System for countermeasures of carbon dioxide

Energy Convers. Mgmr Vol. 36, No. 6-9, pp. 873-876, 1995 Copyright 8 1995 Elsevier ScienceLtd Printed in Great Britain. All rights reserved 0196~8904(95)00142-S 0196-8904/95 $9.50 + 0.00

Pergamon

System for Countermeasures of Carbon Dioxide

YUKIO YANAGISAWA Research Institute of Innovative 9-2, Kizugawadai,

Technology

Kim, Souraku,

RITE/Harvard

for the Earth

Kyoto 619-02,

Japan

School of Public Health

Abstract - Mitigation measures to global climate change are classified focusing on

carbon dioxide in order to cover all potential technologies. A templet is proposed to assess each technology and technological systems under the standardized criteria.

1. INTRODUCTION Many technological measures to reduce greenhouse gases in the atmosphere such as carbon dioxide have been proposed.

Carbon dioxide (CO,

) is considered the most responsible gas for the global climate change.

Reduction of CO, emission and enhancement of CO, fixation into ocean and land are urgently required. In order to evaluate these proposed measures to the global climate change, two important issues should be pointed out, that is, our planet is a materially closed system and the required amount is in the order of several billion tons of carbon. and running costs.

of CO, reduction is huge, which

New technologies have been first evaluated based upon investment

Mitigation measures to the global climate change, however, have to be evaluated by the two

criteria and then the cost. In this study, technology

the promising technologies to prevent the global climate change were classified by developing a

map using top to down approach to cover various aspects. After classifying the technologies,

a templet

was applied to assess each technology from viewpoints of the characteristics of the global climate change.

2. MAP OF MITIGATION

MEASURES

The mitigation measures to the potential global climate change are not only controlling greenhouse gases but also some geoengineering (Table 1).

methods.

In this paper we focus on how to reduce atmospheric CO, concentrations

There are two categories to decrease the atmospheric CO, concentrations:

removal of CO, from air and

reduce CO, emissions. CO, in air can be fixed in land and sea by biological photosynthesis

and chemical reactions.

Enlargement of forests and enhancement of chlorophyll activities are examples to reduce the atmospheric CO, concentrations

by the biological methods.

One of the chemical methods is the formation of calcium carbonate of which

reaction occurs in the sea and on land. The production of calcium carbonate in the sea, however,

accompanies

release of CO, from the sea in some cases. The CO, reaction with silicate on land results in carbonate formation and promises to the CO, fixation. Two kinds of the CO, emission sources are pointed out, natural and anthropogenic one. According to the IPCC report, one to two billion tons of carbon are discharged from the natural sources annually. desertification play a major role in these emissions. Not only socio-economical

Deforestration

countermeasures

and

but also technologi-

cal development to maintain forests and grass land are urgently required. Five to six billion tons of carbon emissions are accounted for the anthropogenic sources. CO, separation from effluent gases, energy source replacement, and energy savings can contribute to diminish the CO, emissions from 873

YANAGISAWA: SYSTEM FOR COUNTERMEASURESOF CO2

874

human activities. After separating CO, from a stack of power generators, for example, CO, can be fixed by disposing into ocean or charging oil fields. The separated CO, is also used as energy transport medium and active materials for enhanced oil recovery. Coal discharges more CO, per calories than natural gas. By replacing coal to natural gas, CO, emission lowers under the same thermal requirements. Usages of treated coal such as hydrogen separation from coal and hydrogen addition to coal are the potential replacement ways if energy and CO, balance are reasonable. Other methods of the replacement are to use energy sources that do not emit CO,. Solar, nuclear and geothermal energy are classified in this category.

The solar energy can be used directly by photovoltaic and photothermic methods, and indirectly by wind

and hydrological methods as examples. Nuclear and geothermal energy have large potential, although social acceptability is important. The energy saving consists of efficient use of energy and change of services.

The improvement of the energy

efficiency can be accomplished within a short period, because very efficient technologies have been already operated in some advanced countries, although further technological developments are required in some areas. The areas are improvements of efficiencies in energy conversion, energy transportation, cement, transportation ature waste,

production processes such as steel and

of men and goods, and domestic uses. Efficient use of waste energy, for example, low temper-

is an important subject of technological developments to reduce CO, emissions.

We sometimes enjoy excess services in our daily life. However, from viewpoints of sustainable developments we should recognize what are excesses and what are reasonable. Recycling of goods and materials, and recovery of energy and materials from wastes are promising approaches toward preventing the global climate change.

Not only

technological development for how to reuse materials but also developments of social systems are needed.

3. TEMPLET

FOR TECHNOLOGY

ASSESSMENT

The identified technology in the map is a subject of the technology assessment taking the requirements of the countermeasures

into account.

As shown in Table 2, each technology or technological system is assessed by

technological feasibility and then side effects and economical aspects. The criteria of the technology assessment are the ratios of CO, emission and energy demand based upon that of representative technologies in use now, and the net amount of CO, reduction. Procedures to use this templet are as follows.

1)

Classify a CO2 reduction technology into an elemental technology and a cascade technology.

2)

Assess the technology from the technological feasibility.

In this stage, there are four levels: 1) theoretical level,

2) present level and 3) future level. The present level consists of experimental level and substantiation 3)

level.

At the theoretical level, technology assessment is performed from the stand point of two theories, which are the ideal chemical stoichiometry and thermodynamics.

4)

At the experimental level, the technology is evaluation based upon the performances of the laboratory experiments or pilot plant.

If the subjective technology needs some supporting technologies or systems, their

ideal conditions are assumed when the evaluation at the experimental level is carried out. Regarding electric power generation with fuel cells, for example, utilization discharged from the cell.

we assume ideal conditions for the fuel supply and heat

At the substantiative level, the performance of the subjective technology is

evaluated under real conditions of the supporting technologies or systems.

This indicates the evaluation of the

specific mitigation measure at current real situations. 5)

At the future level, improvements of the performances of not only the subjective technology but also the supporting technologies or systems can be expected in twenty-first

centuries.

The future level evaluation will

be conducted by estimating technology developments at a certain time in twenty first centuries.

If the time is

specified, it will be shown es a note in the templet.

If the subjective technology cannot meet the criteria at the theoretical level, it is not worthy of further consideration. The differences among these levels tell us the maturity of the technology.

If the performances of the

technology in the laboratory experiments are high enough and close to the theoretical level, but they are not sufficient at a pilot plant stage, we can identify the necessity of research and development on the supporting technologies or

YANAGISAWA: SYSTEM FOR COUNTERMEASURESOF CO2 systems.

875

Similarly if there are significant differences between the present and future level, targets of the research and

development

can be pointed out. Thus promising mitigation measures to the global climate change and the targets of

the research and development can be extracted by following the templet. The quantitative evaluation of the subjective technologies is desirable,

if possible.

Unfortunately

it is not

always a case. If the precise quantitative evaluation is not possible, a quasi quantitative approach will be taken. Alphabetic letters of A, B. F and U are used for the quasi quantitative evaluation indicating excellent, good, failure and uncertain, respectively.

If the ratio of CO, emission is less than 30 Sb of the present representative technology, the

technology is considered excellent one and given A. When the ratio is between 30 and 10096, it is classified as B, good technology.

If the CO, emission increases, the technology fails to meet the global climate change criteria.

There

are many physical, chemical and/or biological processes in our planet, of which contribution to the global climate change is not known.

Reflecting these circumstances, usefulness of some technologies is uncertain.

If the

performances are not certain, U is used to indicate it. Further basic researches are needed to know its usefulness. The energy efficiency is defined by the ratio of energy output to energy input accompanying

CO, emission. The

alphabetic letters of A, B, F and U for the net amount of CO, reduction indicate reductions by over 100 million tons of carbon, between zero and 100 million tons of carbon, net increase of carbon emission and uncertain, respectively. Up to here, technologies are assessed from the three physical and chemical aspects; balances of CO, and energy, and capacity of the CO, reduction. evaluated from different aspects.

After the promising technologies are picked out, they have to be further

Side effects, such as environmental risks and safety,

are the criteria of the further evaluation.

and economical applicability

However, details of the evaluation procedures are not developed yet.

4. CONCLUSION Mitigation measures to reduce the atmospheric CO, concentration were systematically classified by developing the map. Usefulness of each measure could be evaluated by applying the templet. The mitigation measures could be given priorities based upon the technology assessment shown in the templet.

Table 1

Tree of Mitigation Measures for CO,

Removal of CO, from Air Photosynthesis,

Chemical Reactions

Reduction of CO, Emission Natural Sources -Anthropogenic

Deforestration,

Desertification

Sources

CO, Separation -- Ocean Disposal, Oil Field Charge, Energy Transport Medium, EOR Energy Source Replacement from Coal to Natural Gas, Coal Treatment, Nuclear Energy, Geothermal Energy Solar Energy --

Direct Use, Indirect Use

Energy Savings Efficient Energy Use Energy Conversion, Energy Transportation, Transportation,

Production Processes

Domestic Use, Waste Energy

Service Level Change -- Recycling, Waste Recovery

Ratio of CO2 Emission Energy Efficiency Net Reduced Amount

ITheoretical

Nameof Technology or System

Level

Present ILevel IExperimental ISubstantiative

I

Table 2 Templet for Technology Assessment

ISide Effect

I

IFuture Level

l

IEconomy

I

IOverall

IRemarks