31/01/2017

Anaerobic Digestion Economic Feasibility

Study: Generating energy from waste,

sewage and sargassum seaweed in the

OECS

CPI Report Number: CPI-SP-RP-141

Compiled By

Michelle Morrison, CPI

Daniel Gray, The Caribbean Council

Confidential | A report on behalf of The Foreign and Commonwealth Office

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4 CONFIDENTIAL

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Contents

1 Revision History............................................................................................................. 7

2 Glossary ........................................................................................................................ 8

3 Executive summary ....................................................................................................... 9

4 Background, Approach & Objectives ........................................................................... 10

4.1 Background .................................................................................................................................... 10

4.2 Approach & objectives ................................................................................................................... 12

5 Existing Information ..................................................................................................... 15

5.1 Energy............................................................................................................................................ 15

5.1.1 St. Lucia .................................................................................................................................... 15

5.1.2 Grenada .................................................................................................................................... 17

5.2 Waste resources ............................................................................................................................ 18

5.2.1 St. Lucia .................................................................................................................................... 18

5.2.2 Grenada .................................................................................................................................... 22

5.3 Water treatment ............................................................................................................................. 24

5.3.1 St. Lucia .................................................................................................................................... 24

5.3.2 Grenada .................................................................................................................................... 25

5.4 Sargassum ..................................................................................................................................... 26

6 Anaerobic Digestion .................................................................................................... 29

6.1 Biogas production .......................................................................................................................... 29

6.2 Applications & Benefits .................................................................................................................. 30

6.3 Planning and Permitting for AD ..................................................................................................... 31

7 Biochemical methane potential .................................................................................... 33

7.1 Introduction .................................................................................................................................... 33

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7.2 Methodology .................................................................................................................................. 33

7.2.1 Feedstock preparation .............................................................................................................. 33

7.2.2 Substrate blends and controls .................................................................................................. 33

7.2.3 Biogas volumes and composition ............................................................................................. 35

7.3 Treatment of data .......................................................................................................................... 35

7.3.1 Theoretical methane potential .................................................................................................. 35

7.3.2 Higher heating values & energy content .................................................................................. 35

7.4 Results ........................................................................................................................................... 36

7.5 Conclusions from the BMP ............................................................................................................ 40

8 Energy yield & Economics ........................................................................................... 41

8.1 Energy potential – St Lucia ............................................................................................................ 41

8.2 Energy potential – Grenada ........................................................................................................... 44

8.3 Economic case .............................................................................................................................. 47

8.3.1 Explanation of terms ................................................................................................................. 49

8.3.2 Discounted cash flow modelling results ................................................................................... 50

8.3.3 Biomethane as LPG replacement ............................................................................................ 53

8.3.4 Conclusions from the energy yield and economic modelling ................................................... 54

9 Conclusions ................................................................................................................. 56

9.1.1 Viability of AD as a waste treatment and energy generation technology in the OECS ............ 56

9.1.2 Policy recommendations for St. Lucia and Grenada ................................................................ 57

10 Next Steps ................................................................................................................... 58

11 Appendix ..................................................................................................................... 60

11.1 St. Lucia Data compiled by the Caribbean Council ....................................................................... 60

11.2 Grenada Data compiled by the Caribbean Council ....................................................................... 67

11.3 St Lucia Waste tonnage data ........................................................................................................ 79

11.4 Written Responses to Questions ................................................................................................... 80

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1 Revision History

Revision Prepared by Checked by Approved by Comment

[001] Michelle Morrison Emma Stokes Daniel Gray Initial version.

[002] Daniel Gray Polly Hatfield Chris Bennett Comments and edits from The Caribbean Council following discussion.

[003] Daniel Gray Polly Hatfield Michelle Morrison

Additions from The Caribbean Council to Section 5 and 9. Creation of Section 10.

[004] Michelle Morrison Daniel Gray Chris Bennett Further modelling and research from the CPI for Section 8 & 9.

[005] Daniel Gray Michelle Morrison Chris Bennett Final Approval

[006] Michelle Morrison Daniel Gray Chris Bennett Addition of responses to queries following Webinar Presentation on 25/01/17

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2 Glossary

AD Anaerobic Digestion

BMP Biochemical Methane Potential

BOE Barrel of Oil Equivalent

CF Cash flow

CH4 Methane

CHP Combined heat and power

CO2 Carbon dioxide

COD chemical oxygen demand

CSTR Continuously stirred tank reactor

CV Calorific value

DCF Discounted cash flow (model)

FiT Feed in tariff (for electricity)

FW Food waste

GDP Gross domestic product

GWh Giga watt hours

HHV Higher heating value

H2S Hydrogen sulphide

IRR Internal rate of return

kW kilowatts

kWh kilowatt hours

LPG Liquefied petroleum gas

MJ Mega joules

MW Megawatts

MWh Megawatt hours

NPV Net present value

OM MSW Organic matter fraction of municipal solid waste

P Profit

PV Photo voltaic

SBY Specific biogas yield

SLSWMA St Lucia Solid Waste Management Authority

SMY Specific methane yield

STP Standard temperature and pressure (273K, 1.01325 bar)

TMP Theoretical methane potential

Tons Imperial measurement of mass

TPA Metric tonnes per annum

TS Total solids

US$ United States dollars

VS Volatile solids

XC$ Eastern Caribbean dollars

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3 Executive summary

Small island developing states in the Caribbean face serious challenges relating to 1) waste management; 2)

sewage treatment and; 3) energy sustainability. At present, all too often, inefficient and poorly planned delivery

of these key services is having a negative impact on the quality of people’s lives and the environment. Action

across the public and private sector is needed regionwide to address these issues in a cost-effective, controlled

and sustainable manner.

Anaerobic Digestion (AD) is a technology which can provide real benefits to all three areas of concern and

which is currently not being deployed in the Caribbean. This report seeks to study how anaerobic digestion

could be used in a Caribbean context to treat biogenic waste, including sewage sludge and in the process,

generate renewable energy in the forms of electricity, heat and biomethane gas for fuel. AD can be

implemented at all scales and there are existing and well proven technologies available at all scales of delivery.

For the purposes of this study, St Lucia and Grenada were taken as examples of developing island states.

They both exhibit all three problems and could benefit from an AD solution. Available information on St Lucia

has been used to provide an initial estimate of the available tonnage of potential AD feedstocks; 66,000 tpa of

biogenic waste (not including agricultural, food or drinks processing, brewery/distillery or slaughterhouse

waste) could yield between 46,400,000 and 72,300,000 MJ of energy, the equivalent of 13 GWh of power.

Corresponding data on Grenada indicate that there could be 46,000 tonnes per annum of biomass waste

available for treatment through AD which could yield 81,500,000 MJ of energy or the equivalent of 22.5 GWh

of power.

AD could also provide a waste treatment solution for beached Sargassum, a growing problem throughout the

Caribbean. Available information on Sargassum natans and fluitans, the two species of primary concern across

the Caribbean, is sparse. The small BMP assessment carried out showed that ‘old’, beached Sargassum,

when milled to a powder and digested, had a very low BMP at 61 m3/tonne VS added (compare with food

waste at 421 m3/tonne VS added). In spite of Sargassum’s low SMY, it could still be treated through AD, as an

amendment to a plant taking other wastes as its primary feed.

Regarding economic viability of an AD approach to energy generation, modelling suggested that it should be

possible to make a financial return on implementing AD technology in St Lucia and Grenada. The percentage

contribution to electricity and/or heat supply made by AD would be relatively small but significant. In St Lucia,

AD could provide up to 6%, possibly more if all potential feedstocks for AD were treated. In Grenada, that rises

to around 11%.

Varying levels of financial interventions would be required, to help AD investment yield positive returns. Small

scale projects need more incentives to be financially viable, such as generation tariffs and gate fees (where

possible), plus state aid or capital grants. Large scale plants could make a return with less incentives and no

gate fee for waste, depending on the energy content of the waste. Small community scale projects may be the

answer in hard-to-reach communities and could double up as both energy generation and sewage treatment.

Technology at the back end to dewater and purify the digestate could also deliver grey water for non-potable

uses.

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Taken together with other renewable sources, such as solar PV and thermal, plus wind, these renewables

have high potential to replace a large fraction of fossil fuel derived energy, creating more sustainable and

resilient island nations, not completely dependent on, or at the mercy of wildly fluctuating energy markets.

Policy development would need to look at how to structure an energy generation tariff system and remuneration

levels for electricity and heat sales. Examination of existing systems and their faults would be useful. This may

require thought on how best to capture the organic fraction of municipal and commercial waste. As a potentially

valuable source of energy, a source-segregated approach would be the ideal option but this is not without its

challenges. There will need to be some policy and regulation in place for the use of digestate (on land), to

ensure environmentally responsible application. Education of the public is also a major challenge, together

with the logistics of collection. A Food Waste Study could help identify the issues and prepare options for

moving forward. In this respect, there are European examples to draw on, both in terms of the technologies

involved, and the associated public education campaigns.

As explored in Section 10 (Next Steps), further research, experimentation and investment is required to take

forward the use of waste-to-energy anaerobic digestion solutions in the Caribbean. This includes additional

experimentation with samples of Sargassum and more in-depth techno-economic studies into the economic

viability of AD plants in the region. Finally, supplementary research on the politico-economic landscape in

individual OECS states would enhance the policy making process, and help identify which of the Scenarios

covered in this report are most likely to gain support among civil society.

4 Background, Approach & Objectives

4.1 Background

In March 2016, a meeting, Harnessing the Economic Benefits of Sargassum, was organised by the British

Virgin Islands Government and Virgin Unite together with the Foreign and Commonwealth Office, the

Caribbean Council and the Organisation of Eastern Caribbean States and held in the British Virgin Islands.

The meeting was arranged in order to discuss the problems arising from inundations of the pelagic seaweed

Sargassum and also to discuss potential solutions to its management, which could derive financial and societal

benefit for the communities of the British Virgin Islands (and the wider Eastern Caribbean archipelago).

The problems highlighted included; the loss of economic activity for the local fishermen, unable to access or

move their boats during inundations and limited or no access to fishing grounds; detrimental impacts on the

tourism industry, so vital to the islands, due to lack of access to popular beach resorts; odour issues resulting

from the breakdown of the beached Sargassum and the consequent release of trace amounts of the ‘bad-egg’

smelling gas, hydrogen sulphide (humans can detect H2S at very low levels), also deterring visitors. Out at sea

the mats of floating Sargassum offer a vital habitat as a nursery for a variety of fish species, invertebrates and

young turtles and well as a safe stopping off point for migratory species. However, once in the coastal zone it

11 CONFIDENTIAL

has a negative impact on the ecosystem, where coastal fauna can become trapped in the decaying weed;

there have been many sightings of dead turtles and fish.

Although Sargassum has been landing throughout the Caribbean and along sections of the Mexican coast for

several years, tracking and more importantly predicting its arrival is proving to be a complex and difficult task.

Many of the affected nations are now working together, not only to try and devise an early warning system for

the entire region but also to develop methods of management. Currently, there is no publicly available data on

how much Sargassum is being washed up, neither as volume or mass. Historically, there have always been

periods where Sargassum has beached in the Caribbean but the scale of these events was much smaller than

that seen in recent years. The first major, problematic inundation occurred during 2011, with large annual

influxes subsequently until 2015, when there was another major inundation1. 2016 appears to have been less

problematic, with lighter influxes landing later on in the season. Unfortunately, the massive variation in quantity,

location and timing of influxes has resulted in significant data gaps, which are only now starting to be

addressed. At this time it is not possible to say anything on quantities of Sargassum available for treatment or

the regularity of supply in any one place. One consequence of this lack of data and the difficulty of obtaining

good data on these points, is that management strategies to deal with the invasive Sargassum to deliver a

monetary value, which might involve the installation of processing plant [to produce energy, chemicals] at some

cost, are difficult to justify on an economic basis. Intermittency of supply is a very important consideration and

so, allied to availability is the important question of how to effectively store the material that does land, so that

it can be processed through time whilst maintaining its active ingredients.

The topics covered in this feasibility arose out of the Sargassum meeting in the BVI. However, these are

recurring themes across developing states and small island nations. Grenada hosted the first Caribbean Waste

to Energy Technology Expo & Conference in January 2016, sponsored by CARICOM Secretariat/GIZ REETA

– German Federal Enterprise for International Cooperation (GIZ) Renewable Energy and Energy Efficiency

Technical Assistance Programme (REETA); Caribbean Community Climate Change Centre (CCCCC)/SIDS

DOCK; the United Nations Industrial Development Organization (UNIDO); the Swedish Energy Agency (SEA);

and the World Intellectual Property Organization (WIPO).

It has already been recognised that appropriate, effective and sustainable waste management, both of solid

and liquid wastes, is a vital tool in the battle for sustainable and financially viable communities. As the effects

of climate change become apparent, experienced more keenly in some developing island nations, the drive to

improve resilience can largely be met by effective waste management and the implementation of renewable

energy initiatives, which make use of waste resources. A diverse toolbox of technologies for waste

management and energy generation (including solar and wind) would improve resilience across a number of

other sectors including environmental management, management of fresh water resources, health, education

and skills and job opportunities.

On the 30 September 2015 the United Nations (UN), announced the entry into force of the SIDS DOCK Treaty,

giving legal recognition to the intergovernmental sustainable energy and climate resilience organisation

established by Heads of State and Government of Small Island Developing States (SIDS) in 2009, in order to

help finance climate change adaptation through the transformation of their countries to low carbon economies.

1 E. Doyle, E. and J. Franks. 2015. Sargassum Fact Sheet. Gulf and Caribbean Fisheries Institute.

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The concept paper, “Toward the Development of a Caribbean Regional Organic Waste Management Sub-

Sector”, of the 1st Caribbean Waste to Energy Technology Expo & Conference gives a very good summary of

the problems faced by developing island states in the Caribbean and how an emerging and effective waste

strategy could help alleviate against those issues2. There are a number of other useful documents which detail

some of the work completed thus far.3,4

The management of fresh water resources is becoming a pressing issue for many islands. Increases in

population, brought on by improved living standards and greater economic activity, have resulted in greater

demand on existing fresh water resources. The consequence of this has been increased contamination and

degradation of water bodies, both fresh water and marine, due to poor waste water treatment strategies. Again,

governments are recognising waste water treatment as an important issue but limited financial resources

makes implementing better collection and treatment systems very difficult; not enough revenue is raised

through taxation to cover the capital expenditure. In 2013, it was estimated that as much as 85% of the waste

water entering the Caribbean Sea was untreated and around 50% of households across the region were not

linked to a formal and regulated sewer connection4. The end result of the release of poorly controlled primary

treated and untreated sewage to the nearshore, is the inevitable eutrophication of those receiving water bodies,

which contributes to the continuing build-up of algae on reefs and on land, the contamination of ground water

reserves and surface water bodies.

4.2 Approach & objectives

In the big picture, an approach which seeks to treat energy, waste and water resources as interlinked, would

be more likely to result in a well-planned, cost-effective and efficient set of services, where wastes from one

process are used as feeds for another, where mass and energy flows can be maximised and recycled to close

process loops, where possible. This preliminary feasibility study will look at the potential contained within

biogenic wastes, sewage sludge and invasive Sargassum, for treatment by anaerobic digestion (AD). This

process is described in more detail later in the report but the main products from the process are renewable

energy in the form of biomethane and a material called digestate, which generally tends to be used as a useful

replacement for chemical-based fertilisers, either whole or separated into its liquid and solid components.

Figure 1 is a simple process flow diagram which shows the feed materials for an AD treatment system, the

pre-treatment steps which might be required and the outputs. Also included is an option for the treatment of

wastes more suitable to a thermal treatment technology, such as gasification, though this option is not

considered in any detail in this study. A combination of recycled wastes, AD for waste biomass (not including

woody material) and a thermal treatment technology for other residual wastes not suitable for AD or recycling,

2 SIDSDOCK, January 2016, ‘Toward the development of a Caribbean regional organic waste management sub-sector. available at: http://sea.sidsdock.org/download/wte_expo_library/background_papers/REGIONAL-WASTE-MANAGEMENT-MEETING-CONCEPT-PAPER-REVISED-JAN-2016.pdf 3 Caribbean Renewable Energy Development Programme, GIZ, October 2013, ‘A Review of the Status of the Interconnection of Distributed Renewables to the Grid in CARICOM Countries’. Available at: http://www.credp.org/Data/CREDP-GIZ_Interconnection_Report_Final_Oct_2013.pdf 4 SIDSDOCK, May 2015, ‘Toward the development of a Caribbean regional organic waste management sub-sector’. Available at: http://sea.sidsdock.org/download/wte_expo_library/background_papers/01-14-16-DRAFT-NOT-FOR-CIRCULATION-DRAFT-REGIONAL-WASTE-MANAGEMENT-.pdf

http://sea.sidsdock.org/download/wte_expo_library/background_papers/REGIONAL-WASTE-MANAGEMENT-MEETING-CONCEPT-PAPER-REVISED-JAN-2016.pdfhttp://sea.sidsdock.org/download/wte_expo_library/background_papers/REGIONAL-WASTE-MANAGEMENT-MEETING-CONCEPT-PAPER-REVISED-JAN-2016.pdfhttp://www.credp.org/Data/CREDP-GIZ_Interconnection_Report_Final_Oct_2013.pdfhttp://www.credp.org/Data/CREDP-GIZ_Interconnection_Report_Final_Oct_2013.pdfhttp://sea.sidsdock.org/download/wte_expo_library/background_papers/01-14-16-DRAFT-NOT-FOR-CIRCULATION-DRAFT-REGIONAL-WASTE-MANAGEMENT-.pdfhttp://sea.sidsdock.org/download/wte_expo_library/background_papers/01-14-16-DRAFT-NOT-FOR-CIRCULATION-DRAFT-REGIONAL-WASTE-MANAGEMENT-.pdf

13 CONFIDENTIAL

could provide a neat solution to an island’s waste management. However, this would require significant

financial investment and a strategic approach to addressing planning and regulation of integrated services.

This is possible and recent events, which have included multiple agencies working in an interdisciplinary way,

indicate that the political will is gaining momentum.

Figure 1. Linear process flow diagram to illustrate the key components of an approach centred on anaerobic digestion as treatment

technology but also including an illustration of where/how gasification might fit into the overall approach. The products from gasification

are not detailed beyond syngas in this report.

Of the biomass feed materials listed in Figure 1, Sargassum presents its own challenges. As with any intended

seaweed application there will be questions of supply regarding constancy, regularity and quality. Businesses

hoping to make use of beached Sargassum will need to find ways around these particular issues, in the same

way that businesses which harvest natural and farmed seaweeds need to. There are a number of potential

commercial routes to exploitation, depending on the chemical composition of the seaweed. Some seaweeds

lend themselves to certain applications and the application of seaweed as an energy crop is again being

studied5 (after a lull of 20-30 years following some initial studies). The SeaGas Project is looking at the financial

and practical viability, across the supply chain, of farming Saccharina latissima for bioenergy production; there

is a large element of practical work studying the digestion characteristics but also the very important step of

how best to preserve the Saccharina so that it doesn’t degrade over time, once harvested. This work could

inform a similar approach to preserving Sargassum fluitans & natans. There may be the possibility to derive

5 The SeaGas Project. IUK IB Catalyst funded for 2015-2018. Centre for Process Innovation (lead partner), with SAMS, Queen’s University Belfast, CEFAS, Eunomia and ADAS, on behalf of The Crown Estate.

Process Schematic

Sargassum(Periodic)

Organic waste Fraction

Agriculture Wastes

WWT Biosolids

Sorting & segregating

Drying (open air) & Milling,

Ensiling

Shredding/maceration

Pasteurisation

Mechanical/physical pre-

treatment

ANAEROBICDIGESTION

Recyclates

BIOGAS/

DIGESTATE

CHP

Cooling Electricity

Grey Water Soil/Plant improver

(BIO)RESOURCE PRE-TREATMENT TREATMENT PRODUCTS

Gasification

Plastics, tyres, waste oils,

woody materials

Vehicle fuel

Residual waste

Syngas

Michelle Morrison

14 CONFIDENTIAL

higher value end products from Sargassum but its use as a feed for bioenergy would tie in well with the bigger

picture for energy and waste.

Anaerobic digestion is a biological process which runs continuously, providing base load power, hence it

requires daily feeding. Washed up Sargassum we know would not provide that constancy of supply. However,

the other biogenic materials suggested in Figure 1 are available on a regular basis and could form the basis

of the feedstock for an AD process. All of these biogenic materials have some calorific value i.e. they contain

a certain amount of energy which can be utilised to produce power. This energy value is at present not routinely

recovered but lost in linear and open ended processes.

There is then a possible approach to managing both biogenic wastes generated in a location and the invasive

Sargassum. The aim of this feasibility study is to investigate the potential for establishing anaerobic digestion

as a waste treatment technology in St Lucia and Grenada, in particular, and whether stranded Sargassum

could be fed into the AD treatment process. The objectives of the study are as follows:

To take information from the public domain regarding waste materials on St Lucia and Grenada and to

assess how much is available, what the energy content might be and what proportion of renewable energy

could potentially be realised by implementing AD as a treatment technology

To carry out some preliminary practical work to assess the biochemical methane potential of Sargassum

fluitans which was washed up on a beach in St Lucia

To model a number of scenarios regarding the size of an AD operation (based on tonnage throughput),

to assess their financial viability

To discuss the benefits and drawbacks of anaerobic digestion against other treatment techniques, namely

thermal treatment (pyrolysis, gasification, incineration)

To highlight where there are data gaps which impede more accurate analysis

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5 Existing Information

Data existing in the public domain was collated by the Caribbean Council (Project Lead) and included the

following items (Appendix 1 for the full data spreadsheet prepared by the Caribbean Council, including

references to sources of information):

Energy –

o current demand and generation

o fuel import data including consumption and cost

o power plants – how many and size

Waste –

o Information on waste collection methods

o Waste type and annual tonnage

o Current waste disposal techniques

o Costs of waste disposal

o Recycling activities

o Waste water treatment

Policy regarding energy and waste management

Sargassum - unfortunately though not unexpectedly, there was no information forthcoming on Sargassum

with regards to tonnages, temporal and spatial movements, landing locations or periods of strandings.

There is also scant data on chemical composition of the species of interest.

5.1 Energy

5.1.1 St. Lucia

There is a reasonable amount of information available regarding energy generation, consumption and demand.

The headline figures are as follows:

Diesel is the main source of all power generation for St Lucia and around 10.2% of St Lucia’s GDP is

spent on importing fuel. The cost of this is of the order of US$130M per annum

Total energy imported and produced: 3061 BOE/day in 2012 (Ref Appendix 1)

o Only 2% equivalent to 61 BOE/day from renewables (combustion)

o The remaining 98% equivalent to 3000 BOE/day from imported fossil fuel

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Of that 3061 BOE/day, around 1468 BOE/day were lost during distribution, generation and

transmission, which, at around US$55/barrel equates to US$81k/day and approximately 2334MWh

power per day, lost.

The remaining 1592 BOE/day were utilised between transport needs and electricity demand, at 41%

and 55%, respectively.

The energy generator is State-owned (LUCELEC) and controls and operates two power stations on the island;

Union Power Station, which can provide up to 2.5MW of diesel-fuel based power, if required; and Cul-de-Sac

Power Station at 86.2MW, which comprises: 3 units of 6-7 MW (diesel-fuel-based); 4 units of 9.3 MW (diesel-

fuel-based) and; 3 units of 10.3 MW (diesel-fuel-based).

Electricity generation in 2013 was at 382.9 GWh, of which LUCELEC used 4.8 GWh and 334.4 GWh were

used across commercial, residential and industrial applications. The difference between generated and used

electricity was accounted for by 8% losses from the system for that year. Figure 2 illustrates how electricity

generation increased over 23 years, from 1990 to 2013 but appeared to plateau between 2010 and 2013.

Figure 2. Increasing electricity generation in St Lucia.

In 2010, the World Bank forecast an increase in required electrical capacity from 95 MW in 2015 to 148 MW

in 2027, in order to cover the peak demand projected. If this is to be met in any sustainable way, there will

need to be a mixed tool box of energy generating technologies. Diversification of the energy supply will help

build in resilience to both fluctuations in the oil market and some of the effects of climate change.

The most recent figures for 2015 show that, of the 88.4 MW available capacity, demand peaked at 59 MW, a

0.2% increase in peak demand over 2014. Total electricity sales were 337.5 GWh for 2015, of which 57% was

to the commercial sector (including hotels) and 34% to domestic users. The number of domestic consumers

at year end was 59,766. That equates to an average annual consumption of 1.94 MWh per domestic consumer

(household). In contrast the commercial average annual consumption was at 27 MWh per business consumer.

17 CONFIDENTIAL

5.1.2 Grenada

There is a reasonable amount of information available regarding energy generation, consumption and demand.

The headline figures are as follows:

The electricity price in Grenada is among the highest in the Caribbean, costing $0.37 USD/kWh. 55%

of this comes from the costs associated with imported fossil fuel, including LNG.

Diesel and LNG are the main sources of all power generation for Grenada. 6% of Grenada’s GDP is

spent on importing fuel. The cost of this is of the order of US$130M per annum.

Total energy imported and produced: 2785 BOE/day in 2011 (Ref Appendix 1)

o 7% equivalent to 185 BOE/day from renewables (combustible renewable, waste and solar

energy)

o The remaining 93% equivalent to 3000 BOE/day from imported fossil fuel

Of that 2785 BOE/day, around 774 BOE/day were lost during distribution, generation and

transmission, which, at around US$99.8/barrel equates to US$77.2k/day and approximately

1230MWh power per day, lost.

The remaining 2011 BOE/day were utilised between transport needs and electricity demand, at 41%

and 58%, respectively.

The energy generator is GRENLEC. It is a private-public entity, with the state holding a 21% stake, and US-

based WRB Holding serving as the majority shareholder. GRENLEC holds exclusive license of generation,

transmission, distribution, and sale of electricity until 2073, though it does not have an exclusive right on small-

scale self-generated electricity. GRENLEC controls and operates a total of five diesel-fuel-based power

stations, namely:

Queen’s Park: 25.2 MW capacity

Grand Anse: 18 MW capacity

St. George’s University: 2.8 MW capacity

Carriacou: 3.17 MW capacity

Petite Martinique: 0.483 MW capacity

Electricity generation in 2015 was at 204 GWh. Figures from 2013 indicate that GRENLEC used 6.1 GWh of

the total capacity, while 175.8 GWh was used across 5,961 commercial, 37,916 residential and 35 industrial

customers. The difference between generated and used electricity was accounted for by 7.5% losses from the

system for that year, as well as some spare capacity.

While peak energy demand has declined in recent years in the wake of the global financial crisis, energy

demand is expected to double by 2028. To meet this demand, Grenada will need to diversify its energy mix.

Diversification of the energy supply will help build in resilience to both fluctuations in the oil market and some

of the effects of climate change.

18 CONFIDENTIAL

Figure 3. Electricity demand in Grenada.

5.2 Waste resources

5.2.1 St. Lucia

Residential, commercial, and industrial waste collection services are privatized.

St Lucia Solid Waste Management Authority (SLSWMA) is responsible for coordinating and integrating

systems for the collection, treatment and disposal of the island’s solid waste, from both household and

government establishments (i.e schools, hospitals, health centres, prisons, and government offices). The

SLSWMA sub-contracts out the collection of waste to five contractors, who each work in specific waste

collection regions, as shown in Figure 3.

Figure 4. Waste collection areas of St Lucia colour-coded to show the five contractors’ working areas.

0

20

40

60

80

100

120

140

160

180

200

2002 2004 2006 2008 2010 2012 2014

Electricity Demand and Peak Demand in Grenada 2003-2013

Electricity Demand (GWh) Peak Demand (MWh)

19 CONFIDENTIAL

SLSWMA operates two solid waste disposal facilities; Deglos Sanitary Landfill in the north of St Lucia and

Vieux-Fort Waste Management Facility, in the south.

The Deglos Sanitary Landfill received 53,500 tons (48,534 tonnes) of solid waste in the year 2013-2014 (Figure

4). It opened in March 2003 and was designed to be operational over a 25 year period, according to current

waste management practices. The site occupies around 9.5 hectares and receives an average of 4,000 tons

(3,629 tonnes) per month. This facility also has a leachate collection and treatment system.

Figure 5 St Lucia, Deglos Sanitary Landfill (North).

BOX 1

A “Sanitary Landfill” (SL) is understood to mean the spacing, placement, and compacting of waste on an

impermeable bed and its daily covering with a layer of earth or another inert material in order to control the

proliferation of vectors, gas emissions and leaching so as to avoid environmental contamination and protect

people’s health. A SL is the product of an engineering project, with controlled access, weighing, and no

informal recyclers on site.

Source: IDB, 2010.

20 CONFIDENTIAL

Figure 6 Vieux-Fort Waste Management Facility (South), St Lucia.

The Vieux-Fort facility occupies 7.4 hectares and received 21,000 tons (19,050 tonnes) over the same period

(Figure 5). It does not have a leachate collection and treatment system, unlike Deglos, and is referred to as a

Controlled Dumpsite.

There are no waste transfer stations on the island, so there is little opportunity to sort the waste before it arrives

at the landfill sites. Instead of picking lines at a waste transfer station, SLSWMA has formalised arrangements

with waste pickers at the Vieux Fort Solid Waste Management Facility. The waste pickers recover material

such as ferrous metal, scrap wire, and wood6. There has been an increase in recycling activity over the last

few years with most recycled materials going for export; there is only limited recycling of materials for reuse

on the island. Recycled materials comprise metals, plastics, paper, card, electronics and batteries.

There is currently no separation of organic matter from the municipal or commercial mixed waste fraction for

St Lucia, neither at source nor through waste separation technologies. Mixed municipal and commercial waste

is delivered to landfill and buried, resulting in acidic leachate from the degradation of the organic material,

6 Saint Lucia Waste Management Authority, March 2015, ‘Annual Report’. Available at: http://www.sluswma.org/images/pdf/Annual%20Report%202014-2015.pdf

BOX 2

Controlled dumpsites refer to open air dumps that are controlled to some extent or to sanitary landfills that

have been gradually abandoned over the years.

Source: IDB, 2010.

http://www.sluswma.org/images/pdf/Annual%20Report%202014-2015.pdf

21 CONFIDENTIAL

which is collected and treated at Deglos, and release of methane to the atmosphere. As a consequence, there

appears to be no data available on food waste in particular or the percentage fraction of organic material

contained within the mixed municipal and commercial waste. Records are kept on tonnages of waste arisings

and those which might have an organic element are given in Table 1 (the complete table of waste arisings is

given in Appendix 2).

Table 1. Waste tonnages of material which might contain organic matter.

Waste

Category

2011/12 2012/13 2013/14 2014/15

Beach cleaning 249.6 270.43 400.7 407

Commercial 14,857 14,191 10,582 9,846

Condemned

foods 321.7 403.7 1,170 268

Farm waste - - 605 571

Green waste 4,273 7,451 6,647 7,065

Hotel waste - - 6,082 6,398

Residential/

institutional 34,480 31,952 33,903 32,929

TOTAL (tons) 54,181 54,268 59,390 57,484

TOTAL (tonnes) 49,152 49,231 53,878 52,148

There is some data on the organic waste fraction from Grenada7, which we can use as a proxy for St Lucia

given the similarity in population size and GDP, though St Lucia has a larger tourism sector. The study on

Grenada found the organic fraction accounted for around 27% of the total municipal waste arisings. Another

source (SLSWMA, 2008. No further detail provided) put the organic waste fraction as high as 45% of the total

annual waste collection for St Lucia. Taking a range of percentage content for the organic fraction, the tonnage

of organic matter can be estimated; if the total municipal waste fraction is taken to be 52,148 tonnes per annum,

the tonnage of organic matter could lie between 14,000 tpa and 23,500 tpa for 2014/15. The Food & Agricultural

Organisation (FAO) publishes figures on its website regarding food wastage. Figure 6 is taken from the FAO

website and shows how the mass of waste per capita varies across major population groups.

Figure 7. FAO data on food waste generated per capita of population.

7 German Corporation for International Cooperation (GIZ), June 2015, ‘Regional waste-to-energy collaborative’. Available at: http://irena.org/EventDocs/T2%20BW2E%2004%20Andreas%20Taeuber%2020150623%20long%20version.pdf

http://irena.org/EventDocs/T2%20BW2E%2004%20Andreas%20Taeuber%2020150623%20long%20version.pdf

22 CONFIDENTIAL

The Caribbean islands designated as developing states are possibly similar in per capita food waste to South

& Southeast Asia. Grenada generates around 27% organic waste as a percentage of the total8. If we assume

that a third of the total waste generated in St Lucia is biogenic, then around 104 kg/person/year of organic

waste would be generated. If we consider a third of the total given in Table 1, the per capita figure drops to 84

kg/person/year of organic waste. In the EU the mean per capita figure was around 179 kg/person/year of food

waste9 in 2010, which is significantly less than the value in Figure 7, which may be more recent. The differences

in data highlight the inherent problems with extrapolating data across large populations where there is a lot of

variability within any one area. A more accurate and reliable approach would be to conduct on-the-ground

surveys of waste arisings, documenting the data over an extended period. In the UK there is the Waste Data

Flow database, which is completed by council collection services and a fairly accurate reflection of waste

arisings in the municipal and some commercial sectors, where councils collect the waste. There are other

waste arisings which do not fall under council authority and many of these are picked up by the UK Environment

Agency, through waste licensing regulations and permits.

For the purpose of the modelling in this study, the organic waste per capita has been assumed to lie between

84 and 104 kg/person/year. Taking these per capita values, the potential tonnage of organic matter lies

between 15,700 and 19,500 tpa. This compares fairly well with the earlier estimates using percentage OM of

the MSW fraction (14,000 and 23,500 tpa).

It has also been assumed that the organic fraction is 100% food waste. It is assumed that there are currently

no markets for organic wastes.

5.2.2 Grenada

Solid Waste Management in Grenada is the responsibility of the Grenada Solid Waste Management Authority

(GSWMA), which is part of the Ministry of Health. This organisation is funded by levies on both imported

products and household electricity bills. The latter levy, of 10%, applies where household electricity

consumption exceeds 100kWh. Although this levy is currently sufficient for the management and disposal of

solid waste, it will not provide sufficient funds to facilitate the developments needed to implement a waste-to-

energy programme.

Solid waste collection is outsourced to private firms who do charge for waste collection services, although

GSWMA does not charge fees for waste drop-off and disposal in order to avoid incentivising illegal waste

disposal.

8 SIDSDOCK, ‘Toward the development of a Caribbean regional organic waste management sub-sector’, May 2015. Available at: http://sea.sidsdock.org/download/wte_expo_library/background_papers/01-14-16-DRAFT-NOT-FOR-CIRCULATION-DRAFT-REGIONAL-WASTE-MANAGEMENT-.pdf 9 European Commission, 2010, ‘Preparatory Study on Food Waste across the EU 27’. Available at: http://ec.europa.eu/environment/eussd/pdf/bio_foodwaste_report.pdf

http://sea.sidsdock.org/download/wte_expo_library/background_papers/01-14-16-DRAFT-NOT-FOR-CIRCULATION-DRAFT-REGIONAL-WASTE-MANAGEMENT-.pdfhttp://sea.sidsdock.org/download/wte_expo_library/background_papers/01-14-16-DRAFT-NOT-FOR-CIRCULATION-DRAFT-REGIONAL-WASTE-MANAGEMENT-.pdfhttp://ec.europa.eu/environment/eussd/pdf/bio_foodwaste_report.pdf

23 CONFIDENTIAL

Waste collection in Grenada is divided geographically into five separate zones:10

Zone 1: South and north of St George’s and St George’s Town

Zone 2: St David and South St Andrew

Zone 3: St Andrew and St Patrick East

Zone 4: St John, St Mark and St Patrick’s West

Zone 5: Carriacou and Petite Martinique

There is currently one landfill site on Grenada at Perseverance, but this has reached capacity11. GSWMA and

the Caribbean Development Bank (CDB) are currently working together to rehabilitate disused landfill sites,

although it is estimated that these new landfill cells would reach their capacity limits within 7 years without a

reduction in overall quantity of waste production. GSWMA also operates a further landfill site at Dumfries on

the island of Carriacou. The precise amount of waste received at Carriacou is not known, but is estimated to

be less than 2,000 tonnes per year. Neither of these landfill sites has been technically engineered or

constructed using established industry techniques.12

At present there are very few procedures or facilities in place to enable the sorting and separation of waste. In

2013, per-capita waste in Grenada amounted to 1.02kg/day. By 2014, this had increased to 1.08kg/day. The

three largest contributors to overall waste composition in 2009 were as follows:13

Organic waste: 27.1%

Site cleaning waste: 21.3%

Plastics: 16.4%

However major stakeholders surveyed by the German Corporation for International Cooperation (GIZ)

predicted that the quantity of plastic in circulation in Grenada was likely to have increased alongside the growth

in formal and informal start-up food production businesses in the aftermath of 2004’s hurricane Ivan, which

generally use plastic packaging.

Overall, there is little sorting and separation of waste products in Grenada, which results in a high amount of

litter.14 Salvaging of recyclable products in Grenada constitutes a significant source of informal employment,

whereby glass bottles are taken from cities and landfill sites, and exchanged for a refund of XCD0.25 per

item.15

10 German Corporation for International Cooperation (GIZ), 2016, ‘Reducing the input of plastic litter into the ocean around Grenada’. Available at: https://www.giz.de/en/downloads/giz2016-marine-litter-instruments-grenada.pdf 11 Ibid. p.9 12 Ibid. p.11 13 Ibid. p. 11 14 Ibid. p.12 15 Ibid. p.11

https://www.giz.de/en/downloads/giz2016-marine-litter-instruments-grenada.pdf

24 CONFIDENTIAL

5.3 Water treatment

5.3.1 St. Lucia

In St Lucia the Water and Sewerage Company (WASCO) is mandated by law to develop and manage the

water supply and sewerage services in St Lucia. Only 24% of the public receives a 24-hour supply of potable

water, the majority of residents and establishments in St Lucia utilize individual on-site systems (pit latrines,

septic tanks and soak aways) for sewage treatment and disposal. There are two sewerage systems in St

Lucia16:

Castries

o Primary sewage collection and disposal system in the city of Castries, which serves around

15% of the Castries population, including the business district.

Rodney Bay

o Collection, treatment and disposal of sewage waste, using an Advanced Integrated Aeration

Pond system, serving around 13% of the residential population of St Lucia and hotels in the

north of the island

o Treated effluent from the system is discharged via an earth drain to a ravine which leads to

the ocean on the East Coast of St Lucia

o It currently operates under-capacity

The importance of effective waste water treatment cannot be overstated. There is recognition that incomplete

coverage of effective waste water treatment is causing environmental damage and poses a human health risk.

Illnesses which can be contracted through bathing in contaminated water or through consumption of

contaminated shellfish are gastro-enteritis, dermatitis, viral hepatitis, wound infections, cholera, typhoid fever,

and dysentery. In St Lucia there are still communities with no effective waste water treatment, where raw

sewage is discharged directly into receiving water courses, eventually draining out to sea. This has resulted in

nearshore waters, off certain parts of the St Lucian coastline being deemed unfit for human bathing, due to

elevated levels of faecal coliforms. The primary effect can be severe ill health but an important secondary

effect is the negative impact this has on the tourism industry. A report from January 201610 addresses these

issues for a specific community in St Lucia. The WWT options for Canaries is discussed in the report; there

are a range of topographical and areal constraints, which make options for treatment more challenging.

As with the organic solid waste fraction, the data on tonnages of WWT Biosolids or primary sewage sludge

and septage is not complete. Therefore, another estimation has had to be made for the purpose of modelling.

The Canaries report states that the waste effluent flow is in the region of 95 L/person/day; another source

suggests an effluent rate of 227 L/person/day – this high value includes hotels and commercial uses, which

has been estimated to generate up to 10x more effluent per head than the residents of the island. The latter

16 Island Water Technologies. ‘Assessment Of Wastewater Infrastructure And Go-Forward Options For The Village Of Canaries, St. Lucia’, January 2016. Available at: http://islandwatertech.com/wp-content/uploads/2016/07/Canaries-Wastewater-Report-2016.pdf

http://islandwatertech.com/wp-content/uploads/2016/07/Canaries-Wastewater-Report-2016.pdf

25 CONFIDENTIAL

rate is also extrapolated across the Caribbean region17. These estimates have been used to calculate a

possible range for tonnage of sewage. The population of St Lucia is 187214 (as of 13/11/2016), thereby

delivering an annual tonnage of sewage effluent between 17,800 tonnes and 42,500 tonnes.

5.3.2 Grenada

The UNEP Caribbean Environment Programme describes regional sanitation in the Caribbean as largely

inadequate, with poor quality services and insufficient access. This has the potential to impact extremely

negatively on public health.18 Grenada has historically suffered due to its poor sanitation system: in the 1980s,

many shallow reefs around Grenada were degraded and became overgrown with algae. This is believed to

have arisen as a result of a combination of sewage, agro-chemical pollution, and sedimentation caused by

coastal development.19

The information below is adapted from pages 30-34 of Waste-to-Energy Scoping Study for Grenada, a report

published in March 2015 by Renewable Energy and Energy Efficiency Technical Assistance (REETA) and

German Corporation for International Cooperation (GIZ).20

This report highlighted several obstacles facing researchers investigating the scale and functionality of the

current system. As the most recent comprehensive study into wastewater management in Grenada dates from

1999 (Wastewater Management Project, 1998-1999), there is limited up-to-date information available. Some

information nonetheless remains unchanged since the publication of that report.

The National Water and Sewerage Authority (NAWASA) has responsibility for maintaining national water

supply and overseeing domestic wastewater management. Grenada does not have an officially legalised

effluent standard, but instead draws on and partially applies standards outlined in a 1998 document from

Trinidad & Tobago, relating to industrial effluent standards.

As is the case in St Lucia, there are two sewerage systems in Grenada.

1) St Georges

o Sewered system with fall out pipe at the Stadium Bridge

o Fall out point: approximately 500m offshore

o Average flow: 130.000 gal/day (2013)

2) Grand Anse

o Sewered system with a fall out pipe at Point Salines

17 Caribbean Environmental Health Institute for UNEP/CAR-RCU, 2009, ‘Financial Assessment for Wastewater Treatment and Disposal (WWTD) in the Caribbean’. Available here. 18 United Nations Environment Programme (The Caribbean Environment Programme), Undated, ‘Wastewater, Sewage and Sanitation’. Available at: http://www.cep.unep.org/publications-and-resources/marine-and-coastal-issues-links/wastewater-sewage-and-sanitation 19 Ibid, citing Smith et al, 2000 20 German Corporation for International Cooperation (GIZ), and Renewable Energy and Energy Efficiency Technical Assistance (REETA), March 2015, ‘Waste-to-Energy Scoping Study for Grenada’. Summary available at: http://sea.sidsdock.org/download/wte_expo_library/Waste-to-Energy_Potential_Grenada_150316.pdf

https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0ahUKEwj584PX0-TQAhUFymMKHebLD48QFggdMAA&url=http%3A%2F%2Fwww.cep.unep.org%2Fcontent%2Fgef-crew-caribbean-regional-fund-for-wastewater-management-unep-iadb-gef-partnership-project%2Fmicrosoft-powerpoint-financial-assessment-ww-treatment.pdf%2Fat_download%2Ffile&usg=AFQjCNGEva3urt2LGU5TP3jQ46oIgirMFg&sig2=6o96QK7LUNuVK-YyrrHe0A&cad=rjahttp://www.cep.unep.org/publications-and-resources/marine-and-coastal-issues-links/wastewater-sewage-and-sanitationhttp://sea.sidsdock.org/download/wte_expo_library/Waste-to-Energy_Potential_Grenada_150316.pdf

26 CONFIDENTIAL

o Fall out point: Approximately 300m off shore

o Average flow: 660.000 gal/day (2013)

o This system receives a lot of wastewater generated in hotels (which tends to be less polluted

than domestic wastewater.) This effect may, however, be offset by the fact that there are a

number of industries and a brewery also connected to the system.

These two systems meet the needs of approximately 45% of households in Grenada. The other 55% of the

country depend on pit latrines and cesspit systems. In Grenada, most domestic septic tanks only receive waste

from the toilet flushing system: other liquid waste, including from showers and kitchen usage, is diverted to

‘soakaways’ or gardens. NAWASA oversees and provides licences for the operations of tanker companies,

who empty these pit latrines/ cesspit systems into either the St Georges or Grand Anse sewage system. These

septic tanks and pit latrines are emptied, on average, every 3-5 years. NAWASA does not monitor the amount

of septage (solid waste) which is collected by these tankers and subsequently released into the national

sewage system.

Wastewater in Grenada is released into the sea with little to no treatment. The fall out point at Point Salines is

problematic, as it releases much of the effluent it carries much closer to the shore than its intended endpoint

(located 300m out to sea), as it has previously sustained significant storm damage.

In theory, wastewater emitted into the ocean receives ‘marine treatment’: it is released at a sufficient depth to

dilute and oxidise it as it moves towards the water surface. In practice, however, increased organic load and

changing currents have combined to make this wastewater damaging for marine environments. It is generally

accepted that current fall out points are in need of extension in order to protect marine wildlife and tourist

attractions, and that Grenada’s wastewater system as a whole is in need of significant modernisation and

improvement. However, high initial start-up costs, high running costs and a shortage of space for a full-scale

waste treatment plant are all cited as reasons for apparent national reluctance to make the necessary changes.

5.4 Sargassum

There are many applications for seaweed and the East and South-East Asians have been exploiting seaweeds,

at a vast commercial scale for over a century, mainly for food production. Data from the FAO indicates that, in

2014 out of a total global production of 27.3M tonnes (wet weight) of seaweed, approximately 26.7M tonnes

came from the Far East, with 26M tonnes produced between China and Indonesia alone, almost all of which

was in a marine setting. The only producer in Western Europe was Ireland with 100 tonnes. Norway harvests

the most seaweed in Europe at around 155k tonnes, but this is all from natural stocks.

The value of this global market stood at just over US$5.5B per annum in 201421 and has been estimated at

US$11B in 20163. In 2014, US$5B of this was used for human consumption, mainly across Asia; the remainder

of the market was generated through the extractions of compounds such as the phycocolloids (alginates, agars

21 Food and Agriculture Organisation of the United Nations, 2014, ‘Fishery and Aquaculture Statistics’. Available at: http://www.fao.org/3/a-i5716t.pdf

http://www.fao.org/3/a-i5716t.pdf

27 CONFIDENTIAL

and carrageenens), some specific compounds with medical applications, cosmetics and such uses as animal

feed in agriculture. According to one market analyst22, the market is predicted to rise sharply over the next 5

years, up to US$17B. Hence, the market is predicting a strong and growing demand for seaweed products.

How does this relate to invasive inundations of seaweed, which are uncontrolled, irregular and difficult to

process? It demonstrates that there are markets at a commercial scale for certain seaweeds and that there

may be a similar potential for the Sargassum of the Caribbean.

The available data on Sargassum and in particular the species which dominate across the Caribbean, S.

fluitans and S. natans, is very sparse. Information in the literature focuses on the ecological aspects of these

holopelagic seaweeds, trying to understand the origins and movements of the mats/rafts of Sargassum and

approaches that have been taken to manage the seaweed once it comes into conflict with human activities.

There are a number of approaches to managing Sargassum which can be implemented. Most methods at this

time are concerned with removal and disposal, composting and allowing the material to degrade naturally on

the beach (a good approach where the beach is off the tourist trail). These methods are becoming more

sustainable as the negative impacts of standard techniques such as beach clearance by heavy moving

vehicles, have become clear. A recent publication23 out of collaborative work by CERMES, CAR-SPAW-RAC

and GCFI provides some insight and advice on successful and sustainable Sargassum management. There

are some small private and commercial enterprises which use applications of Sargassum to land as a fertiliser

or as a horticultural plant stimulant e.g. Algas Organics and their Sargassum extract. This small company has

shown some very positive results and their Sargassum extract is being marketed locally in St. Lucia. The

potential of Sargassum natans and fluitans is only now being investigated to assess its potential as a revenue

stream.

Chemical composition data is sparse for Sargassum natans & fluitans but the following four tables (tables 2 –

5) represent some of the work done and published.

Table 2. Ultimate analysis of Sargassum species

Species C H O N Ash Source Reference

1Sargassum natans 25.9 5.57 24.18 3.58 nd Guangdong,

China Shuang W et al, 2013

2Sargassum muticum 33.36 4.85 24.01 5.46 31.85 Kent,UK Milledge &

Harvey, 2016

3Sargassum fluitans 34.29 5.27 54.53 1.15 23.55 St Lucia,

Caribbean CPI, 2016

Sargassum fluitans nd nd nd nd 19 BVI,

Caribbean CEVA, 2016

1Sargassum was dried from fresh sampling. 2Sargassum was processed from fresh frozen samples 3Sargassum used was collected from a beach in St Lucia. It was around 2 months old and dried through exposure on the beach. nd = not determined

22 Markets and Markets, undated, ‘Commercial Seaweeds Market worth 17.59 Billion USD by 2021’. Available at: http://www.marketsandmarkets.com/PressReleases/commercial-seaweed.asp 23 Ecomar Belize, 2016, ‘Sargassum Management Brief’. Available at: http://www.ecomarbelize.org/uploads/9/6/7/0/9670208/sargassum_management_brief__-__cermes_-_august_24_2016_final[2]_copy.pdf

http://www.marketsandmarkets.com/PressReleases/commercial-seaweed.asphttp://www.ecomarbelize.org/uploads/9/6/7/0/9670208/sargassum_management_brief__-__cermes_-_august_24_2016_final%5b2%5d_copy.pdfhttp://www.ecomarbelize.org/uploads/9/6/7/0/9670208/sargassum_management_brief__-__cermes_-_august_24_2016_final%5b2%5d_copy.pdf

28 CONFIDENTIAL

Table 3. Carbohydrate content of Sargassum species

Species Mannitol Laminarin Fucans Glucose Total

sugars Alginic

acid Source Reference

Sargassum muticum

7.7 0.3 8 2.2 18.2 16.7 Isle of Wight

Gorham & Lewey, 1984

Ascophyllum 8.886 13.25 5.956 nd nd 17.18 Not

provided

Faulkner, Ocean Harvest

Sargassum fluitans

10.245 12.6 6.19 nd nd 15.55 BVI,

Caribbean

Faulkner, Ocean Harvest

nd = not determined

29 CONFIDENTIAL

6 Anaerobic Digestion

6.1 Biogas production

Anaerobic digestion is the breakdown of complex organic matter such as proteins, carbohydrates and lipids

(fats) into smaller organic molecules, eventually resulting in the production of biogas. This process of

degradation takes place in the absence of oxygen i.e. anaerobically and is facilitated by a complex population

of bacteria and archaea. The conversion of complex organic matter into biogas is a relatively slow process

compared with aerobic digestion (composting) but the result is a gaseous product which comprises around

60% (50 – 70% range) methane and 40% (30 – 50% range) carbon dioxide and also a digestate, which can

be used as an effective fertiliser or plant stimulant. The biogas generated has an energy value due to the

methane content and can be passed through various boilers and engines to produce electricity and or heat.

Generally, 1m3 of biogas has a calorific value of around 22 MJ m-3 (6kWh), which can be upgraded by scrubbing

the gas to remove the CO2 and other impurities to produce biomethane, which has a calorific value of 36 MJ

m-3 (10kWh). Therefore, by knowing what the biogas and methane yields are for a particular feedstock (or

blend of feeds), it is possible to then calculate how much energy could be produced. In reality, the maximum

potential is never reached for a number of reasons:

Efficiency of the AD conversion process is not 100%

The efficiency of a CHP engine to convert methane to electricity is around 35 – 40%. Quite often the 50%

heat produced through CHP is not utilised. There is the potential to make use of this heat either for heating

space or cooling through refrigeration.

The efficiency of a boiler to produce heat is around 85%

There are other small process losses from the system, which can amount to as much as 15%

In light of these process efficiencies and losses, it becomes very important to try to optimize the AD process

to produce the best possible methane yield. Process optimization involves studying the plant data generated

over a period, making adjustments to operating conditions (as suggested by the data) and possibly introducing

further technology at the front end to help release more of the feed’s active components. However, before

optimization there is the important step of achieving a steady state of operation.

In the recent past there has been a failure to understand the sensitivity of AD. Not all feeds are equal, in fact

feed types vary enormously in their chemical composition and this variability can prove to be quite a challenge

for AD operators. The microbial population in any AD plant is sensitive to changes in chemical composition

e.g. salt content or fat content, pH and temperature. Small but significant changes can shock the system and

cause it to fail and there have been many instances of this in the UK over the last 20 years. Ideally, once

established, with a reasonably consistent feedstock, any AD plant should operate at a steady state, producing

fairly constant and consistent biomethane yields. Hence, the importance of a stable feedstock cannot be

underestimated.

Biogas yields are governed by a number of factors; the type of organic matter used to feed the digestion

process; the operating conditions of the AD plant, in particular the temperature, pH, the amount of time the

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materials spends in the digester (retention time), the amount of bioavailable organic matter loaded into the

digester per day (organic loading rate) and whether any nutrient amendments are required; the requirement

or desirability of any pre-treatment technology to treat the feed before it reaches the digester. Getting all these

elements right so that the best yields can be realised is an important and at times lengthy process.

6.2 Applications & Benefits

AD technology has been used for decades, from the first AD plant built in a leper colony in India in 1859 and

the early Victorian waste water treatment systems in the UK for treating sewage sludge, first established in

1895, to a broader application today which includes the use of other biomass wastes and also purpose-grown

energy crops, such as maize, sugar beets and grass silage to produce biogas. The rate of uptake of this

technology has been variable across continents and countries but the technology is now considered to be

proven and well established.

AD benefits from a number of attributes which compare favourably with other waste treatment solutions. In St

Lucia and other Caribbean states, thermal treatment is being considered for the MSW waste arisings. Thermal

treatment comprises incineration, pyrolysis and gasification. The benefits of AD can be summarised as follows:

Well suited to wet feedstocks – a ‘wet’ AD system generally handles feed materials with ≤ 15% total solids

(TS), whereas a ‘dry’ AD system can handle TS content between 15 % and 40%. No drying of feed is

required for AD, which saves on operating costs.

AD makes use of biological processes to break down organic matter and so does not require a large

energy input. Generally, the process itself can generate more than enough energy to be able to run itself

by taking off the small parasitic load from the power generated through the engine.

AD can be applied at a range of scales, from micro-digestion (< 10kW) for individual households, small

scale (10 – 250kW) for small communities or businesses, to medium scale (250 – 1MW) for larger

business, towns and finally larger scale (>1MW) for municipal, centralised applications. The economic

viability at this range of scales is variable and generally harder to make money on for the smaller scale

operations. However, making a quick return may not always be the driving force behind a project. More

importantly might be delivering environmental improvement, improving the health of the community,

reducing waste disposal costs, off-setting expensive and volatile fossil fuel imports and becoming more

resilient as a community; a slower, lower return on investment might be seen as acceptable under these

drivers.

O&M costs are generally much lower than any of the thermal treatment options, as is the initial investment

on an AD plant of similar capacity. The difference in capex is an order of magnitude, a few US$M for AD

compared with multiples of US$10M for thermal treatment. Thermal treatment only becomes financially

viable at large scale.

Easier process control, with no requirement for high temperatures, pressures or sterility. ‘Ease’ of process

control, should not be equated with ‘no control’; an AD system can be shocked and fail if the composition

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of the influent feed is not adequately managed. Inconsistent and variable feed will upset the balance of

microbes within the system and cause the production of biogas to change and the quality (%CH4) to

change. This could directly impact power generation and financial return.

AD technology could address current problems with sewage treatment as it is possible to treat raw sewage

and sewage which has undergone some degree of waste water treatment (primary and or secondary

sludge). This may form part of a water treatment and recycling solution for more remote communities.

Community waste (food, sewage, agricultural) could be treated through a small AD plant – there are some

very nice solutions on the market for small and micro systems. The resulting digestate could be dewatered

either through mechanical/physical separation or more passively over a longer period of time. There are

systems which will treat the sewage first, separating the liquid and solids; the liquids could pass through

a passive water treatment system based on bioreactors with plants; the solids could be fed into an AD

plant. For small communities, there could be a number of options for combining waste water treatment

with energy generation.

Thermal treatment is being considered as a solution for waste management and energy provision. This

technology definitely has a place for treating certain types of waste, which cannot be readily disposed of

via other means, such as waste wood, discarded tyres, used engine oil and the residual municipal waste

fraction. However, this technology is not the ideal treatment option for wet biomass wastes. Biogenic

wastes not only have an energy value, they also contain macro and micronutrients, which pass through

an AD process almost unchanged; these useful components would be lost through thermal treatment.

Thermal treatment is an expensive treatment option, which provides a return on investment when

implemented either at large scale or supported by generous tariffs and gate fees for waste. Capex costs

are much greater than for AD; 40,000 tpa incineration plant, can cost around US$40M24, compared with

US$4+M for a 30,000 tpa AD plant (this study).

Incineration is straight forward combustion with excess oxygen, at high temperature, generating CO2 and

water as gases (harmful other components are scrubbed out). Gasification is the sub-stoichiometric partial

combustion of waste to produce syngas – a mixture of H2, CO and CH4. Part of the reason why gasification

requires greater financial intervention and incentives to give a positive return is that syngas has a much

lower calorific value than biogas from AD; syngas values tend between 4 – 10 MJ/Nm3, compared with

biomethane at 38 MJ/Nm3 (biogas at 22 MJ/Nm3).

6.3 Planning and Permitting for AD

In the UK, there are regulations in place which govern where plants can be located or rather, where they cannot

be located. There are also regulations on how to operate the plant to protect both human health and the

environment. All waste operators have to apply for and fulfil the conditions of an Environmental Permit or, for

very small operations, an Environmental Exemption. There are annual charges associated with these permits,

which contribute to the costs of administering and enforcing the regulations.

24 Waste to Energy International, 14 September 2015, ‘Cost of incineration plant’. Available at: https://wteinternational.com/cost-of-incineration-plant/

https://wteinternational.com/cost-of-incineration-plant/https://wteinternational.com/cost-of-incineration-plant/

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An application for planning consent, in the UK, addresses particular issues by way of an Environmental Impact

Assessment (EIA). An EIA will consider the following elements and make a judgement, based on knowledge

and evidence, on the following aspects of the proposed development;

Any planning policies which support the development and any policy documents relating to renewable

energy, climate change, greenhouse gas emissions etc.

The waste type and tonnage throughput

The footprint of the intended development, its location and the boundary of the parcel of land in which it

would sit and in which any operations connected with the development, would take place

How far away would be the nearest residents, water extraction boreholes, water courses, any sensitive

land uses (sites of special scientific interest etc)

What the impacts on the local community would be from traffic (waste trucks), odour (from the untreated

waste), noise (traffic and any waste moving vehicles), pests (requirement for proper control of wastes),

and would there be a loss of amenity value, for instance, would the development involve taking over a

park, which is used for recreation? The destination of the digestate would also be discussed as would the

proposed use of the energy liberated from the process.

Some of these aspects might be applicable to a development in St Lucia and Grenada. The planning stage

provides the community with the opportunity to view the plans and ask questions of the developer. It also

provides an opportunity to register support or rejection of the proposal. Hence, in the UK, the planning process

is an important time for trying to get the community on board, answering their questions and concerns so that

they have the facts of the proposal.

Environmental Permitting is concerned with the details of operation and regulates how a plant is run, what

records are maintained, controls on waste, air quality, health and safety. There is guidance to help operators

comply with the conditions of their permits. To ensure that new operations do not result in potentially harmful

activities to either humans or the environment, some measure of regulation and control may need to be devised

for the developing island states.

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7 Biochemical methane potential

7.1 Introduction

A biochemical methane potential assessment is a methodology which is used to determine the maximum

methane yields potentially achievable from any given feedstock. The test is always a batch experiment, where

a known amount of feed and inoculum are digested anaerobically and the volume and quality of the resulting

biogas measured over an incubation period. This test is not representative of plant situations and cannot,

should not be used to scale a full scale process. However, it does provide useful information on the suitability

of a potential feedstock for treatment through AD. If further investigations are carried out in bench scale or pilot

scale digesters, the BMP data can be used as a benchmark against which the efficiency of the digestion

process to produce methane, can be assessed.

7.2 Methodology

7.2.1 Feedstock preparation

The Sargassum test material was received as dry fronds. A sieving test showed the material to be around one

third by weight beach sand.

The sample for the BMP was washed several times with distilled water to remove the bulk of the sand. The

washed sample was then dried overnight at 80 C in an air oven and then ground up in a Nutribullet. Grinding

reduced the sample to a fine powder but with a significant amount of larger, harder particulates ranging in size

up to about 2-3 mm. The whole ground sample was used for the BMP.

7.2.2 Substrate blends and controls

In Table 6, the composition of the set of substrates for the BMP experiment are set out. The inoculum was

digestate from another seaweed/food waste AD experiment and the loading of each batch was determined

from the analysis of the raw materials VS components. Batches were loaded according to a number of blend

ratios calculated from the VS of Sargassum, Saccharina and FW and then a final 1:1 VS ratio of inoculum to

feed.

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Table 6.Treatment compositions for each BMP experiment, as calculated for an approximate 600 mL volume. The blend ratios (*) are calculated on a VS basis as the sargassum [and Saccharina] was dried. Where SW = seaweed, Sm = Sargassum fluitans, Sl = Saccharina latissima and FW = food waste . The FW was not dried but added as a wet slurry.

Treatment Set Inoculum SW FW

(mL) (g) (mL)

Inoculum DI Blank 1 600 0 0

FW only C1 560 0 40

Sm only C2 592 8 0

Sl only C3 591 9 0

Sm + FW 1:1* B1 575 4 21

Sm + FW 2:1 B2 581 6 14

Sm + FW 3:1 B3 583 6 11

Sm + FW 1:2 B4 570 3 27

The substrate weights or volumes, as appropriate, for each treatment were calculated and then prepared to