Energy, the Carbon Cycle, and Enduring Greenhouse Gas Management 

Duane Pendergast 

 Computare, 30 Fairmont Park Lane S, Lethbridge, AB, T1K 7H7, Phone: (403) 328-1804

Email: duane.pendergast@computare.org, Website: www.computare.org 

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Abstract 

Knowledge of energy has allowed humans to flourish in numbers unimaginable to our ancestors. Some are concerned that emissions from the fossil fuels we use will lead to changing climate with possibly disastrous consequences. 

Many propose that we improve the efficiency of energy use and conserve resources to lessen greenhouse gas emissions and avoid climate catastrophe. It is unlikely such initiatives will have a perceptible effect on atmospheric greenhouse gas content. 

All life on earth depends on energy and the cycling of carbon. Humans have just recently learned how to recover fossil fuels and are recycling them by burning them in power plants, planes, trains, and automobiles, thus modifying the carbon cycle with additional greenhouse gas emissions. 

We need to step back from micro management of greenhouse gas emissions to more fully appreciate human influence on the carbon cycle. Potential future human modifications to the cycle as means to manage atmospheric greenhouse gas are considered. It is suggested humans will need to ingeniously exploit even more energy to integrate its use with control of atmospheric greenhouse gases. 

Keywords: greenhouse gas management, energy, carbon dioxide, carbon cycle, climate change, efficiency

INTRODUCTION

Knowledge, especially in use of energy, has enabled our species to flourish in numbers and with living standards unimaginable to our ancestors. Humans now influence much of life on earth. Many are concerned that greenhouse gas emissions from the fossil fuels we burn for energy will lead to changing climate with disastrous consequences. Others are not so sure.

Should we finally determine there is an imperative to manage atmospheric greenhouse gases, there are many technical solutions which may be considered. As we seek to develop them it is imperative our strategy remain focused on the primary goal to maintain these gases at an appropriate level.

Some organizations, for example the David Suzuki Foundation (Boyd, 2004) and the Pembina Institute for Appropriate Development (Hornung, 1998), have provided governments and citizens with extensive plans and advice on the resolution of the climate change issue. Inevitably, their advice tends to focus narrowly on an imperative to improve the efficiency of energy use and conserve resources. We are led to believe this would lessen greenhouse gas emissions and avoid climate catastrophe. Of course, there is still considerable scope for improving energy efficiency. We will continue with such improvements as are achievable within the environmental and economic constraints of sustainable development

The most optimistic outcome for a greenhouse gas management strategy based on efficiency improvement and conservation is modest postponement of the climatic doomsday, should it really be on the way.

We began our heavy dependence on fossil fuels some two hundred years ago. We have been continuously improving the efficiency of the machines which deliver useable energy - to the point some are near perfection. Improved efficiency, in turn, encourages new applications. Our population grows, thanks to improved food supplies resulting from efficient access to energy. Our neighbors in developing countries recognize the benefits of energy use. They strive to emulate our technology. Our collective greenhouse gas emissions increase enormously even as efficiency increases. Improving energy efficiency is a commendable way to spread energy benefits to more people now and in the future. Using fossil fuels more efficiently has not reduced overall greenhouse gas emissions. This is not a newly observed phenomenon. Economist William Stanley Jevon documented this kind of response to Watt’s improvement of the steam engine in 1865. This phenomenon of a free economic system has become known as Jevons paradox (Wikpedia). Clearly, we need to develop a different paradigm if we are to control the greenhouse gas content of the atmosphere.

How can we break out of this efficiency improvement trap? Perhaps we need to step back and re-consider the role of humans and their knowledge of energy use. Life on earth depends on energy and the cycling of carbon. Perhaps close examination of the carbon cycle will reveal means to assist natural forms of carbon storage outside of the atmosphere.

This paper focuses on reviewing the carbon cycle from the point of view of past and present human influence. Some examples of potential future human input to the cycle through science and technology to manage atmospheric greenhouse gas are considered.

The review suggests that humans will need to ingeniously exploit even more energy and integrate its use with control of atmospheric greenhouse gases. In any case, continuing development and application of energy is essential if the development of human society is to be sustained through the coming centuries. Bold engineering initiatives to produce useable energy will continue to be needed.

THE CARBON CYCLE

We learned early in our education that plants take carbon dioxide from the atmosphere, lakes and oceans to manufacture their food using water and energy from light. Plants and animals use that carbon carrying food as an energy source. Carbon bearing material from plants and animals is incorporated into the soil, oceans, fossil fuel and other carbon reservoirs or “sinks”. Humans have learned how to recover fossil fuels. We are recycling them by burning them in power plants, planes, trains, and automobiles to release carbon dioxide and water vapor to the atmosphere. Their carbon content is thus returned to the cycle of life. The whole complex process is driven by flows of energy. The scientific report of the Intergovernmental Panel on Climate Change provides much useful explanation and quantitative information on the carbon cycle. The remainder of this section reviews and summarizes the carbon cycle based on text and figures from the report (IPCC 2001).

The greenhouse gas “problem” is often boldly stated as “driven by fossil fuels and land clearing”. This human activity is said to add some 8 billion tonnes of carbon to the atmosphere annually. About 4.6 billion tonnes of this is estimated to be absorbed by earth’s plants and oceans leaving a net accumulation in the atmosphere of about 3.3 billion tonnes per year.

The atmosphere contains some 760 billion tonnes of carbon in the form of carbon dioxide. Living land plants store about 500 billion tonnes of carbon in the materials they manufacture from water and carbon dioxide as they grow. The total store of fossil fuels is estimated at 3,000 billion tonnes of coal and 300 billion tonnes of oil and gas deposits. Earth’s complement of soil stores about 2,000 billion tonnes of carbon in materials produced by once living things. Another 40,000 billion tonnes is dissolved in earth’s oceans. Some 100 million billion tonnes is incorporated in sedimentary rocks such as limestone. These massive deposits of carbon bearing materials are all considered to be products of earth’s life over eons.

Some interesting information can be inferred from the numbers in the foregoing paragraph. Our oil and gas deposits will last less than fifty years at current usage rates. Coal could provide us with fuel for another 500 years. The carbon content of the atmosphere would be doubled from its current amount in 230 years at the current addition rate, and tripled by the time estimated fossil fuel reserves are depleted. Of course these estimates are simplistic in the extreme. We need to look at details of the carbon cycle.

Some 120 and 90 billion tonnes of carbon are estimated to be circulated annually between the atmosphere and the land and oceans, respectively. Plants absorb about 120 million tonnes of carbon from the atmosphere, as carbon dioxide, per year. About the same amount is returned to the atmosphere by the process of respiration of plants and animals and decay of dead organic material. The oceans absorb and release about 90 billion tonnes with a great deal of this due to circulation from cold to warm ocean regions. Earth’s plants use carbon dioxide at a rate equivalent to cycling the entire carbon content of the atmosphere in only about six years. Note that this part of the cycle is deemed, in the IPCC science report to be “natural” even though humans manage and influence much of the plant and animal life on earth. Perhaps this terminology is misleading. It tends to, perhaps unduly, focus attention to the burning of fossil fuels and land clearing as the “human perturbation” of the carbon cycle.

Life in the ocean seems to go on almost in carbon cycle isolation from that on land – at least in the short term of a few centuries. Ocean organisms absorb about 103 billion tonnes of carbon annually (GPP – Gross Primary Production) to produce food. They use 58 billion tonnes themselves (autotrophic respiration) as food and incorporate 45 billion tonnes in their structure (NPP – Net Primary Production). Animals consume a major fraction of this and return carbon to the water (heterotrophic respiration – 34 billion tonnes). Detritus from plants and animals moves some carbon bearing material to deeper water. Some is diverted through shells and dissolved material into the deep ocean. The net absorption of some 2 billion tonnes annually from the atmosphere is thought to be a simple result of maintaining equilibrium with the rising carbon dioxide content of the atmosphere.

Finally, and perhaps of most importance to us, we come to the carbon cycle on land. Details on the fate of the 120 billion tonnes of carbon absorbed annually from the atmosphere by plants (GPP – Gross Primary Production) are of interest. Half of this (autotrophic respiration - 60 billion tonnes carbon) is almost immediately used by the plants themselves as food, returning carbon dioxide to the atmosphere. That leaves 60 billion tonnes (NPP – Net Primary Production) to be incorporated in their leaves, stems, roots, fruits and seeds. Some 55 billion tonnes carbon content is co-opted by animals – of many sorts - and ultimately returned to the atmosphere as carbon dioxide (heterotrophic respiration). Some 4 billion tonnes is consumed by combustion. That leaves about 1 billion tonnes to be incorporated into soil or dissolved in water and washed down rivers to the ocean.

Humans directly control and manage a major part of earth’s vegetation and animal life through agriculture. We also influence the carbon cycle through our use of forests. This review of the carbon cycle thus raises some questions. Are IPCC figures and data subtly downplaying the role of human influence on the carbon cycle? Is human use of fossil fuels overemphasized as the source of the problem? Are humans involved in other major activities which influence the carbon cycle and composition of the atmosphere? Is it possible that some aspects of the carbon cycle, other than fossil fuel use, could be modified to play an important role in greenhouse gas management?

HUMANS AND THE CARBON CYCLE

During the past 100 years the potential for human influence on climate has, indeed, focused on the growth of industry driven by use of fossil fuels. Human development of agriculture tends to be overlooked as a possible initiator of carbon cycle and climate change. Some investigators are beginning to consider the role of early agriculture. William Ruddiman, Professor Emeritus of Environmental Sciences, University of Virginia is one. He considered the possibility that the development of agriculture some ten thousand years ago years ago may have subsequently influenced greenhouse gases and modified climate much earlier than that attributed to the industrial age. His review (Ruddiman, 2003), suggests agriculture may have begun to alter the composition of the atmosphere as early as eight thousand years ago.

The influence of agriculture has expanded many-fold since those early days. What role does, or could, it play in the management of greenhouse gases? Vitousek (Vitousek, 1986) suggests that humans appropriate about 40% of land plant production. It was noted above that plants absorb 60 billion tonnes of carbon annually from the atmosphere. Thus, humans control about 24 billion tonnes annually of the carbon removed from the atmosphere by plants. That’s much more than the 6.3 billion tonnes we added from fossil fuels in 1998 (IPCC, 2001). Is it possible we have greater opportunities to control atmospheric greenhouse gas levels than to simplistically reduce fossil fuel consumption? Could we take lessons from the carbon cycle and strategically use more energy to help us manage levels of greenhouse gases in the atmosphere?

MANAGING THE CARBON CYCLE – THE PRIMARY GOAL

Introduction

The carbon cycle itself provides much insight into methods of managing carbon and the production and use of energy. It seems that with our already broad involvement in Earth’s carbon cycle through agriculture, forestry and energy science we may be able to develop the means to manage carbon bearing atmospheric greenhouse gases. If we are to be successful, we must re-focus our attention to the problem. We will need to concentrate our intellectual energy on maintaining an appropriate level of greenhouse gases on the atmosphere. We will need to integrate our energy use with other activities which influence the carbon cycle. We may need to expand the use of energy to ensure the primary goal of managing greenhouse gases.

Some examples of proposed technologies which directly address the primary goal of atmospheric greenhouse gas reduction are discussed in this section. It seems many of them will require humans to use even more energy.

Greenhouse Gas Free Energy

Let’s start with sources of energy which are deemed greenhouse gas free. Solar energy and resultant wind energy are supplied to us on a regular basis from fusion energy in the sun, and generate few greenhouse gases once energy extraction systems are constructed. Wind turbines are a beautiful expression of engineering art. Unfortunately, although the fusion energy source from the sun is steady and reliable, the rotation of the earth and the vagaries of weather make both solar and wind energy intermittent and unreliable. An interesting study of a system to provide electrical energy to the United States from wind and solar generation is available from the University of Victoria’s Institute for Integrated Energy Systems (Love, 2003).

Nuclear energy provides another source of near greenhouse gas free energy (Andseta, 1998) (Dones, 1998). A presentation (Van Adel, 2004) by Atomic Energy of Canada provides an impressive photograph of two CANDU 6 reactors in China. The beautiful earth tone of this photograph, particularly the sky and water, reminds us of human influence on the environment. No doubt intensive agriculture in China has contributed to the erosion of land by water. Hopefully the reactors will help reduce the haze in the air.

Nuclear power is often somewhat simplistically touted as an alternative energy source to avoid greenhouse gas emissions from the fossil fuel we now depend on. It is more than that. It is a bounteous energy source which can be developed to sustain human society far beyond that seemingly possible with dwindling fossil fuels. Another paper (Lightfoot, 2006) in this session demonstrates the enormous energy potential of nuclear fission. Nuclear energy can be used for an expanded range of applications, by developing applications for the direct use of heat and/or the production of alternate fuels such as hydrogen.

These sources of energy all have shortcomings relative to the convenience of portable liquid fuels. Solar and wind energy also require complementary storage to compensate for their intermittency. They are all limited to stationary applications except for very large or very low power installations such as ships or portable electronics, respectively. The long dreamed of development of hydrogen technology to store and transport energy is expected to extend their range of application and make these greenhouse gas free sources of energy more relevant to transportation.

Interestingly, the extra processes involved in the production and use of hydrogen will tend to reduce overall energy efficiency and tend to increase overall energy use as we seek to switch to less greenhouse gas intensive sources and new sources of energy to fuel our transportation systems.

Capture and Sequestration of Carbon Dioxide from Power Plants

Current fossil fuel power plants burn their fuel with air, producing an exhaust stream of carbon dioxide, water and nitrogen which is released to the atmosphere. Perhaps taking a clue from nature’s initiatives to sequester excess carbon, we are considering pumping the carbon dioxide back into the ground. Some schemes use recovered carbon dioxide to flush out additional oil and natural gas. Others simply store it in emptied oil and gas reservoirs or in underground saline water. Another variation contemplates burning fuel in pure oxygen to avoid the separation from nitrogen.

Substantial new science and technology initiatives are needed to develop and prove these concepts. It is underway. These applications will require increased energy use for separation and pumping. Some will recover additional fossil fuel resources.

Zero Emission Coal

Another group of energy pioneers is also taking a cue from nature’s lessons on carbon sequestration. They propose to feed a mixture of coal, lime and water into a chemical reactor to produce hydrogen and carbon dioxide. In an additional step, the carbon dioxide could be combined with minerals to capture the carbon dioxide and sequester it in the form of rock. Development work is underway supported by governments and industry. More information can be found at the website of ZECA Corporation (ZECA).

Iron Fertilization of the Ocean to Enhance Atmospheric Carbon Dioxide Absorption

A proposal from the 1980’s suggested a scheme to remove carbon from the ocean surface and deposit it deep in the ocean. More carbon dioxide could then be dissolved at the surface. Essentially, the ocean is fertilized with iron to increase plankton growth which would then sink. Results of a test did produce sinking plankton. A press release (Moss Landing, 2004) suggests “billions of tonnes of carbon dioxide could be removed from the atmosphere each year”.

Much more development work needs to be done to demonstrate the practicality of this initiative. If it works, and we decide to control atmospheric greenhouse gases, another new energy using industry could evolve to mine and spread iron over the ocean simply to remove carbon dioxide from the atmosphere.

Agriculture and Forestry

Our brief review of the carbon cycle, above, indicated human agricultural activity cycles about four times as much carbon annually as is released from fossil fuel combustion. Science and technology have increased the productivity of plants under our control tremendously. Irrigation, fertilizer, and plant selection and breeding increase the annual turnover of carbon. The first two of these are subtly integrated with energy production. Energy to supply irrigation water is taken from potential renewable electricity production provided by the hydrogeological cycle. Fertilizer production requires energy – and some is made from fossil fuels. At the same time stocks of carbon in standing forests have decreased as land is converted to food production.

Growing plants absorb carbon dioxide and incorporate it in their structure. Some is moved into the soil by roots. Decay of plant material releases carbon dioxide to the atmosphere. Some more durable carbon compounds tend to remain in the soil. Large quantities have been trapped in the soil over long times. Current agricultural practice tends to release some of it to the atmosphere by enhancing oxidation and decay of plant derived materials.

Scientists and agricultural engineers are involved in trying to better understand the part of the carbon cycle related to plants interaction with our soil. No-till farming is cited as one means of capturing carbon from the atmosphere and returning it to the soil carbon sink. Research is underway to better manage animal wastes from intensive farming. Some promote the preservation and extension of forests as carbon sinks.

So far the role of agriculture and forest based carbon sink management is fraught with ambiguity. The scientific basis is uncertain. How much of the organic material left on the land is incorporated in soil? How long will it stay there? How much can be incorporated in soils? The basic approach to management for potential carbon sinks is undecided. Should we account for carbon taken from forests and built into our houses? Could carbon in lumber used to build houses be kept from the atmosphere? How should we manage carbon bearing wastes now going to landfills and sewers? Is it wise to dispose of carbon bearing organic materials deemed waste in landfills or sewers? Are there better uses for these materials which would allow humans to help control carbon dioxide in the atmosphere?

We may ultimately harness growing plants to more effectively remove carbon dioxide from the atmosphere and incorporate its carbon into long lasting sinks. An emerging concept focuses on anthropogenic production and use of charcoal as a soil amendment and carrier of fertilizer. Some charcoal, presumably from forest and grass fires centuries ago, is found in soil demonstrating its durability. Deposits of carbon rich black soils have been found in the Amazon (Lehmann, 2003). Archeologists are discovering evidence it was possibly man made some two or three thousand years ago. Some scientists suggest it was deliberately produced by a variation of slash and burn agriculture. These soils allegedly remain highly productive long after their formation.

Interest is building in this concept. One organization (Eprida) is proposing a process (Day, 2003) which produces charcoal based fertilizer and hydrogen fuel from agricultural and other wastes. The raw materials include a wide range of materials including waste wood, straw, manure, and sewage sludge. This appears to be another opportunity to integrate energy production with greenhouse gas management. Some sacrifice of hydrogen fuel output will be required to produce charcoal. The Eprida website outlines the process and provides a great deal of illustrated background information. Ongoing research and development of this concept has potential to resolve much of the uncertainty associated with agriculture based carbon sinks.

An earlier section indicated humans are responsible for agriculture and forestry activity which absorbs 24 billion tonnes of carbon from the atmosphere annually. Permanently sequestering a portion in soil could dwarf the relatively modest emission reductions mandated by the Kyoto Protocol while re-building our soil resource. The magnitude of the carbon sink which might be realized could conceivably even exceed the current annual release of some 6 billion tonnes carbon from fossil fuel. It is reasonable to speculate the associated processing would consume considerable energy.

ENERGY, THE CARBON CYCLE AND SUSTAINED DEVELOPMENT

There are many other technical approaches to keep and/or remove greenhouse gases from the atmosphere. There is also the possibility of modifying heat input to the earth from the sun through other technical means (Salter, 2005). The examples cited illustrate that many of them may increase energy use. It seems the key to managing climate and sustaining development in the face of expanding human population will be to think very hard about ways to expand the production and use of energy.

Indeed, energy could be deployed to help manage the carbon cycle as suggested by the examples in the preceding section. Water and soil may also become limiting constraints to sustainable development. Incentives may develop to reduce the use of water for hydroelectricity and use the energy otherwise generated to expand irrigation and the carbon dioxide absorption capability of living plants. Other energy sources can be developed to replace the loss of electricity. In some areas fresh water could be pumped from regions of little use to enhance agriculture. The use of energy for desalination has long been considered and is done in some very dry regions which are rich in energy. Perhaps this may become another opportunity to expand agricultural production should means of producing copious commercial scale energy be established.

Future integration of energy supply with greenhouse gas management could come from development of technology associated with building and enhancing earth’s soils as suggested in the examples above. Conversion of a fraction of waste organic materials into charcoal soil enhancements seems a promising technology to explore as a means of coping with greenhouse gas emissions. Should this prove workable we might even come to view greenhouse gas emissions as an asset. We might wish we could generate more.

SUMMARY AND CONCLUSIONS

More efficient use of energy is often touted as the way to managing greenhouse gases. Experience, over the past couple of centuries tells us increasing efficiency of energy use simply expands applications and human population to increase overall energy use. Since we depend mostly on fossil fuels for energy now, there is a strong correlation between energy use and greenhouse gas emissions. Many have come to see those emissions as a constraint to sustainable development as they may result in damaging climate change. That possibility is still under scientific investigation. Continuing study may eventually convincingly demonstrate it really is a problem.
There is by no means a hard and fast correlation between energy use and greenhouse gas emissions. There are means of producing energy, even from fossil fuels, while controlling emissions. Technology and engineered projects can be envisaged which will actually manage the make up of the atmosphere. Such technology will depend on careful human use of possibly even more energy.

There are many potential constraints to sustainable development. Foremost of these is the developing shortage of fresh water. Humans also depend on earth’s limited stores of soil. There may come a time when humans have to restore and build soil as a part of sustainable development. Recent observations on the historic development of soil, driven by considerations of the potential need to sequester carbon dioxide, point the way toward a possible solution based on integrating our energy use with nature’s management of carbon, water and life on earth as represented by the carbon and hydrogeological cycles.

Obviously the challenges presented by the potential need to control atmospheric greenhouse gases are enormous. So are the opportunities. Future generations will need to exercise their imagination to sustain development.

BIOGRAPHY 

Duane Pendergast

Education - Mechanical Engineer, B.Sc. (U of A), M.Sc. and Ph.D. (New Mexico State University)

Experience - Manufacturing and design engineer, pressure vessels and transportation, 3 years.  

Assistant Professor, 4 years.  

AECL - CANDU power plant safety analysis, design and environmental assessment, 26 years.  

Computare, Principal Scientist - consulting and website (www.computare.org) on energy and greenhouse gas management, 5 years.  

Retired member of Professional Engineers of Ontario.  

Life member of The Association of Professional Engineers, Geologists and Geophysicists of Alberta.  

Member of the Canadian Nuclear Society.

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