Generation of electricity and heat from biomass:

Technology options and potential pitfalls

Nick Ash

Principal Consultant

Ricardo Energy & Environment, U.K.

RICARDO ENERGY & ENVIRONMENT…

…provides strategic consultancy and project leadership for national and local governments, the European Commission, multinational

corporations and a wide range of public and private sector organisations in these sectors:

Owned by Ricardo plc

RICARDO ENERGY & ENVIRONMENT…

…has a portfolio of more than 200 projects delivered in Africa in the Energy sector…

Countries shaded blue indicate Ricardo Energy & Environment project references

…and a Johannesburg-based subsidiary, PPA Energy (Pty) Ltd.

WHAT WE’LL COVER IN THIS SESSION

Benefits & drawbacks of

biomass

Specialist advice for

project development

Fuel considerations

Technology options

Conclusions

BENEFITS & DRAWBACKS OF BIOMASS

THE BENEFITS OF BIOMASS

A renewable energy source to substitute

fossil fuels

A dispatchable technology to complement

fluctuations in solar, wind & hydro

Provides a sustainable approach to managing

bio-waste from agriculture & industry

Can allow processing plants to reduce reliance

on electricity from the grid

Potential additional revenue stream(s) for

processing plants through sale of

electricity and/or heat

Processing plants often require heat, creating an opportunity for higher-efficiency cogeneration

Can provide enhanced energy security as an

additional (home-grown) energy resource

Potential for development at a range

of scales drawing on local resources

Can be a catalyst for local economic

development, up-skilling and increased employment

BUT THERE ARE SOME DRAWBACKS

In a shifting environment where the capital costs of solar, wind and storage facilities are decreasing…

• Investment decisions need to be made carefully considering the full lifecycle costs & benefits

Leve

lise

d c

ost

of

ele

ctri

city

($

/MW

h)

Source: Lazard (2017)USA

Source: BEIS (2016)UK

Source: Ricardo (2016)South Africa REIP Round 3

50

80

110

Biomass combustion plants already have a higher LCOE

than onshore wind and utility-scale solar PV

Onshore wind

Utility-scaleSolar PV

Biomass boiler plant

CONSIDER THE BUSINESS CASE CAREFULLY

Without government support, it can be difficult to make a business case for a biomass plant that only exports electricity

• Existing processing plants with biomass by-products are ideal candidates

• Where self-generation can reduce reliance on imported electricity

• The business case is enhanced further where there is also a demand for heat (increased efficiency through cogeneration)

It should be considered as one technology option in a coherent energy strategy

• Through integrated resource planning

The economic benefits to the local community should be considered in addition to the financial aspects…

• But this is difficult for a developer to justify financially (internalize)

SPECIALIST ADVICE FOR PROJECT DEVELOPMENT

SPECIALIST ADVICE IS REQUIRED TO…

Assist with project technical, financial and legal preparations

Prepare and evaluate the business case

Manage project-specific risks

Prepare project documents

This is especially the case if you need to secure external financing

CONSIDERATION MUST BE GIVEN TO THE FULL PLANT LIFECYCLE

• Fuel availability & properties

• Grid connection

• Site availability

• Plant technology

Feasibility stage

• Capital costs

• Financing

• Risk management

Financing, design, procurement, construction • Sale/substitution of

electricity & heat

• O&M costs

• Reliability

Operation

• Environmental impact

• Social impact

Decommissioning

Enabling environment is critical

Government policy supportLegal frameworkRegulatory environmentPlanning & ESIA processesMarkets for electricity and/or heat

THIS SESSION WILL CONCENTRATE ON FUEL CONSIDERATIONS AND TECHNOLOGY OPTIONS

And the implications

for O&M

Can you get the feedstock at the required:• Cost• Quantity• Quality • TimeTo produce the energy required?

Will you be able to sell/use the energy you produce?

FUEL CONSIDERATIONS

ASK YOURSELF: WHERE WILL I GET THE FUEL AND IS THERE ENOUGH?

• The amount of fuel available will determine the plant output in terms of electricity/ heat

Availability and cost of feedstock

• Haulage costs in Africa are significant

• Long distances increase risk of supply disruptions

Site location is critical

• Cost of fuel, transport and preparation required

• It has a direct influence on the business case

Cost of feedstock

• Mitigate against supply uncertainty

• Long term agreements mitigate against short-term fuel price volatility

Fuel supply agreements

ASK YOURSELF: WILL THERE BE A RELIABLE FUEL SUPPLY?

• Availability of suitable vehicles in sufficient quantities

• Quality of roads

Transport infrastructure

• Logistics of delivery vehicles to provide a steady fuel supply

• Avoidance of bottlenecks to minimise weighing and offloading time

Fuel offloading efficiency

• Supplementary sources in the off-season of the primary fuel

Seasonal variations

• As a buffer to compensate for supply disruptions

Storage facilities

THE CHEMICAL PROPERTIES OF THE FUEL DETERMINE THE PLANT TECHNOLOGY

Calorific value

Moisture content

VolatilesAsh

content

DON’T IGNORE THE ASH CONSTITUENTS

Biomass fuels tend to have high proportions of alkali-earth minerals in the ash

Alkali oxides are associated with boiler “fouling“ (insulation), reducing efficiency

Fouling can be minimised by increasing furnace height

Fouling indices can be used to predict fouling propensity

High silica content tends to mitigate against fouling

OTHER NASTIES TO BEWARE OF

Higher combustion temperatures increase

the risk of aggregation of solid materials in the

boiler, called “slagging”

This is also dependent on ash properties

Check for high concentrations of

sulphur and chlorine in the fuel

These can form acids within boilers and lead to

accelerated corrosion

PLANT TECHNOLOGY OPTIONS

BIOMASS PLANT TECHNOLOGY OPTIONS FOR AFRICA

Grate boiler

+ steam turbine

Fluidised bed boiler

+ steam turbine

Thermal gasification + engine /

gas turbine

Anaerobic digestion + engine /

gas turbine

GRATE BOILER + STEAM TURBINE

Mature technology; unit sizes up to ~40 MW

Relatively reliable; moderate operator skill required

Used throughout Africa for many decades

Relatively limited fuel range; suited to solid fuels with moderate moisture (40 – 55%) content

Prone to fouling with high-alkali fuels (high combustion temperature)

Efficiency of converting fuel to electricity ~30% (assuming no cogeneration)

Lowest capital and operational costs of options presented here (similar to fluidised bed boiler)

Large ash residue volume requires disposal/storage; risk of NOx, SOx & particulate emissions (depending on fuel)

Source: John Thompson Boilers

Note: It is possible to clean up gaseous emissions, but this adds cost & complexity

FLUIDISED BED BOILER + STEAM TURBINE

Source: ESB

Mature technology; unit sizes can be greater than 40MW

Relatively reliable, but require highly skilled operators

Limited references in Africa, especially for biomass applications

Suitable for wide range of fuels (but not wide variations in one application)

Some fouling with high-alkali fuels (lower combustion temperature than a grate boiler)

Efficiency of converting fuel to electricity ~30% (slightly higher than equivalent grate boiler)

Lowest capital and operational costs of options presented here (similar to grate boiler)

Large ash residue volume requires disposal/storage; risk of NOx, SOx & particulate emissions (depending on fuel)

Note: It is possible to clean up gaseous emissions, but this adds cost & complexity

THERMAL GASIFICATION + ENGINE / GAS TURBINE

Source: Siemens

Emerging technology for biomass; unit sizes up to ~10 MW

Complex plant (esp. for syngas cleaning) requiring highly skilled operators

No known references in Africa at industrial scale

Limited variability in feedstock tolerated (high moisture fuels require drying)

Good for high-alkali fuels due to absence of combustion

Efficiency of converting fuel to electricity ~20%

Highest capital and operational costs of options presented here

Large ash residue volume requires disposal/storage; complex clean-up to remove NOx, SOx & particulates

Note: Syngas can also be processed to produce chemicals or liquid fuel.

ANAEROBIC DIGESTION + ENGINE / GAS TURBINEMature technology; unit sizes up to ~4 MW (small-scale

applications)

Relatively reliable but biogas clean-up equipment adds complexity; requires moderate operator skill

Multiple project references in Africa

Sensitive to feedstock variability; best suited to high moisture & starchy fuels*

Good for high-alkali fuels due to absence of combustion

Efficiency of converting fuel to electricity ~40%

High capital and operational costs (lie between boiler plant & gasification)

Digestate by-product is a good fertiliser; lower risk of harmful gaseous emissions than boilers or gasification

* Anaerobic micro-organisms can’t break down the lignin within wood products and straw.

Additional note: Large land area per unit electricity produced compared with other options quoted here.

PLANT TECHNOLOGY OPTIONS AND FUELS

Technology Woody biomass

Herbaceous/ crop residue

Seeds, husks and shells

Food and animal wastes

Liquid residue/ wastes

Grate boiler + steam turbine

Fluidised bed boiler + steam turbine

Thermal gasification + engine / gas turbine

Anaerobic digestion + engine / gas turbine

CONCLUSIONSBiomass has many benefits, but it should be considered as one

option in an integrated resource plan

Develop a comprehensive understanding of the fuels from the start of the project

Ensure that there will be buyer(s) of the energy products for the full life of the plant

To navigate the many risks, engage specialist advisors from the feasibility stage to commercial operation

Select the technology to suit the fuels and skill base of O&M personnel

Ensure the technology has an established, comprehensive support network within Africa

BIBLIOGRAPHY

• BEIS (2016) Electricity Generation Costs.

Department for Business, Energy & Industrial

Strategy, Govt. of United Kingdom, London.

• International Finance Corporation (2017)

Converting Biomass to Energy. International

Finance Corporation, Washington D.C.

• Lazard (2017) Lazard’s Levelised Cost of

Energy Analysis – Version 11.0.

• Magasiner, N. et al (2001) Characterising Fuels

for Biomass-Coal Fired Cogeneration. Proc. S.

Afr. Sug. Technol. Ass., Durban.