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Re-Inventing Terra Preta

Duane Pendergast, June 17, 2007

Using nuclear energy to establish a carbon sink

Several years ago I started thinking about ways to turn nuclear energy into a carbon sink rather than just a carbon emission avoider.

Plants absorb carbon dioxide from the air during growth. Diagrams of the carbon cycle show huge quantities of carbon have been retained in soils over the eons.  The  "National Climate Change Process" I was involved in discussed  the role of agriculture in sequestering carbon. Attention focused on modifying agricultural techniques to sequester more carbon in the soil. The "no till" technique which had evolved on the prairies was one way toward that goal as plant wastes, including roots, were left in the soil. Composting of organic materials for soil enrichment was another technique being investigated.

It seemed to me at the time that  nuclear energy could be used to to help grow plants through enhanced access to water and irrigation. Nuclear electricity could be substituted for water power - thus making water more readily available for irrigation.    Perhaps  nuclear energy could even be used for desalination and the production of fertilizers. I had once circa 1965 - designed a farm tank wagon  sold to local farm implement dealers and used for the storage and application of ammonia fertilizer. At the time I read an imaginative article which proposed using a portable nuclear reactor to produce ammonia for use as a vehicle fuel. That was the same ammonia our customers were spreading on their fields as fertilizer.

Alberta is blessed with an abundance of fresh water in the north. Southern Alberta is short of water but has a much longer and warmer growing season. My first attempt to evaluate the potential of nuclear energy as  growth enhancer thus focused on pumping fresh water from north to south  to expand irrigation. A presentation to the Canadian Institute of Energy on January 23, 2002, provided a public  opportunity to broach the concept. I concluded that half of the water from a major northern river would  grow crops  which could absorb about 160 million tonnes of carbon dioxide annually. I suggested - I thought tongue in cheek - that if the crop was converted to charcoal to make a carbon sink that it might be be more valuable than it would be as food. I also found that pumping the water up some 700 metres in elevation and and 1000 kilometres to the south would take at least 12,000 MWe. A dozen big nuclear reactors, massive pumps and pipes and a great expansion of irrigated land would be needed to  accomplish the task. Possible, but likely not an economically practical way to  achieve Canada's Kyoto goal.

So far so good, but it seemed that the soil carbon sequestration initiatives being talked about in climate circles about 2000-2002 were limited. Initially farming of new land apparently exposes carbon bearing materials in soil to oxidation and carbon content goes down. Proposed sequestration processes depended on composting or  low till yielded  a very small, and diminishing, amount of carbon trapping. Indeed, papers on the topic indicated soil carbon sequestration could only approach something like that which had existed on the land before farming was started. So, to turn  nuclear energy, in concert with agriculture, into a carbon sink something more was needed to ensure that sunk carbon stayed sunk.

The farm I was raised on in the Alberta bush had a great variety of soil quality. The good stuff seemed to be collected in the valleys and was black and presumably carbon rich. Hill tops tended to be gray soil and presumably very low on carbon. My father had told of homesteading the place in the late 30s. When he first saw it much of the high ground was covered with fallen trees killed by a forest fire to such a depth it was impossible to ride a horse through it. A subsequent deliberately set forest fire took care of that but burned the soil badly in places. I began to think that the thought about charcoal expressed above was not so facetious. Indeed, perhaps forest fires played quite a major role in building soils since the last ice age. I started to investigate that possibility. I came across papers exploring soil structure  using carbon 14 dating of guess what charcoal samples in the soil going back hundreds and thousands of year. A letter to the editor of our local newspaper raised the possibility fire played a role in building soil and creating the soil carbon sink.

Finally I became aware of, and attended, a seminal conference in Georgia in 2004. It brought together archaeologists, soil scientists  and experts in bioenergy. There my speculation that charcoal, or bio-char, might play a role in soil enhancement was backed by substantial evidence established over many decades.

Eureka!  There is a way to use nuclear energy to get carbon into the soil and keep it there.  Energy diverted to the supply of water and fertilizer for growing plants could absorb carbon dioxide and convert it to plant material. Some additional energy could be used to convert the plant material to  carbon in the form of charcoal as well as other materials such as hydrogen gas. These materials  in turn could supply some process energy or be used in other ways. Much  attention is focused on using biomass for energy to produce the char as well as to produce hydrogen as a source of fuel. Although some believe there are sufficient land resources to provide most of human energy needs, there is room for doubt. I believe that through integration of nuclear energy into energy supply the potential for these techniques to actually increase the earths productivity  is substantially enhanced.

Reinventing terra preta at the United Nations

Using the soil as a carbon sink while enhancing it's fertility seemed such a logical process, for those familiar with proposed greenhouse gas management techniques, that I thought the concept must have already been discovered or perhaps even patented. I began an Internet search. I didn't find a lot. What about the Intergovernmental Panel on Climate Change? They had conducted an exhaustive review of mitigation techniques in 2001. Surely that would be a good place to look. A diligent search using relevant key words revealed not a single thought that charcoal in soil could serve as  a carbon sink. My quest for information then is the basis for another article on this site. It notes my introduction to papers and articles by Danny Day, Michael Antal, William Sombroek, Johannes Lehman and Christoph Steiner. I concluded that the concept would not be patentable as the process is such a natural outcome of thinking about how atmospheric carbon dioxide might be managed. It seems likely many others have reinvented it. Amazonian natives apparently invented or discovered the soil enrichment aspect thousands of years ago.

I mentioned in my 2004 article that I was looking forward to the 2007 version of the Intergovernmental Panel on Climate Change Assessment Report (IPCC) on "Mitigation of Climate Change". It is finally available in draft. I've searched the agriculture and forestry sections for any mention of the terra preta concept. I've looked for relevant authors, char, pyrolysis and other key words. It seems there is still no discussion.  The report does come quite close to reinvention though. There is discussion of a concept called "Bio-energy CO2 capture and storage (BECCS), where CO2 emissions are captured during biomass energy combustion for storage in geologic formations".  "Negative emissions" are associated with the concept. Others have discussed this, coining a shorter acronym "BECS" for "Bio-Energy with Carbon Storage" These ideas apparently derive from  work that has been done to establish methods of capturing and sequestering carbon dioxide from fossil fuel combustion.

The IPCC mitigation report lists nearly 200 authors and reviewers.  It does seem amazing they have not come across the concept that carbon could be added to soil  as a carbon sink while simultaneously enhancing it. I'm reminded of the "not invented here" syndrome. Researchers and inventors seem disinclined  to explore the ideas of others. Perhaps there are vested interests within the IPCC authorship which blinds them to other means of carbon dioxide control. On the other hand perhaps they are just so busy writing they don't have time to smell the roses - or are so skeptical they don't believe the concept is worth a mention.

Perhaps by the time of the next mitigation report - maybe by 2013 - those many authors and researchers who work on IPCC reports may realize they don't need to convert the carbon in plant material all the way to carbon dioxide for capture and sequestration. They may appreciate that soil resources may be expanded with charcoal or char which could be produced from decomposition of plant material. Some  more reinvention is needed.

Terra preta information centre

Information on the making of terra preta soils as a means of controlling greenhouse gases is  burgeoning over the last couple of years. Major science magazines have published news articles. Erich Knight, Michael Bailis, Ron Larson, and Tom Miles deserve great credit for establishing the Terra Preta Discussion List in early 2007. Their goal is to "strive to be the primary world web location for technical discussions on a new possible important use for biomass." I thank them for providing a reference to one of my papers when the site was first established to provide an estimate of the carbon cycled by growing plants under human husbandry. The Terra Preta Discussion List is attracting an eclectic excited group of "Neo Terra Preta" enthusiasts and researchers. If you have questions, want more information, or want to join the invention, verification  and development process, it is the place to go.

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