Human knowledge allows us to flourish, in numbers, and with living standards unimaginable to our ancestors. Our main advantage is mastery of energy. We  started on this path with agriculture. We co-opted animals to work for us. Then we discovered fossil fuels and the steam engine. Our productivity – and numbers - increased many fold. This presentation focuses on managing  greenhouse gases by taking lessons from the carbon cycle and using energy wisely. We know plants take carbon dioxide from the atmosphere and combine it with water to produce food. Carbon is cycled continuously through  the environment by life on earth.  Our knowledge of the cycle provides us with  insight to tackle management of greenhouse gases head on. I have just two main points to make.  Managing greenhouse gases will be a monumental task. Major expenditures of mental and physical energy will be needed.

This figure, from the Intergovernmental Panel on Climate Change (IPCC) provides an overview and indicates  it’s  magnitude. It is deemed the “natural” carbon cycle. Carbon is the common accounting currency of the materials involved. Carbon stores are shown on these figures in billions of tonnes. Annual flows are indicated with  arrows.  The atmosphere contains 730 billion tonnes of carbon in the form of carbon dioxide. Living plants contain about 500 billion tonnes of carbon.  Soils store about 1500 billion tonnes.  Fossil fuel stores are around 3000 billion tonnes. Humongous amounts of carbon are dissolved in the ocean and stored in rocks. About 120 billion tonnes of carbon is cycled between the land and the atmosphere annually thanks to plants and photosynthesis. Similar processes take place in the ocean, and carbon dioxide is exchanged with the atmosphere.

This subset of the cycle quantifies carbon input from fossil fuels and land use changes. It is  called the human perturbation by the IPCC. It shows 5.3 billion tonnes added to the atmosphere annually from fossil fuel use. Humans are converting some land to new uses adding another 1.7 billion tonnes to the atmosphere.

Here we see more detail on the fate of the 120 billion tonnes of carbon taken up annually by plants. Half  is almost immediately used for food by the plants themselves, returning carbon to the atmosphere. Nearly another half (55 billion tonnes) is co-opted by animals and other organisms and ultimately returned to the atmosphere.

Ocean plants absorb   almost 100 billion tonnes of carbon from the water. They and other organisms return most through respiration and decay.

Consideration  of the carbon cycle raises some fundamental questions. Does division of the cycle into “human” and “natural” components tend to excessively  focus on   fossil fuel use as the “problem”?  There is reason to think so. A recent paper addressed human  influence on climate through the development of agriculture. The author concluded humans began to influence climate nearly 8000 years ago. Humans cultivate 10 to 15% of land – and we control forests. We appropriate about 40% of plant production. It follows that we are responsible for 24 billion tonnes of the 60 billion tonnes of carbon absorbed by plants annually. Contrast that with the 6 billion tonnes from fossil fuels. Thinking about the carbon cycle suggests opportunities to better integrate our energy use with management of carbon.

Let’s start with energy  from the sun. It is the prime driver of the carbon cycle. We’ve tried to tap it directly for generations. Wind turbines are beautiful expressions of engineering art as are  photoelectric cells for small loads. Greenhouse gas emissions, even from the full manufacturing cycle, are quite small. Unfortunately, the rotation of the earth and the vagaries of weather make both solar and wind energy intermittent and unreliable. Reliance on these renewables for human needs thus requires expensive excess capacity, energy storage systems and alternate generation. Establishing those systems will compel us to use even more energy thanks to the inefficiencies introduced through the multiple energy conversions needed.

Nuclear energy provides beautiful images  too and is also very close to greenhouse gas free. This photo shows two recently completed CANDU 6 reactors in China. We are reminded of human interaction with the  environment. The sky is hazy. The water is brown from  soil washed down from upstream land. We often promote  nuclear energy simply as a greenhouse gas free substitute for other fuels. It can be more than that. Nuclear energy could be used to make more water available for agriculture via pumping or possibly desalination. Energy employed that way could play a role in  absorbing carbon from the atmosphere. The integration of nuclear energy into control of the carbon cycle can turn thus it into  a creator of  carbon sinks through influence on agriculture and forestry. Doug Lightfoot will tell us how to get more from nuclear fission resources.

We are considering separating and sequestering the carbon dioxide component of fossil fuel exhaust gases by pumping it back into the ground. These concepts  will require increased energy use for separation and pumping.

A proposal from the 80’s suggested one  scheme to remove carbon from the atmosphere. The ocean is fertilized with iron to increase plankton growth, which dies and sinks to move carbon dioxide away from the surface.  More could then be absorbed from the atmosphere. Tests are underway. If this scheme works another new energy using industry could evolve.

Our review of the carbon cycle indicated that agriculture and forestry cycle about four times more carbon annually than is added by human use of fossil fuel. Irrigation, fertilizer and plant breeding have  greatly  increased the productivity of plants. Could we modify agricultural  technology to help remove carbon  from the atmosphere?

Some carbon absorbed by plants  is deposited in the soil. Large quantities have been trapped over millennia. No-till farming practices are cited as one means of keeping carbon sequestered in the soil. So far this carbon sink technology is fraught with uncertainty. How much organic  material left on the land is incorporated in soil? How long will it stay there? Will soil reach an equilibrium of carbon content and then absorb no more?

Long lasting carbon is found in soils. Some of this is simply charcoal, presumably from forest and grass fires and has been there for centuries. Unusual charcoal  rich soils have been found in the Amazon basin.  This soil was most likely man made.  Some scientists suggest it was deliberately produced by a variation of slash and burn agriculture.  It remains highly productive centuries after it was formed.

Some organizations are proposing to produce charcoal from agricultural wastes as a soil amendment. One proposal generates energy and adds fertilizer as shown in the slide. Conversion of a fraction  of the wastes from our 24 billion tonnes of agricultural production into long lasting charcoal  could  help counter the 6 billion tonnes of emissions from fossil fuel. We burn fossil fuels to release carbon dioxide. Plants absorb it.  We heat plant material to establish a durable carbon sink which enhances the soil.

In summary, we may need to control greenhouse gases if human development is to be sustained. We’ve touched on just a few examples. Some of them are close to practical reality now. Others are closer to science fiction than to engineered solutions. Much research is needed to establish the science to evaluate and develop hypothetical solutions. Much ingenuity and effort will be needed to establish the infrastructure to apply them. Continued development of science and the application of engineering principles can establish more intelligent human intervention with the carbon cycle.

James Lovelock came up with an interesting hypothesis when he worked with the National Aeronautics and Space Administration.  He suggested the existence of “a complex entity involving the Earth's biosphere, atmosphere, oceans, and soil; the totality constituting a feedback or cybernetic system which seeks an optimal physical and chemical environment for life on this planet." This later became known as the “Gaia” hypotheses after the goddess of earth from Greek mythology.  Perhaps we more often refer to Gaia as Mother Nature. Some say humans are using and abusing Gaia. I wonder if Gaia is using us to maximize her influence and productivity.