Posts Tagged ‘phosphorus’

International Fertiliser Society: Meeting Challenges through Innovation

December 9, 2012

Conference Cambridge Dec 2012.

What challenges?

The growing world demand for food. Scarcity of land and water. Ecological limits are almost reached. We must produce more with less environmental impact. Sustainable intensification.

Some believe that organic agriculture is the solution. But the production is too low. We need increases, not reductions. We need an ecologically better general agriculture.

What innovations?

Higher and more reliable yields. The ambitious English project Wheat 20-20 (20 tons/ha year 2020), a combination of plant breeding and agronomic development.

Better adaptation of inputs and resources. More efficient phosphorus fertilization, for instance placement (common in Sweden) and maybe foliar or seed application as complements.

Focus also on potassium and magnesium. Deficiencies, also shortterm, reduce stress tolerance and yields.

Cover crops. They reduce nitrate leaching and in addition provide organic matter and are positive for life in soils. They function also as break crops in rotations.

Manure is a great problem. Theoretically a good solution is to move animal production back to crop producing farms. Go back to mixed agriculture. But that does not work in our economic reality.

Two ways are worked on: to improve the manure efficiency at farm level and to process manure to marketable or at least transportable products which can be removed from the farm. However, it is not an easy problem to solve.

The longterm nitrogen efficency of manure is low. The most efficient method, injection,  has a longterm efficiency of 55% compared to mineral fertilizer. In practice the efficiency today is only half of that.

A problem mentioned is that economic realities often do not permit use of improved agronomic measures. This a big problem for the world development.


Recycling. Phosphorus should have priority.

November 24, 2012

The food we eat contains nitrogen and phosphorus, important elements for everything living. It ends up as toilet waste. After treatment in sewage works most of the phosphorus and some of the nitrogen end up in sewage sludge. This contains also some heavy metals, bacteria, hormones, medicins and various chemicals.  Sludge (biosolids) is a kind of fertilizer containing especially phosphorus but some nitrogen and above-mentioned impurities. To apply it on food-producing soils , is that right?

There are processes where the sludge is burnt, pure phosphorus compounds are extracted and a clean phosphorus fertilizer is produced. Then we miss the nitrogen. Is that right?

Systems can be developed where the toilet waste is collected, hygienized and used more directly as fertilizer. Then we take care of both phosphorus , nitrogen as well as potassium and other nutrients. Unfortunately hormones , drugs and chemicals are included.  Physically it is a thin sludge to transport and distribute. Is that right?

We need some guidelines to choose.

Phosphorus is special for two reasons:

1. It is a limited resource. We know about mineral deposits for 10-20 generations, but then ?

2. All we take out from mineral deposits ends up in our environment, in fields, gardens, waste dumps, waters.  It is active and causes eutrophication. And we never get rid of it. It might move, but is still active.

These are two, as I see it, overriding reasons to give phosphorus priority, to keep down extraction from mineral deposits by recycling as much as possible.

Nitrogen is different.

1. We have unlimited resources,  80% of the air is nitrogen. But we need energy to make it active, and all kinds of energy can be used. The present oil and gas can be replaced by hydro- or solar energy or even bioenergy.

2. An important process, denitrification, removes active nitrogen from the biosphere and gives it back to the air. There is no unavoidable  accumulation.

3. Active nitrogen (ammonia, nitrate, nitrogen oxides) are environmenal pollutants. Research has suggested that we already exceed the limits of the globe in this respect.

The main priority for nitrogen is to avoid losses of active nitrogen. To handle the farm nutrients as efficiently as possible. (Organic nitrogen in for instance sludge is in fact a disadvantage in this respect). Environmental analysis should guide the development

Conclusion: Extract pure phosphorus when possible. The loss of nitrogen is no great disadvantage (provided there is no nitrogen pollution from that process)

There are local needs for more smallscale processes.

Phosphorus, use and recycling

January 24, 2011

There are two legs for Swedish P recommendations: adequate level in soil and maintenance (mostly= removal). This leads to much lower P use than some decades ago. Removal seems a sound and fairly sustainable base once the soil and cropping system are in equilibrium, a process which takes some decades.

If removal can be compensated by recycling we could talk about sustainability. How is it in practice? What can be recycled?

The sewage works take care of the waste flows. The input of P to the sewage works is the theoretical upper limit for recycling. But this covers only 16% of the removal from agricultural land.  And the practical amount, the P in sludge, covers 11%.

So- there are other waste streams to consider and work on, some within agriculture itself, others in the food industry.

And sludge – we have a controversy in Sweden. Some argue that sewage sludge is a beneficial soil amendment beside the P supply, others that sludge contains unwanted metals and organic compounds which should not be applied to food producing soils.

My view is that the critics are right if we take a long term view, which we should.There is technology to remove the P in the process and avoid all question marks about heavy metals and biological agents.

Our society could need a purification step in the nutrient cycling.

Phosphorus recycling.

January 3, 2011

Does such a thing exist? Only to a small extent as sewage sludge to farmland. Metals and organic contaminants are discussed. Extract a pure fraction of phosphates?  Too expensive? In fact, there are several methods both in practical use and under development to solve this problem at a very moderate cost.

So – the fundamental problem:  Lack of phosphorus recycling is no real problem. Let us solve it.

A new authority for the Baltic?.

March 6, 2009

The issue shall be investigated according to a press release from the Swedish Secretary for Environment.

As expressed in this blogg the agriculture in Sweden is environmentally efficient. Not only the nutrient efficiency is high, the actual losses are low, comparably. But that does not mean that improvements not are possible.

Manure is mentioned in the press release. And there is a problem. The animals keep producing manure and nutrients which the soil not always needs. The rules of today have only stopped continued nutrient accumulation.

Clearly, it would be better for the Baltic if this production moved to Denmark or the Netherlands. This will probably be the result of new restrictions.

A couple of other proposals:

A crash program on manure treatment, transports and spreading technology. In the complete picture there are more gains than often believed. The receiving soil increases fertility and carbon content. This should be considered in the transport ecology. Greengard Farming Perspectives can be of help here. Also biogas alternativs should be considered.


Soil which is not disturbed from Autumn to Spring gives less erosion and moderates water flow. Nitrogen outflow is considerably reduced, as well known. There are many advantages. This was proposed in a workshop in January organized by the Environmental Protection Board, and is under consideration.


A picture of the situation in the Baltic (started by massive inputs of  N and P in the 1900s, inputs which continue from some areas):

A conflagration with lots of inflammable material is going on. On one side a group of desperate people with buckets and handsprayers try to improve their work, but on the other side another group is pouring oil in the fire.  (I do hope I am wrong).


In Science 20 Febr a Policy Forum (Controlling Eutrophication: Nitrogen and Phosphorus) it is stressed that both N and P should be reduced. The Baltic and the crucial influence of the P in bottom sediments is mentioned.


Country differences.

January 30, 2009

At the conference in December arranged by The International Fertiliser Society (see tag Recycling) phosphate was an issue. We have to economize with this limited resource. Some figures for UK (minus N Ireland) were mentioned, meaning that the agriculture (and river banks) looses about 0.8 kg P per hectare agricultural land (incl pastures) to surrounding seas. We in Sweden are struggling to reduce a loss of 0.4 even further.


In England the Cd content in sewage sludge now is reduced to 70-120 mg Cd/kg P (“not much different from mineral fertiliser”). The Swedish figures are about 40 and 10 respectively.

The regulations for sewage sludge in England say that the content 3 g Cd/kg soil shall not be exceeded and the additions of Cd are maximized to 150 g in a ten year period. The average Cd content in Swedish soils is about 0.5 g/kg and we do not want any increase at all. The goal is balance, but a problem is that about 0.5 g/hectare is deposited from the atmosphere.


For phosphorus it might be a question of stage. We started to adapt the nutrient management a couple of decades ago and are leading in Europe.

The base for the differences in cadmium is unclear. Different interpretation of scientific reports?

But this favourable situation for Swedish agriculture gives no advantages for the farmer, only costs. And more pressure.That is the problem with products influenced by commodity pricing in a global scale.


The whole and the details.

January 8, 2009


The Swedish Environmental Protection Agency is arranging a workshop next week in order to squeeze out ideas for further reduction of emissions to The Baltic. That is needed, for large commitments have been made in Baltic Sea Action Plan.


It is about N and P. But I hope that the topic can be widened to include the integrated function of the soil. And that is almost necessary, since we have gone very far in correcting malpractices and errors. Few simple solutions remain. But there are possibilities to improve the functioning of the soil. Better structure, better stability and surface protection will help reducing P outflow. The very work in this direction will also reduce N outflow and greenhouse gases. Biodiversity and yield capacity will increase. Cover crops are more than just N catch crops.

Have a look at my post of 30 Dec.


In general, segmentation and specialization is a problem, both concerning authorities and research. Different units have there own segments. Integration is difficult. The economists should perhaps integrate, but also they have got specialized tasks.


A flower to Greppa Näringen (Focus on Nutrients) who has dared to integrate many aspects in “The soil fertility module”.

A ghost from the past.

October 28, 2008


This is a phrase from yesterday, which concerned phosphorus from toilets, but I thought it could be a provoking headline. But maybe a quesionmark is needed.


In some respect we have gosts from the past also in agricultural lands: soils with excessively high phosphorus contents. Also in that respect Sweden is in a favourable position. Our situation is a distant goal for many neighbouring areas.


However, there are large areas with unnecessarily high phosphorus contents. These should be reduced, which is more interesting with the high P prices of today. But a reduction of the soil content takes time.


A soil content of P-AL 6 is enough for normal agricultural crops. Higher content is a resource to utilize. A true win-win situation for economy and environment.


The problem is farms with animal production and fully utilized spreading area for manure. They cannot adjust the P application easily. Cooperation with neighbours – easier said than done.

There is a modification of my system Farming Perspectives which could help.


In fact there is a kind of market failure. When the individual enterprise is optimized the longterm aspects cannot fully be considered for reasons of competition.


When the rules of the society are compromizing longterm environmental aspects a change is needed. In a global market it should be a global action, but while waiting for that national programs are possible: adequate rules with economic compensation

Phosphorus in the seas.

October 27, 2008


New programs are discussed: Wind powered pumps to bring oxygen-rich water to the bottoms. Maybe feasible.


But let us think about the latest hundred years. How was the situation for the Baltic hundred years ago? A fine mesh of water courses and wetlands dominated the landscape. It was not easy for the phosphorus to escape to the sea.

The population was less than half compared to today. The toilet refuse was to a large extent used together with manure. In the cities it was collected as latrine and used as fertilizer.

But within a few decades things happened.

The water toilet was introduced. The phosphorus was brought directly to the seas or lakes.

The farmland was much improved by ditches and drains opening up for water transport as well as phosphorus transport from the fields.


The phosphorus from the toilets, before the modern sewage works, must remain in bottom sediments of the seas. It is not easy to get rid of this ghost from the past. And some additions continue to come from some places.


And the drainage is there, continuously. Without it we would hardly have an acceptabel agriculture. The wetland program – a good effort but compared to the filtering effect of the old landscape its effect is negligible.


Probably we are deceiving ourselves if we believe that we can reduce the phosphorus outflow to levels from hundred years ago. In an international comparison Sweden scores well. And there are improvements to work on, but a radical  reduction is not possible without sacrificing or maybe completely redesigning the drainage system.