Contamination

Phosphate use for fertilisers, essential in modern agriculture, is hitting an all time high while resources are being heavily depleted. Flo discusses the background, numbers, geopolitics and potential solutions behind the issue of ‘the end of phosphorus’.

The Issue

Modern agriculture has developed in-line with the availability of high quality phosphate-rock fertilisers. Source – João Felipe C.S, Wikimedia Commons.

The dilemma over diminishing natural resources is a topic of our times with the daily bulletins filled with reports related to resource shortages. These mainly focus around water, energy and food which are imperative for human survival. Whilst energy and water are often debated in the media and political chamber, an area that gets much less attention is agriculture, and in particular diminishing phosphate resources used for industrial fertiliser. Modern agriculture, particularly in developed countries has used mined phosphate for fertilisers for decades but this finite resource is being depleted at an alarming rate.

A combination of growing population, aspirational lifestyles and the demand for phosphate-intensive meat and crops has caused the rapid reduction of phosphate rock resources. In the past, prior to the advent of phosphate mining, additional phosphate for farming and agriculture was sourced from manures

Prior to use of phosphate rock, it was replenished through the use of manure. Source – Malene Thysson, Wikimedia Commons.

and organic waste, but as agriculture intensified, the hunt for easier, more accessible phosphate began. From the mid-20th century onwards, the use of rock phosphate was used as a high quality, easily accessible sources of phosphorus which gave rise to the modern fertiliser industry as we see it today. Farmers in rich countries such as Europe and North America became hooked on the cheap and easy phosphorus which readjusted agriculture practices and set phosphate demand through the roof.

Background

Phosphorus (P) is a non-metallic element which is almost always present in a maximally oxidised state (PO₄^3-) as inorganic phosphate rocks due to its reactivity. Elemental phosphorus can exist as red and white (known for its use in weapons and artillery) phosphorus but almost never found as a free element in nature.

It is one of the building blocks of life and life simply wouldn’t exist without it. It is a key component of DNA, RNA, ATP and phospholipids and is essential to cell development, reproduction and in animals, bone development. The use of phosphorus compounds in fertilisers is due to the need to replace the phosphorus that plants remove from the soil.There is no substitute for this element. Supplies are limited and much is currently wasted, creating concerns about future supplies in the EU and worldwide.

Peak Phosphorus?

A graph of world phosphate rock production vs. year from 1900-2009 obtained from the U.S. Geological Survey. Source – Thomas D. Kelly and Grecia R. Matos, Wikimedia Commons.

Recently there has been a proliferation of articles and discussion over the potential for ‘peak phosphorus’ in the next 20-30 years. World production recently peaked at <160 million metric tonnes (mmt) in 2008. Whilst the majority of people agree that phosphorus is a resource that is of concern, not everyone agrees with the peak phosphorus hypothesis or its potential timing. Proponents of the argument include this group of academics who published a paper entitled ‘The story of phosphorus: Global food security and food for thought’ and Jeremy Grantham, co-founder of the investment firm Grantham, Mayo, Van Otterloo, who recently wrote a piece in Nature. On mined-phosphate fertilisers, Jeremy Grantham stated that ‘There seems to be only one conclusion: their use must be drastically reduced in the next 20–40 years or we will begin to starve’. Much of the peak phosphorus argument comes from a widely produced diagram from a 2009 paper in Global Environmental Change depicting peak phosphorus to be around 2030 followed by production declining at an accelerating rate. Detractors to this theory say that the markets are likely to adjust to this problem and cause the price to rise thus forcing a reduction in use and a push for technology to advance to find new sources or recycle current phosphate use. The International Fertiliser Development Center (IFDC), through extensive data gathering state that there is “no indication that a “peak phosphorus” event will occur” in the next 20-25 years.

Resources and Geopolitics

Phosphate mine near Flaming Gorge, Utah. The large size of phosphate mines is dictated by the dispersed nature of phosphate in the rock. Source – Jason Parker-Burlingham, Wikimedia Commons.

Phosphate rock is typically mined at high volume due to its dispersed nature in the rock. Phosphate, in the mineral form of apatite in phosphate rock, is not bioavailable to plants and must be processed to convert it to a plant-available form. The concentrate is used to produce phosphoric acid which is then used in fertiliser products. Phosphate rock can come in either a sedimentary or igneous form, with sedimentary making up >80% of total global production.

Topographic map of Western Sahara. Western Sahara is disputed territory but is currently controlled by Morocco and therefore the Moroccan Royal Family. Source – Sadalmelik, Wikimedia Commons

In addition to the concern over the amount of resources and rate of use, also of concern is the location of much of the world’s supplies. Europe in particular has scant phosphate resources with a small amount in Finland. According to the IFDC report from 2010, 72.1% of the world’s phosphate rock production was accounted for by China ( 31.5%), U.S.A (18.7%), Morocco and Western Sahara (15.5%) and Russia (6.4%). However a significant proportion of the world’s high-grade supplies are located in the disputed territory of Western Sahara in North-West Africa, currently controlled by Morocco. This has been termed by Jeremy Grantham as ‘the most important quasi-monopoloy in economic history’.

Country	Mine Production 2007	Mine Production 2008	Reserves	Reserve Base (estimated)
China	45,700	50,000	4,100,000	10,000,000
Morocco and Western Sahara	27,000	28,000	5,700,000	21,000,000
Russia	11,000	11,000	200,000	1,000,000
United States	29,700	30,900	1,200,000	3,400,000
World Total (rounded)	156,000	167,000	15,000,000	47,000,000

Table adapted from USGS Mineral Commodity Summaries January 2009. Data is presented in thousand metric tonnes.

Phosphate rock resources in Western Sahara are extremely large and still incompletely explored and therefore it is not understood if the rock is producible at current prices and costs as there is little to no data. The IFDC estimates global resources of 290,000 mmt but if Morocco and Western Sahara resources are included (340,000 mmt) it may increase to 470,000 mmt, as seen in the above table.

Environmental Impacts

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Eutrophication in a pond in Lille, France. Eutrophication is caused by the enrichment of an ecosystem with chemical nutrients such as phosphorus. Source – F. lamiot, Wikimedia Commons.

The use and mining of phosphorus also carries risks. In agricultural use not all of the phosphorus is absorbed by crops which results in leaching into the water. This causes the much discussed eutrophication effect causing algal blooms. Phosphorus mining is also difficult environmentally as it generates a large amount of the waste product phosphogypsum which contains both toxic heavy metals and low levels of radiation. This is very difficult to dispose of and often results in mounds of unprocessed waste material.

As lower-cost phosphate resources will be mined out, mining companies will utilise lower grade ores which will incur the use of more energy and water and will cause the price to go up. Availability of water is of high importance to mining operations and indeed this can dictate the feasibility of phosphate extraction, areas of low water availability may completely restrict development of the mine. Another way in which water, energy and food are interconnected.

What next?

Wastewater discharge pipe – New studies show useable phosphorus can be recovered from wastewater. Source – Department of Agriculture, Wikimedia Commons.

Regardless of the proximity of ‘the end of phosphorus’ it is very much a finite resource and thus development towards more effective use and recycling needs to take place. Recently, the Environment section of the EC launched a consultation into how to use phosphorus in a more sustainable way, following on from a conference held in March on Sustainable Phosphorus. They have also posted a series of informative videos that can be found here. Much work has been done on the ways in which we can curb our phosphate use or recycle it more effectively. More must be done to monitor and reduce phosphate use as well as recycle wasted phosphate. A few of the potential solutions are listed below.

Phosphate reduction

Changes in people’s daily diet away from phosphorus-intensive foodstuffs such as meat.

Since much of phosphorus is lost from the food cycle through waste, a reduction of food waste and its reuse in composts etc could reduce demand.

Current agricultural practices result in a very high use of fertilisers. A switch to techniques and practices that conserve more soil nutrients would go some way to reduce phosphorus waste. This includes organic agriculture and use of permaculture (sustainable and self-sufficient agricultural practices).

Genetic engineering could produce plants that can flourish with much lower phosphorus use.

Recycling

We can recover useable phosphorus from waste streams including urban sewage, since current systems already remove phosphorus from sewage to preserve water quality. Wastewater carries a lot of struvite, a mixture of ammonium, magnesium and phosphate which builds up in the pipework.

A team of canadian researchers believe struvite can be turned into environmental friendly fertiliser, as discussed in this national geographic article. Together with the local government they have set up a lab next to a waste water treatment plant. This process works by altering the pH and allows the wastewater chemical to bond together into pellets through a turbulence process. Currently a working prototype can turn out several tons of pellets a month. Since 2010, the technology has been incorporated into 5 waste water facilities in North America. Whilst there are some cost issues to address, there is relatively little further work required to reproduce this technology on a wide scale. Higher phosphate prices would push wastewater recovery to be economic.

Flo Bullough discusses the meaning of good and bad water quality, what’s in our tap water and what policies control the content of drinking water.

Pressure on water supply and quality has been high on the public and media agenda over the last 18 months. The widely publicised drought in early 2012, recent reports that we are due to run out of clean water in this generation and the controversy around potential contamination from fracking and the water industry itself have got a lot of people talking about good and bad water quality.

Water is the most important, interesting and unique compound on the planet. In addition to its necessity for all life, it also plays a fundamental role in industry and agriculture. For this reason the provision of reliable supplies of water of an adequate quality is imperative for health and for the economy. Geoscientists and hydrogeologists are involved at many stages in the water provision process, including characterising the geology and geochemistry of groundwater and surface water systems, identifying contaminants and the development of materials for the remediation of polluted drinking water.

Water carries the signature of the many parts of the water cycle it has passed through and so is never as simple as H2O. Source – USGS, Wikimedia Commons

What’s in our water?

For a water scientist, the purity of water is considered differently depending on its intended use. For the purpose of this post, I’ll be looking at what’s required to make drinking water ‘fit for use’ which applies to all water intended for human use. 100% pure water is the compound H₂O, but in nature, however, this doesn’t exist as water acts as the universal solvent and is often a much more complex and heterogeneous mixture of dissolved salts, inorganic and organic compounds and bacteria. This is due in part to the extremely variable nature of the geology and soil that water interacts with. Water is as unique and variable as the geological strata through which it passes creating a fingerprint of the local geology.

The dissolved minerals in water such as magnesium and calcium bicarbonate is what clogs up our kettles! Source – Julo, Wikimedia Commons.

It is the impurities it collects along the way that make the difference between hard and soft water; hard water contains more calcium and magnesium bicarbonate (leading to that nasty build up in your kettle!) but has no negative impact on health. Many of these impurities are either completely harmless or exist at concentrations below those posing a risk to health.

Some of these components create better tasting and higher quality water such as a balanced amount of magnesium, potassium, calcium and silica – chlorine, on the other hand, often ruins the taste of water. In addition to the compounds and chemicals that enter the water system in the environment, many water companies also add certain chemicals to drinking water. At the disinfection step, chlorine is often added to remove harmful bacteria, and some of this chlorine remains in the water until the point of consumption to ensure the water remains fresh as it makes its way through the pipe network. An issue of long-standing controversy is the addition of fluoride to drinking water. Fluoride is typically added to reduce tooth decay but its wider impacts have been debated extensively. Fluoride is a complex issue in that it can have beneficial health impacts at low concentrations (0.5 – 1 parts per million (ppm)) but acts as a contaminant at slightly higher doses. The threshold set by the World Health Organisation (WHO) guidelines is currently 1.5 ppm. The intense debate around this has led many countries to stop artificial fluoridation of their drinking water.

Areas with groundwater fluoride concentrations above 1.5ppm. Source – Eubulides, Wikimedia Commons.

It is largely not practiced in Europe with the exception of Ireland, Spain, Switzerland and the UK, where approximately 5.8 million people receive artificially fluoridated water. This variability in the UK is accounted for by the differing regional policies on fluoridation.

How do we define contamination and where do contaminants come from?

Rio_tinto_river_CarolStoker_NASA_Ames_Research_Center

Some water contamination is very colourful and visible such as Acid Mine Drainage seen here in Rio Tinto, Spain. Source – Carol Stoker, NASA, Wikimedia Commons.

Contamination can occur in many forms. It may or may not be visible to the naked eye and it can occur at very low concentrations (in the parts per billion range) or at much higher concentrations. This has implications for the wider public and policy-makers in communicating and understanding the issues around water contamination and decontaminating drinking water since the presence of contamination is often far from obvious. Contamination in drinking water is assigned by threshold values: since at least trace amounts of most elements are found in drinking water due to reasons discussed above. It is only when the concentrations of these chemicals exceed an assigned threshold that there is cause for concern. Contamination is normally defined by comparing concentrations in freshwater to a set of pre-determined evidence-based threshold limits that protect humans, flora and fauna from harmful levels of certain chemicals. These contaminants can come from a wide range of sources: acute spills associated with point sources such as industry, acid mine drainage and landfill – often coined anthropogenic sources – but also natural sources, where contamination is geogenic is origin, i.e. naturally present at elevated of harmful concentrations. Geogenic sourced contaminants can be unleashed through the drilling of wells for groundwater as seen in the arsenic crisis in Bangladesh.

What are the current policies covering water quality and its improvement?

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The restriction of pharmaceuticals in drinking water could incur high financial and energy costs. Source – LadyofProcrastination, Wikimedia Commons.

Substances which pose a risk to the aquatic environment are regulated in the Water Framework Driective at EU level and member states are requried to control these substances and prevent concentrations exceeding the threshold limit. There are currently over 50 standards to which drinking water is compared and these are listed by the Drinking Water Inspectorate (DWI) in the UK. The job of the DWI is to ensure that private water companies are producing water to the standards outlined in law. These health-based standards derive from those outlined by the EU in 1998 (with the exception of a few national limits), themselves based on strict guidelines outlined by the WHO. A recent inquiry carried out by the UK Government Science and Technology Committee investigated water quality threshold limits and the potential addition of new chemicals to the list of controlled substances. The main concerns were the inclusion of pharmaceutically-derived products to these legal thresholds, the extent of damage they cause, and the financial and energy costs of treating wastewater to remove them.

Problems with threshold limits

Clearly, the protection and decontamination of drinking water is of high importance in the context of a growing population and environmental change. However, adherence to current limits – which can be prohibitively low – and extension of the controlled substances list has complicated implications. Firstly, threshold limits can be extremely low, sometimes sitting at or below the levels which can be measured with current instrumentation. This can make the monitoring of contaminants both difficult and expensive, particularly in developing coutnries where sophisticated analysis instruments may not always be available. Additionally, many people argue that threshold limits are too low due to their basis on risk-derived limits and the lack of clear or ample toxicological or epidemiological studies to aid in deriving the standard value.

As issues of water and energy provision continue to converge in a difficult economic climate, knock-on impacts to intensive water remediation will only become a more important consideration for decision makers. The challenge now is to effectively communicate and manage the intensifying water issues associated with water security and quality in the light of economic factors, feasibility and the rising cost of energy.

Contamination

What’s all the Phos about?

Murky waters – what counts as good water quality?