GHG/07/48
IEA GREENHOUSE GAS R&D PROGRAMME
32nd EXECUTIVE COMMITTEE MEETING
USE OF BIOMASS WITH CCS
(Proposal number 32-1)
Introduction
Combustion plants which use sustainably grown biomass can be deemed to have near zero
net CO2 emissions, because the CO2 emitted to the atmosphere is assumed to be absorbed by
growth of the biomass fuel. If the CO2 is captured and stored, instead of being emitted to the
atmosphere, the net emissions would be negative. The ability to generate energy while
reducing the quantity of CO2 in the atmosphere would be a unique feature of biomass fired
plants with CCS.
Another option would be to co-use small proportions of biomass in coal-fired plants with
CCS, to achieve zero net-CO2 emissions.
In 1997 IEA GHG carried out a study to assess the costs of small scale (20-60 MWe) biomass
fired power plants in Spain but that study did not consider CO2 capture.
Biomass sources and utilisation technologies
Most of the biomass that is currently used for energy production is by-products and residues,
including bark, sawdust, straw, palm kernels, rice husks, sugar cane bagasse and black liquor
from pulp mills. Much of these materials are already used for energy production. Biomass
can also be produced specifically as a source of energy, for example crops for production of
liquid fuels (bio-diesel and ethanol), and fast-growing wood, grasses etc. for heat and power
production.
In some regions, e.g. the EU and USA there are incentives to increase the use of biomass to
reduce greenhouse gas emissions and reduce the dependence on imported fossil fuels. This
means that use of biomass energy crops is likely to increase in future, although there are
some concerns regarding the impacts of this on food availability and prices and increased
deforestation.
Biomass can be used in the following types of plants:
 Combustion of biomass on its own in heat and/or power generation plants
 Co-combustion of biomass and coal, usually in larger power plants
 Gasification of biomass on its own in heat and/or power generation plants
 Co-gasification of biomass and coal, usually in larger power plants
 Fermentation and other types of plants for liquid fuels production.
Plants which use solely biomass are usually smaller than coal-based plants, because the
quantities of biomass that can be grown close to a plant are limited and biomass has a
relatively low density and high transport costs.
The CO2 capture processes that could be used in biomass combustion and gasification plants
are similar to those that would be used in coal fired plants of similar sizes. Applicable
capture technologies include post-combustion, pre-combustion and oxy-combustion capture.
There are therefore many combinations of types of biomass, types and sizes of utilisation
plant and types of CO2 capture process. Detailed assessment of the many possible
combinations would be unrealistic. This study will therefore include a high level comparison
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of biomass and coal based plants with CO2 capture and a more detailed assessment of
selected cases.
Outline scope of the study
The aim of this study is to assess the costs of CO2 capture in biomass utilisation plants. The
broader issues of the advantages and disadvantages of biomass as an energy source and
sustainability issues are beyond the scope of the study. The study will include the following
major tasks:
Biomass types
The main types of biomass and their analyses will be summarised. This will include byproducts, residues and purpose-grown biomass.
Combustion and gasification plants
The main factors which would be different between CO2 capture units in biomass and coal
combustion and gasification plants will be identified. These could include for example flue
gas CO2 concentration, quantity of CO2 per unit of useful energy, impurities concentrations
and typical plant sizes. Significant differences between different types of biomass will be
identified.
The implications of these differences for CO2 capture processes will be discussed. Any
factors which may make certain capture technologies more or less suitable for biomass-based
plants would be identified.
CO2 capture in liquid fuels production plants
Processes for producing bio-ethanol and bio-diesel will be described. Opportunities for coproduction of heat and power in these processes will be identified.
The CO2 capture processes which could be used in bio-ethanol and bio-diesel plants will be
identified and compared.
Life cycle emissions
The life cycle emissions of greenhouse gases associated with production and delivery of
various types of biomass will be complied from published information and contacts with
other organisations
Taking into account life cycle emissions associated with fuel production and delivery, the
quantities of biomass that would have to be used in a co-combustion plant to achieve zero net
CO2 emissions will be estimated. The feasibility of co-combusting the required quantity of
biomass will be considered.
Assessment of selected cases
Four cases will be selected for more detailed assessment of CO2 capture plant performance
and costs. The cases will be selected during the course of the study but they may include for
example a large ‘zero net CO2 emissions’ co-combustion power plant, a large plant using
only purpose grown biomass (e.g. in the US mid-west or Brazil), a smaller combined heat and
power plant using biomass by-products or residues and a liquid fuels production plant.
The energy consumptions and costs of CO2 capture in these plants will be estimated.
The sensitivities of costs of capture to various technical and economic parameters, including
plant size, biomass price and economic discount rate will be presented graphically.
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Collaboration with other organisations
The IEA Bio-Energy Agreement and other relevant organisations will be contacted to ensure
that existing information and expertise on biomass analyses, utilisation technologies and life
cycle emissions is used as far as possible.
Proposal
It is proposed that a study should be carried out on the use of biomass with CCS.
RESOURCES REQUIRED
Financial
Average
Project management
Average
The committee is requested to
i)
Approve proceeding with this study.
ii)
Suggest possible contractors
iii)
Suggest possible expert reviewers for the completed study
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