Monday, December 14, 2015

COP21 and "4 per thousand" - Storing Carbon in the Soil.

It would have been a remarkable oversight, had not our use of the land and its soils featured among the discussions about climate change mitigation in Paris at COP21. However, at the conference was hosted a side-event and official launch of the "4 per thousand" initiative, which aims to increase soil carbon over a 25 year period, with the effect of halting the annual increase in CO2 in the atmosphere. It is important to be aware of what "4/1000" means: it is not an increase in the overall soil carbon by an annual 4 grams per 1000 grams of soil as has been claimed, but an increase in the existing carbon in the topsoil by 0.4%/year. This has been described from an Australian perspective:

"Let us start with the analogy of a football field (Soccer, not rugby!). Imagine it is a fifth larger than normal – making it one hectare in size. The top layer of soil on the field, 30 cm deep, is known as the topsoil.

"Carbon is the main ingredient of organic matter, so organic matter is often referred to as ‘soil organic carbon’. In Australian soils, this organic matter makes up on average, between 1 and 3 percent of the topsoil. For the purpose of the exercise, we will assume that the topsoil on the football field contains 1.5 percent carbon. This equates to 58 tonnes of carbon in the topsoil across the whole football field.What the French Government is calling for is to increase that 58 tonnes by 0.4 percent per annum – in our imaginary football field that would equate to an increase of 0.2 tonnes (or 200 kg) of carbon in the topsoil each year."

Thus, the annual carbon increase is 0.4% of 1.5%, or 0.006%, giving a total soil carbon content of 1.506% after year 1, and 1.65% after 25 years, with around 6 tonnes of carbon having been captured per hectare. Done on the global scale, the impact could be enormous. The “4/1000 Initiative: Soils for Food Security and Climate” aims to integrate agriculture as part of the climate change solution, rather than being the major problem it is often deemed to be, which along with forestry and other land-use, contributes 24% of global greenhouse gas emissions. The total amount of carbon stored in soils is reckoned at 2,400 billion tonnes, making it the largest terrestrial carbon pool. The total carbon emissions by humans amounts to an annual 8.9 billion tonnes, and so the ratio 8.9/2,400 = 0.4%, which is where the "4/1000" figure comes from.

However, it is the annual rate of carbon sequestration per hectare which is the critical determinant of how successful the strategy is likely to be. As has been noted:

"The land area of the world has 149 million km2, and it would be estimated that on average there are 161 tonnes of C per hectare. So 0.4% of this equates to an average sequestration rate to offset emissions at 0.6 tonnes of C per hectare per year. We know that soil varies widely in terms of C storage, for example peat soils in the tropics hold about 4000 tonnes of C per hectare, while sandy soils in arid regions may only hold 80 tonnes of C. The type of above ground vegetation and how quickly the soil biota uses the carbon also can affect this rate. Taking this into account, we would need to add about 4 times the amount of organic matter to meet this sequestration rate."

Previous studies have concluded that a global mean storage rate of 0.5 tonnes of carbon/hectare/year is possible, and research from the Rodale Institute concluded that if their regenerative practices were carried out across the world's agricultural lands, it would be possible to capture all human carbon emissions. Thus, while achieving a global "4/1000" poses an appreciable challenge, even approaching this target would be of considerable benefit, not only in terms of helping to balance the global carbon books, but in improving and restoring the quality of the world' soils. The world's cultivated soils are estimated have lost between 50 and 70% of their original carbon content, a trend that can be reversed by using defined agricultural methods. The result is more productive, carbon-rich soils, and so the strategy is able to “reconcile food security and climate change.”


The essential methods for 4/1000:
  • Avoid leaving the soil bare in order to limit carbon losses
  • Restore degraded crops, grasslands and forests
  • Plant trees and legumes which fix atmospheric nitrogen in the soil
  • Feed the soil with manure and composts
  • Conserve and collect water at the feet of plants to favour plant growth
If good practices and introduced and sustained, it is expected that the carbon capture will continue for 20 to 30 years.

Applied to the surface horizon of the world's soils, which contain 860 billion tonnes of carbon, the 4‰ target would result in 3.4 billion tonnes carbon being stored annually, which amounts to around 40% of anthropogenic CO2 emissions. The majority of soils, not only agricultural soils, could be so addressed, including forests. The above practices could be undertaken by almost half the world's population, those living in rural areas, working 570 million mostly small farms.

The likely costs?

For crops, $20 to $40 (US) per tonne of CO2. For grasslands and forests, $50 or $80 (US) per tonne of CO2.

Tuesday, December 08, 2015

Phytoremediation - Using Plants to Cleanse the Earth.

Phytoremediation1,2 may be defined as the treatment of environmental problems by using plants in situ to avoid the need to excavate the contaminated material for disposal elsewhere. It can be applied to the amelioration of contaminated soils, water, or air, using plants that can contain, degrade, or eliminate metals, pesticides, solvents, explosives, crude oil and its derivatives (refined fuels), and related contaminating materials. Phytoremediation has been used successfully for the restoration of abandoned metal-mine workings, and cleaning up sites where polychlorinated biphenyls have been dumped during manufacture, and for the mitigation of on-going coal mine discharges. Phytoremediation uses the natural ability of particular plants (“hyperaccumulators”, described below) to bioaccumulate, degrade, or otherwise reduce the environmental impact of contaminants in soils, water, or air. Those contaminants that have been successfully mitigated in phytoremediation projects worldwide are metals, pesticides, solvents, explosives, and crude oil and its derivatives, and the technology has become increasingly popular and has been employed at sites with soils contaminated with lead, uranium, and arsenic. A major disadvantage of phytoremediation is that it takes a relatively long time to achieve, because the process rests upon the ability of a plant to thrive in an environment that is not normally ideal for plants.

Advantages and limitations of phytoremediation.
  • Advantages:
    • The cost of phytoremediation are lower than those of traditional processes, both in situ and ex situ.
    • The plants can be easily monitored.
    • There is the possibility of the recovery and re-use of valuable metals (by companies specializing in “phyto-mining”).
    • It is potentially the least harmful method because it uses naturally occurring organisms and preserves the environment in a more natural state.
    • Trees may be used in phytoremediation, since they grow on land of marginal quality, have long life-spans and a high flood tolerance. Willows and poplars are most commonly used, and can grow 6-8 feet (ca 2 metres) per year. For deep contamination, hybrid poplars with roots extending 30 feet deep have been used, which penetrate microscopically sized pores in the soil matrix and each tree can cycle 100 L of water per day, functioning almost as a solar powered and self-contained pump and treatment system.
    • Phytoscreening is possible, in which plants may be used as biosensors for particular types of contaminants, thus giving a signal of underlying contaminant plumes, e.g. trichloroethene has been detected in the trunks of trees.
    • Genetic engineering may confer improvements to phytoremediation, e.g. genes encoding a nitroreductase from a bacterium, when inserted into tobacco, increased the resistance of the plant to the toxic effects of TNT and the uptake of the material. Plants may be genetically modified to grow in soils even when the pollution levels in the soil are lethal for non-treated plants, and to absorb a greater concentration of the contaminant.
  • Limitations:
    • Phytoremediation is limited to the surface area and depth occupied by the plant roots.
    • Slow growth and low biomass require a long-term commitment.
    • Using plants, it is not possible to prevent entirely the leaching of contaminants into the groundwater (without the complete removal of the contaminated ground, which in itself does not resolve the problem of contamination).
    • The survival of the plants is affected by the toxicity of the contaminated land and the general condition of the soil.
    • Bio-accumulation of contaminants, especially metals, into plants which then pass into the food chain, from primary level consumers upwards, or that the safe disposal of the affected plant material is required, i.e. if the plants might be eaten by animals.
    • The procedure is slow.
Hyperaccumulators and biotic interactions. 
If a plant is able to concentrate a particular contaminant, to a given minimum concentration (> 1000 mg/kg of dry weight for nickel, copper, cobalt, chromium or lead; or > 10,000 mg/kg for zinc or manganese), it is categorized as a hyperaccumulator. This capacity for accumulation is a result of genetic adaptation over many generations in hostile environments. Metal hyperaccumulation can affect various different factors, such as protection, interferences between different species of plants, mutualism (e.g. mycorrhizae, pollen and seed dispersal), commensalism, and biofilm.

Different possible phytoremediation methods.
Various processes that are mediated by plants or algae might be used to address environmental problems:
  • Phytoextraction — uptake and concentration of substances from the environment into the plant biomass.
  • Phytostabilization — reducing the mobility of substances in the environment, for example, by limiting the leaching of substances from the soil.
  • Phytotransformation — chemical modification of environmental substances as a direct result of plant metabolism, often resulting in their inactivation, degradation (phytodegradation), or immobilization (phytostabilization).
  • Phytostimulation — enhancement of soil microbial activity for the degradation of contaminants, typically by organisms that associate with roots. This process is also known as rhizosphere degradation. Phytostimulation can also involve aquatic plants supporting active populations of microbial degraders, as in the stimulation of atrazine degradation by hornwort.
  • Phytovolatilization — removal of substances from soil or water with release into the air, sometimes as a result of phytotransformation to more volatile and/or less polluting substances.
  • Rhizofiltration — filtering water through a mass of roots to remove toxic substances or excess nutrients. The pollutants remain absorbed in or adsorbed to the roots. 
Phytoextraction.
In phytoextraction (or phytoaccumulation) plants or algae are used to extract contaminants from soils, sediments or water into harvestable plant biomass (those organisms that take larger-than-normal amounts of contaminants from the soil are called hyperaccumulators). Phytoextraction has been used more often for extracting heavy metals than for organic contaminants. The plants absorb contaminants through the root system which they then contain in the root biomass and/or move them into the stems and/or leaves. A living plant may continue to absorb contaminants until it is harvested. After harvest, a lower level of the contaminant will remain in the soil, so the growth/harvest cycle must usually be repeated through several crops to achieve a significant cleanup. The process can be repeated to affect further decontamination. There are two forms of phytoextraction:
  • Natural hyper-accumulation, where plants take up the contaminants in soil unassisted.
  • Induced (assisted) hyper-accumulation, in which a conditioning fluid containing a chelator or another agent is added to soil to increase metal solubility or mobilization so that the plants can absorb them more easily. In many cases natural hyperaccumulators are metallophyte plants that can tolerate and incorporate high levels of toxic metals.

Examples of phytoextraction:
  • Arsenic, using the Sunflower (Helianthus annuus), or the Chinese Brake fern (Pteris vittata), a hyperaccumulator. Chinese Brake fern stores arsenic in its leaves.
  • Cadmium, using willow (Salix viminalis): willow has a significant potential as a phytoextractor of cadmium (Cd), zinc (Zn), and copper (Cu), as willow has some specific characteristics like high transport capacity of heavy metals from root to shoot and huge amount of biomass production; can be used also for production of bioenergy in the biomass energy power plant.
  • Cadmium and zinc, using Alpine pennycress (Thlaspi caerulescens), a hyperaccumulator of these metals at levels that would be toxic to many plants, although its growth appears to be inhibited by copper.
Phytostabilization.
In phytostabilization the intention is to stabilize, or contain the pollutant over the long-term. There may be a number of contributing factors to this, e.g. the reduction of wind (soil) erosion by the body of the plant, but the roots of the plant can resist water (soil) erosion, immobilize the pollutants by adsorption or accumulation, and provide a zone around the roots where the pollutant can be deposited in an immobilized form. In contrast with phytoextraction, phytostabilization aims mainly to sequester pollutants in soil around the roots but not in the plant tissues. Hence the pollutants are increasingly less bioavailable, such that exposure to livestock, wildlife, and humans is reduced. Mine tailings may be stabilized by growing a vegetative cap.


Phytotransformation. 
 Some plants, e.g. cannas, are able to detoxify organic pollutants - pesticides, explosives, solvents, industrial chemicals, and other xenobiotic substances  - by metabolising them. The metabolic functions of microorganisms living in association with plant roots may also metabolize these substances, as present in soil or water. Due to the complex and recalcitrant nature of many of these compounds, they cannot be broken down entirely (mineralised) to basic molecules (H2O, CO2, etc.) by plants and hence the term phytotransformation represents molecular alterations rather than the complete decomposition of the compound. Phytotransformation may be viewed1 as a "Green Liver" because plants behave analogously to the human liver in processing these xenobiotic compounds, introducing polar groups such as –OH to them. This is known as Phase I metabolism, similar to the way that the human liver increases the polarity of drugs and foreign compounds. In plants, it is enzymes such as nitroreductases which carry out these transformations, whereas in the human liver it is enzymes such as the Cytochrome P450s that perform the task. Phase II metabolism in the second step in phytotransformation, in which the polarity of the xenobiotic molecule is increased by combination with plant biomolecules such as glucose and amino-acids. This is called “conjugation”, and is once more similar to processes such as glucoronidation (addition of glucose) and glutathione addition reactions, catalysed by appropriate enzymes. The effect of the two metabolic steps may serve to detoxify the xenobiotic and aid its mobilization via aqueous channels. In Phase III metabolism, the xenobiotic becomes sequestered, by incorporation in a complex “lignin-type” structure, where it is kept apart from the normal functioning of the plant. The phytotransformation of trinitrotoluene (TNT) has been well studied, and a detailed mechanism proposed for it.

Phytostimulation and rhizoremediation. 
This term identifies the process where compounds released from plant roots enhance microbial activity in the rhizosphere, which is the narrow region of soil around the roots of plants, and associated soil microorganisms. Soil which is not part of the rhizosphere is known as bulk soil. In rhizoremediation, microorganisms degrade soil contaminants in the rhizosphere. It is usual that those soil pollutants which are remediated by this method are highly hydrophobic xenobiotics, and are hence unable to enter the plant. Rather than the plant being a main protagonist in this process, it creates a haven in which microorganisms in the rhizosphere are able to perform the degradation.The plant acts as a solar-powered pump, which draws in both water and the xenobiotic agent, simultaneously producing substrates (e.g. root exudates and root turnover) that assist the growth of the microbes which act as pollutant degrading agents. Microbial activity is stimulated in the rhizosphere through a number of different routes: (i) exudates, e.g. sugars, carbohydrates, amino acids, acetates, and enzymes, nourish indigenous microbe populations; (ii) root systems bring oxygen into the rhizosphere, meaning that aerobic transformations are supported; (3) the available organic carbon is enhanced through the growth of fine-root biomass; (4) mycorrhizae fungi, which are an essential component of the rhizosphere, provide unique enzymatic pathways lending the capacity to degrade pollutant molecules that would not be degraded by bacteria alone; and (5) the presence of plants (and their roots) creates a domain for microbial populations, which are activated in the rhizosphere. There have been five enzyme systems identified in soils: (i) dehalogenase (which acts in dechlorination reactions of chlorinated hydrocarbons); (ii) nitroreductase (essential for the initial step of nitroaromatic degradation); (iii) peroxidase (a critical catalyst for oxidation reactions); (iv) laccase (able to begin the decomposition of otherwise robust aromatic ring structures); (v) nitrilase (another key factor in oxidation processes). The method is limited in that when there are high concentrations of pollutants present, the plants may be overwhelmed and die. The successful use of phytostimulation has been demonstrated in the remediation of chlorinated solvents from groundwater, petroleum hydrocarbons from soil and groundwater and PAHs from soil. 

Phytovolatilization.
Probably, this is the most controversial of the phytoremediation technologies, since it involves the release of contaminants either directly, or in a metabolically modified form, into the atmosphere. Phytovolatilization3 has been used principally for the removal of Hg2+ ions which are transformed into less toxic elemental mercury4. Tritium (3H), a radioactive isotope of hydrogen with a half-life of about 12 years, decaying to helium, has also been removed by phytovolatilization5. A good deal more research is necessary before this strategy becomes mainstream, since there are various negative features to be addressed. For example, mercury that is released into the atmosphere from plants is likely to be recycled by precipitation and thus returned the ecosystem, and the method is restricted both to sites where the concentration of contaminants is toward the low side, and where the contamination is no deeper than the roots of the plants being used. 

Rhizofiltration. 
Rhizofiltration6 involves filtering contaminated water through a mass of roots for the extraction of contaminants, or excess nutrients, e.g. phosphorus. The contaminated water can either be collected from a waste site and taken to where plants are being hydroponically cultivated, or the plants may be planted in the area directly. In both cases, the roots draw up the water and its associated contaminants. This process is very similar to phytoextraction in that the contaminants become sequestered in the form of harvestable plant biomass. Then new plants are grown and harvested until a satisfactory degree of decontamination is achieved. It is the concentration and precipitation of heavy metals that is sought principally. While noting these similarities, the fundamental difference between the two approaches is that rhizofiltration is used in aquatic environments, while phytoextraction is applied to the decontamination of soils. There are limitations to rhizofiltration. As usual in phytoremediation methods, any contaminant that is below the rooting depth will not be extracted, and if the level of contamination is too high the plants will not grow. Depending on the type of plant and contaminant, the process may need to be continued over a protracted period, before regulatory levels are achieved. It is generally true that many different kinds of contaminants will be present – in some cases a mixture of organics and heavy metals – and thus the use of rhizofiltration alone is unlikely to succeed. Importantly, the plants chosen should be non-fodder crop to minimize poisoning animals, which might eat them in contaminated form.  That noted, the effective removal of heavy metal cations, e.g. Cu2+, Cd2+, Cr6+, Ni2+, Pb2+, and Zn2+ from aqueous solutions has been demonstrated7, and the removal of low-level radionuclides, from liquid streams8. In that latter application, a “feeder layer” of soil is suspended above the stream through which plants grow, from which the plant roots extend downward into the water. In this way, fertilizer can be used to help the plants to grow, while avoiding adding to the contamination of the stream, while the latter is cleansed of heavy metal cations9. Rhizofiltration is cost-effective when large volumes of water must be treated containing low concentrations of contaminants. Inclusive of the costs of the capital outlay and final waste disposal, the cost of removing radionuclides from water using sunflowers was reckoned (at 1996 prices) at $2─6 per thousand gallons of water treated10.
 


References. 
(1) Burken, J.G. (2004), "2. Uptake and Metabolism of Organic Compounds: Green-Liver Model", in McCutcheon, S.C.; Schnoor, J.L. (Eds.), Phytoremediation: Transformation and Control of Contaminants, A Wiley-Interscience Series of Texts and Monographs, Hoboken, NJ: John Wiley, p. 59, doi:10.1002/047127304X.ch2, ISBN 0-471-39435-1.
(2) http://en.wikipedia.org/wiki/Phytoremediation.
(3) http://www.unep.or.jp/Ietc/Publications/Freshwater/FMS2/2.asp.
(4) http://tede.ibict.br/tde_busca/arquivo.php?codArquivo=431.
(5) Dushenkov, S. (2003) “Trends in phytoremediation or radionuclides.” Plant and Soil, 249, 167. (6) http://en.wikipedia.org/wiki/Rhizofiltration.
(7) EPA, (1998) “A Citizen's Guide to Phytoremediation,.” U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response,” EPA 542-F-98-011, August. 
(8) Dushenkov, V., Motto, H., Raskin, I. and Nanda Kumar, P.B.A. (1995) "Rhizofiltration: the Use of Plants to Remove Heavy Metals From Aqueous Streams." Environmental Science Technology 30, 1239. 
(9) Raskin, I., Smith, R.D. and Salt, D.E. (1997) "Phytoremediation of Metals: Using Plants to Remove Pollutants from the Environment." Current Opinion in Biotechnology. 8, 221. 
(10) Cooney, C. M. (1996) "Sunflowers Remove Radionuclides From Water in Ongoing Phytoremediation Field Tests." Environmental Science and Technology 30, 194.

Wednesday, November 18, 2015

The Whispering World of Plants: "The Wood Wide Web."

The notion that plants can "talk" to one another was, until relatively recently, dismissed as fantasy, but the reality of inter-plant communication is now becoming an accepted part of mainstream science. Although plants, by definition, being "planted" in the ground, cannot move per se, they are able to send signals to one another, by means of volatile organic compounds, and it is thought that not only can a plant communicate with other plants, it may also engage in a "soliloquy" by communicating between different parts of itself. Although this mere fact is fascinating enough, it appears that plants may both send out chemical messengers as airborne species that other plants can receive, and send messages to one another via a network of connections within the soil, provided by the fungal networks known as the "mycorrhizal mycelium". This has been described as a kind of below ground "internet" which is appropriately termed "The Wood Wide Web".

It is quite well documented that if a plant is attacked by an insect or fungal pest, it can signal to its neighbours, so that they release compounds that repel the pests directly, or attract other organisms that are antagonistic to them. While the airborne action of such messenger compounds is established, the idea that one plant can warn another that it is in danger via a common (shared) mycelial network (CMN) is rather more novel. According to a recent study: “Key roles in facilitating nutrient transport and redistribution” are played by the CMN, but they can also “facilitate defense against insect herbivores and foliar necrotophic fungi by acting as conduits for interplant signaling.”

This is a beautiful illustration of the interconnectedness of natural systems, and it has been proposed that there are dominant "Mother Trees", which act as hubs for the mutual connection of all the trees that grow in a forest. This connection is thought to function to some degree through the mycorrhizal mycelium, which lives in and around the tree roots, and serves as a conduit for the transport of carbohydrates, nutrients and water between the trees, via the fungal hyphae. The mother trees serve to "feed" the younger ones, and without them, most of the seedlings would not survive. Recent research has shown that without mother trees, attempts to regenerate forests often fail, and when a mother tree is felled, the survival rate of seedlings tends to be dramatically reduced. As a tree dies, it may also deliver resources to neighbours of different species, feeding them, and contributing to the overall biodiversity and resilience of the forest ecosystem.

The implications of inter-plant communication via fungal networks are potentially far reaching. For example, forest management (harvesting) practices should involve preserving the Mother Trees to nurture new growth. In agriculture, too, practices that leave the mycorrhizal (mycelial) network intact, are thought to aid the absorption of water and nutrients from the soil, and to improve the ability of plants to resist pathogens. Hence the practices of heavy and deep ploughing, which break-up the mycelial networks, have been called into question.

Not everything that is transmitted between plants is beneficial to an individual plant, since toxins may also be transported via mycelial networks. The influence of one plant to influence (usually restrict) the growth of another is termed allelopathy, and functions via chemical messengers, e.g. the production of juglone by walnut trees, which was found to reduce the weight of tomato seedlings by about one third. The whole system is integrated, holistic and complex, and a new area of research has emerged which aims to understand inter-plant communication at the molecular level. It appears that plants may use a form of "language", in which different molecules act as "words", although the precise nature of the dialogue has yet to be deciphered.

In a study of the action of a parasitic plant (dodder) with two host plants, Arabidopsis and tomatoes, it has been found that messenger RNA (mRNA) is transferred between the two species on a massive scale. Since RNA acts as a translator of information from the DNA of an organism, it is possible that the parasitic plant may be giving orders to its "victim", to weaken its defenses, BUT the host might also be signalling a masochistic response. The question arises of whether information can be similarly transmitted between other organisms within the soil food web, i.e. earthworms, bacteria, nematodes and other microbes, along with the plant roots, and their associated mycorrhizal fungi. These organisms are, collectively, the vanguard for the recycling of nutrients in the soil, which enhances the growth of plants.

To seek an understanding of the complex communications and interactions that take place between the soil food web organisms, at the molecular level, may be a worthy aim, since the soil contains perhaps one quarter of all the biodiversity on Earth. Until this is achieved, however, and in any case, it is clear that by supporting this hidden biodiversity below the ground, the more visible biodiversity above the ground is further buttressed. Practical actions to preserve and build the soil are paramount to a viable future, and their implementation should not be delayed.
that all trees in a forest ecosystem are interconnected, with the largest, oldest, "mother trees" serving as hubs. The underground exchange of nutrients increases the survival of younger trees linked into the network of old trees. Amazingly, we find that in a forest, 1+1 equals more than 2. - See more at: http://www.karmatube.org/videos.php?id=2764#sthash.wUDpgflR.dpuf
that all trees in a forest ecosystem are interconnected, with the largest, oldest, "mother trees" serving as hubs. The underground exchange of nutrients increases the survival of younger trees linked into the network of old trees. Amazingly, we find that in a forest, 1+1 equals more than 2. - See more at: http://www.karmatube.org/videos.php?id=2764#sthash.wUDpgflR.dp

Saturday, October 31, 2015

The Global Oil Supply: Implications for Biodiversity?

The following is an overview of my recent lecture to the Linnean Society of London, which is named in honour of Carl Linneus, who among many other accolades has been described as "The father of modern taxonomy", and is also considered as one of the founders of modern ecology. It is the world's oldest active society for the biological and environmental sciences, and the roll call of its Fellows includes such illustrious names as Charles Darwin and Alfred Russel Wallace.

The lecture itself can be viewed here: https://vimeo.com/143163653

The link between the global oil supply and biodiversity is not directly causal; rather, the two are elements of a broader and more integrated picture. Of the energy used by humans on Earth, crude oil represents the lion's share (33%), followed closely by coal (30%), with gas in third place at 24%. Traversing the gamut of energy sources, we find nuclear energy (4%) and hydro-power (7%), with renewable energy (wind and solar) entering the final furlong at just above 2% of total energy use, meaning that around 88% of our energy is furnished by the fossil fuels. 100 years ago, oil could be produced at an EROEI of 100, while this is now nearer to 17 as a global average, and falling, as unconventional oil sources increasingly make up for the decline in conventional production. So it's becoming increasingly harder to maintain the oil flow into global civilization.


The Global Oil Supply.

We produce around 30 billion barrels of oil every year, which is absolutely staggering, and depending on exactly what you count as oil, this works out to 84 million barrels a day, or about 1,000 barrels every second. The major producers are Saudi Arabia and Russia, who between them produce around one quarter of the world's oil supply. Crude oil is a very various material: light oils are quite freely flowing, while the very heavy oils can be like the black stuff on the road outside. Sweet oils are relatively low in sulphur and easiest to handle, while sour oils contain 2% or more of sulphur and are more difficult to deal with. The big question is how much oil is remaining across the world? Much of what is left contains a lot of sulphur and is heavy, e.g. from the Orinoco belt in Venezuela, and takes a lot of costly processing. And, sometimes when it is claimed, e.g. there is supposed to be 500 billion barrels of oil present in U.S. shale, only a few percent of that is likely to be recoverable. This is the difference between a resource and a reserve: a resource is everything that is, or might be, in place, whereas a reserve is what can be recovered not only technically but economically. It's also sometimes said that America has 2 trillion barrels of oil in the form of oil shale, but this isn't actually "oil" at all, but kerogen, which is "immature oil", which if it had been put by geology in hotter regions of the ground, it would have been cooked into something that we recognise as oil. If you want to convert kerogen into oil, you have to heat it up, which takes a lot of energy, and so the energy returns are correspondingly less.

We need oil to fuel most of the world's transportation, but it is also the raw chemical feedstock to make plastics, pharmaceuticals, and pretty much everything we use. But also, without oil, and natural gas to make fertilisers, modern agriculture couldn't exist in the form that we know it. You need oil to fuel the tractors and combine harvesters etc., but food isn't consumed where it is grown, by and large, it's got to be moved around nations and the entire world. This (slide) is a bit of a poster child, for the unsustainability of agriculture. This is a field of soya beans growing in Brazil, and at one time this field was actually rainforest, but it has been cleared, and the mighty array of machines used to harvest it, run on diesel-fuel refined from crude oil, but the dust that is thrown up behind them is actually the top-soil. And so this is prone to erosion, which is one of the major problems that we have in maintaining agriculture into the future.

Existing conventional oil fields are showing a 4.1%/annum production decline rate which, put into context, means that to maintain the current flow of oil into global civilization, it is necessary to find a new Saudi Arabia's worth of production every 3-4 years. A hard enough task in itself, and all the more so, when the new "oil" has to come from fracking shale, increased drilling in deeper waters, heavy oil, and processing bitumen from tar sands, all with typically lower EROEI than for conventional oil production. "Regular" oil production probably peaked around 2005, and according to the Paris-based International Energy Agency, to maintain the overall oil production rate, it will be necessary to increasingly produce from unconventional sources, but this is only viable if the oil price rebounds once more. In this overall scenario, oil production from shale by fracking, while significant, is not likely to account for more than 6% of the total global production. However, due to the current very low oil price, overall investment in fracking, and also tar sands, is likely to fall. However, it is speculated that due to the Kingdom's necessarily high fiscal break-even cost, Saudi Arabia may go broke before the U.S. oil industry buckles.

If we must look toward a society that doesn't have the level of oil flowing into it that it does now, then what are we going to do instead? We need to find alternatives in terms of fuels, and everything else that we depend on oil for. The other aspect is that burning oil contributes 30% of the total global CO2 emissions budget, and so there is the climate change impact to be considered too. Some people argue that perhaps this is a good thing, because a falling consumption of oil will lead to lower CO2 emissions, but so maintaining a complex and oil-driven civilization will prove a considerable challenge. Much attention is given to biofuels, e.g. bioethanol, but the reality is that if, in the U.K., we turned over the whole of our arable land to growing sugar beet, and stopped growing food crops, we could only produce enough ethanol to match 45% of the liquid fuels that we currently get from crude oil. Yields of cellulosic ethanol from miscanthus are about the same as from sugar beet (5 tonnes/hectare) and so although non-arable and marginal land can be used, huge land areas are still required and we still can't match our liquid fuel budget as is currently obtained from crude oil. Biodiesel from rapeseed (canola) is a worse choice, since the yield is only about one tonne per hectare, meaning that perhaps one seventh of the U.K.'s liquid fuels could be produced from it, even if we stopped growing food crops entirely, and all vehicles were fitted with diesel engines. Another issue is that oil-based liquid fuels are required to grow and harvest all the biofuel crops, along with large quantities of freshwater.

An alternative is to grow algae and convert it into biofuel. In principle, this has many advantages, including a much higher yield per hectare than land based crops, that wastewater/saline water can be used rather than freshwater, and that although the tanks to grow it in have to be engineered, they can be placed on any land (so avoiding a compromise with arable land for food crops) and even floated out at sea! While replacing the current 30 billion barrels of oil annual production by algal fuels is a massive and probably unrealistic challenge, on the smaller scale, growing algae can be combined with wastewater treatment and absorption of CO2 from the flue gases of fossil fuel fired power plants, as an integrated approach to solve two significant environmental pollution problems while making some amounts of liquid fuels in the process. The extraction of crude oil by fracking ("hydraulic fracturing") can be considered as yet another attempt to fill the enlarging gap in conventional crude oil production, with its own problems and limits.


Biodiversity. 

Building Soil.

The 68th UN General Assembly has declared 2015 to be the International Year of Soils (IYS), some objectives of which may be summarised:

• to create full awareness of civil society and decision makers about the fundamental roles of soils for human’s life;
• to achieve full recognition of the prominent contributions of soils to food security, climate change adaptation and mitigation, essential ecosystem services, poverty alleviation and sustainable development;
• to promote effective policies and actions for the sustainable management and protection of soil resources;
• to sensitize decision-makers about the need for robust investment in sustainable soil management activities aiming at healthy soils for different land users and population groups;
• to advocate rapid enhancement of capacities and systems for soil information collection and monitoring at all levels (global, regional and national).

This is part of a global effort to raise awareness of soil degradation, which is one of the critical “woes” of current civilization. In France, the intention has recently been announced to increase the soil organic carbon by 0.4% per year as a strategy to store carbon from the atmosphere in the soil, and to simultaneously improve soil quality and fertility. Soil and water are vital elements for life, and are connected via the hydrologic cycle; soil is also a critical component of the carbon cycle, and hence preserving and rebuilding soil (improving its organic matter content, and structure) is fundamental to stabilising the climate and securing food and water supplies. Of all the actions we might take, building soil is truly sustainable and regenerative, and central to “Earth Stewardship”, which is one of the “possible future scenarios” that we discuss later.


Some salient facts about soil:

• One quarter of all the Earth’s biodiversity is in the soil, i.e. one quarter of the number of organisms hosted by Planet Earth live in the soil, most of which are bacteria.
• 52% of the land used for agriculture is moderately to severely affected by soil degradation: mostly by erosion.
• It takes 200─1,000 years to form just an inch of soil, depending on the climate and other local conditions.
• Soil from agricultural land is being eroded at 10─40 times the natural rate.
• In the last 40 years, one third of the world’s crop land has become unproductive as a result of soil degradation.
• It is estimated that 44% of the world's food production systems and 50% of world livestock are vulnerable, as a result of land degradation. This is likely to be exacerbated by climate change.
• Food production in 2050 will need to be 70% greater than it is now, to feed an expected population that has risen to 9.5 billion (from 7.3 billion), and with relatively more meat being consumed.


Ways to protect and regenerate soil:

• Avoid bare ground: reforestation, planting cover crops (peas, beans, buckwheat, clover, etc.).
• Build Soil Organic Matter (SOM); no-till farming methods.
• Shield the soil through the use of sand fences, shelter belts, woodlots and windbreaks; plant trees.
• Farmer-Managed Natural Regeneration: five million hectares of barren land have been “reforested” in Niger, at a density of 40 trees/hectare.
• Protect existing forests: huge stores of carbon both in the biomass and the soil, and oxygen producing bodies, “the lungs of the Earth”.
• Mulch from pruned trees, and straw to cover fields: increasing soil water retention and reducing evaporation.
• Tree planting: aids in the infiltration water into soil, and reduces flooding.
• Build the “Soil Food Web”: one teaspoonful of healthy soil can contain one billion microbes. The active presence of the soil fauna and flora improves the cycling of nutrients and water in the soil.


Permaculture.

Not an entity, but an active design system.
•Permaculture = Permanent (Agri)Culture
•Regenerative NOT merely sustainable.
•Permaculture = a good design!
“You cannot solve a problem from the same consciousness that created it. You must learn to see the world anew.” Albert Einstein.
•Seeing the whole picture, and placing design elements together to support one another.
•“The problem is the solution.” 
•Companion planting; no-till, building soil structure, efficient use of water, smaller PNK inputs; capturing carbon; best use of light; exploit “3rd dimension”.
•“Three sisters planting”: bean + corn + squash = N-fixer + 3D "stalk" + broad leaves (shades soil).




A forest garden is a beneficial arrangement of plants etc. that exploit the 3rd dimension, both above ground and below it, in terms of the different rooting depths of plants. Such an arrangement can be highly productive, as in the RISC roof garden, which thrives on top of the Reading International Solidarity Center building in the heart of Reading.

The RISC Roof Garden with 200 different plants, including TREES, all growing in just 30 cm of soil on the roof of a building in the centre of Reading. Clearly, many of the roots grow outward.


The World’s Woes.
(...the changing climate)

Much attention is given to global carbon emissions and climate change, and rightfully so, yet this is just one feature of the “changing climate”. Many challenges that confront humankind (“The World’s Woes”) are often regarded as though they are individual problems, but actually are merely symptoms of a single problem - a too rapid consumption of resources of all kinds, and the attendant consequences. Some of these are:

• Carbon emissions: leading to global warming and climate change.
• Population increase: 9.5 billion by 2050, possibly rising to 11 billion by 2100?
• Declining (“peak”) resources: water, oil, gas, coal, uranium, metals, phosphorus, soil, fish stocks.
• Land degradation: soil erosion – desertification. 30% of global arable land has become unproductive in the past 40 years, and much of this has been abandoned. The connection between soil and water via the hydrologic cycle means that the degradation of soil leads to increased drought, but also flooding.
• Loss of biodiversity: it is believed that we are in the midst of the “Sixth Mass Extinction”, since the current rate of biodiversity loss is estimated to be at least as high as (or even higher than) occurred in the previous five mass extinctions.
• Increasing poverty: rising food costs, high prices of imported fertilizers, unfair global trade practices.


All are symptoms of a single problem – excessive (once-through) consumption:
•PRESENTLY: “The sins of the fathers”, an impoverishing scenario where finite resources are exhausted year on year, and the Earth increasingly polluted by those same processes that consume them, e.g. carbon emissions.
•GROWTH: “growing our way to hope”, where growth is possible, if not globally, on the local scale. Resource resilience, as opposed to resource depletion.Transition Towns.
•Using permaculture, can provide much of our food and materials on the local scale, with greatly reduced inputs of crude oil, natural gas, fertilizers, and freshwater. 
•Soil is rebuilt from carbon taken out of the atmosphere, thus acting to ameliorate climate change.

More biodiverse systems are more resilient to water stress and pests, and tend to be more productive.


Carbon-emissions/Climate-change.

Nature (2015, 517, 187): study estimates that  for a 50% chance to avoid G.W. >2 oC (2100), one third of the world’s oil reserves, half of its gas reserves and 80% of its coal reserves must be left in the ground (up to 2050).
 
“Development of resources in the Arctic and any increase in unconventional oil production are incommensurate with efforts to limit average global warming to 2 oC throughout the 21st century.”
In terms of production rate: 

─5% (oil), +58% (gas), ─68% (coal): predicted reduction in emissions from 48 Gt CO2-eq (2010) to 21 Gt CO2-eq (2050) = (─56%).

And yet:
B.P. Statistical Review of World Energy 2014: Most of our energy still derived from fossil fuels by 2035, by when CO2 emissions  = (+29%).


The Future of Energy?

Key effort should be toward energy efficiency.
Retrofitting existing building stock.
Renewable (low-carbon) energy. Limited quantity?
Nuclear power, including thorium MSRs?
Reduction in oil-fuelled transport.
Local production of food, energy and materials.
Rebuilding and protection of soil: water-soil nexus.
Can’t decouple energy from water and soil. Need an integrated, durable system to meet human needs.

....we live in interesting times....


Related Publications. 

(1) R.G. Miller and S.R.Sorrell, “The Future of Oil Supply,” Phil. Trans. R. Soc. A. 2014, 372:20130179
(2) J. Murray and D.King, “Oil’s Tipping Point has Passed,” Nature, 2012, 481, 433.
(3) C.J.Rhodes, “Making Fuel From Algae: Identifying fact Amid Fiction,” in Algal Fuels: Phycology, Geology, Biophotonics, Genomics and Nanotechnology, R.Gordon and J.Seckbach (eds.), Springer, Dordrecht, 2012, p177.
(4) M.Inman, “The Fracking Fallacy,” Nature, 2014, 516, 28.
(5) C.McGlade and P.Ekins, “The Geographical Distribution of Fossil Fuels Unused when Limiting Global Warming to 2 oC,” Nature, 2015, 517, 187.
(6) C.J.Rhodes, “Thorium-Based Nuclear Power,” Science Progress, 2013, 96, 200.
(7) S.Devlin et al., “Urgent Recall: Our Food System Under Review,” New Economics Foundation, Nov. 2014, ISBN 978-1-908506-72-6