabling the
simultaneous production of renewable electricity and heat (GOV.UK,
2013).

Despite these positive developments, challenges persist within the sector,

including feedstock availability, regulatory complexity, and public
perception. Variability in feedstock quality and composition can impact
the stability and efficiency of AD processes. Additionally, navigating the
regulatory landscape, including waste management regulations and grid
connection requirements, poses challenges for project developers
(Uddin,2022). Understanding the historical trajectory and current
dynamics of AD in the UK provides a foundational basis for assessing its
potential benefits and addressing challenges associated with its
implementation. As the country continues to pursue renewable energy
targets and sustainable waste management practices, AD is anticipated to
play a pivotal role in achieving these objectives.

Environmental and economic benefits

Anaerobic digestion stands as a cornerstone in the UK's sustainable waste

management strategy, wielding environmental and economic benefits
that resonate with the nation's commitment to a greener future. A
principal environmental advantage lies in its ability to significantly reduce
organic waste, diverting it from landfills. By capturing and treating organic
waste through anaerobic digestion, the process effectively mitigates the
release of methane, a potent greenhouse gas produced during the
decomposition of organic matter in landfills (Bracmort, 2011). This
reduction directly addresses climate change concerns and upholds the
UK's commitment to minimizing its carbon footprint. The significance of
this waste diversion extends beyond environmental impact, as it
symbolizes a shift towards circular economy principles, where organic
materials are recycled and repurposed, diminishing the burden on
conventional waste disposal methods.

Moreover, anaerobic digestion emerges as a renewable energy

powerhouse, producing biogas primarily composed of methane and
carbon dioxide. This biogas serves as a sustainable energy source,
contributing to the nation's renewable energy targets. Harnessing biogas
for electricity and heat production offers a promising alternative to
conventional energy sources, reducing reliance on fossil fuels and curbing
carbon emissions. The dual benefits of waste reduction and energy
generation present a compelling case for anaerobic digestion as a catalyst
for transitioning towards a more sustainable and resilient energy
landscape. Anaerobic digestion fosters sustainable agriculture practices
through the production of nutrient-rich digestate. This by-product acts as
an organic fertilizer, offering an eco-friendly alternative to synthetic
fertilizers. By substituting traditional fertilizers with digestate, the
agricultural sector experiences reduced dependence on chemical inputs,
promoting soil health and fertility. The closed-loop approach of anaerobic
digestion, where organic waste transforms into valuable resources, aligns
with principles of circular agriculture, emphasizing resource efficiency and
reduced environmental impact (Møller et al., 2009).

On the economic front, anaerobic digestion plays a pivotal role in

advancing the principles of a circular economy by significantly
contributing to decentralized renewable energy production. The
integration of Combined Heat and Power (CHP) systems optimizes energy
utilization, thereby enhancing the economic viability of anaerobic
digestion projects. This not only fosters economic opportunities within the
energy sector but also bolsters energy security by reducing dependence
on centralized sources. The circular economy ethos is further embraced as
anaerobic digestion projects create jobs across various stages, from
construction to operation and maintenance, fostering a sustainable and
inclusive employment ecosystem. As the industry expands, the demand
for skilled labour and support services grows, creating a positive economic
ripple effect, particularly in rural areas where agricultural and waste
management activities are prevalent. This underscores the role of
anaerobic digestion in contributing to economic diversification and local
development, aligning with the circular economy's emphasis on
regenerative practices.

Anaerobic digestion in the UK transcends its role as a waste management

solution and emerges as a multifaceted driver of sustainability within the
circular economy framework. Its environmental benefits, such as waste
reduction, renewable energy generation, and support for sustainable
agriculture, seamlessly intertwine with economic advantages. This
approach encompasses job creation, decentralized energy production, and
local economic diversification, aligning with the circular economy's core
principles (Stahel, 2016). As the UK steers towards a future grounded in
sustainability, anaerobic digestion stands out as a pivotal solution,
encapsulating the essence of a circular and resilient economy.

References

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Energy Generation.
 Chakraborty, D., Obulisamy Parthiba Karthikeyan, Ammaiyappan Selvam, Sankar
Ganesh Palani, Ghangrekar, M.M., and Wong, J.W.C. (2022). Two-phase Anaerobic
Digestion of Food waste: Effect of semi-continuous Feeding on Acidogenesis and
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https://doi.org/10.1016/j.biortech.2021.126396

 Department for Business, E.& I.S. (2021) Plans unveiled to decarbonise UK Power
System by 2035, GOV.UK. Available at: https://www.gov.uk/government/news/plans-
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 Department for Environment Food and Rural Affairs (2011). Anaerobic Digestion
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 GOV.UK (2013). Combined Heat and Power. GOV.UK. Available at:

https://www.gov.uk/guidance/combined-heat-and-power

 GOV.UK (2023) UK statistics on waste, GOV.UK. Available at:

https://www.gov.uk/government/statistics/uk-waste-data/uk-statistics-on-waste

 Jadhav, P., Khalid, Z.B., Zularisam, A.W., Krishnan, S. and Nasrullah, M. (2022).
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 Mohan, R. et al. (2006) ‘Sustainable Waste Management in the UK: The Public
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 Møller, J., Boldrin, A. and Christensen, T.H. (2009). Anaerobic Digestion and
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