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Keeping you informed about TecEco sustainability projects. Issue 85, 8 March 2009

The Role of Soils in Sequestration

Soils are an important part of the carbon cycle with some two to three times the terrestrial biosphere carbon than plants. Soil processes influence carbon sequestration and transport. The dynamics of carbon transformations and transport in soil are complex and can result in sequestration in the soil as organic matter or in groundwater as dissolved carbonates, increased emissions of CO2 to the atmosphere, or export of carbon in various forms into aquatic systems. The key to sequestration in soils is good management of them and well managed forests and farmlands sequester significant amounts of carbon and as they are then also more productive, sequestering carbon in this way is important[1].

"It is life that gives soil its structure. It is life that provides fertility and balanced nutrition. It is life that retains soil moisture, restoring water balance and reversing the effects of dry land salinity. It is life that retains carbon and nitrogen from the atmosphere and balances the greenhouse equation."[2]

According to Dr Christine Jones [3] "In a healthy ecosystem, vibrant, living soils are a dynamic part of the carbon cycle. The carbon compounds added to soil as exudates from active plant roots and the decomposition of plant and animal residues, fuel the biological processes that improve soil structure, which in turn increases oxygen and moisture retention and creates better conditions for more life." The process of creating and improving top soils sequesters more carbon than is lost to the atmosphere and as a consequence soils are the largest carbon sink over which we have control. According to Dr Jones "Groundcover management is the prime determinant of whether agricultural soils act as a source (net loss) or a sink (net gain) for atmospheric carbon. Organic carbon (such as humus) has many benefits in soils, making effective carbon management the key factor for productive farms, revitalised catchments and a greener planet." "Around 50-80% of the carbon has been lost from the topsoil in many farmed soils, often as a direct result of the loss of the soil itself. Even today, most farming businesses continue to lose soil carbon - their most valuable asset. As a result, landholders invest a great deal of time and effort in forcing ‘dead’ soils to be productive using chemicals that further compound the problem. Carbon equilibrium levels in soil are determined by carbon inputs and outputs, which in turn are influenced by temperature, rainfall and management. In general terms, soil carbon accumulation is positively correlated with rainfall and negatively correlated with temperature. That is, more carbon can be stored in soil in cold, moist environments than in hot, dry ones. Landholders cannot alter rainfall or ambient temperature regimes, but they can markedly improve water infiltration rates, soil moisture retention, the buffering of soil temperatures and carbon inputs and outputs, through changes in groundcover management. Carbon cannot be sequestered in soils if we continue with the same forms of land management that caused the carbon losses in the first place. People cannot function without a skin. Soil cannot function without cover." We need to improve groundcover using mulches and other methods like leaving crop stubble in the ground. "Managing groundcover for increased soil carbon levels results in improved soil structure, lower bulk density, greater porosity, higher infiltration rates, more effective use of rainfall, enhanced water quality, higher cation exchange capacity, greater sequestration of nitrogen and sulphur, enhanced availability of phosphorus and trace elements, reduced costs, reduced inputs, improved biodiversity and increased productivity."

 

Soil Sequestration Processes [4]

What Land Management Practices are Best for Increasing Soil Sequestration?

Soil conservation practices not only reduce soil erosion but also increase the organic matter content of soils. Principal conservation strategies, which sequester carbon, include converting marginal lands to compatible land use systems, restoring degraded soils, and adopting best management practices. For example, removing agriculturally marginal land from annual crop production and adopting an ecologically compatible land use, such as livestock grazing and/or wildlife habitat, can lead to increases in total biomass production and an increase in carbon content in the soil.

The following best management practices have been proven to sequester soil carbon:

  1. conservation tillage practices like direct seeding systems;
  2. elimination of summer fallow;
  3. extending crop rotations to include perennial forage crops for hay or pasture.
  4. management of crop residue and application of organic materials and manures;
  5. soil fertility optimization through improved fertilizer placement and site-specific management;
  6. reductions in the use of chemicals.
  7. other techniques that may improve crop yields, and reduce on-site and off-site production risks.

If soils are completely devoid of carbon and life because of the use of chemicals or for some other reason that are a number of new techniques and products emerging including "agrichar"[5] and various new fertilizers made of bio waste with the pathogens removed.

How Much Carbon Sequestration Would Occur as a Result of Improving Soils?

The Permanence of Carbon Sinks [6]

There seems to be no clear understanding of exactly how much carbon has been lost around the world from bad agricultural practices but common figures in the literature are in the range 50-80%.

If 50% is assumed and currently there are some 1600 gigatonnes of carbon in soils[6] then at least a further 1600 gigatonnes could be taken up over say a 20 year period of dramatic improvement in soil management practices amounting to 80 gigatonnes a year which is much much more than the current annual net flux of CO2 into the atmosphere of around 8 gigatonnes. We could achieve safe levels of CO2 of say 300 ppm in this way provided nothing goes wrong. In spite of better agricultural practices that result in soil sequestration having many other advantages Murphy's law predicts that only 1/4 of what could easily be possible will be achieved.

Our conclusion is that raising the level of carbon in soils is very important but given obstacles including widespread ignorance and the large chemical company lobbies should not be totally relied on. The TecEco Gaia Engineering opion of putting carbon away as man made carbonate also has no downsides and is easily implemented through building approval systems. Both alternatives have much in common and mean changing the way we live.

Footnotes and References

[1] DOE, 1999: Carbon Sequestration Research and Development [Reichle, D., J. Houghton, B. Kane, J. Ekmann (eds.), S. Benson, J. Clarke, R. Dahlman, G. Hendrey, H. Herzog, J. Hunter-Cevera, G. Jacobs, R. Judkins, J. Ogden, A. Palmisano, R. Socolow, J. Stringer, T. Surles, A. Wolsky, N. Woodward, and M. York]. Department of Energy, Oak Ridge, TN.

[2] Jones, C. E. (2006). Healthy Soils through Communication. Symposium, Federation of Biological Farmers Inc.,. Seymour, Victoria, Australia.

[3] Jones, C. E. (2007). Australian Soil Carbon Accreditation Scheme (ASCAS). Managing the Carbon Cycle. Katanning Workshop.

[4] DOE, 1999: Carbon Sequestration Research and Development [Reichle, D., J. Houghton, B. Kane, J. Ekmann (eds.)

[5] Agrichar is char produced in low intensity fires and when added to soil mimics the practice of Brazilians in the formation of Terra Preta over the last few thousand years. See Newsletter 67

[6] Ziock, H. J. and D. P. Harrison. "Zero Emission Coal Power, a New Concept." from http://www.netl.doe.gov/publications/proceedings/01/carbon_seq/2b2.pdf.

Reading and Resources

Putting Carbon back into our Soils to Help Reverse Global Warming?

The Wonderful World of Humus and Carbon

Carbon Farmers of America

Fire Resistant Buildings using TecEco Binders

The ongoing fires in Victoria, Australia give warning of a warmer drier world and the need to rethink the way we build houses to reduce the loss of life and property. At the same time as energy prices rise there are calls for materials and products that can reduce the lifetime requirement for the heating and cooling of buildings.

Research makes if very clear that flames from bush fires generally only last a few minutes during the passage of a fire front past a building [1]. Ignition from embers is however a risk factor that can last for hours depending mainly on wind strength. Burning embers may come into direct contact with combustible parts of a building or ignite litter of other debris in close proximity.

Litter is a problem of the Australian bush because leaves and debris do not decay quickly and blow up against or into buildings collecting in just about every place imaginable. We may not be able to make people clean up the litter around their houses but we can build them so they are less combustible in the first place.

The way we currently build is like constructing a slow combustion stove; we generally use bricks on the outside that will encourage and contain a fire if it starts on the inside. Our houses are not well sealed and drafts can come in through small gaps under the floor, or tin or tiles on the edges of our roofs carrying embers that ignite the insides. Much can be done about the design of buildings and the materials we use to make them with. The challenge is to improve lifetime energy performance and do something about other problems at the same time.

Consider the main risk areas

1. Ignition from under the sub - floor space.

This problem can be eliminated using slab on ground construction methods. If a timber floor is an absolute must then other options including filling under around the edges with insulating non combustibles and the management of surrounding vegetation are essential.

If a slab is specified then insulation can be improved underneath by reducing direct contact with the ground. If the insulation is vented properly the amount of cancer causing radon[2] entering a building can also be reduced. The smaller the individual voids the better the insulation and various materials can be used including gravel, kibble stones and other cheap alternatives. Builders should be careful not to create a water tank under a slab unintentionally by providing good drainage..

2. Ignition from burning embers.

When buildings warm up hot air rises and comes out through cracks and other openings. What goes out must come in somewhere and air containing embers can be sucked into a building during a bush fire that will ignite the many combustibles inside.

For bush fire resistance it is important to make sure a building can be well sealed. Air vents should be located nowhere near vegetation and doors and windows should be able to be properly closed.

Attics are very warm places during a fire and the air convection currents can be quite strong, always rising upward and generally sucking in through under the roofing surface be it tiles or tin - on the edges - right near very combustible timber. Fires often get into buildings in this way so consideration should be given to using materials that are non combustible in the detail of the design of roofs.

The challenge for TecEco is to show the world better ways of building that will not only reduce damage from bush fires but also make our houses more comfortable to live in, cheaper to heat and cool and more sustainable. The key to implementation of this dream will be cost and overcoming the dogma.

For insulation and fire reasons we have to stop building our houses like pizza ovens. If we put the insulation on the outside where current wisdom dictates it should be then the challenge becomes one of finding materials that can perform this function that are much less combustible.

Roofs especially require attention. Slopes and guttering are necessary in this country and tin and tiles are not combustible so it gets down to what we build all the supporting structure and sealing areas with and our suggestion is that non combustable composites or lightweight steel should be materials of choice.

In fires hot enough to exceed the Curie point of steel the properties change and strength reduces - think about the failure of the twin towers. That's where TecEco come into the picture as all our binders are suitable for making concretes or composites[3] and are very good fire retardants releasing water, CO2 or both as the temperature rises. We can make roof trusses and the like out of composites or if the inside and outside walling of a building are made with TecEco cements with steel trusses above then fires will never get hot enough to weaken steel. The outside walling should be insulating and the inside should have high thermal capacity and using our binders this is not hard to achieve. Furthermore TecEco cements as a result of strong polar bonding stick very well to just about anything and so a large range of composites can be made utilising wastes.

MgCO3.3H2O => MgO + CO2 + 3H2O

Mg(OH)2 => MgO + H2O

Low Temperature Decomposition Reactions of MgO Binder Components

According to Jane Blackmore[4] "A preliminary look at the BCA [5] reveals obvious problems with the non-combustibility test as a measure of performance, whatever performance is intended. Many materials which are accepted from experience and common practice to be effectively “non-combustible” fail when subjected to the test procedure. It has therefore been found necessary by the regulators to include a list of materials in the BCA that are deemed to be non-combustible, and hence allow them to be used in circumstances where they would be prohibited on the grounds of results from the combustibility test. The list includes pre-finished metal sheeting, plasterboard and some bonded laminates."

The use of plasterboard will probably continue provided the other changes I have suggested are made. Manufacturers should note that there is another product that is challenging plaster board and I will call them SIPS which is short for structural integrated panels. Most of these come from China and many are made with castable Sorel type cements as a binder and incorporate a wondrous mix of waste materials to provide tensile strength, insulation and other properties. The don't burn well but unless they are properly waterproofed with for example a coating of magnesium phosphate type cement then they will eventually break down in the weather. Fortunately most seem to be waterproofed and provide a good surface for finishing.

I have no doubt that composites will be important in the years to come and already many building materials are made from composites such as for example the abovementioned boards. Many of these new composites contain magnesium compounds because they tend to stick well to other materials used as components or fillers. The use of composites help solve another problem which is how to utilise wastes.

For walling we need to go lighter, larger and therefore faster to reduce construction times as well as manufacturing, transport and erection costs. A product that is being developed with our assistance to address this challenge is Ultrapanel from Bendigo in Victoria. So far larger has been addressed thereby reducing erection times - lighter and more insulating versions are on the drawing board. Other new composites on the drawing board with clients include foamed hemp hurd boards that have both specific heat and are good insulators. Spray on walling, foamed concretes etc. are also important. If building components were made using composites in factories to fine tolerances they can be quickly and cheaply erected. Better does not necessarily mean more expensive.

To wrap up this article I must also mention colour. Imagine a black roof in a bush fire. It would get very hot and thus easier to ignite. Light colours do not absorb heat so much and so the colour we make materials matters.

Footnotes and References

[1] Ramsay, C. and L. Rudolph (2003). Landscape and Building Design for Bush fire Areas, CSIRO Publishing.

[2] See the BBC News Article "Radon gas linked to cancer deaths" http://news.bbc.co.uk/2/hi/health/4113765.stm

[3] I define a composite as a complex material in which two or more distinct, complementary substances are combine to produce structural or functional properties not present in any individual component. Concrete is just a special kind of composite.

[4] Blackmore, J. (2008). "Non-combustibility in the Building Code of Australia (BCA): Implications for a New Global Standard."

[5] The acronym "BCA" is short for the Building Code of Australia

 

The TecEco Tec-Kiln

If lime and magnesia were made without releases and much less energy then the production and use of major building materials such as cement would be much more sustainable

The Tec-Kiln is a top secret kiln we have designed for low temperature calcination of alkali metal carbonates and the pyro processing and simultaneous grinding of other minerals such as clays with the above objective in mind.

Hydraulic cements including TecEco's own binders can be made without releases and with much less energy and therefore at lower cost and TecEco are looking for funds to build the first prototype of the kiln.

Roman cements were made from lime and pozzolana (a volcanic ash containing significant quantities of SiO2 and Al2O3) or lime and ground brick and tiles. Learning from them it is possible to split the manufacture of Portland cement into the making of lime and the manufacture of clinker. In this way a lower, more precise amount of non fossil fuel energy can be untilised in a closed system that does not allow releases and much more consistent quality cements produced.

TecEco have demonstrated that reactive magnesia [1] is destined to become a major componenet of hydraulic and hydraulic/carbonating binders of the future and the diagram below depicts the role of the Tec-Kiln for the calcination of magnesite in the thermodynamic cycle of mangesium

Cement made without chemical releases has huge market potential as it represents a solution to the CO2 in the air problem without legacies that is potentially profitable and thus politically acceptable.

In the simplistic representation of the magnesium thermodynamic cycle shown below the TecEco kiln provides de carbonation of MgCO3.

Summary

The TecEco Tec-Kiln is an essential part of TecEco's grand plan to sequester massive amounts of CO2 as man made carbonate in the built environment and has the following features:

Availability

The kiln technology is being developed as funding permits.

If you are interested in our Tec-Kiln technology please contact TecEco.

Footnotes and References

[1] Reactive magnesia is also variously known as caustic calcined magnesia, caustic magnesia or CCM. We prefer to define reactive as magnesia with low lattice energy, however lattice energy is not possible to directly measure. It can only be calculated inidirectly. The temperature of firing has a greater influence on reactivity than grind size as excess energy goes into lattice energy. Technical information about reactive magnesia is available in the technical area of our web site.

[2] Grinding is only 98-99% efficient, nearly all the energy used ends up as heat.